About 4 years ago, I had a leaky intake manifold gasket replaced on the 350 in my full-size 1991 GMC Jimmy. The mechanic recommended that while he was there, that I allow him to rebuild the TBI injectors, which I gave the OK on.

Ever since that time, after starting the engine on hot days (90 - 100 degrees or more), and putting the transmission into gear (700r4), the idle would drop, and the engine would almost die, (occasionally it would die). The RPM would then pick back up to 600 or so.

If the engine did die, it would continue to die each time I started it and put it into gear. I learned that if it died, the next time I started the engine, I could tap the throttle, which seemed to clear the problem, because after doing so, and letting it idle back down to normal (600 or so), I could put it into gear, and it wouldn't die.

Once it's running, and in gear, everything would work fine.

At the same time the dying problem started, I also noticed that when putting the transmission into gear (drive or reverse), that it would go into gear "really hard", causing the vehicle to lurch. I discovered though, that after having driven the vehicle and getting it up to operating temperature (180 degrees or so), this problem would go away, and I could turn the engine off, start it back up, and put the transmission into gear without it going into gear really hard. I normally warm the engine up to 100 degrees before I ever drive away, but that’s not hot enough to get around the problem.

Since the engine dying problem and transmission going into gear really hard, both started after having the TBI injectors rebuilt, I figured the injectors may be the cause, and recently had brand new (not rebuilt) GM OEM TBI injectors and a new carburetor base gasket installed, which seems to have improved the a little bit, so that it doesn't drop so much when putting the transmission into gear, but it still goes into gear really hard if the engine isn’t at operating temperature. Plus, the enginedied on me again today when the transmission was in neutral at a drive up window (the engine was at operating temperature).

I’ve been driving this Jimmy for the last 14 years. It’s my favorite vehicle of everything I’ve ever owned. I’ve babied it, and it’s the cleanest truck you could hope to find...208,000 miles, and other than these two symptoms, still drives like new.

Could these problems be related to a leaky vacuum hose somewhere? Is there something else I can look at?

Thanks!

Clay

 

Well when you were first talking about it, it almost sounded like it could be transmission related........maybe torque convertor isn't working right.

But after saying that it doesn't stall in gear anymore and the last time it did stall it was in neutral I don't think that is the problem anymore.

Being that it does have 208,000 miles on it, it may not be a bad idea to have the tranny looked at anyways.

But overall how does it run, when not in gear? No misses or anything? Idles at normal rpm?

I suppose it could be a vacuum line, probably on the carburetor somewhere since that is what has had the most work done to it. I would suggest tracking down all the vacuum lines on the carburetor and making sure that they are connected at both ends. That is really all I can think of, until I get some more info.

 

Good info. Thanks.

The transmission was replaced with in February 1996 with a GM rebuild, whenthe vehicle hadalmost 108,000 miles on it, and I'vechanged the fluid/filter/gasket every 10,000 miles, because I didn't want toreplace the transmission again.

Also, I haven't done any towing since the transmission was replaced.

I had earlier stated that it idles as 600rpm, which is actually low...in checking, I noticed that it actually idles around 800rpm, but doesn't always idle smoothly. It tends to bounce up and down between 800rpm and 600rpm every 1 second, which isn't quiteas bad once the engine is warm.

Other than that, it runs pretty good...there aren't any misses.

It may not be a bad idea to tune up the ignition though. I recently got the cap/rotor/plugs/wires to do it...just haven't gotten to it. yet.

Thanks again!

Clay