Misfire when hot, replaced everything I could think of... Options

[cv7713]

The aftermarket seals were $24 for all four but they did not work. I do not know the Toyota part # or the price. Maybe someone here can help with that. I have an appointment today to have my injectors remanufactured by a guy in Sunrise. He charges $25 per injector and said it takes about an hour. He also replaces the seals with new OEM-type ones. I should have them installed by the weekend. I'll let you know....

Installation is pretty easy. I can do it in about 20 minutes but I have done this many times. If you want to do it yourself I can probably make a how-to when I do mine.

[cv7713]

didn't work...

completely out of ideas... going to sell the celica

This post has been edited by cv7713: Nov 8, 2007 - 9:25 PM

[supradog1]

didn't work...

completely out of ideas... going to sell the celica

you have to be kiding me!!!! wtf is the deal with this misfire!!!! did you ever replace the igniter box on the drivers side fire wall??? im thinking that might be the sourse... or it could be the cat!!! cause remeber (it onlly happens when the car is hot...)

This post has been edited by supradog1: Nov 9, 2007 - 12:39 AM

[lagos]

didn't work...

completely out of ideas... going to sell the celica

calm down!
its only simple problem that can be fixed. have you checked the exhaust manifold and gasket? how about the rest of your exhaust? any rust or holes in it?

if you think its a vac leak, you can do a "boost leak test" (google it). it will help you track down any vac leaks that might be giving you problems.

have you checked the ecu for codes? the cel light might not be on, but you might have a code stored. so make sure you check them.

This post has been edited by lagos: Nov 9, 2007 - 1:01 AM

[cv7713]

you have to be kiding me!!!! wtf is the deal with this misfire!!!! did you ever replace the igniter box on the drivers side fire wall??? im thinking that might be the sourse... or it could be the cat!!! cause remeber (it onlly happens when the car is hot...)

yes, igniter was changed

calm down!
its only simple problem that can be fixed. have you checked the exhaust manifold and gasket? how about the rest of your exhaust? any rust or holes in it?

if you think its a vac leak, you can do a "boost leak test" (google it). it will help you track down any vac leaks that might be giving you problems.

have you checked the ecu for codes? the cel light might not be on, but you might have a code stored. so make sure you check them.

exhaust appears to be in great shape, no rust, holes, etc. i cannot hear or feel any leaks around the gaskets. i need to get some wrap for my headers then I will be installing them. i have not taken the manifold off to look down the cat though... but if it was plugged, wouldn't a vacuum test reveal that?

a vacuum test was done and checked ok. I think it was 21-22psi... i don't think it is a vacuum leak because it still stutters at WOT

no codes (on or stored). I even drove around in test mode and no codes were triggered.

[cv7713]

OK, let's think about this... the car misfires when hot. This means the car is in "Closed Loop", correct? In closed loop, the car is taking the signal from the O2 sensor and adjusting the A/F ratio.

I replaced the O2 sensor a while ago but just recently noticed the that the white wire coming from the ECU is brown (burnt) in one spot. Is there some CRAZY possibilty that the resistance is too much in this section of wiring and sending an incorrect voltage to the ECU?

just shooting in the dark here!! (before I drive the celica off the highway and call Geico!)



This post has been edited by cv7713: Nov 9, 2007 - 10:56 AM

[Rayme]

Are the spark plug gapped to spec? I see nobody mentionned it.
You chagned teh whole distributor, so I assume the rotor and cap are installed correctly. too right?



If you want to trouble shoot the o2 sensor, just disconnect it and see if you still have the problem, a car runing rich should not "misfired".


One thing I can think of also is the coolant temp sensor, this can really richen up the mixture and actually make it run like crap, I had a 5th gen with a bad coolant sensor and it was randomly going bad. To check this, disconnect it while the engine is warm, the ecu will assume the car is warmed up and adjust the ratio accordingly while ignoring the sensor input. Drive around and check for the symptoms.
but it looks like you have a hardcore problem there

This post has been edited by Rayme: Nov 9, 2007 - 11:29 AM

[cv7713]

Yes on the plugs (.44 if I recall correctly). The distributor was complete with rotor cap and coil. I will try and disconnect the O2 sensor to see if that helps... thanks

but it looks like you have a hardcore problem there

yes, its killing me!! love the celi, but dam!!!!

[Enrique]

This was happing to me the last couple of days....So I went outside this morning and cleaned the distributor and put new plugs, new O2 sensor and the bolts from the down pipe to the turbo where loose, so I tightened them.........After that no more misfire, but now my belts are making noise….oh, and there was a loose wire under my fuse box that I connected better (now that I think about it, that might of been it).

[lagos]

a vacuum test was done and checked ok. I think it was 21-22psi... i don't think it is a vacuum leak because it still stutters at WOT

im not talking about checking your vac with a gauge. im talking about filling your throttle body with an air compressor, then you listen for anything that is hissing, and spray soapy water on it to track down the source. yes, a vac leak could cause issues at WOT.

the other thing that it could be, is an exhaust leak. one way to test this, is to give your car the sea foam treatment. if you get any smoke in the engine bay, then youll know you have an exhaust leak.

[cv7713]

OK, no vac leak or exhaust leak. Got the headers installed this weekend (sweet!).

Could a failing throttle position sensor cause a misfire (even at idle)?

[cv7713]

what about a bad ground? it's definately heat related. i was cruising on the highway without a single hesitation/misfire. as soon as I got off the highway and sat in traffic it started again...

[supra12big]

omg i have the same prob, when my car is not hot its fine, but when its at normal operating temp is starts doing it a bit, what does urs idle at, mines at 850 then misses every 10secs drops to 700 then back up to 850, i have a 3sgte setup , and I have a couple ideas of what it could be, check idle control valve, clean maf meter, check timing, and go from there

oh ya and its something also to do with electrical issues, when i turn my lights on the idle increases and it kinda stops, as i watch my air fuel ration meter, when it does it its at rich then drops to lean and doing it constantly, i gonna check out my maf meter

[lagos]

OK, no vac leak or exhaust leak.

how did you come to that conclusion ?

[roelamizzle]

Have you tried getting a shop to run a diagnostic test on it? I'm not sure if it would tell you anything but it couldnt hurt and the mechanic may have some suggestions as well.

[GriffGirl]

I had this problem only when my car was cold; try replacing the cap & rotor, it really could be that. I know it sounds too simple, but after toiling over this for 2 months I finally gave in and did it and it's like night and day, 90% better. Next week I will replace my spark plug wires (plugs were done last week).

[supradog1]

i know what the problem is!!! low compression... it only happens when the engin is hot because the metal expanding from the heat causes the the compression to drop!!!! in other words " i need a new engin ":(

[Guillermo]

I have a ST202 with 3S-FE engine and I had the same problem.
Solved after changed the fuel pressure regulator:
http://www.toyodiy.com/parts/p_J_1997_TOYO...BLMGK_2211.html
The original code is 23280‑74151, but I can´t find that, then we use the 23280‑74100 and it works.
Besides that changed the spark plugs: Denso K20PR-U11
This is a late response, but I hope helps someone anyway

[RocketScott]

Have you changed your thermostat and/or water pump? Maybe the engine is just overheating and then knocking.

[stephen_lee]

old thread, but a weak coil will cause this