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

[cv7713]

OK, been chasing a misfire for quite some time. The car runs great first thing in the AM but misfires once normal operating temp is reached. Misfires at idle and while driving. First, I have replaced all fuel and ignition components and all vacuum lines. I decarbonized the combustion chamber (MOPAR CC Cleaner, good stuff!). I have replaced the MAP sensor, O2 sensor, and some various wires that looked corroded. Stock 5s-fe.

The engine bay seems to be getting extremley hot! (but not overheating). Yesterday I pulled the plugs to see if they show any evident signs of wear and I was confused by what I saw. The firing end looked great (brown to grayish color), however the insulator on top of the plug was brown and blistered (burnt)?! Anyone ever see this? They are NGK plugs with the factory heat range. Also (not sure if this has to do with the misfire) but every now and then I hear a pop come from my gas tank. Is the "pop" just releasing pressure from the tank? Is it supposed to do that? Sorry so long, I am just truly stumped!!

List of parts replaced:
Fuel Pump, Filter, Pressure Reg, Charcoal Canister, EGR Valve, and injectors
Brand new distributor, wires, plugs, igniter, O2 sensor, MAP sensor, and even the ECU!

Could this be a bad cat causing the heat? Cracked head? Thanks for input...

This post has been edited by cv7713: Nov 9, 2007 - 11:21 AM

[cv7713]

any suggestions?

[Blakout16]

check your coolant thermister, see if its not opening (possible)
put higher-octane fuel in it.
any CEL's?
check your coolant - for any mixtures of oil.
also, the piston rings.... misfires tend to happen under higher temp due to piston rings going out the window.
mileage?
timing, some retarding could help.

[cv7713]

thanks for the reply. no CEL. tried 87, 89, and 93 octane with same issue. car has 150k. had the coolant system flushed today. looked fine just a little too much water. I will try the timing. it just may be time for a rebuild. I planned on changing the head and the head gasket, may just need to spend a little more time and do the rest... pistons, pumps, etc. anything else you could think of? also, getting VERY poor fuel economy (17-18mpg) thanks again

[Bitter]

could be a lean issue, sticking or dirty injectors. have it ran on an injector cleaner machine or send them out to a place like witch hunter performance for clean and balance.

[95CelicaST]

or buy new injectors.

[x_itchy_b_x]

you replaced everything that i would suspect to be causing the problem.
the only time i had horrible miss firing is when i had old plug wires. they would leak voltage to the head or any ground it could find but only under boost.

[cv7713]

ok, compression checks ok. 190 +/- on all cylinders. vacuum is ok, 21 psi. installed injectors from a vehicle with 60k miles, same problem. coolant temp sensor is functioning properly. .2-.3 volts when warm.

this is definately a heat related problem. misfire occurs more frequently during the day (south florida) with the hood closed. I just had the car idling with the hood open and the sun has long been down and it only misfired a hand full of times during the hour I was standing there.

is it possible that the dizzy and coil are getting so hot it is causing it to intermittently stop firing? the wrap around the wires next to the exhaust man (oil pres send, cool temp sens, etc) has melted!!!

could the exhaust be causing the excess heat (carbon buildup)?

would headers cool it down a bit?

This post has been edited by cv7713: Nov 9, 2007 - 11:34 AM

[95CelicaST]

headers would make the engine bay warmer... unless you heat wrapped them.

Could you post a picture of your engine bay? and the wire that is melted..

[supradog1]

THANK GOD!!! SOMEONE IS HAVING THE SAME PROBLEM!!!! I live in South FL also and i to have a low misfire when the car is hot!!! i realy sucks cause when im at a light with my foot on the brake the car will misfire and jump foward some times!!! it also misfires more offten i turn the system up in the car...
PLEASE HELP!!!!!!

This post has been edited by supradog1: Oct 21, 2007 - 11:45 AM

[lagos]

can you describe "missfire" in more detail?
when you replaced your plugwires, cap and rotor, what brand did you use?

[supradog1]

can you describe "missfire" in more detail?
when you replaced your plugwires, cap and rotor, what brand did you use?

OK... i start the car up first time that day and it drive about 10 to 20 min car runs perfect... after this time frame the car is at full working temp, any time you stop after this time frame the car misfires whille idleing and during the launch from the dead stop... after 2k rpm misfire is gone but power is is week and gas mileage is crappy... also if you turn the bass up on the system the car misfires eaven more than before while idling!!! i have done full tuneup on celi inclueding autozone timeing belt, cam and crank seals, water pump, cap & rotor, bosh 02, ngk plugs and wires, puroltor fule filter, 93 oct fule with lucas fule additive, cleand egr system and replaced pvc, reset ecu and no check engin light... after tune up car runs good for about 20 min then misfire returns!!! put new ngk plugs in 3 times and dose not fix the problem!!! i am lost on this one, but i have also been told it could be the igniter... but i dout that because its eletronic and woud just fail altogether... right???

