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I'm having some serious problems with my truck.

It started out as rough idling and then it got worse. I have replaced all 4 O2 sensors, temperature sensor, knock sensor, distributor wires, distributor and cylinder 5 spark plug. It hasn't changed at all and still runs like crap. I've replaced cylinder 5 spark plug twice now. The electrode was burnt and the porcelain broke both times. Theres a bad knocking/pinging sound going on too.

The truck also wants to try to reach 260 on the temperature gauge. There's air in the cooling system and I don't know how to bleed it.

Also, I looked up how to test the EGR valve but it only showed symptoms of a bad EGR valve. My truck has all of them. But before I replace it I want to test it with a vacuum pump.

Can anyone tell me what else could be the problem? I've already spent $500 on parts. My list of problems was: catalytic convertors, EGR valve, computer, O2 sensors, monitors, 2 Inc, and other.

Help would be much appreciated. Thank you

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  • I suppose you used the correct type of spark plugs?
    – Martin
    Commented Sep 17, 2016 at 16:54
  • Got the distributor also got changed?
    – Martin
    Commented Sep 17, 2016 at 16:57
  • I have AC Delco plugs in. I was told that's best for my truck. And distributor was changed back in March
    – Skyler.kay
    Commented Sep 17, 2016 at 22:13
  • I suppose the problems where present before changing the distributor? Can you post the exact model (typecode) of the plugs?
    – Martin
    Commented Sep 17, 2016 at 22:27
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    These problems didn't show up until after the distributor was replaced. And I don't know what theyou would be
    – Skyler.kay
    Commented Sep 17, 2016 at 22:51

2 Answers 2

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I see the following possibilities:

  • Like dlu said: wrong range of spark plugs. Perhaps you can try some colder ones. When trying this: be sure to check the spark plugs soon, a too cold spark plug tends to get soot buildup.
  • Engine running lean. Is there a matching trouble code stored?
    • Try to run the engine with disconnected maf sensor. Should things get better: replace the maf sensor.
    • Test for vacuum leaks. While idling spray gently some flammable aerosol (brake cleaner, start pilot, deodorant, wifes chanel no. 5) around the intake tube/manifold, starting from the maf sensor. If the engine sound changes there is a vacuum leak on this part of the intake.

Attention: I would recommend to correct this issue soon. This type of malfunction could, under circumstances, melt a hole in the pistons

Your newest comment was enlighting: find out if some distributor cables got plugged in in the wrong order

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    A caveat with the "disconnect MAF" - the vehicle could fallback to a conservative tune that would make it difficult to determine whether the MAF really was bad.
    – Zaid
    Commented Sep 17, 2016 at 17:39
  • It could also be running lean due to a clogged injector or poor fuel pressure.
    – Robert S. Barnes
    Commented Dec 20, 2016 at 18:14
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My first thought here is to tackle the problems methodically, one at a time.

The one that sounds most significant to me is the plug 5 damage – from what you've said it sounds like detonation (aka pinging, due to premature ignition), but I would also double check that the spark plugs are the correct ones, it could be that you've got plugs in there with a reach that is just slightly too long and that you're seeing mechanical damage.

I suppose the cooling problem and the detonation could be linked, especially if air in the system gathers around cylinder 5. I did a search on

chevy silverado 5.7 bleed cooling system

and found some promising looking links – but I don't have any experience with Chevys so I can't say if any of them are right in the details.

Finally, check out the EGR and see if both the valve and its control system seem to be operating correctly.

My take from your list of potential other problems is that it is a "shotgun list" and that you'd do better to tackle the known problems first so that you can be confident that they are out of the way.

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    To test the EGR, if the back side is open to atmosphere, you can push on the diaphragm (gently). If the engine changes running pitch the EGR is not blocked. To test it further, reroute the vacuum line from the EGR to pull directly from the manifold, bypassing the EGR solenoid. If this causes a change in how it's running, you can assume the EGR valve itself is working correctly. You can check the function of the EGR solenoid by applying power directly to it and listening to the "click" ... if this causes the engine to run differently when engaged, the entire system should be good.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Sep 17, 2016 at 17:16
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    Nice! I'm used to diesels, no vacuum except what the vacuum pump makes... Also, worth confirming that you are getting vacuum on the control hoses – there could be leaks or a blocked filter. Just pull the hose from the supply side of the EGR solenoid and listen for hissing.
    – dlu
    Commented Sep 17, 2016 at 17:19

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