I have a '87 Suburban with a 350 TBI. While I know that the vehicle application isn't totally relavent, I see that many of you use the same drivetrain. I was having a problem with the truck that I think is ignition timing related, maybe someone can help. Driving along and the truck starts acting really weird, won't accelerate past 3000, scantool is showing knock under very light throttle conditions, hesitating while taking off, and genernally not running good. I got on the highway and it was okay at speed (65mph) for about an hour, then it starts missing, popping, audible knock until rpm cam down. I stopped at the nearest rest area, shut it off and it would never restart. When I tried to restart it, it sounded like the timing was advance, a lot. It was fighting back, hard. I then took the coil wire off to check for spark and it had spark and the engine would turn over with no problem, no fighting back.
I could also see fuel be sprayed from the injectors.
The only code it ever threw was for EGR, but I have the EGR vac hose disconnected because it was sticking on, another project.
I have gotten a code for the map sensor in the past and it looks like it is reading high sometimes, acording to turbo-link.
I know the O2 is shot too.
I don't think that any of these prior conditions would affect what is going on now since it was running before.
Is there anything is the ignition system on these engines that can go bad and advance the timing a bunch?
I have heard the pickup coil can do this?
The vehicle is away now, so I can't do any more testing than the couple of hours I spent on it at the rest area. I would like to hear if anyone else has had a problem similar to this and what the fix was.
I think that is it, sorry for the long post.
Thanks for any help!

Mike
mgloff@hotmail.com

 

Your best bet is to fix what you know is wrong first then work on the rest. The egr will cuase a lot of what you are experiencing and the bad o2 doesn't help anything either.

Steve

 

I have the same problem. but if I disconnect the bypass wire it runs fine. its a 89 305 tbi.anybody seen this B4?

 

found my problem. It was a faulty pick up coil. Also while your there clean all the contacts on the distributer