1988 Chevy S-10 Truck runs, but bucks

MARY FIGURA

MEMBER
1988 CHEVROLET S-10
6 CYL
4WD
AUTOMATIC
9,000 MILES

Hi,
I have done extensive testing on my truck, but I am not a mechanic, just someone determined to fix it myself. Truck runs, but bucks terrible. Loves 15mph, smooth as glass. Before it went down totally, on freeway, truck would hesitate at high speed (70mph). Now it is throwing a code 22 (tps) and 34(map). The ESC has juice from B terminal. I did several tests for the map and tps, egr solenoid, replaced egr, injectors are firing and at wot, they do their thing (conical spray). Replaced fuel filter, had fuel pressure checked (12psi) which is within spec, relays work, throttle works, but if you step on the gas, it bucks and dies. I pulled the ECM, it is getting just under 12v on both orange wires. Map and tps at the ecm has the correct voltage with key on engine off. I am thinking I need a new ecm. The one on the truck is the original. BTW, the engine was replaced 2008, and tranmission shortly thereafter. Spark plugs are all firing and are clean. I am tired of trying to find this problem. Any suggestions would be awesome. Thank you, mary

1 Reply

HMAC300

MECHANIC
48,601 POSTS

Acouple of things to try are to see if hte vacuum hose is any good going to the map sensor. They tend to get soft and suck together so the map can't read the vacuum and give you trouble. Also TBI's tend to blow the gasket under the unit which gives you a vacuum leak. Then take some choke cleaner and spray around the tps to make sure that it's not sticking. Open the throttle after doing this a couple of times. You could still have a bad tps and map sensor, I wouldn't go for the ecm right away yet as sensors can do the same thing.