1992 Chevy Suburban Engine running rough between 1k and 1.5

AARON.WHEELER

MEMBER
1992 CHEVROLET SUBURBAN
V8
4WD
AUTOMATIC
200,000 MILES

My Suburban runs rough around 1000 to 1500 rpm in gear, in neutral, and in park. When taking my foot off the pedal it dropps down to around 200 Rpm running real rough then smooths out and goes back up to about 500 to 600 rpms idle. Periodically, it will die over and over again and it is hard to restart, once started it will die again if I let the rpms drop down or if I put it in gear without holding the rpms up at around 1.5k to 2k rpms to get it going without the engine dying, engine runs very rough during this time. Eventually after maybe 10 times of restarting or driving for a while without stopping it quits dying and goes back to just running rough at 1 to 1.5 k rpms and dropping down to 200 rpms running rough, smoothing out then raising back up to 600 or 700 rpms to idle as described before. I've changed spark plugs, air and fuel filter. Have not changed distributor or wires. Could this be a fuel pump or TBI injector problem? Or does it sound more like a timing / spark issue. Any help greatly appreciated.

1 Reply

AEW48

MEMBER
1 POST

My truck finally died for good and after checking fuel lines, filters, catching the throttle body on fire, cutting an access hole to get at the fuel pump (an air chisel did the trick), and ripping the seat of my favorite work overalls on the hood latch it turns out that it was the electronic ignition. The injectors quit firing off below around 1500 rpm. I could prime the engine by pouring gas into the throttle body (thats how I lit the throttle body on fire-I give it a pucker factor of 7.4) and keep it running above 1500 RPM, but as soon as it dropped below that mark it died. Visual inspection showed no fuel from the injectors at low RPMs. I broke down and bought a manual and after starring at the wiring diagram for several days I figured that the low RPM reference signal from the ignition module to the ECM was faulty. Replaced the ignition module and it started right up.