Question about 2005 GMC Yukon

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Rough idle / varying oil pressure when accelerating

Purchased 05 yukon four months ago (50,000 miles). only have had oil change and auto start put in since then. Auto start installed three weeks ago, starting seeing engine light come on spiratically (manual says light is triggered by emissions issues). then vehicle started idling rough on and off. both problems have steadily gotten worse. today when accelerating the oil pressure would increase from normal (40) at stop to (60) while accelerating. the exhaust seems to get real strong smell recently (here and there) and seems as though black residue on driveway after letting vehicle warm up for a while.

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  • jersey007 Jan 05, 2009

    We had the trucj scanned. The issues are random/multiple cylinser misfire, system to lean bank 1, O2 sensor circuit low. We just replaced the spark plugs. Engine light is still on. The lights in the vehicle are dimming. We also replaced the battery. Any Ideas on what else it could be?

  • jersey007 Jan 05, 2009

    We have only done the plugs and battery. We will try the coil pack. I will post a responce later. Thank you . The plugs on the right side of the engine were completely blackened. Where the left was fine.

  • jersey007 Jan 05, 2009

    When I go to the auto store do I have to give any more information other the a coil pack?

  • jersey007 Jan 05, 2009

    We ended up taking it to the dealer ship to have them read it. They ended up replacing the o2 sensor and injector flush and it needed a softwear update. Thank you for all your help

  • Anonymous Mar 15, 2014

    this is a new problem, just started over the last couple of days

  • Anonymous Mar 20, 2014

    When starting vehicle, it begins to accelerate as though one is stepping on the gas. Does the same thing when sitting at a light, etc. Could a vacuum leak cause such a problem?



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Ok not to keen on newer vehicles actually prefer the carburated ones, but oil pressure is supposed increase on your gauge when accelerating. If it wasn't going up before and just staying at 40 the needle might have been stuck. But idle should be 40 lbs and when you work the moter (reving or driving down the road) the guage should show an increase for every 1000 rpm above idle. Second if you can get a hand held scanner (bought mine off ebay for $30) check for any codes in your computer you will probably find that you either have a bank running wrong or some other sensor that needs to be changed. I'd go with getting my own scanner it saves alot of money and time, garages make their money here.

Posted on Jan 03, 2009

  • Michael Sharar Jan 05, 2009

    A missfire code usually means you have a problem with a coil pack. I had the random missfire code and went the same route. I replaced plugs and wires ran fine for about a day then the code came back. Didn't get rid of it till I replaced the coil pack. The engine light will stay on aslong as you have a code so if you still have a bad O2 sensor or other things that would send a fault that light will keep coming back on even if you temp. erase the codes. With the lights dimming I would check and see if maybe you have a ground problem and check to see how much voltage is coming out of the alternator altho if the engine isn't running right it may not be allowing the alternator to sufficiently recharge the battery.

    What all did get replaced besides the battery and plugs? Also if you have a missfiring cylinder it isn't burning all the fuel in the chamber so it goes out the exaugst.

  • Michael Sharar Jan 05, 2009

    When you go to the auto store just give them the vehicle info (year, model, make, engine size) and tell them what you want.



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