87 350 tbi runs fine until i stop

[gmbellew]

if you dont turn it off, and take off does it run fine after it starts stumbling? is it only when stopped in drive? what about putting it in park and reving it after you stop and it stumbles? if you just let it warm up at idle, will it stumble when it is fully warmed up?

if it isn't related to closed loop, you may need to try a new distributor. if thats not it, it could be a mechanical issue like low compression?

if it is only in drive, it could be transmission related.

 

[RecklessWOT]

About 6 months after I got my '87 'Burb it started running bad mysteriously no matter what I replaced/tested. Sometimes would run perfectly normal, sometimes stumble, and sometimes shut off entirely. Turned out it was actually the ECU that went bad, they do fail sometimes. If you have a friend that's a mechanic and they can use their fancy snap-on ECU scanner to put it into "limp home mode" (which is just base timing and open loop fuel map) and the truck runs like it's regular ol' bastard of a self but just gets really crappy gas mileage, it is safe to assume the computer is bad. Or if you know someone else who has another '87 and you can try plugging in their computer for a little while to see if it makes a difference. Hell, the one I replaced mine with is from a 305 truck despite mine being a 350. It still runs plenty good enough you can't tell anything is up. Just grab any ole TBI computer will probably work fine at least just to test the theory

 

[Matt69olds]

Converter clutch solenoid sticking? Usually those stick when they get hot, it feels like driving a car with a manual trans, coming to a stop, and not pushing in the clutch. However, the engine usually restarts fine and then immediately dies when you drop the trans into gear again.

That’s my first thought.

 

[diesel_lv]

Not sure if the EGR solenoid and the EGR valve are the same thing, it's been 5 yrs since I had to mess with mine. On mine, the EGR valve would test good, pulled it off and looked good. But when I completely disconnected it, my truck ran great. Put new EGR valve on and it ran great. I had read that the valve can get weak and test good but not function properly. The test was disconnecting vacuum from it and plugging line then driving it.

 

[eric 87]

and then people wonder why some of us say let me stop spending on this TBI/ computer version and revert back to a carb and no sensors. I have done all these parts you did PLUS the computer and distributor. And still it idles fine at 650 or so. THen shuts down going down road. Or at stop sign. THen restart and idle is 1800-2200 rpm. Oh when it is running and not shutting down with all these new parts and plugs etc it runs like it did when new. But these issues make me hate the truck when I really like it. I jokingly said if it continues I will take the 4.2 v6 engine out of my ford farm truck and put in it to spite it! That thing is NEVER failing me. 276k miles on it. Right now I have to walk past bay 1 in garage with 87 GMC to bay 3 with 98 f150 that you can hear rusting if you put your ear to your computer. But I gotta call it as I see it.
TBI to carb swap will happen or it gets sold. Can't own something I don't drive.

 

[Hugomartin]

Latest update to my horror story; start the truck it idles fine. Drive it and as soon as you go to stop it starts missing and cutting out. Put it in park and turn it off then restart it, runs fine again until the next stop. No trouble codes. Parts replaced to this point: spark control module, egr solenoid, map sensor, 02 sensor, temp sensor (3 times), idle air control valve, throttle position sensor, throttle body gasket, spark plugs, distributor cap, rotor button, ignition module, fuel filter. Fuel pressure is 13 psi, cant find any vacuum leaks. Is something resetting when i turn it off and restart? If so, why? About ready to go from stumped to bald.

Sounds like your distributor needs to be turned to the right or left , you also need to play with your idle screw