3.1 stalls when put in gear when engine warm

[pcheffernan]

I've been fighting this issue for a week now, and I'm at odds where to go now. A week ago, driving home, the tach started to drop quickly to zero then recover, like the ignition was turned off and then back on. I was able to make it home. The car was due a tune up. I replaced the crank position sensor (OEM), replaced sparkplugs (Autolite Iridium), air filter, fuel filter, no help. I ohmed the coil packs, secondary resistance showed good, replaced the ignition control module (aftermarket). After this, engine would stall after it was at temp, could restart, once put in gear it would stall, but I could go in reverse and drive home backwards (LOL). Reinstalled original OEM ignition control module. Towed to GM Dealership, mechanic said fuel pump was bad, ignition wires needed replaced, one injector ohmed bad. I took car home, replaced fuel pump (OEM), ignition wires (OEM), no help. Removed plenum, found pcv valve clogged, and hose kinked, replaced both, ohmed all 6 injectors, 5 injectors read 12.3 ohms, 1 injector was 11.6. Replaced all 6 injectors, (Napa), plenum gasket, still same problem. GM dealership said computer said no data, they though perhaps ignition control module was bad, but I don't think so. I hooked up my Actron shorting plug, reads code 12 which means no faults, no other codes. I noticed EGR valve has a lot of carbon in the hole, thought about changing it, but I'm really not sure where to go now. The car is a 1994 Chevy Lumina with 230,000 miles, spent about $500 the last week doing brakes, and tryng to fix this engine. Need some advice where to go from here.

[maxwedge]

Basically the engine can't tell if it in d or r, if it stalls immediately after putting in d but is ok in rev., suspect something in the trans could be locking up in dr. Also look for something pulling on a critical harness connector when the engine torque acts to pick up the engine slightly.

[Tech II]

3 speed or 4 speed?

[rkvons]

I worked on a car that would stall in reverse, but not drive, or vice versa. It turned out to be the Crank Position Sensor wire would touch the exhaust manifold on one direction, but not the other.

[jeffcoslacker]

Originally Posted by maxwedge

Basically the engine can't tell if it in d or r, if it stalls immediately after putting in d but is ok in rev., suspect something in the trans could be locking up in dr. Also look for something pulling on a critical harness connector when the engine torque acts to pick up the engine slightly.

Beat me to it. Yeah engine torque roll is pulling on something, or pinching it and shorting it out. Doesn't happen until harness gets warm enough to sag into someplace it shouldn't be.

Should be able to reproduce it idling in park if you push/pull/shake all the harnesses until it stumbles or dies.

Ran into one like this...crank sensor wiring to ignition module would touch exhaust manifold and ground in gear...had been happening for a while, wires cooked. Finally got burned through enough to ground out on contact. Wiring had come out of a keeper it was supposed to run through.

[pcheffernan]

The car is now fixed. I towed it to the transmission shop, and it was troubleshot by Aamco Transmission. The wiring harness to the crank position sensor was burnt about a foot back from the cannon plug. This was caused because the engine was rocking in the engine compartment earlier this year because the engine mounts were badly worn. The wiring harness contacted exhaust manifold. When the transmission was put in gear, the engine would torque forward, shorting out the wiring, causing the ignition to die. Reverse was ok because the engine would torque the other direction. A new pig tail wiring harness was spliced in, and now everything is good and I'm rolling again.