2003 Corolla Running Rough and Misfiring - Really need your help, Madison WI

[dspiffy]

I have a 2003 Corolla I bought a year ago with 100k on it. I added about 40k to it, and have been consistent with my oil changes and tune ups.

Now it is running extremely rough and does not appear to be safe to drive. I need to get it fixed ASAP as it is how I get to work, but I am broke at the moment and cant afford to throw money at solutions that may or may not fix it. I'm hoping if I post the symptoms, someone recognize them and guide me in the right direction. I can do VERY BASIC stuff myself, I have a couple very competent mechanic friends who will help me with whatever work needs to be done, however the only diagnostic equipment we have at our disposal is whatever they let you use free at OReilly's/AutoZone/etc.

In order of occurrence, over the course of the last month or two. The symptoms that severely affect driveability just started this week:

1. Check engine light came on, initially no change in driveability. At first the only code that popped was P0171 "system too lean bank one".

2. If you floor the gas pedal, after you hit 60mph the engine will stop revving like it's not getting any gas. If you ease off the pedal and back on, it will rev all the way

3. Occasionally will start hard, where you have to keep cranking it.

4. Occasionally when it starts hard, it would run real rough for the first few yards, then drive normally

4a. At this point is when misfire codes started popping up (P0300, P302, etc)

5. Occasionally after starting, for the first few yards, it wont drive faster than idle speed, then will drive normally but ROUGH

6. Occasionally when you idle at a stop sign, it will do the same thing as #5. This one is EXTREMELY rare

7. Now it is consistently running rough and throwing the misfire codes.


So far I have:

A. Changed the spark plugs. I did notice there was greater than normal amount of oil on the threads of the plugs so I also

B. Tightened the valve cover

C. Cleaned the MAF and throttle body. After doing this, I got a LOT more power, and it took a WHILE for the P0171 to come back, but it is still running rough and misfiring.


So far mechanics have suggested I

I. Replace the O2 sensor

II. Replace the coil packs

III. Replace the valve cover gasket

IV. Replace the fuel filter.


But right now I cant afford to do anything that's not actually going to solve my problem.

I am in Madison, WI if anyone is local to me. If you can help, I'm not cheap, just poor-- I'll take care of you to the best of my abilities!

Thanks, guys

[TrdSpeed140]

no need to replace O2 sensor or coilpacks, your problem probably lies in a vacuum leak. most likely culprits are the Intake manifold gasket (common problem, gaskets were updated because of this problem), vacuum hose(s), or Throttle Body gasket. you might be able to have an Oreilly/autozone/advace auto, etc. lend you a vacuum gauge to check your vacuum readings either for free or for rental. that's what I'd do first. someone who suggest that you start replacing parts as a method of diagnosis is probably not a good or trustworthy technician.

[dspiffy]

I called the dealership and they said this gasket issue did not apply to my VIN, or at least their was no note made of it . . . was it a specific service bulletin?

[mikered30]

Did it get cold in Madison when the rough idle occurred? I agree with Trd that it is likely a bad intake manifold gasket, there is a revised gasket from Toyota to fix this known issued. They even issued a TSB on it. Spray carb cleaner around the intake manifold gasket and listen for an change in the idle.

[mikered30]

Yes, there is a specific bulletin that applies to your car, see this thread: 2004 Corolla P0171 code (system to lean)

Since it is a TSB and not a recall and you are way out of warranty, the work and labor are on you. Try spraying carb cleaner around the gasket before you dive into changing the gasket to confirm a leak.

[dspiffy]

Actually, the very day it started hard and then ran rough (for the first time) was the first day it dropped below 50 degrees. Not sub-freezing, however.

[invader]

If you're still on original intake manifold gasket, it most likely is leaking (vacuum leak) and the main cause of your problems. New revised Totota gasket is orange instead of black, and is only about $10. Oily dark residue by the gasket will be visible where the intake manifold sits on engine head if it is leaking. It's easy enough to replace.

Originally Posted by invader

1st pic shows elusive brake booster vacuum hose on intake manifold, which is hidden once throttle body is installed... Intake manifold gasket was easily replaced on friend's 2005 without draining any coolant or disconnecting throttle body coolant lines, by setting (+cleaning) throttle body aside.

[dspiffy]

I take it I need to order the gasket from Toyota, not from AutoZone or wherever?

Looks like something beyond my experience, but one of my mechanic friends should be able to help. Provided I can convince them to put aside their own opinions of what's wrong to try it.

Any tips on driving the car in the meantime? I mean, besides "dont do it?"

[invader]

Yeah, get Toyota's revised gasket. You can still drive it if it's still driveable, but have it done ASAP.

[dspiffy]

It barely drives. I'm worried about messing up the timing or something with it misfiring so much. But I still have to get to work, and I have to give back the car I borrowed on Sunday.

[invader]

What can I say?... Get the gasket tomorrow and have it replaced over the weekend.

[dspiffy]

I'll see if the parts dept is open tomorrow.

Any other ideas, comments, etc are appreciated.

Thanks everyone that has helped so far.

[invader]

Most Toyota dealeaships in Madison WI are open for parts on Saturdays. At least one of them has your gasket in stock. Start calling them to check first thing tomorrow morning.

[mikered30]

Try the carb cleaner trick and look for any loose obvious vac lines. If it is really that harsh at driving it maybe something else besides the intake gasket. The leaky gasket issue is fairly common in cold climates but i don't remember it causing driveability issues that bad as you describe.

[invader]

Make sure your coils' wires ground bolt is good and tight on the valve cover, and possibly down the side of engine. Were your spark plugs and coils properly reinstalled?