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New To Me 1993 Corolla Rough Idle!


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#1 abhaya

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Posted 11 November 2011 - 02:38 PM

Good day all!

I have a few questions for loyal Corolla owners. I had a 1994 Toyota Tercel base model which I got rid of and upgraded to the Corolla 1993 DX with a four speed automatic. I love the car it has 121569 miles on it. I replaced the spark plugs with NGK platinum plugs and a new wire set. I raised the idle speed but I have a couple of issues. It is a little un responsive when I press on the gas pedal. There is a lag. Also it idles really rough. You can feel the car shaking and it feels like it is going to die. I had a mechanic look at it when I bought it but he did not test drive it. He said everything looked good. The spark plug burn on the old plugs was good. There are no majot leaks anywhere. It does burn a little oil but not bad.

He said it may be the EGR or the emmissions control. He said I needed to get it cleaned. Could this be right? Anyone else have this problem? What did you do to rectify it. My 94 Tercel ran great no shakes or nothing and this engine is better but the lag and shaking or rough idling is a problem.

I also wanted to know what the timing belt replacement schedule was? I have no records on this car and I have no idea when the timing belt was changed if it ever was changed? I would like to know if a car with 121000 miles on it how soon should I replace the belt assuming the worst that it never had a change? The water pump is seperate on this engine so I would like to replace the tensioner and spring and belt all at the same time. I would like to know if there are other seals I should replace at the same time and how much would it cost to repair the EGR and replace the timing belt and spring and tensioner. I would like to do it all at once.

Any suggestions on my problem would be helpful. It could be something else and I am no expert and I am hoping someone else had a similar issue and can shed some light to help me!! I appreciate it!!

#2 fishexpo101

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Posted 14 November 2011 - 11:05 AM

Rough idle and slight hesitation on acceleration can be attributed to a clogged EGR system and/or other emissions related components including a faulty or dying O2 sensor, clogged catalytic converter, exhaust leak, etc. A dirty throttlebody or vacuum leak can also cause the issues you are seeing. I'd try to clean the throttlebody, check for vacuum leaks, and then try cleaning the EGR. Especially the vertical tube that connects the EGR valve to the intake manifold - can get completely clogged with carbon. If cleaning/checking those items does not improve the idle quality and performance - I'd do a little more diagnostic work to find the real cause. Try not to get into a habit of just swapping parts to diagnose this - as that will get real expensive very quickly.

As for the timing belt replacement interval - they recommend 60K miles as a conservative interval. The A-series family of engines (1.6L 4A-FE and the 1.8L 7A-FE) are non-interference, means that no engine damage will occur if the belt breaks - but you don't want this to break at the most inopportune time (middle of a busy intersection, right when you merge on the freeway, when you need to get somewhere immediately, etc.) I'd suggest you just replace the belt, belt tensioner, and waterpump now - just to know for sure that they are changed. Given that it sounds like you just picked up the car and it didn't idle quite right - I'd take that as an indication that the car didn't see regular maintenance as it should.

#3 abhaya

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Posted 14 November 2011 - 02:40 PM

Rough idle and slight hesitation on acceleration can be attributed to a clogged EGR system and/or other emissions related components including a faulty or dying O2 sensor, clogged catalytic converter, exhaust leak, etc. A dirty throttlebody or vacuum leak can also cause the issues you are seeing. I'd try to clean the throttlebody, check for vacuum leaks, and then try cleaning the EGR. Especially the vertical tube that connects the EGR valve to the intake manifold - can get completely clogged with carbon. If cleaning/checking those items does not improve the idle quality and performance - I'd do a little more diagnostic work to find the real cause. Try not to get into a habit of just swapping parts to diagnose this - as that will get real expensive very quickly.

As for the timing belt replacement interval - they recommend 60K miles as a conservative interval. The A-series family of engines (1.6L 4A-FE and the 1.8L 7A-FE) are non-interference, means that no engine damage will occur if the belt breaks - but you don't want this to break at the most inopportune time (middle of a busy intersection, right when you merge on the freeway, when you need to get somewhere immediately, etc.) I'd suggest you just replace the belt, belt tensioner, and waterpump now - just to know for sure that they are changed. Given that it sounds like you just picked up the car and it didn't idle quite right - I'd take that as an indication that the car didn't see regular maintenance as it should.


Thank you for the response!! I appreciate the help! I will look into doing as you said. Is this a project I can do with limited mechanical experience. I.E. changing oil, air filters, other small items is about as mechanical as I get. I do not have much money right now as I just bought the car but I do want her to run good. If I could clean the throttle body and egr and save money and get a mechanic to change the timing belt then I would be good to go. I have about $200 right now to do repairs. Not much considering.

