I bought an oldsmobile bravada from someone i know. they bought it brand new back in 92 and they drove it until it had 219,000 miles on it. it started making a popping noise in the drivetrain and they let it set for 6 months. i bought it and now the fun began! first off it was running very rich, wouldnt idle right and it was spewing gas out of the exhaust. i changed the oil (full of gas) oil filter, throttle position sensor, new plugs, plug wires, new distributor. it fired right up but it backfired at first startup. after changing oil very little smoke was comming out of the exhaust. i let it warm up and i started driving it around the yard. after a minute it loaded up and shut down.

i pulled a spark plug and turned it over and gas shot out of the hole. determined an injector was stuck open. seperated the plenum and i had gas leaks out of the main lines inside the plenum. replaced the lines and the o2 sensor and it fired right up. after letting it idle till warm i drove it around the neighborhood. no trouble. it quit smoking entirely and ran great minus the popping noise in the drivetrain. transmission shifts right on.

i shut it down for the day and i went to work. i bought new CV joints for the front end and after installing them i fired it up again and tested it. still popping. [:@]

shut it down and removed the front driveshaft. put crossmember back on and was going to drive it without the front wheel drive.

i went to start it and BOOOOOOOOM!!! black smoke came rolling out from under the vehicle. looked under it and the muffler blew out sideways. im guessing i still had gas in my oil due to changing it before finding fuel problem. changed the oil...

now it wont start. when i turn the key on i hear the fuel pump run for about 3 seconds then shut down (replaced leaking pressure reg too) when i try to start it it starts to fire up for half a second then nothing. just cranks over. after several tries it stopped even trying to fire. checked plugs and they are igniting. got frustrated and quit for the day. this morning i decided i would try it again. i noticed if i try starting it after the fuel pump quits running it does nothing and right after i stop trying to start it the fuel pump is running again.

i did notice that if i turn it on and let the fuel pump prime for 2 seconds and try to start it before the fuel pump quits it really tries to start but cant. when the vehicle WAS running i could hear the pump running pretty loud. i havent checked fuel pressure yet but i am suspecting a fuel pump problem.

 

I would be very worried about what a violent back fire did to your engine... I would definitely check fuel pressure both at the back of the plenum and at the fuel pump to isolate the pump from the rest of the fuel system. I also would recommend a compression check to see if you might have broken a ring or otherwise damaged the motor with the back fire.

 

this weekend i was planning on buying a fuel pressure gauge. ill get a compression gauge as well. exactly what numbers should i look for psi wise? for fuel and rings.

 

For fuel, 55-60psi is required to start. As far as compression, that isn't so clear cut. All of the cylinders should be within +/-10 psi of the average pressure reading. Due to wear, carbon buildup, and other factors which affect compression pressure, it is quite hard to say exactly what you should be looking at. I would say you should see pressures between 110psi to 140psi given the compression ratio of the engine.

 

when an engine backfires like that can it damage the valves? i know valves are spring return and pressure buildup of that magnitude would make me believe that it could force the valves open. this vehicle has 219k miles on it but i know the oil and everything has been changed/checked on a good schedule. when the motor did run it ran very well. i hope i didnt blow a ring. i got the vehicle for little to nothing and i hope to have very little in it.

 

today it iswarmer outside and i bought a fuel pressure gauge and engine compression gauge. i went outside and hooked the fuel pressure gauge up and turned the car on and it charged up to a little above 60 and when the fuel pump shut off it held steady at 57 or 58psi. after 10 minutes it retains about 50psi.

after doing that i attempted to start it and it fired right up. kinda noisy but it ran. i let it sit and idle for about 5 minutes then i started driving it around the neighborhood. turns out the popping noise i was hearing in the drivetrain is something up front. the vehicle doesnt pop without the front driveshaft in.

i drove it for approximately 3 minutes ; got it up to 50mph and when i let off the gas it started hessitating and died. now it wont start again. fuel pressure while idling was 60psi

any takers on this problem?

iac, tps, o2, plugs, plug wires, distributor cap have been replaced

when it starts it runs fine
while trying to crank i have spark but it acts like its not hitting while cranking when it goes through these spells.

 

Get your ICM, ignition control modual tested. It controls spark timing. You may still have spark, however if it isn't happening at the right time your engine wont start.

Verify you dont have any more gas in your oil.

And what do you mena you removed the front axles?
Did you remove the front cv axles? If so, dont drive the truck again until you replace them. They hold the everything together in the hub/steering knuckle. Without them the wheel will fall off, the bearing will slide out becausethere is nothing to hold it in place.

 

i replaced the cv joints. only thing removed is the front driveshaft. everything else is in place. oil is clean with no gas in it

where is the icm located? do i take it to autozone and can they check it?

 

Its on a bracket mounted to the engine, typically on the passengers side valve cover.
Yes, take it too your favorite autoparts store.

Some ICM dont have a harness at the autoparts stores and the guys have to use the aligator clips to hook it up. If they dont have a clue, they wont know that. Also get them to test it like 10 times in a row, you want it to get hot and see how it performs. You will need new grease that goes between it and the heat sink bracket before you reinstall it. Without the grease it will fry in no time.

 

the icm was located under the distributor cap. i took it out and took it to autozone. they tested it and it was bad.
i bought a replacement and installed it. now the vehicle will start if i push in the gas pedal but it wont idle good. if i take my foot off the gas pedal it'll die on me but when i rev it up it has good response...no hesitating. if i push in the pedal enough to hold it at 2k rpm it studders and it sounds like a sleeper motor. i replaced the IAC valve and im wondering if that is causing the idling issue.