Can't get it running right -

[davejyd]

Greetings all - - I have a 1998 GMC Suburban K1500 with the 5.7 Vortec engine. Recently, I have had issues with the way it runs - - I will be driving along and all is good, and then all of the sudden it will lose power, start sputtering, and sometimes even dies. I shut off the key (I can put it in neutral and do this while driving down the road) - wait about 10-15 seconds, and start it up, and it will run fine for a while - -then it will do the same thing. Sometimes it won't act up for days - - sometimes it will act up 2-3 times a day. I have taken it to a shop, and they did a diagnostic on it, and told me the cats were plugged, and that it needed a tune-up. Soooo - - here is what I have done so far - - replaced the fuel pump & filter, "Bypassed" the cats, replaced the coil, cap, rotor, plugs, and plug wires. When it runs, it runs very well, but when it acts up, it is bad, and can be somewhat dangerous depending on where you are at. I am at a total loss here - -I have the "parts cannon" loaded and ready to go, but would like an idea on what to try next? It has been suggested to replace the distributor (although it felt solid when I replaced the cap/rotor). I have thought also that maybe it's an issue with the spider injection system? I'm prepared to replace it, but - - - -

This may be mentioned in another forum post, but so far I haven't been able to find what I need?

 

[RawbDidIt]

Greetings all - - I have a 1998 GMC Suburban K1500 with the 5.7 Vortec engine. Recently, I have had issues with the way it runs - - I will be driving along and all is good, and then all of the sudden it will lose power, start sputtering, and sometimes even dies. I shut off the key (I can put it in neutral and do this while driving down the road) - wait about 10-15 seconds, and start it up, and it will run fine for a while - -then it will do the same thing. Sometimes it won't act up for days - - sometimes it will act up 2-3 times a day. I have taken it to a shop, and they did a diagnostic on it, and told me the cats were plugged, and that it needed a tune-up. Soooo - - here is what I have done so far - - replaced the fuel pump & filter, "Bypassed" the cats, replaced the coil, cap, rotor, plugs, and plug wires. When it runs, it runs very well, but when it acts up, it is bad, and can be somewhat dangerous depending on where you are at. I am at a total loss here - -I have the "parts cannon" loaded and ready to go, but would like an idea on what to try next? It has been suggested to replace the distributor (although it felt solid when I replaced the cap/rotor). I have thought also that maybe it's an issue with the spider injection system? I'm prepared to replace it, but - - - -

This may be mentioned in another forum post, but so far I haven't been able to find what I need?

If it's sporadic and always after warmup, I'd look at the EGR system. I'd also recommend replacing the PCV and check the elbow and coupler for cracks causing a vacuum leak. With the cats being plugged as well, this would lead me to do fuel pressure and vacuum tests as well as hooking it up to a scanner and looking at the fuel trims.

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[PlayingWithTBI]

If it's sporadic and always after warmup, I'd look at the EGR system.

^^^X2 although I would think it will throw a code if the EGR is bad. How about the ICM? They can give you issues and won't throw a code either. As @RawbDidIt said put a scanner on it.

 

[RawbDidIt]

^^^X2 although I would think it will throw a code if the EGR is bad. How about the ICM? They can give you issues and won't throw a code either. As @RawbDidIt said put a scanner on it.

If EGR is completely stuck or has a broken diaphragm, yes a code would throw, with it being intermittent, it could be sticking in between normal cycles and the starting cycle may knock it into submission. Probably not, but worth looking into.

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[Schurkey]

What is the fuel pressure?

Connect a scan tool, look at the data stream.