One other thing could I wait on the egr? Will it cause damage to the car if it is clogged? I am thinking I should change the timing belt first and then the egr. I can live with a rough idle but can't without an engine running.

Thanks again for the help!! I really appreciate it!

#4 fishexpo101

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Posted 14 November 2011 - 03:05 PM

Throttlebody and EGR cleaning should be well within the limits of your average DIYer. Not really hard or complicated - just time consuming, depending on how much carbon build-up is in there. You can wait a little bit on the EGR - try cleaning the throttlebody first, see how that turns out. Vacuum checks can be done visually at first - for hard to detect leaks, you'll have to spend more time.

Timing belt is the more critical component - so if you have the funds now, you should do that first. The idle issue, hesitation/stalling are more of a nuisance. But one that should be addressed sooner than later. A faulty EGR can lead to more serious engine problems - depending on how it is failing. Some cases, leads to burned valves, loss of compression. Usually, I like to do a compression check and tailpipe emissions test on a older used car - as they are quick tests that will shed lots of information on the engine/emission health. Should be part of every good used car inspection program, before you buy anything.

If your mechanic can do a compression check inexpensively - I'd have them do it to see how the compression is across all the cylinders. If the compression varies more than 14PSI between cylinders or falls below the minimum compression spec (142PSI) - then you have a more serious problem on your hands and should hold onto the money before you pump it into possible a bad engine. Granted - this is a worse case scenario. The A-series engines have a near legendary reputation for being bulletproof - takes a lot of abuse/lack of maintenance to kill one of these engines. But without known the maintenance history - best to assume the worse and go from there.

#5 abhaya

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Posted 14 November 2011 - 04:07 PM

Thanks again for the very valuable information.

Man I was hoping it would cost less to fix. I am looking at $300 lowest price quote to $500 just for the timing belt and spring and tensioner. I have literally $200 available now and a lot of bills.

I will not be able to make this repair for at least a month to raise the additional money plus I need to drive about 400miles on it for thanksgiving. Is there anything I can do to get a few extra miles before I do the timing belt change? I.E. tips? Does the way I drive have an impact on the timing belt. I.E. driving fast, fast starts or stops, or does driving habits make no difference?

I have heard of people who go 200,000 plus miles and all they do is change the oil? Is this just not real or are they just really lucky? I do not want to push my luck but I am just really strapped right now. I can come up with the $300 but it will be after I take the car on a long drive up steep inclines too.

Any advice is appreciated and I really appreciate all the help up to now!!!

Thanks!!!

#6 tashirosgt

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Posted 15 November 2011 - 12:56 AM

I have heard of people who go 200,000 plus miles and all they do is change the oil? Is this just not real or are they just really lucky? I


It's unlikely that you can go 200,000 miles without replacing at least one alternator and one water pump. (When you do replace the timing belt or the water pump, you usually have both done at the same time since it involves similar disassembly.)

You better think about what you will do if you breakdown? Are you an AAA member? Or do you have a cousin that owns a towing service?

#7 abhaya

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Posted 15 November 2011 - 04:39 PM

Thanks for the response. I am not sure you really understood what I was asking. I know I need to change the timing belt it is not a question. I just do not have the funds to do so right now. In a month or so I will. I just wanted to know if there were any driving tips to reduce the chance of the belt having a problem or does driving fast, slow, etc. not make a difference.

To Fish I really want to thank you for all of your help. I cleaned the throttle body today and it did not even look that dirty but it made a huge difference in how the car is running. It is not as rough and responds much better. It is not perfect but it made a big difference. I am having a problem though. I can't seem to locate the EGR on my 1993 Toyota corolla DX 1.8 automatic with the 7afe engine. I have a haynes manual and it says it should be at the top near the throttle body but there is no egr valve there. Is it in another area?? I would like to clean that next and I am also thinking I should clean the whole manifold. I know there are some gaskets I would need to buy before hand but I figure if just cleaning the throttle body made a difference then cleaning the whole system would be a good idea, which is also why I want to find the EGR valve. I have heard on some models of this engine there is no egr valve but I just do not believe mine would be that model. Could a bad mechanic have simply taken off a faulty egr and not replaced it?? It is an expensive part.

Can you tell me what gaskets I would need and if I should even try to clean the whole intake assembly or should I just leave it alone?

