My brother just bought a 91 v6. He drove it home ,ran rough but made it, drove it the next couple of days, seemed to smooth out then died on the road. Since then Ive done nothing but try to fix this problem and search this site. Here are the symptoms...

no start(duh)
popping through intake and exhaust
plugs black and wet

Things Ive checked ...

fuel presser (good)
injector leakdown (none)
timing (set at ~10)
firing order (OK)

Things Ive replaced

plugs wire cap rotor (ran for about 10 min then black and wet)
map sensor
ignition modular (thought for sure)
cleaned plugs (ran for about 5 min then black and wet)

Any other ideas would be helpful.
Tomorrow I'm checking compression i read these can jump time although it only has 66000 miles (what should that be ~)

Thanks for your help. I don't know why I'm having such a hard time with this(I do it for a living).

 

popping through intake and exhaust...


this is what mine is doing..
i had to replace the timing chain the other day and got in there and the plastic guide plate was broke into pieces on on corner...had a timeing light on it and it was jumping all over the place...thats why that got replaced...not it is set at about 11*
but still backfiring through the exaust,...."STRAIGHT PIPES NO CAT" some say because i have no back pressure

 

No the back pressure thing is bs. I KNOW that.(i still have full exhaust with cat) Anyone know what the pressure should be while cranking?

Thanks in advance.

 

timings probably off sounds to me like its 180 out cause with small block chevy motors the motor will only run it its 180 out or within 10 degrees make sure motor is TDC then take the cap off and make sure the rotor is pointing at the number 1 wire and make sure you have all of the wires in order driver side is 2,4,6 pasanger side is 1,3,5

 

^^Mine is doing the exact same thing. I have also done everything you have plus a little. It runs fine most of the time. Usually it starts hard. Sometimes i just tap the key and fires right up. Something isnt right. Mine like yours has low miles(68,000). Only thing i have not checked is the timing and compression. Let us know if you figure this out. It seems like alot of people have been having this exact same problem. Good luck man. Im in the same situation as you.

 

did you ever get this problem fixed?

 

sorry been away from the cpu for awile and yes we have fixed it. turns out we had very low compression on some of the cyls. removed the heads and found carbon holding some of the valves open. ive never seen carbon this bad of course it had a bad egr. long story short all back together and running like a dream.thanks for the help.