Engine Light - Corolland: the Toyota Corolla Forums

I have a 2000 Corolla. When my engine light went on I went to the local Autozone to have it checked out. The dealership wanted $80.00 just to hook my car up to the computer. Autozone does it for free. Anyway, the computer says a couple of cylinders are misfiring. I replaced all 4 spark plugs. Erased the code, and now the engine light is back. I'm not sure what it could be. The spark plugs are new. 2000 and later models don't have spark plug wires. I'm clueless.

and so are the guys at autozone

whats the code now? it may not be the same code. either way, they sold you stuff so they did their job well.

was that the ONLY code set? the way that OBD2 testing works is it goes down a check list, at certain problems it STOPS and sets a light, and DOES NOT continue testing.
case in point, a camry had a code for cam position sensor, replace distributor, clear code, code is gone, drives nice.
comes back 3 days later, check engine light is on again, now its insufficient EGR flow.
neat how that works huh?
jeep comes in for an engine light, small evap leak, fix that, goes home, 5 days later, is back, another evap code, ldp (leak detection pump) circuit problem or mechanical fault, replace the ldp, problem is gone.
a misfire code stops the checklist pretty early on, if thats been the sole code for the past however long, your light may come back on for other problems.

from another board on misfires and multiple codes ,but a good primer on diagnosis.

Originally Posted by chubbygoatboy

99 Corolla -- To make a long story short as possible, the car had 5 stored codes. Two Cyl. 1 misfires, Two cylinder 4 misfires, and one random, multiple misfires. I then cleared the codes.

I replaced spark plugs, and wires. Drove it, and immediately it was still missing. Codes now read cyl 1 and cyl 4 misfires, one each.

So, now it looks like maybe coil pack, since both 1 & 4 are on the same pack. So, I bought new coil pack and replaced it. Still runs like crap, and now I get only cyl 4 misfire. So I swapped plugs and wires around just in case one of the new ones was bad, still cyl 4 misfire, P0304 code.

I checked compression, and got 210, 210, 190, 190, so I think that looks OK.

The #4 plug is damp, and clearly not burning. HELP, and Ideas are greatly appreciated!!

Now, I switched coils to rule out the new coil being bad. It still has the same misfire code. So it appears that the plugs, wires, and coils are OK. WHATS LEFT?? Could the fuel injector do this??? Any thoughts are appreciated!!

Well, I have answered my own questions. So I will post what I found in hopes that it might help someone else!! I swapped the #4 injector, with #3, and guess what, the misfire moved to #3 cyl. So a new injector is on order.

and another:

I found on line that the p300 coad is a random missfire in all cylinders and that the last number in a p300 code is the cylinder that is misfiring. Your p302 & p303 would be #2&3 cylinders.

Answer

injectors are often the cause of misfire codes on this year and model.

Answer

The first thing to try would be new spark plugs plugs and plug wires. This fixes misfires the majority of the time. If that doesn't help check the rotor and fuel injectors.

Answer

Either a bad coil or bad fuel injectors. try switching coils with other cylinder and see if code changes. if yes, you got a bad coil, if not, you must change all 4 injectors, cause they will all go bad eventually. I've seen it. I was a Toyota technician.

your vehicle does not have plug wires ,but you probably have a bad injector. I would clear codes and buy a code checker.

http://www.harborfreight.com/cpi/ctaf/disp...temnumber=94168

i hope this helps.

Do you still have the original CEL codes from Autozone? There are specific "Toyota Only" engine codes that may be confused with generic OBD-II DTC codes. Very possible that Autozone read misfire when it really meant something completely else.

Also, did you notice anything unusual or different between any of the old plugs you pulled? Any look like they have a different color, heavy deposits, wet? How has the car been driving since the code popped up - does it idle or accelerate strangely? Did you notice any driveability issues - poor fuel economy, hesistation on acceleration, etc.?

Do you still have the original CEL codes from Autozone? There are specific "Toyota Only" engine codes that may be confused with generic OBD-II DTC codes. Very possible that Autozone read misfire when it really meant something completely else.
Also, did you notice anything unusual or different between any of the old plugs you pulled? Any look like they have a different color, heavy deposits, wet? How has the car been driving since the code popped up - does it idle or accelerate strangely? Did you notice any driveability issues - poor fuel economy, hesistation on acceleration, etc.?

The tips on spark plugs I pulled out looked really bad. Three of them were white and corroded. The other one was black. I've noticed that with the new plugs the car seems to drive smoother. Though it still seams to idle roughly. Especially after I just start it up. It continues until I press the gas. Then it seems to be fine. If I come to a light or stop sign and sit for a while, its starts to idle roughly again.

Fluffy white deposits on the tips? Does the car burn any oil between oil changes? Sounds like either deposits from gasoline or the "ash" left over from oil consumption. A little bit is OK, if it actually starts to bridge the gap between the electrodes - then you have a bigger problem.

Couple of other common occurances to look for (last point is especially common on the VVTi version of the 1ZZ-FE engine (2000+ Corollas)):

- clogged PCV valve could cause hesitation and poor idle (also a common cause for slight oil consumption - clean or replace valve, oil consumption goes away)

- gummed up throttle body can also cause poor idle and driveability (pretty good idea to clean this on a regular basis - varies according to driving conditions)

- dirty MAF/IAT sensor (plugs into airbox), generally not something that is cleaned on a regular basis, but many have reported extremely good results (better idle, no more hesitation, better drivability, engine throttle response, etc.) when it is cleaned carefully.

All of the above are talked about in detail on this site. I would try cleaning the above first - you have already got the plugs done. Next would be to verify fuel. Clogged / damaged injectors might be an issue, as DT mentioned above. Want to make sure it isn't a simple (ie. cheap fix) issue first - then start diagnosing the more expensive bits.

start with this:

http://www.autobahnpower.com/main.asp?cate...and+BG+Products