Starting about a week ago I have started to have a pretty concerning problem pop up on my rig (no pun intended). I have noticed that when IÆm driving that I will occasionally have a backfire through the TBI, to the point when the engine hesitates and loses power (for just a fraction of a second), and then it will pick right back up. It usually happens when IÆm in too high of a gear and the engine is under a load. The funny thing is that once it happens, it doesnÆt happen again when IÆm driving. Any thoughts on what might be the cause?

could it be timing? maybe you timeing belt is jumping groves

No timing belt on a 3.1, it has a chain. However, you timing may be off.

Too retarded, or too advanced? It is unlikly that the chain has jumped, as it has less than 4K miles on it, and as I mentioned before, it only happens once per road trip. Might it be a bad injector?

I think that there is a chance that it is an injector. I went through hell a couple of years ago (along with a lot of money) for a similar sounding problem that eventually turned out to be an intermittent short in a splice when I installed a Holley TBI.

Sometimes a bad MAP sensor can do this. Of course backfiring thru the TBI can also ruin a MAP sensor so now you've got the chicken-and-egg thing.

I think if you disconnect the MAP sensor it'll still run, maybe not so great but if it still backfires you could certainly eliminate the MAP as the problem.

If it doesn't backfire with the MAP disconnected the solution is not so clear, but you might try scrounging the local junkyards for a used sensor. Lots of GM TBI vehicles use the same one. And you'll find one on every TBI S-10 2.8.

HTH and Good Luck............ed

Shortly after my last post on this subject, my rig started to develop an intermittent misfire, which was more pronounced as the engine was cold. I decided to do a little old fashion trouble shooting and started with the vacuum lines, of which one was disconnected. This didnÆt fix the problem, so the search moved onto the ignition wires. I used the old trick of looking at the wires once it was dark to see if I could find any misfires. I noticed a pretty good glow at the ignition coil, and another that ran the length of one of the wires. I pulled the ignition coil wire to find that it had corroded completely right at the coil. Sanded the coil plug, and as well changed the coil wire. Still, the car misfired, so I replaced all the plugs and wires. As I went to pull off the fifth of six wires I found the cause of the problem. The terminal was attached to the spark plug, and the wire was broken inside the plug boot û DOH!!! A new set of wires, and plugs and it fired up as good as new! As well, no more backfires!!!

As fate would have it, after allowing the engine to warm I discovered a 2 inch crack in the upper tank of the radiator û DOOOOHHHHHH AGAIN!!! $118 later, a new ALL METAL radiator from http://www.globalradiatordist.com/ and IÆm rolling again!!!

Cool, light shows are nice but not under the hood!

BTW thanks for the tip on the radiator, I needed one for my '89 Spacecab and best price I could find was around $134 at www.radiatorbarn.com.

Just looked it up at your site and it was $104 with free shipping. Sweet! Time to place an order. <img src="/forums/images/graemlins/kewl.gif" alt="" />

Glad to help!!! I had to wait 2 days (ordered Monday, arrived Wednesday morning), but for the money, it was worth the wait!