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Need Vortec 5.7 advice

Discussion in 'Chevy Trucks' started by MarkEagleUSA, May 27, 2011.

  1. MarkEagleUSA

    MarkEagleUSA Senior Member
    Messages: 321

    I'm out of ideas (not to mention a ton of money) and really need some adivce.

    97 K2500, 5.7 Vortec, 4L80E, 156,000 miles.

    About 5 or 6 weeks ago the truck died on my way to work. At first I thought it was a fuel pump but the pressure tested ok (about 60 psi). I decided to change the filter whish gave me another couple of psi but still nothing. Pulled the distributor and found a severely worn gear so I replaced the whole works and got the truck running again after setting the cam ******. I decided to do a full tune up and changed the oil and all the filters as well.

    While I got her back on the road, it developed a skip at idle and a dead spot during acceleration. Earlier this week while on my way home she started skipping really bad, almost like it was running on 7 (or less) cylinders. I bit the bullet and ordered a new, upgraded MFI fuel injection spider. Tonight after work I replaced it and cleaned the plenum area as best I could. Put it all back together and she started right up and idled rough for about 3 minutes and then cleared out.

    I let everything warm up while I put away the tools and then connected the scanner. No codes, and everything else seemed ok. Took her out for a road test and immediately noticed much improved throttle response and it seemed like she had a ton more power too. Drove around for 15 or 20 minutes, probably about 10 or 15 miles and then it started skipping again at idle with that dead spot on acceleration. For the record, everything seems fine at speed... this only happens at under 1000 or so rpm. What gives?

    What else can I do? What next? The only things not changed are the coil, ignition module, MAP, MAF, IAC, TPS and fuel pump. So far I've dumped over $500 and countless hours into it and nothing has helped. Could it be as simple as a bad cap/rotor or plug wire(s)?

    I'm out of ideas and patience so any advice would be welcomed.
  2. ABES

    ABES PlowSite.com Addict
    from MN
    Messages: 1,322

    Yes it very well could be. When its completely dark outside and no light around start the truck and look for any arcing around the plug wires. Ive had brand new ones (NAPA) that had hairline cracks that made the truck run much like you described.
  3. MarkEagleUSA

    MarkEagleUSA Senior Member
    Messages: 321

    I've done the check for arcing a few times and never found anything.

    However, I think I may have found the problem. A friend who knows of the situation stopped by this morning and took the truck for a ride. He felt it was definitely electrical as opposed to fuel related. We popped the cap and he scrutinized it for cracks. It and the rotor both appeared fine.

    He looked at me and asked what kind of plugs I had put in. When I told him Autolite's, he said that he's had nothing but trouble with them and suggested I replace them with either AC Delco or NGK. Reading on other forums I saw that the AC-Delco 41-993 plugs are made by NGK so I bought a set of them and threw them in. For the most part, the hesitation/dead spot has gone away. There's still a very slight skip that's nowhere near as bad as it was.

    I also picked up a new set of wires from NAPA but won't be able to put them in until later tonight or tomorrow morning. At least I feel like I'm gaining on it even though the money is still falling out of my pocket.
  4. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    Don't overlook the Crankshaft Position sensor, and the connector. Mine didn't throw a CKP code until it completely died and wouldn't start at all. Replacing the CKP and pigtail, along with a new cap & rotor made her run mulch better.
  5. MarkEagleUSA

    MarkEagleUSA Senior Member
    Messages: 321

    From what I've read, the CKP either works or it doesn't. If it's bad the engine won't start at all. I did check the wiring and tested it according to the service manual and everything was fine.

    I just got back from a 25 mile ride after installing the NAPA wires and she runs like brand new! No more skip, no more hesitation. Hopefully I'm done with this issue for now.

    Obviously the cheap junk from Advanced Auto isn't worth the money. I brought back the 8 Autolite's and the wires (less than 300 miles on them) and at first they didn't want to know anything since they were used. When I explained that with the AC Delco plugs they sold me ealrier today and the NAPA wires the truck was back to running fine, the guy just shook his head. I asked for the manager and firmly told him I wanted my money back. At first he was reluctant but I kept pressing the issue and, with about 6 other customers in the store listening intently, he relented and we met halfway. He refunded me the full price of the plugs and gave me 50% of the wires in a store credit. In the end it cost me $15 but that's chump change considering what I've put into this in the last month.

    Time to enjoy the weekend. Remember all those who sacrificed as well as all those currently serving.
  6. KSikkema

    KSikkema Senior Member
    Messages: 179

    It pays to only run the premium quality cap, rotor, wires and plugs on those trucks. The caps especially have a bad tendancy to crossfire inside the cap. You will not see any arcing but they will crossfire between the passageways built into the cap. The cheap caps are complete garbage.
  7. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    From my experience, they can work for a while and stop. All within a matter of minutes.
  8. 70monte

    70monte Senior Member
    Messages: 468

    I only run AC-Delco Caps, rotors, and plugs in my 98 with the 5.7L. On the wires I currently run Magnacor as I was not having good luck with the AC-Delco replacement wires. They kept arcing.

    Another thing I've noticed on these 5.7's is that the coils start getting white burn marks on the outside of the case next to the metal bracket thing that encircles the coil. Mine has actually arced from this bracket to the case body and is where I have found the burn marks.

    There for awhile, I was having all kinds of ignition electrical problems and still never figured out what the problem was. So far, everything has been good for awhile.