Do you have any photos/illustrations that can guide me? Where is the cylinder head? I know the throttle body is after the air filter box. Any wiring connections I should be aware of? I really have looked over for 15 minutes now. . .
Do you have any photos/illustrations that can guide me? Where is the cylinder head? I know the throttle body is after the air filter box. Any wiring connections I should be aware of? I really have looked over for 15 minutes now. . .
Intake manifold gasket sits on cylinder head. It tends to leak on 9th gen Corolla, which is replaced with revised orange silicone gasket # 17171-22060... Vacuum leak can be there, in intake manifold, between manifold and thrrottle body, on throttle body (downstream of throttle valve where vacuum exists), or any channel (vacuum and PCV hoses) between throttle valve and cylinder head.
The 8th gen have a metal tubular intake - so it doesn't have the warping issue that some of the composite intakes on the 9th gen have. But the hoses connecting to the throttle body, brake booster hose, EVAP, etc. are all fair game.
So, the intake manifold connects to big rubber hose that exits the air filter box? I took the VVT-I cover off and, with engine idling (at 1,200 RPM after a few minutes on a 73-degree day), checked around in the vicinity of vacuum hoses, including the PCV area and EVAP hoses. Didn't hear any hissing sounds. I rocked the air filter box as the intake to the box (as fish may recall) doesn't sit flush. So, I forced it flush, but fish is correct it would have no bearing on idle quality.
Here are some photos, really explaining nothing except for the one with hose disconnected. In regard to cleaning the throttle body, can I spray carb cleaner into this hole? And, where is the brake booster hose?
I want to replace the hose that connects to the PCV just because I found a nicer one at the yard, but it looks like the best way to get to it is removing that coolant hose. I ordered Toyota red on eBay for $31 w/shipping and it should arrive later this week. I thought I would just take that hose off when doing the coolant change.
Does it have to be a hose that's causing this problem?
https://s1279.photobucket.com/user/Scenic720/media/003_zps3516cf5d.jpg.html]https://i1279.photobucket.com/albums/y525/Scenic720/003_zps35
Intake manifold connects to throttle body, with a gasket in between... Your intake manifold gasket between intake manifold and cylinder head (engine) could well be where you have a vacuum leak, if any. Don't expect to be able to hear a vacuum leak induced hissing sound with the engine running over normal intake rushing air noise.
By the way, I just have to ask... Why do you call yourself 'autotech...' ?
Sounds like it would be difficult to get replace the intake manifold gasket, correct?
Just for the fun of it
Intake manifold gasket is inexpensive. It is very easy and fun to replace, but I can only speak for myself.
I recommend a FEL-PRO gasket.
http://www.rockauto.com/catalog/moreinfo.php?pk=446629&cc=1432912
http://www.rockauto.com/catalog/x,carcode,1432912,parttype,5424
Fun is good. Easy is good. Have other Corolla owners experienced this gasket as failing/leaking requiring its replacement? Common cause of higher idle?
How long did it take you? Did it solve the problem if you had it? I did help replace intake gasket in a '98 Metro three-cylinder, but I "helped" (supervised) and it was three years ago.
Intake manifold gasket vacuum leak is a common problem with 9th gen Corolla's original black nitrile gasket with its composite manifold, but a vacuum leak there results in the same idle hunting problems and lean code P0171. The revised 9th gen orange silicone gasket completely cures the problem.
Vacuum leak could also be at fuel injectors' O-rings or throttle body gasket... There are endless 8th gen Corolla discussions on looking for the cause of very common lean condition which does raise idle rpm, and P0171 lean code. MAF sensor is often blamed, but the real cause never seems to be found... I wonder if there's a hidden vacuum leak within the intake manifold itself. Maybe the intake manifold plenums welds are cracking, or a pressed section's seam lost its proper seal over numerous heat cycles? Perhaps a 9th gen composite manifold could fix it.
http://www.toyotanation.com/forum/131-8th-generation-1998-2002/420555-p0171-help-bank-one-lean.html
9th gen intake manifold (includes both gaskets): http://www.rockauto.com/catalog/x,carcode,1432915,parttype,5536
By the way, VICTOR REINZ # MS19590 is exactly the same as Toyota's revised # 17171-22060:
http://www.rockauto.com/catalog/x,carcode,1432915,parttype,5424
All right, please afford me at least two days to digest this and do some further exploration under the hood. Just know I do follow through with what you and Fish recommend to me. I appreciate it.