I just bought the timing belt and kit from autozone. There whole kit was $117 and I called the Toyota dealer and they wanted $207 for the same parts. The dealer parts are OEM and made in Japan he assured me? The parts from autozone the belt is made in Italy and the tensioner and spring are made in Korea. Should I fork up the extra money for the better parts or is autozone or Duralast a decent brand? The warranty is the same and I have been burned by dealer parts before. The dealer seems to give the crappy parts to consumers and the good parts to their service dept and other mechanics. The warranty on both is the same 1 year warranty. I would rather save the money. One thing I was thinking is to just by the timing belt from Toyota and the other parts from Autozone? Does it matter. I think Duralast is the same as Dayco which is a huge manufacturer. I am not going to be racing my Toyota but I do want a reliable repair. I am willing to spend more at least on the belt but the Toyota belt is $51 and the Duralast is $23. Big difference. I am going to pay a mechanic to do the work but I like buying my own parts. Never know what they put in and then they charge more than what I can get it at retail!! I guess they like to profit at both ends. I just personally like to know what is going in my car.

Thanks for the advice and help!! I love my Corolla and plan to keep it for a long time. I was lucky to get one in very clean condition at least the interior. It only has 120000 miles and I hope to run it to 300000 and keep it for at least 3-5 years. I hate making car payments and I really think the older Toyota's were the best. Simple to work on, well made just a great car. If I could afford a new car I would buy a new Corolla just so I could know how it was treated from day one!!

Thanks again Fish for the help!!

Abhaya

#8 fishexpo101

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Posted 16 November 2011 - 01:06 PM

You should be able to see the vacuum modulator by the firewall - the EGR valve is right below that. Both on the intake manifold side, with a little metal tube running to the exhaust manifold for the exhaust recirculation. The valve is on the bottom, the vacuum modulator, should should see sticking above. Usually it is the metal tube between them and the valve itself that get choked with carbon deposits. See if this pic is better or not:


Posted Image


As for anything you can do to "extend" the lifespan of the timing belt / water pump / belt tensioner / etc. - with driving habits, speed, start/stop cycles, etc? In short, nothing will help - if the part is worn, it will fail - just a matter of time. The mechanic saying that parts are made in Japan? Possible, if it is the OEM Denso kit - but in most cases, he'll just pick up the cheapest kit he can get his hands on. Unless the mechanic shows you the exact kit he plans on using and watch him install it - I wouldn't believe a word he says. Most house brands (Duralast, Wearever, etc.) are made by major manufacturers - but I wouldn't bank on them being the same quality. I'd get the Dayco belt or better - don't go with house brands. Waterpump and tensioner - those critical items, I'd only go OEM. For timing belt maintenance, generally best to go with OEM. You'll pay more - but given what the system has to do, it needs to fit perfectly and work just right. As for Mega-mileage cars with no regular maintenance - I probably only know 1 or 2 that are that way. Those are exceptional cases, not the norm - I've seen people push 100K miles on a timing belt, but they are really rolling the dice there. Sometimes it is not the belt that is the problem, could be a bad bearing on the tensioner or failing waterpump that takes out the timing belt.

Edited by fishexpo101, 16 November 2011 - 01:07 PM.

#9 abhaya

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Posted 16 November 2011 - 07:52 PM

Hey Fish,

Posted Image


Looking at the picture above I can't see where in relation to the throttle body or intake is the egr? I followed the tube/line from the O2 sensor from the exhaust manifold and it goes to a black cylinder the cylinder is then hooked up from the top to the throttle body and there is another tube from the top of the throttle body which attaches to a few other tubes. I looked between the firewall and the whole intake and near the cylinder and I do not see the egr? I have looked at all the emissions connections I can see and there is thing that looks like pic 3 that is attached to where the fuel injectors are but I can't find the egr anywhere. Ihad a mechanic friend and he can't find it either. I took out the air filter box and hose attached to the throttle body and I looked all around and no EGR?? Could there have been a problem with it and in order to save money they just disconnected it? Can a car run without the egr? IF so what damage will it cause? I really have no money right now. Since I cleaned the throttle it runs better but I can tell there is still a vacuum leak somewhere and I have checked all the hoses and connections. I would like to replace all the hoses and go to a junkyard and find a egr off another corolla clean it and install it. I simply can't afford $159 for a new one. If I could find a used egr that was good could I install it and could you give me directions. Also could you give me a better diagram or picture of where the egr is. In the Haynes manual it is right above and along the right side of the throttle body if you are looking in. It is certainly no where to be seen. It could be somehwere else but it would have to be pretty hidden. Could a mechanic trying to make a car pass smog just disconnect it? I called the guy who sold me the car and he acted like he did not know anything. He did say he could get his mechanic to install and get the part cheaper than I could find just the part. He said he would call back nothing so far.

