Engine Surge

[piratemike]

Hey everyone. I have a 1989 Silverado, 5.7, 4x4, auto. This is a truck that was owned by a family member and I now have the truck. I have noticed that anytime you are going a steady speed(could be 30 mph or 80 mph) there seems to be the feeling of a "surge". The truck starts and idles fine. Accelerates fine(does spark knock a little). It only seems to occur when you are at a steady speed. Truck has new filters, spark plugs, wires and cap. Any ideas on what this is and how to fix it?
Also, regarding the spark knock. Could someone point me in the right direction as to how to set the timing correctly?

Thanks,

Mike

 

[LC2NLS6]

I always like to check fuel pressure first. Rent one from any parts store (you get your money back for free), remove fuel filter, install T fitting and test. If you have say like 9 psi, that's already on the low end, and then if you give it gas and it drops to 6 or so, then its time for a new fuel pump.

 

[evilunclegrimace]

Hey everyone. I have a 1989 Silverado, 5.7, 4x4, auto. This is a truck that was owned by a family member and I now have the truck. I have noticed that anytime you are going a steady speed(could be 30 mph or 80 mph) there seems to be the feeling of a "surge". The truck starts and idles fine. Accelerates fine(does spark knock a little). It only seems to occur when you are at a steady speed. Truck has new filters, spark plugs, wires and cap. Any ideas on what this is and how to fix it?
Also, regarding the spark knock. Could someone point me in the right direction as to how to set the timing correctly?

Thanks,

Mike

Bring the truck to operating temp, remove the plastic cover on the passenger side of the firewall and disconnect the EST by-pass wire ( single wire with a black tracer) loosen the distributor hold down clamp,set timing with a timing light to 0 degrees by adjusting the distributor. Once you have the timing set at 0 degrees tighten the clamp down, shut the truck off, reconnect the EST by-pass wire, install the plastic cover and clear the EST by-pass failure code from the ECM.

 

[piratemike]

Bring the truck to operating temp, remove the plastic cover on the passenger side of the firewall and disconnect the EST by-pass wire ( single wire with a black tracer) loosen the distributor hold down clamp,set timing with a timing light to 0 degrees by adjusting the distributor. Once you have the timing set at 0 degrees tighten the clamp down, shut the truck off, reconnect the EST by-pass wire, install the plastic cover and clear the EST by-pass failure code from the ECM.

Thanks for the info. I am new to this so, how do I clear the EST code from the ECM?

 

[piratemike]

I always like to check fuel pressure first. Rent one from any parts store (you get your money back for free), remove fuel filter, install T fitting and test. If you have say like 9 psi, that's already on the low end, and then if you give it gas and it drops to 6 or so, then its time for a new fuel pump.

Thanks for the info. I will give that a try.

 

[evilunclegrimace]

Thanks for the info. I am new to this so, how do I clear the EST code from the ECM?

Use a scan tool to clear the codes or disconnect the Battery for 15 seconds. You may have to drive the truck to have it "relearn" its base parameters. You will also probably have to reset your radio presets.

 

[PlayingWithTBI]

I have noticed that anytime you are going a steady speed(could be 30 mph or 80 mph) there seems to be the feeling of a "surge"

It could be your ICM (Ignition Control Module) inside the distributor or a bad connection/ground on wire 453 here's an article that may be related to your problem.

http://www.misterfixit.com/code45.htm

Here's the wiring diagram for the 7747 ICM, which I'm guessing you have.

http://www.gearhead-efi.com/gearhead-efi/wiring/1227747/747ecm6.jpg

If you replace the ICM buy a good quality (AC Delco) one with good insulating grease that goes underneath it. That may be your problem if it only surges when warmed up after a while.