2001 - Troubleshooting Possible Fuel Problem - Toyota Corolla, Chevy Prizm (1998-2008)

Guest catchthekiller

Hi there,

I'm trying to nail down the cause of some pretty serious performance problems I'm having with my 2001 Corolla.

The basic symptoms are:

1. When starting from a stop, there is a major hesitation (or dead spot) - push the accelerator and the engine bogs down completely, then after a second it will engage correctly and get moving.

2. There was a knocking/rattling/pinging sound when I would accellerate. Even if I was already going at a solid pace (40 or 50) when I would accelerate I would hear this rattling sound. This "seems" to have been partially cured by cleaning the MAF sensor, but I'm not positive yet, because I only cleaned that the other day.

3. When I floor the gas pedal, the car shifts down into passing gear, but then nothing happens - there is no acceleration. This happens regardless of the speed I'm driving, or even if I'm starting from a stop. If I floor it, I can hear the trans shift into passing gear, but as far as acceleration goes it acts as though I've put it in neutral. If I back off, it will accelerate gradually.

4. The check engine light was on, and I diagnosed it and it came back with the code P0171 - which is "Fuel injection system lean." Obviously there are any number of possible reasons for this. When I researched this issue, I saw some recommendations to clean the MAF sensor - I did that, but the code is still appearing and performance has not improved.

A few months back I had my car worked on, did a basic tune-up, with trans and radiator flush and also "cleaned out" my fuel injection system...which, I think consisted of the guy spraying a can of something into a hose somewhere near the fuel injection set up. A few day later I started experiencing these symptoms. At first it was just a small dead spot, and only occasionally-so I was hesitant to take it back to the shop. But, it is getting worse and worse all the time. For instance, this morning I experienced a fifth symptom where my car would just not accelerate past maybe 10 mph, acting surgey and sputtery all the while... finally after it warmed up a bit, it got going.

There seem to be a lot of possibilities: oxygen sensor, vacuum leak, clogged fuel filter, dirty injectors (though I have run two tanks of gas with Lucas cleaner through the car already).

I've pretty much decided I have to take it in, since I've reached the end of my knowhow and my tools - but before I do so, I just wanted to see if anyone had anymore ideas for things I could check, clean, change myself before handing it over to the mechanics.

And, finally, if anyone can recommend a good mechanic in the Los Angeles area (pref. west l.a.) - I would greatly appreciate it.

Thanks in advance!

J-

friendly_jacek

Hi there,
I'm trying to nail down the cause of some pretty serious performance problems I'm having with my 2001 Corolla.
The basic symptoms are:
1. When starting from a stop, there is a major hesitation (or dead spot) - push the accelerator and the engine bogs down completely, then after a second it will engage correctly and get moving.
2. There was a knocking/rattling/pinging sound when I would accellerate. Even if I was already going at a solid pace (40 or 50) when I would accelerate I would hear this rattling sound. This "seems" to have been partially cured by cleaning the MAF sensor, but I'm not positive yet, because I only cleaned that the other day.
3. When I floor the gas pedal, the car shifts down into passing gear, but then nothing happens - there is no acceleration. This happens regardless of the speed I'm driving, or even if I'm starting from a stop. If I floor it, I can hear the trans shift into passing gear, but as far as acceleration goes it acts as though I've put it in neutral. If I back off, it will accelerate gradually.
4. The check engine light was on, and I diagnosed it and it came back with the code P0171 - which is "Fuel injection system lean." Obviously there are any number of possible reasons for this. When I researched this issue, I saw some recommendations to clean the MAF sensor - I did that, but the code is still appearing and performance has not improved.
A few months back I had my car worked on, did a basic tune-up, with trans and radiator flush and also "cleaned out" my fuel injection system...which, I think consisted of the guy spraying a can of something into a hose somewhere near the fuel injection set up. A few day later I started experiencing these symptoms. At first it was just a small dead spot, and only occasionally-so I was hesitant to take it back to the shop. But, it is getting worse and worse all the time. For instance, this morning I experienced a fifth symptom where my car would just not accelerate past maybe 10 mph, acting surgey and sputtery all the while... finally after it warmed up a bit, it got going.
There seem to be a lot of possibilities: oxygen sensor, vacuum leak, clogged fuel filter, dirty injectors (though I have run two tanks of gas with Lucas cleaner through the car already).
I've pretty much decided I have to take it in, since I've reached the end of my knowhow and my tools - but before I do so, I just wanted to see if anyone had anymore ideas for things I could check, clean, change myself before handing it over to the mechanics.
And, finally, if anyone can recommend a good mechanic in the Los Angeles area (pref. west l.a.) - I would greatly appreciate it.
Thanks in advance!
J-

You can do a little more yourself. Check fuel pressue, should be 44-50 PSI. Check for any vacum leaks visually, by sound or by propane. I bet the problem is between fuel delivery or air leak.

Edit: I reread you post and sounds more like the guy "cleaning" the injectors contaminated or otherwise damaged the injectors. Maybe you need to check injectors first, which is not exactly a simple thing.

Guest catchthekiller

Thanks for the info, I'll definitely investigate the pressure and the vacuum leaks. I was planning on just using the "soapy water" in a spray bottle technique for vaccum leaks. Can you explain more how I would use propane?

One more thing I wanted to mention - based on some information I found at another online source, I decided to test the Mass Air Flow sensor by simply unplugging it and seeing how the car runs.

Interestingly enough, disconnecting theMAF sensor did, eliminated the hesitation on start problem, and the lack of acceleration when I floored it. However, it did create a new problem of severes stumbling each time I accelerated to a point where the transmission would shift gears.

Unplugging the MAF sensor did also make two new MAF-specific codes show up, though... so, clearly the sensor is functioning somewhat...but this test made me wonder if it's just malfunctioning in some way.

It's a tough call, because I don't want to spend the $80-$100 for a new MAF when it doesn't really need to be replaced.

I found that cleaning the MAF in different solvents cause some weird issues. The best that worked for me is Throttle body cleaner and blowing it dry with an air compressor. Make sure you get the IAT sensor on the side of the MAF unit - that gets fouled pretty quickly.

I also have heard of the propane trick to find vacuum leaks around the intake - though I still go old school with water or carb cleaner. Works the same way except when you find a leak - the engine will rev up. Sometimes it is hard to tell otherwise. But both methods should work well.

I would check the PCV valve to make sure the hose is on tight - be the first thing I check. Even a small leak will make the car run very badly.

If you haven't already done so - pull the plugs and give them a look. Could be a bad injector causing you problems - even with the fuel treatment. Then take a look at the coil over plug packs for anything usual looking, cracks, burns, etc.

Another valve that most people over look is the brake booster check valve - that can go bad and cause vacuum issues.

Otherwise - you've pretty much eliminated everything else. Good luck.