I took back the autozone parts and am going to buy the toyota dealer oem parts instead. The tensioner is way more expensive and the belt and spring are not too bad. I will buy the parts and then save up to get the labor. Do not want to spend a bunch on labor and then the part fails or never runs right. It is just not that much more expensive to use Toyota parts.

Thanks again for all the help!!

A

#10 fishexpo101

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Posted 17 November 2011 - 10:50 AM

The EGR vacuum modulator should be behind and slightly to the left of the throttlebody itself. Sort of at the midpoint between the brake booster and the pulleys on the engine.

Here are a couple of pics that I pulled from the net - circled the vacuum modulator in red:

Posted Image

Posted Image

It is possible to defeat the system by using an EGR blocking plate - some people use this to avoid dealing with a troublesome emissions issue or for a tracked cars, to boost performance. Depending on your state laws, selling a car with a known defeated system is illegal - though the "known" issue is a sticky one. I'd take a peek and see if there is a plate covering the EGR port (might have to look at it from the under the car) and/or cap plugs on the now unused vacuum connections on the intake manifold.

#11 abhaya

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Posted 17 November 2011 - 12:58 PM

Yes, just as the Haynes manual showed. The pics show what I do not have. I will take some photos of my engine but there is certainly NO EGR where it is supposed to be. So since I now know for sure there is no EGR what do I do? Could it be causing the problems I am having? There is a vacuum leak somewhere I can tell the car just does not have the power it should. It is much better than when I bought it but it drops out and still shakes at idle like it is reving up and down. I only see one port where there is a tube connected to it at the top of the throttle body. I do not see any other open or covered ports. I will take a look more closely now. I will not get a chance to take a photo until this weekend. It just amazes me how people will cheat you these days. I paid this guy a good price for this car and now I have a vacuum leak and no egr! I also have no idea the state of the engine. I just did not have a lot of choices at the price I had for a car. I learned a lesson but still now have to deal with the cards I was dealt. I have to figure out how to fix the car as in-expensively as possible.

I think I am going to have to shelf the timing belt and figure out what is goig on and take this to a mechanic. Hopefully I have a few months left on my belt and this will not be a huge expensive issue!! The problem is I shelled out all the money I had saved on this used car and like an idiot I trusted the guy who sold it to me. I just spoke with him and he is not going to do anything other than give me the mechanic he uses on his cars and I will get a good price. I do not trust him and how can I trust his mechanic.

The crazy thing is I had a mechanic look at the car and he said it looked good. He checked the spark plugs and took them all out and inspected them. Looked the engine over but he missed the egr and did not say anything about timing belt. When I talked to the guy that sold me the car I asked if he had the timing belt changed and he said no but it had to have been changed once before. He said they go for 80,000 miles so I should have until 160,000 miles before I have problems assuming the last person got the belts changed at 80000 miles which he does not know for sure.

I have a feeling I should still do the timing belt change first and then worry about the missing egr. The joys of used cars!!

Thanks again for all the help Fish I really appreciate it!!

You helped me out a lot!

Abhaya

#12 fishexpo101

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Posted 17 November 2011 - 01:11 PM

Yup, if it the engine has its EGR disabled, could be a very good source of much of your troubles.

Disabling the EGR can cause higher than expected cylinder pressures and temperatures - which could lead to detonation/pinging. I know people that have disabled this run premium fuel to help limit detonation issues. Running regular fuel, you run a good chance of burning a valve - which can lead to power loss / poor engine running. Disabling the EGR can be as simple and blocking the vacuum ports with plug caps and replacing the EGR with a blocking plate. Some 1994 cars have an electrical signal wire that keeps track of the valve position - but generally only on Cali-spec emission cars.

Sounds like someone ran into an EGR issue and instead of diagnosing the problem, just disconnected it. You "mystery" vacuum leak is liking coming from a missing or damaged vacuum plug cap.

#13 abhaya

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Posted 17 November 2011 - 03:22 PM

Wow!! I just bought a bottle of octane boost and added what I could of 91 octane gas and the car almost runs completely normal. What a huge difference. I always use 87 octane because I have heard that you are just paying for nothing unless you have a high performance car designed for it. I am going to get an EGR installed pronto. Glad you helped me figure out exactly what the problem was. I did clean the carbon out of the throttle body and that helped too. Once I get this done then onto the timing belt with genuine Toyota parts!!

