IRONDOG442 Posted May 18, 2010 Report Share Posted May 18, 2010 P0300 Random misfire no other DTCs set Knowns: Symptoms indicate car is dumping raw fuel into catylitic convertor and its getting red hot. it actually caught fire yesterday (before you ask what the fuel source was -I used Black RTV for the seal between the down pipe and resonator and it caught fire-YEah it was that hot.) Doesnt misfire until car is warm or until it has time to build fuel into exhaust pipe. I took my 3.8 liter catylitic converter to the exhaust shop yesterday and asked him to cut the head pipe off the old 3.8 cat and install it onto a 3.5 liter cat thinking the cat was either plugged or had gotten wet then he explainted to me the function of the cat is to convert unspent gases into water vapor therefore water cannot make a cat non functional. he said the engine is dumping raw fuel into your exhaust and its getting hotter the longer you run it. The engine ran fine in roaches bitch ever since it has been transplanted into roach it has not run right. What has changed: 1. new ignition wires 2. new plugs Bosch Platinum 3. Cradle was replaced 4. Entire harness was removed and reconnected I know what could possibly cause this condition and know what order of their probability. That is: 1. vacuum lines 2. ignition wires/plugs 3. fuel pressure / stuck injector 4. malfunctioning MAF 5. Bad motor mount or electrical ground 6. Bad ICM What I don't know is, is the guy at the exhaust shop full of shit because when I run the car with no exhaust or just a down pipe the car does not misfire and no dtcs appear. I am going to go through the factory service manual tonight and go through the diagnostic order but wanted your insight before doing so. never dealt with this problem. When the car is first turned over while cranking something sometimes literally stops it, like it is hydro locking it doesnt do this everytime but more often than not. Thsi indicates some type of timing problem, yet I am unsure anything there has been changed. Thoughts, opinions, etc at this point anything is welcomed. Link to comment Share on other sites More sharing options...
BXX Posted May 18, 2010 Report Share Posted May 18, 2010 If it runs fine with the cat not on it, then the cats plugged up and bad.. Install a new one. Clogged cats cause high ass backpressure which causes engines to misfire and not have much power. Kinda hard for an engine to fire correctly when it cant get the exhaust gases shoved outta the cylinders. However, an engine misfire can destroy a cat very quickly.. Link to comment Share on other sites More sharing options...
White93z34 Posted May 18, 2010 Report Share Posted May 18, 2010 I would like to think that if the engine is dumping fuel it would ruin a set of spark plugs in very short order. pull a plug or 2 see if they smell like raw gas or if they smell like they have been hot. that should tell you there if it really is dumping fuel. Link to comment Share on other sites More sharing options...
93cutty Posted May 18, 2010 Report Share Posted May 18, 2010 I agree with pulling some plugs out. My blazer was doing the exact same thing and I found the fuel pressure regulator was dumping more fuel than it should. Link to comment Share on other sites More sharing options...
BXX Posted May 18, 2010 Report Share Posted May 18, 2010 If you wanna pay for my fuel, i'll come out to Toledo today or tomorrow and help ya fuck around with the Roach.. Im off for two days and have nothing to do at all.. Link to comment Share on other sites More sharing options...
IRONDOG442 Posted May 18, 2010 Author Report Share Posted May 18, 2010 If you wanna pay for my fuel, i'll come out to Toledo today or tomorrow and help ya fuck around with the Roach.. Im off for two days and have nothing to do at all.. I will definitely be pulling the plugs possibly tonight. Tomorrow I cant work on roach because I have a softball meeting all night I am the manager the coach and the captian and I have to be there. I do appreciate the offer though Bob. Link to comment Share on other sites More sharing options...
BXX Posted May 18, 2010 Report Share Posted May 18, 2010 No prob, always willing to lend a hand.. especially when im bored at home:p Link to comment Share on other sites More sharing options...
IRONDOG442 Posted May 19, 2010 Author Report Share Posted May 19, 2010 Went home found out that my #3 injector was stuck open, thus dumping fuel just like I thought, roach is home. And is my DD for the next 10 - 14 days! WOOT. She is amazing mods can lock this !! Link to comment Share on other sites More sharing options...
Addicted to eaton Posted May 19, 2010 Report Share Posted May 19, 2010 I would like to think that if the engine is dumping fuel it would ruin a set of spark plugs in very short order. pull a plug or 2 see if they smell like raw gas or if they smell like they have been hot. that should tell you there if it really is dumping fuel. Agree. I my 97 GT had the same problem it was a stuck injector on cylinder 1. pull the plugs. you will know i replaced the injector and it ran amazing after that! Link to comment Share on other sites More sharing options...
Addicted to eaton Posted May 19, 2010 Report Share Posted May 19, 2010 reading on down > me! Link to comment Share on other sites More sharing options...
mfewtrail Posted May 19, 2010 Report Share Posted May 19, 2010 Went home found out that my #3 injector was stuck open, thus dumping fuel just like I thought, roach is home. And is my DD for the next 10 - 14 days! WOOT. She is amazing mods can lock this !! Link to comment Share on other sites More sharing options...
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