2001 Suburban missing, bucking at 60mph

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by bazar01, Sep 10, 2012.

  1. bazar01

    bazar01 Rockstar 100 Posts

    I was driving down I-85 south from Atlanta to Leesburg and still 150 miles away from home when it started missing and bucking at 60 mph and the whole vehicle was jerking back and forth. I slowed down to 55 mph and it was still doing it. I turned on the tow/haul switch to at least raise the rpm hoping it will help with the isse but it did not. Whenever I accelerate to 65-70 mph the whole vehicle will start jerking back and forth as if it was missfiring on some cylinders or running out of fuel. Oh, %#$t! my fuel pump is dying and may get stranded on the side of the road!

    Well I decided to try one more thing before I gave up. I turned off the A/C and open the front windows. It was a nice low 80F outside so it would be a nice breezy drive. Wow! the jerking disappeared and I was able to cruise at 70 mph with no issues.

    Question: Is it possible my a/c compressor is siezing up and affecting a 5.3L >250hp engine? I would think that the a/c compressor is so little to affect the engine. But I could be wrong.

    I will check my a/c compressor tonight for internal mechanical binding by spinning the magnetic clutch pulley. Any other ideas? Thanks
  2. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    I would figure that if the compressor was siezing the belt would just break. Does it do the same thing at idle with the AC on? I would check the egr valve. (if equiped, my 02 5.3L did not have one) They are easy to clean and the gasket is around $2 at autozone.
  3. bazar01

    bazar01 Rockstar 100 Posts

    That's what I thought too. It will just break the belt. Maybe it is on it's way out, not completely seized yet. I will not turn it on for fear of locking up and spreading metal pieces in the system which will require thorough flushing. Trying to avoid that and just replace the compressor.

    Well, for awhile now, maybe during the last 3 years, at idle when started from cold, the engine idles smooth. After it has been driven and you turn it off, and turn it back on while engine is warm, idle fluctuates a little maybe between 500-600 rpm and I can feel it surge up and down. So far, I just blip the throttle and the hunting disappears and the idle smoothens out.

    Not usre if I have an egr valve but I will check.

    I have never turned on the A/C since last night. I drove it around with the A/C off and the idle was really smooth even when I turn it on with a warm engine. I never had to blip the throttle to smoothen out the idle. Weird.
  4. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    When was the last time the plugs and wires were changed? If you clean the valve (just search egr valve cleaning for recommendations) I would also use compressed air to blow out the tube that it connects to. No sense in cleaning it, reinstalling it, and then having all the crap in the tube go into your clean valve.
  5. bazar01

    bazar01 Rockstar 100 Posts

    Well. got a chance to inspect the a/c compressor tonight. I had to remove the skid plate to be able to get to the a/c compressor. Once I got that out, the compressor clutch is now accessible then I started spinning the a/c clutch to check resistance. The a/c compressor is very stiff to turn but it was turning with great resistance. Very unusual since I know a good a/c compressor should be easy to turn. It looks like it is about ready to sieze up. I have a bad a/c compressor. I caught it just in time before the internals lock up.
  6. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    If you end up buying a replacement from a place like autozone be sure to read the fine print on the warranty. I have seen many people lose their warranty coverage due to not replacing the orifice tube. That is something that the kids at the counter forget to tell you. If they don't see the compressor and orifice tube on the same bill they don't cover it.
  7. bazar01

    bazar01 Rockstar 100 Posts

    I am getting the whole kit which includes the front orifice tube, rear expansion valve, 0-rings and new compressor for $300.
    Thanks for reminding.
  8. bazar01

    bazar01 Rockstar 100 Posts

    Well, I checked my 2011 5.3L a/c compressor and compared it with the 2001 burb. The resistance to rotate the compressor are pretty much the same for both. I do not think the a/c compressor is going out.

    I checked the 2001 burb fuel pressure just for kicks and found it pressurized to 45 psi then dropped to 15 psi in 1 minute and dropped to 10 psi over 2 minutes. I think this is a little on the low side.

    I also decided to pull the 2001 burb fuel injectors to verify that no injector is leaking or stuck open. none was leaking. I must have a fuel pump that is getting weak and with a bad check valve. I checked my 2011 5.3L fuel pump pumps to 55 psi and stays at 55 with the ignition off.

    Iwill drive it around until the gas level in the tank drops and change the fuel pump.
  9. moogvo

    moogvo Epic Member 5+ Years 1000 Posts

    The compressor should not spin freely. If you don't have any resistance then it is worn out. It is just like a miniature engine.

    Your problem is either a lack of fuel or a lack of spark. Does it misfire if you "power brake" it in the driveway? If so, you likely have a plug wire breaking down. If not, you probably have a fuel problem.

    The AC compressor adds drag to the engine when it is running, and if you are not getting enough fuel, then it will start bucking and running bad because it is starving for fuel. Check your fuel filter first, then move on to testing your fuel pressure.
  10. bazar01

    bazar01 Rockstar 100 Posts

    Thanks Moog.

    I already changed the filter 3k miles ago.

    I also checked the spark on each wire with a timing light. All 8 are firing.

    I will try the power braking and report back.

    You also mentioned the EGR. I will also get that thing cleaned up as well as the metal tubes.

    It think it is fuel related.

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