[cv7713]

Misfires at idle, when accelerating, and when driving steady (cruise control). Pretty much any scenario but it only happens when the car has been at operation temp for awhile. Usually 30 minutes of driving.

The plug wires are from Toyota, the distibutor is Dorman (which i am not thrilled about), and the plugs are OEM spec NGK copper core V-Power. The ignition components are (or were) fine. I have tried 3 different dizzys and 2 different types of wires.

Been to the Toyota dealership 3 times who are worthless and also an individual mechanic. All unable to diagnose the problem.

Any suggestions are appreciated

This post has been edited by cv7713: Nov 9, 2007 - 11:35 AM

[supradog1]

i puled my distibutor cap off and every thing looks fine... what is the dizzys??? that black thing with 2 wires runing to it inside the distibutor??? i checked all conections and wires, everything is good... whats causing this misfire???!!!!

[cv7713]

dizzy is the distributor. the black thing inside the distributor is the coil. our problems sound identical! i replaced the igniter with one from a newer car in the local junk yard and still had the same problem. i am stumped

This post has been edited by cv7713: Oct 21, 2007 - 2:30 PM

[supradog1]

is the timing off??? if i ajust the timing a little would this help maybe???

[cv7713]

i've tried adjusting the timing. if you want, paint a mark on the distributor and the head where they meet, then loosen the two bolts that hold the distributor on enough so you can twist the distributor. start the car and twist the distributor slowly both ways to see if it helps you any. if not, line the original marks back up and tighten the distributor.

[lagos]

i've tried adjusting the timing. if you want, paint a mark on the distributor and the head where they meet, then loosen the two bolts that hold the distributor on enough so you can twist the distributor. start the car and twist the distributor slowly both ways to see if it helps you any. if not, line the original marks back up and tighten the distributor.

thats not how you set the timing. you have to use a timing light, and bridge the diagnostic box to set it at 10tdc.

if you guys can. try to make a video of your problem.

[cv7713]

that's what I did, bridged TE1 and E1 and set to 10 degrees. i was just suggesting to advance or retard the timing a bit and see if there is a difference. if not, the original timing marks will be there to return the timing to where it was (without a timing light)

I will try to make a video sometime tommorow.

[supradog1]

i think i know what the problem is!!!! "a failing altanator!!!" i will prove this theory tomarow when i can put the altanator on a test bench but i think its the cause of the misfire... reasons why: #1 when i have the car up to runing temp and have no a/c or radio on the car has no misfiring (or at least its very rare) then when i turn on all my goodes(a/c, radio) the car starts misfireing like a m/f!!! reason#2 driving in normal cool weather with no goodies on car is fine, i drove onto southbeach and got stuck in traffic to see what happens when it gets hot with no goodes on and as i thought, it started misfiring more and more the the hotter it got... because the alt is is old and week the hotter it gets along with all the extra current draw from a/c and radio is causing it to start to fail and the warning sighn must be this misfire!!!

[supradog1]

ok alt tested out a little low but ok (13 .1 volts) now i am being told its the intank fule pump filter... is this possable??? i also had somthing ealse wired happen today, when i was at a drive up window geting KFC the drive up win. had a steep bank to it causing the car to sit higher on the driverside. while waiting for the food celi started misfireing like crazy with everything off and it was cool outside, as soon as i got the food and drove onto level ground the misfire went away!!!!! some one please tell me what the hell is wrong with my car!!!

[LewFX]

o2 sensor? did you clean your aic?

[cv7713]

in tank fuel filter is posisble. mine was never changed and was pretty gunked up but didn't fix my problem. i also added a new fuel pump at the same time.

i am starting to think my problem is mechanical (valve, piston, head, etc)

how many miles does your engine have? you have the 3sgte, correct?

[supradog1]

my car has about 200K on it and is a 5s auto... i did notice i have a slight valve tap at full wot in my car last night but it on klicks a fuy times in first gear and is gone after that...

[cv7713]

mine has 150k but I think the owners before me ran the little 5S like it was a top fuel dragster!!

I was going to replace the pistons, rings, and bearings but I am not burning oil or smoking out the exhaust so I believe they are ok. Compression tested ok.

have you done a compression test?

