:frown: ok heres my problem. i was towing a jet ski up a steep hill 4 days ago in 2nd running about 2500 RPMS... when all of a sudden i got a loud bang (possibly backfire dont quite remember) and complete loss of horspower. i pulled off the road and looked under the hood. engine was running a little hot, but not redline. no leaks anywhere. i recenty rebuilt the motor (6 months ago) and bored it .040 over, new everything internally, but havent had any leaks or problems AT ALL till now and this has got me and my mechanic stumped... as well as the OBD computer. :banghead: i've changed the coolant temp sensor, map sensor, Idle air control valve, TPS, plugs, cap and rotor have less than 10k on them, and still completely lost. i can get the motor to turn over fine, and start occasionally... but only for about 4 or 5 secs if that. when it DOES start, it idles very rough, sucks alot of air, then shuts off, usually with a small puff of air out the intake. i checked the fuel pressure and for the few seconds it runs its 39 psi. im completely lost. its been a great vehicle till this and now i cant even get it to run. someone, anyone PLEASE HELP ME OUT!!!

Usually when you hear it sucking in alot of air, and runing rough these are symptoms of a low fuel to the engine.

Whats the fuel pressure with the key in the ON position without the engine running?

thats my guess.... bad fuel, low fuel, no fuel. who the hell knows! but i'll check that and get back to you. think ill shoot for the fuel filter or pressure regulator next.

ok... fuel pressure with JUST the key in the ON position is 40psi... then slowly falls down to 0... but i think thats due to my fuel pressure gauge leaking. and i can hear the fuel pump kick on. just bought a fuel filter and going to put that in. dont think it will do any good, but i havent done it in 100,000 miles so i think its due. any one else got sum more ideas? we're all stuck here!

I'm thinking if your O2 sensor crapped out you'd be getting a CE code and telling us the light was on and all that.

I wonder did you jump your timing chain.

I wonder did you jump your timing chain.
I'm leaning toward something internal also, and that's a definite possibility.

well I KNOW its nothing internal... everything is new... not saying that new stuff doesn't break too, but it does turn over, can turn it by hand, and no leaks. And your right, if it was the O2, i would get a check enging light. but it wouldnt do this. i've run without before. Jumping the timing chain. Hmmm.... i guess very possible. it does WANT TO START, but its just havin a hard time doin it. Usually it would jump the timing if the chain was loose. i dont THINK it is since its got less than 5000 miles on the chain and gears.

Sounds to me like your catalyst melted and is clogged... I had the same thing happen to my 96 JGC under no load... I thought it was the transmission, and took it to a transmission shop... they told me my tranny was shot and quoted me 2000 to fix it... I took it to another shop for a second opinion, and they immediately told me to check my catalyst first... sure enough, it was melted and clogged in the exhaust...