I've got a question about my 1989 Chevrolet K2500 4x4 pickup. Engine is a 5.7L TBI with manual trans with 208000 miles.
The problem I'm having is a single engine stumble durring hard or soft acceleration the first time the truck is moved for the day in first gear. The engine will start off fine then cut out like low fuel then accelerate off again fine. It will do this with a cold engine or after warming the engine. After it stumbles that single time it runs like a champ through all gears both city or highway driving. It will not occour again until the engine is allowd to sit over several hours again. Spark plugs, wires, distributor cap, and rotor have been replaced. TBI has been rebuilt with new regulator and injectors. Fuel filter is also new. Vacuum presure is 21 psi at idle and 15 at highway speeds. Gauge needle stays steady. Spark timing is also right on the money. For a while it was stumbling like this all the time along with back firing, black smoke out exhaust, and code 44 for lean exhaust. I found the egr valve bad and the air managment valve bad putting the engine in open loop stopping the A/F Learned and setting the Integrater to 138 (rich). Repairing that repaired all but the one single stumble I'm getting now. Any Ideas on where I should look next?
Sunday, December 31st, 2006 AT 11:00 AM