Failing injectors were also known to cause issues with the 8th gen Corollas. I haven't really heard of an intake manifold failing on an 8th gen - though it is entirely possible. Be easy enough to check and mark that off your list.
I know that a number of people have modified the 8th gen with a composite intake from the 9th gen. They fit without issue and give you a little bump in the higher RPM range (shorter intake runners, less thermal conductivity). You'll lose some in the low end, but most would gladly trade that for more juice in the high end. Not sure what it will do to your overall MPG. Might be something to think about down the road as a future project.
When I swapped in the composite intake from a Celica some years ago - there was no apparent change, but the throttle response was improved. Might be due to having a slushbox transaxle sucking too much of the power. Unfortunately, that intake is long gone, as I entertained the idea of running boost. Might try again - the issue now is free time to play around with the car.
A dirty and/or sticking idle air control valve on throttle body can also cause high idle.
Does you check engine light go on for lean code P0171 at all? Have you ever replaced your exhaust manifold's 'donut' flange gasket?
Where is the idle air control valve, still can't find it. Can you provide a photo?
CEL does not light up for a P0171. I have two codes (EVAPs) currently: :P0441 and P0446.
The exhaust manifold's donut gasket? I have no idea if it has ever been replaced. I got the car at 214,000 and there are records for oil changes and tires, but that's it. I wish I knew the previous owner. The exhaust system is solid condition right now and has no leaks. Very quiet.
Failing injectors were also known to cause issues with the 8th gen Corollas. I haven't really heard of an intake manifold failing on an 8th gen - though it is entirely possible. Be easy enough to check and mark that off your list.
I know that a number of people have modified the 8th gen with a composite intake from the 9th gen. They fit without issue and give you a little bump in the higher RPM range (shorter intake runners, less thermal conductivity). You'll lose some in the low end, but most would gladly trade that for more juice in the high end. Not sure what it will do to your overall MPG. Might be something to think about down the road as a future project.
When I swapped in the composite intake from a Celica some years ago - there was no apparent change, but the throttle response was improved. Might be due to having a slushbox transaxle sucking too much of the power. Unfortunately, that intake is long gone, as I entertained the idea of running boost. Might try again - the issue now is free time to play around with the car.
How would I know if I have a failing injector?
Last night the ambient temperature when I left was 52 degrees. I idled at 1,500 RPM in the driveway for a minute, then around the block when I got to that stoplight again (waited two minutes again), I was in neutral and it gradually went down to 1200 RPM just before I accelerated.
Try unplugging the injectors one at a time while idling the engine. The injectors that cause the least amount of idle instability are likely the suspect "dying" injectors.
I haven't gotten around to this issue yet. Been distracted with a few things, thus, I haven't been posting as much on the Forum. . .
Car goes in Monday morning for the clutch replacement. My mechanic is having NAPA resurface the flywheel, but sometimes turnaround time on that can be up to three days, depending on NAPA's workload. I told him there's no rush.
Back to finding the vacuum leak or whatever is causing the high idle. Fish, did you say to ignore the manifold area? I was thinking about replacing the gasket. Below are three photos of bolts to be removed to do this. Do I have to remove the fuel rail too? Does the manifold just back off a little, just enough so I can put a new gasket on? Etc...
Bad intake gasket usually is confined to the 9th gen Corollas (composite intake manifold), but if you already have a gasket or can source one pretty inexpensively - doesn't hurt to replace the one you have. Might help out in your case, as you've looked pretty much everywhere else. Just keep the original, just in case the new gasket makes it worse. As for the bolts, those should be it - might have to loosen some other ancillary stuff to get clearance to pull the manifold. Might take some persuading with a mallet, as those through studs could be stuff with corrosion.
Haven't ordered a gasket yet. Stay tuned. . .
