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1997 GMC C1500 problems

This is a discussion on 1997 GMC C1500 problems within the Technical / Maintenance forums, part of the General Discussion category; Hello all. I've scoured the internet and can't find a solution to my problem. 1997 GMC C1500 with the 5.0 ...

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    1997 GMC C1500 problems


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    Hello all. I've scoured the internet and can't find a solution to my problem.

    1997 GMC C1500 with the 5.0 Vortec. Auto Trans. 200k. I got this truck cheap and figured it was an easy fix. Not so much.

    When I got it, it would start right up, idle was a little rough. When you give it gas, it stalls. If you ease on the gas, you can drive it. Under a load it misses and sputters. Bought a scanner and pulled the codes, and there were plenty. Put a TPS, EGR valve, O2 sensors, MAF sensor, fuel pump, strainer, and filter, new plugs, wires cap and rotor, and found and fixed a vacuum leak. Still had the same problem, but no more trouble codes. Fuel pressure is good. If you unplug the TPS and drive it, it runs great. No hesitation, and even does ok under WOT. It does rattle a little like this, but I figure it's because it's running rich with the TPS unplugged. I don't want to drive it like that, so it's been parked for a few weeks while I tinker with it.

    So then I replaced the cam position sensor. Now it won't start. I even put the old sensor back in and it still won't start. It sputters and tries, and it bucks when you let off the key, but it won't run. Hooked a timing light up just to make sure it's sparking, and it is. It's getting fuel. Still no trouble codes and no snapshot data.

    Any ideas? Thanks in advance.

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    Re: 1997 GMC C1500 problems

    Anyone?

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    Registered User ToyHauler's Avatar
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    Re: 1997 GMC C1500 problems

    it sounds like possibly some wiring issues. try looking at the tps on the scanner, if you move the throttle down and it doesnt flake out its fine. see what the maf readings do when running. what is the fuel pressure and did you turn the key on engine off and see if it goes away?
    99 GMC Yukon SLE 4dr
    KYB monomax, air lift, tekonosha, reese dual cam, bfg at/ko

    87 Firebird, 07 Monte Carlo lt, 98 Bonneville SSE, 04 F550 CC 4wd service body

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    Re: 1997 GMC C1500 problems

    I've checked the TPS with a voltmeter, it is doing what it is supposed to. The fuel pressure with key on, engine off is around 62, and it stays there.

    I can't check anything while it is running because it won't start anymore.

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    Registered User shamrock246's Avatar
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    Re: 1997 GMC C1500 problems

    Any fuzes blown?do you still have spark?could be a dead crank sensor
    Sean

    97 4x4 burb

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    Re: 1997 GMC C1500 problems

    No fuses blown. I have reddish-yellow spark.

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    Registered User shamrock246's Avatar
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    Re: 1997 GMC C1500 problems

    If it won't fire by pooring some gas down the throttle body then it looks like you have weak spark probably a bad coil had the same problem on a 94 toyota camery
    Sean

    97 4x4 burb

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    Registered User ToyHauler's Avatar
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    Re: 1997 GMC C1500 problems

    if you got good spark and drop some fuel down the tb and it doesnt change anything, most times its the crank position sensor or its wiring. most times the cam sensor isnt bad, but since that is when it stopped running i would go over that connector and wiring pretty thoroughly too
    99 GMC Yukon SLE 4dr
    KYB monomax, air lift, tekonosha, reese dual cam, bfg at/ko

    87 Firebird, 07 Monte Carlo lt, 98 Bonneville SSE, 04 F550 CC 4wd service body

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    Re: 1997 GMC C1500 problems

    Thanks for all the advice. I ended up towing it to the dealer in frustration. Somehow it was out of time. They rotated the engine to TDC and re-stabbed the distributor. That got it started again. It was intermittently throwing a TPS code still. They plugged their fancypants scanner into it and did a TPS relearn. Someone figured out the MAP sensor was bad even though it wasn't throwing a code for it. $575 later, it runs like new.

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