It is really great to have this forum. I really appreciate the time of people like Fish who give such extremely useful and valuable advice. Without your help who knows what I would have been told by a less than trustworthy mechanic. I can't believe the guy that sold me this car was so cheap. I know the part is expensive but you would think the least he could do is go to a junk yard and get a used part and clean it and install it. Just shows you really can't trust anyone who is trying to make money off of you.

At least now I have a good starting point. I figure I will spend about $1000-$1500 to get this car running the way I want it too. I will first do the egr fix, then the timing belt and then the water pump. From there I will check the breaks and replace as needed. Then I will get new tires. Then I will be pretty happy. OH I forgot to ask are there seals on the engine like valve gasket etc. I should replace. There is only a small engine oil leak at the top of the engine where there is a bolt near the oil cap and it has a rubber gasket around the bolt which is leaking a small amount of oil. It gets burned off as I drive but I want the whole engine running good. As I said I plan to keep this car for a while. I really like it a lot and after getting it running good without an egr it has some good pep. I put ina K&N air filter, NGK platinum plugs and new wire set. I need to get a new distributer cap and rotor and a good set of wires. I have a mobil one oil filter and I change the oil every 3000 with a premium regular oil. I have used synthetic but for the extra cost I feel it is better to do more oil changes with a good oil filter specially with an old engine. The synthetic will leak more often because it is thinner. However I do want the best performance and protection I can get so would it be better to go 6000 miles with a synthetic or just keep what I am doing. I am very interested in the top down oil change machines that actually pull the oil out of your car and store it in a container you can use to bring to your local pep boys or wherever you recycle oil at. That way there is really no mess and no need to change the oil plug unless it leaks? Any thoughts?


Again thanks to everyone specially Fish for your wealth of information. I am sure you saved me a lot of time and money in wrong diagnosis!!

Abhaya

#14 fishexpo101

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Posted 18 November 2011 - 10:05 AM

I'm glad that you finding this info helpful - just repaying the valuable help this forum gave me several years ago when I first came aboard. Always nice to hear what others experienced - more information for you to bring to a mechanic or see if a mechanic is trying to scam you.

I'd double check that the bolts on the valvecover's perimeter are torque down correctly. A loose bolt could leak a small amount of oil leak by that gasket. Given the history of the car, probably won't hurt to replace the valvecover gasket in the future - the gasket is likely hard and brittle from exposure and age. It will also give you chance to look at the top of the engine (valvetrain) - see if it is clean or really dirty and even check valve clearances if you feel overly ambitious.

A leak like this is more of an annoyance than anything else - but if you are willing to put in the time and effort, when worth the time to replace it. Will make future diagnostic work much easier, if you don't have dirt and oil caked engine to work with. Sounds like you have good plan already, coupled with good maintenance - these 7th gen Corollas have a reputation to last a very long time.

For a shorter drain interval of 3000 or 5000 miles, conventional motor oil works just great. Synthetics don't shrink seals like they used to - but their enhanced solvency can dissolve deposits that could lead to a leaky engine. Conventional motor oil formulations now are nearly as good as early synthetics - so protection and performance advantages between them is shrinking. If you want to try synthetic, try the high mileage variants of motor oils. Many are synthetic-blends - mixing the solvency power of synthetics and adding a health dose of additives to help keep the engine clean. But that can be saved for later.

Right now - a couple of short oil change intervals with regular motor oil will work perfectly. Once you get the to a point where it is running like you want it - I'd highly recommend sending in a sample of the used motor oil for testing. Blackstone Laboratory (http://www.blackstone-labs.com/) is one that I use - costs about $25 for a standard test. Done once a year - you can track the wear of the engine and catch any issues (like coolant leaks) before they turn catastrophic. A oil forum, like BITOG (Bob Is The Oil Guy) - www.bobistheoilguy.com/ - can shed more information on UOAs (Used Oil Analysis), if you are interested.

If you want to run extended oil changes - then UOA is almost a requirement. Not all engines are run an extended oil change interval, and many others can run quite a bit longer than their owners expect. One car could go 20K-25K between oil changes, where another could only run 3000 on the exact same oil. Only a UOA will give you a definitive answer. A "good" top down machine is geared more for lube shops - that need to minimize time needed to drain the oil out of the car. More cars they can do in a day means more money - but these machines tend to run in the thousands of dollars. The stuff they sell to consumers are pretty flimsy at best - lot of them leak after a few uses. Some use a manual fluid pump, which tend to be more robust, but pretty time consuming to use. Plus you don't get the benefit of "flushing out" the metal shavings and heavier debris from pan drain. Some cars, an oil extractor is the only way to get most of the oil out (like Mercedes and a few other European imports). For the 7th gen - I'd stick to the old school method.