OT 1989 Suburban Stalling At Idle When In Drive

I took it to the reputable garage that I use, and they said it"s a torque converter or transmission peoblem with something locking up when it"s put into drive. So I took it to a reputable tranny shop who tested it and said the tranny is fine and there"s nothing wrong with it, and that the engine is the problem. They said that the converter in the 400 transmission would not have a lockup problem (?).

So I took the vehicle to another reputable repair shop where it is today. This shop specializes in full diagnostics. They have been over every component under the hood, including the sensors, and have tested everything and have only found a slight vacuum leak which they fixed. But the stalling continues when shifted into park or reverse. They are at their wits end.

The engine idles smoothly in park. When put into drive or reverse, it almost feels like there"s too great of a load put on the idling engine, causing the stalling. At this point, nobody really knows what"s causing this stalling, and I"m back to square one. All the mechanics so far said that it could be tranny, computer, or even something else. I just want to get this problem fixed before it costs me an arm and a leg. Do any of you mechanics have any insight about this problem?

If that doesn't fix it, replace the fuel pump. It's in the fuel tank. There was a trick to removing the sensor wire, like a quarter turn or something. I almost broke it off the first time I replaced one.

Sticky IAC will not respond quick enough, (or at all) to computer's command upon increased load from putting tranny in gear, and engine will stall, WITHOUT setting a trouble code.

The Subs and One-tons were the very last models that GM changed over to the "new stuff".

First off, which body style does it have? Is it the older “square- body” type? Does it have the serpentine belt?

Does that engine have a carburetor or a throttle body fuel system? Could possibly be either way in ‘89.

Also, look at the pan on the transmission. Is it indeed a kidney-shaped, three-speed 400? ‘Cause, those were somewhat rare.

Need to know for absolute sure what you have,

Allan

They should look at the EGR valve and/or solenoid, and like Brad says, the pickup coil and/or dist bushings.

Make darned sure that the engine/drivetrain is grounding electrically. Check those little star washers. If the torque of gear engagement is causing the engine to lose it’s ground, it will not run right.

And also, I would definitely run the numbers on the ECM. I had one that nobody in four states could figure out; come to find out, somebody had swapped out the ECM for a California/Federal equipped unit and that thing would die every time ya dropped it in gear.

Is the truck real doggy on acceleration? Does it act like it is totally overloaded at launch? The problem could still be down in that torque converter stator even tho it is not a lock-up type (but I doubt it).

Hope ya get ‘er figured out. It’s just a hunk of iron and something is causing the problem. :>)

Allan