Mekanik Posted June 21, 2011 Share Posted June 21, 2011 I'm working on a 2002 Chevy Express 5.7L with 170,000 miles. The customer's concern is that it stalls, and also stumbles sometimes on accel. I didn't get the truck to stall but it did stumble. It didn't feel like an ignition misfire; it was as if the engine just shut off, but so brief that it didn't stall actually stall. I don’t have any DTC'S; I sprayed down the plug wires and didn't find anything. I did remove the distributor cap and noticed some corrosion on the contacts, but I really don't think it would cause the truck to stall. I know this isn't a Ford, but does anyone have any ideas? I would really appreciate it. Jim Quote Link to comment Share on other sites More sharing options...
Fredsvt Posted June 21, 2011 Share Posted June 21, 2011 What brand of ignition parts are on it? The flat cap Vortec engines don't like any aftermarket caps. They will internally bridge the contacts in the cap, sometimes causing minor hesitation issues, to dead misfires and in time they cook the module. Same goes for the wires and plugs. It'll eat up the module over time with junk parts on it. Fuel trims? What's base fuel pressure? 62-66 koeo? Running? 55-60 would be nice. The poppets don't like to stay open if it drops too low. Quote Link to comment Share on other sites More sharing options...
cbriggs Posted June 22, 2011 Share Posted June 22, 2011 Check your maf sensor as well, the old 5.7 vortec in the pickups would hesitate and stumble with a dirty maf sensor. Quote Link to comment Share on other sites More sharing options...
Mekanik Posted June 22, 2011 Author Share Posted June 22, 2011 Thanks for the replies. Yesterday, after a hot soak the engine wouldn't idle. It would run fine if I was giving it a little throttle, but not if I took my foot off the gas. I removed and cleaned the throttle body, then it seemed fine. I'm planning on driving it tonight to see whatt happens. I wish I cleaned the MAF last night when it was off, maybe I'll do that too. Quote Link to comment Share on other sites More sharing options...
Mekanik Posted June 23, 2011 Author Share Posted June 23, 2011 Well it's back to the drawing board. I drove this truck home tonight and it cut out a few times. When it happened my ABS light came on and the "Check Gauges' light also came on very briefly. I think I'm losing power or a ground. I think it'll be easier to pursue as an ABS problem. I'll check tomorrow but I'm expecting to see a loss of power ABS DTC. Then I just need to trace back the ground or power source. One thing I noticed it that it always happens on accel, like maybe I’m not drawing enough current through a corroded connection. Quote Link to comment Share on other sites More sharing options...
Fredsvt Posted June 23, 2011 Share Posted June 23, 2011 Pull the PCM and check it for green death. 1999 and 2000 had issues with the PCM itself letting water into the box, and through the plugs, rotting them. Might be worth a look on your '02. There are all kinds of chafe points on these, where the PCM is, follow the harness over the cowl, and down to the abs modulator on the frame rail. There's also chafe points at the left a pillar area, causes all kinds off odd issues. Quote Link to comment Share on other sites More sharing options...
Mekanik Posted June 24, 2011 Author Share Posted June 24, 2011 Do you mean by the ABS HCU? My ABS light was flickering on so I checked the ground circuit (for the warning lamp)for a short, then made sure I had a good solid power and ground to the HCU. I disconnected the connector at the HCU and the problem seems to be gone. The ABS light doesn't flicker anymore either. I did check the PCM connectors and they appear to be okay. Quote Link to comment Share on other sites More sharing options...
Fredsvt Posted June 25, 2011 Share Posted June 25, 2011 They have so many issues over time with the harnesses wearing where they cross over the frame rails or body seam and weld flange areas. I'd guess it's pretty well rusty under there? How bad did the brake and fuel lines look? We have major issues with rotted brake and fuel lines on 1998-2004 G vans, and 1999-2003 Silverado trucks. They go way too early. So does a lot of frame and suspension hardware. Is the ground strap on the right side of the frame, near the starter still there? Glad to see it's doing better. Quote Link to comment Share on other sites More sharing options...
Mekanik Posted June 25, 2011 Author Share Posted June 25, 2011 It's not as rusty as a lot of other vehicles I've seen. I do live in rust country though. The ground strap is intact, and my voltage drop of was minimal. It did act up twice today, but not nearly as bad as before. I did SOMETHING to the problem. I did notice a wiring harness rubbing on the dipstick tube, but I didn't think it was a problem because when I moved it away the ABS light was still flickering. That doesn't mean that I don't have wires shorted together in there. I'll take a closer look on Monday. Thanks for your help! Quote Link to comment Share on other sites More sharing options...
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