Service Engine Light-Computer?

[momonusa]

Hi Folks,

Here's the deal, If I'm driving at 3/4 throttle...say passing a row of traffic for a mile uphill...halfway up the hill, it will feel as if I dropped a cylinder and lose power. The service engine light will come on and stay on until I shut off the ingnition for 3 seconds and restart the truck. Once restarted, the truck runs fine and the service engine light shuts off. I figured out how to do this while driving. Although its dangerous, the truck falls flat on its face without the restart. After the restart it may or may not repeat the same thing. Is this a computer problem? All throughout the rpm range the service engine light comes on and off depending on what throttle I'm using at that moment without the "dropping a cylinder feeling" unless I'm at 3/4 throttle for a long time. I've had this problem for a while now and I've replaced the fuel pump, replaced the cylinder heads, replaced the FSD, added the FSD cooler, replaced the water pump with a high flow upgrade kit, replaced the radiator, the list goes on and on. All this done over the last 2 1/2 years.
I think the FSD driver may still be the problem or the computer. I figured I'd get some advice before buying more parts. Thanks in advanced for your help.

PS. The truck is a 1994 GMC Suburban 4x4 with the 6.5 TD (HO-F model)

Mario

[Marlin]

Mario,

You need to pull the codes. Go to kennedydiesel.com and click on 6.5 tips to find out how to pull codes. If you have a code 54, your computer is going to take a dump. Other codes that may or may not show are 17, 18, 35, 36. Replace the ECM if code 54 shows.

Marlin

[DennisG01]

In addition to what Marlin said, you're first point of order should be to clear the codes and start fresh. That way you'll know what is recent.

If you're getting loss of power strictly (and consistently) with more throttle, maybe you're having a problem with the temp's (IAT or EGT) getting too high and the computer defueling (does this happen in a '94? - I'm not sure). Maybe something (like the soot trap) is clogged up? It's just my initial thought - I'm sure some more knowledgable guys will help out.

Anyways, clear the codes first.

[momonusa]

I'll check the codes then clear them. I'll let you know what I found out.
DennisGO1-- Is you turbo noisier without the cat? I put a 3 1/2" exhaust on, but my exhaust mechanic convinced me that without the cat, all I would hear is the turbo-really loud. Are you happy the changes youv'e made to your Sub?

[DennisG01]

No, removing the CAT didn't make the turbo noticably louder. The most noticable difference came from removing my "turbo silencer", although I don't think a '94 has one of these. However, even without the silencer, without a CAT and with an open-air intake, the turbo is nowwhere near annoying. I can hear it easily, but it is not bothersome. If it was, I'm sure my wife would have told me! The less restriction you have in the intake/exhuast the better - the turbo will spool up quicker.

[Doug Thom]

had a similar problem a couple of years back. tried everything I could think of to no avail UNTIL I decided to check the fuel separator filter and it wasn't sealed properly and was seeping a small amount of fuel. Cleaned it all out and installed a new filter and problem solved. Just a thought! Maybe yours is as simple as that was. Good luck!
Doug