This post has been edited by cv7713: Nov 9, 2007 - 11:36 AM

[supradog1]

no not at this time i will by fri cause this has gota stop!!!

[lagos]

i am starting to think my problem is mechanical (valve, piston, head, etc)

i dont think thats it.
the problem you guys have sounds like something small and easy to fix.

like i said, get a video. its hard to diagnose car problems over the internet.

ok alt tested out a little low but ok (13 .1 volts)

thats too low. you should be getting about 14v.
you need to remove your battery and alt from your car, and have them BOTH bench tested.

[cv7713]

ok, here's a couple of vids... tonight it only appeared to misfire after the fan would turn on? I am not sure if this is a coincidence or consistent....

1st, spark plug tester. car misfires with 14 seconds left and again with 10 seconds left. when you see the image shake, that's when it misfires... you can't really hear it though over the fans...

http://s223.photobucket.com/albums/dd75/cv...nt=PA240411.flv


2nd, engine and exhaust. you can hear the misfire about 10 seconds after the fan turns on (again, very hard to hear over the fans) but when I go to the exhaust you can clearly hear the misfire with about 9 seconds of video left (the fan turns on with about 26 seconds left)...

http://s223.photobucket.com/albums/dd75/cv...nt=PA240417.flv


i tried to make a video while driving but you can't hear it at all... it's more feel than sound. just bogs down

This post has been edited by cv7713: Oct 24, 2007 - 8:32 PM

[supradog1]

my misfire is identical to that!!!!

[cv7713]

my misfire is identical to that!!!!

annoying huh?

This post has been edited by cv7713: Oct 24, 2007 - 8:40 PM

[lagos]

really hard to tell from that vid, but to me, it sounds like you have an exhaust leak. i would check to make sure there are no missing nuts or cracks on the exhaust manifold and exhaust.

[cv7713]

thanks for all your suggestions lagos...

I am putting headers on and eliminating the cat in the next week or so... also, I am going to have my injectors sent to be cleaned. when I get them back I will replace the grommet that goes into the head. I never did that when I replaced them the first time. there may be a vac leak there...

[lagos]

yeah thats your problem then. it sounds like either the gasket for the header is leaking, or the cheap header cracked.

make sure you get a brand new gasket from toyota. not those cheap silver mesh gaskets they give you.

[cv7713]

it sounds like either the gasket for the header is leaking, or the cheap header cracked.

no headers yet, will be installed next week or so... I'm definatley getting better gaskets though... i was talking about the injector grommets that might be leaking

This post has been edited by cv7713: Oct 24, 2007 - 9:04 PM

[GriffGirl]

yeah thats your problem then. it sounds like either the gasket for the header is leaking, or the cheap header cracked.

make sure you get a brand new gasket from toyota. not those cheap silver mesh gaskets they give you.

Could a leaking header gasket cause the same problem only when the engine is cold, too? I'm having the exact same problem, but it goes away when the engine warms up. I noticed a leak coming from the header somewhere when I ran Seafoam through the vacuum yesterday.

[Bitter]

yeah thats your problem then. it sounds like either the gasket for the header is leaking, or the cheap header cracked.

make sure you get a brand new gasket from toyota. not those cheap silver mesh gaskets they give you.

Could a leaking header gasket cause the same problem only when the engine is cold, too? I'm having the exact same problem, but it goes away when the engine warms up. I noticed a leak coming from the header somewhere when I ran Seafoam through the vacuum yesterday.

yes, things heat - expand - and then seal. very common for an exhaust leak to only make noise on a cold engine, then go away when hot, however it will get worse to where it'll do it when hot as well.

[roelamizzle]

Sounds like something with your battery connections or your alternator connections. Maybe your battery itself, since it really happens bad when you start pulling power for your ac blower and radio. Also since it acted up when you stopped on the incline makes me think its a loose wire thats arcing across and causing a short.

[cv7713]

OK, I think I finally figured it out!!!! I believe it is the injector seals that go into the cylinder head. When I took the old ones off, they were cracked and chipped and one was even broken in half. So i purchased an aftermarket injector seal kit (B&A) and there is still the same problem but now its worse! It is a lot more frequent with the aftermarket seal kit. They do not seal as well as the Toyota ones. I am going to buy the ones from Toyota and hopefully that should solve it.

Also, got a present in the mail yesterday....

[roelamizzle]

sweet!

[supradog1]

i havent had time to realy mess with it but i hope you are right... i am so sick of this problem!!!! how difficult is the job and how much are the parts???

[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

[Guillermo]

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

The thermostat was changed about 2 years ago