The lurching saga continues...

Discussion in 'GM Powertrain' started by Springthing, Oct 2, 2008.

  1. Springthing

    Springthing Epic Member 5+ Years 1000 Posts


    If you've been following the problem, feel free to skip to the ******.

    To recap:

    When I drive at cruising speed, the 'burban lurches. When I start it up it's fine, when I'm under power it's fine, and when I have the foot off the gas pedal it's fine. The lurching/hesitation only happens when I want to cruise at a certain speed. If I press on the pedal enough to keep myself going 70 it feels as though the engine misses, causing it to feel like I'm towing a car dolly with a huge car on it - those that have hauled someone on the dolly will most like know what I'm talking about.

    ---update---I've now got a tiny bit of rough idle, especially right after cold start.

    I have now tried three fixes!

    The first was a new fuel filter. Cheap, easy, and step #1.

    The second comes about because I have a twitching [COLOR=blue ! important][COLOR=blue ! important]fuel [COLOR=blue ! important]gauges[/COLOR][/COLOR][/COLOR]. The needle twitches/buzzes really fast and gives inaccurate readings at times. Because of this combined with the hesitation I changed out the fuel pump assembly and replaced it with a new one.

    That didn't help either.

    I actually broke down and went to the dealership and paid the $80 to have them diagnose the problem. Now, I don't mean any disrespect, but for the last few years of going to the dealership (or any garage) for a diagnostics I felt it's been more of a 'guess-nostic'. 95% of the time they being wrong as to what the problem is.

    When it came back they told me O2 sensors needed replacement, both banks, sensors 2.

    ******So I changed both of the post cat sensors and..... the problem continues!!!!

    Went back to the dealership this morning and tossed them the keys again, told them to diagnose again.

    This time they came back with... $675.00's worth of "spark plugs, wires, distributor, and cap."

    I didn't have the energy to say "Wait... so ALL the plugs need replacement, ALL the wires need replacement, AND the distributor AND the cap.... all those need replacement!?"

    SO!... I bring this to your scrutiny once again. WTH is going on here?

    Anyone feel like coming to help diagnose what may actually be wrong with this thing before I start to dislike it and sell it just to do without the hassle?! :mdr:

    ME =====>:fighting0072: <======Dealership

    Comments, ideas, insights all welcome!
  2. 04sierracrewcab

    04sierracrewcab Epic Member 5+ Years 1000 Posts

    i wish i could fix your problem or help but i cant sorry :neutral:

    but i do understand the fusteration .:fighting0090:
  3. dwill3015

    dwill3015 Epic Member 5+ Years ROTM Winner 1000 Posts

    I would have done the same things you already have and at this point, I would also be at the mercy of a professional.

    Keep us posted if anything changes.
  4. vncj96

    vncj96 Epic Member 5+ Years 1000 Posts

    Whew!! Ummm....Ahhh....maybe bad gas? 675 for a full tune-up holy crap!! Not sure what to tell ya. Try cleaning the throttle body and upper intake could be full of crap. Mass air flow sensor could not ne reading right. My guesses are all pricey though:neutral:
  5. Springthing

    Springthing Epic Member 5+ Years 1000 Posts

    cha-chiiiiing!!! Starting to not like the 'burban so much! :frown:
  6. vncj96

    vncj96 Epic Member 5+ Years 1000 Posts

    I am gonna say go with air flow sensor. Under power it could be easier for it to read more air movement over it. And with no gas peddle it knows what it needs at idle. while trying to cruise it may just not be getting good flow. When you say only at cruise are you trying to engage the CC or just holding the peddle at one speed? Does your sensor have the screens in front of the wires, start by cleaning those or just taking the screen off if you have one.
  7. Springthing

    Springthing Epic Member 5+ Years 1000 Posts

    Just holding the vehicle at one speed. aka - most of the highway driving.

    I have no idea what it's got where but I'll go ahead and give it a whirl. Worth a shot! Thanks
  8. phoebeisis

    phoebeisis Epic Member 5+ Years 1000 Posts

    Wow, that is a B of a problem.
    Any chance you have an aftermarket oiled air filter- like a K&N etc.Like vncj said the air sensor-think they call it a MAI Mass Air ?? sensor - can "go bad". I've heard that filter oil can kill MAIs.

    Pure long shot, but...

    The screens in fromt of the MAI sound like a good bet.The total tune up-for $700 bucks- is expensive. You could DIY for maybe $125 or less.
  9. Springthing

    Springthing Epic Member 5+ Years 1000 Posts

    Unfortunately no. Pure stock there until I can get a few key issues dealt with. Once I'm up and running well I'll start on with the modifications and upgrades.

    Sounds like a good bet and will be put into action here within a few hours. I totally wish I could go ahead and do this all myself but still so much to learn. It's a perfect example of if you know how to do it, it's easy and can be done without a worry. If you've never done it before break out the check book.
  10. Springthing

    Springthing Epic Member 5+ Years 1000 Posts

    Mass airflow sensor has been pulled, cleaned with the appropriate cleaner, air filter changed out while I was at it, and the wonderful lurching continues. As an aside... what's with the price of that sensor!? $150 or so? WOW!

    Was talking to someone at a shop I have a restoration project at and mentioned the ongoing issue. He said that it could very well be the distributor. Said he's had to change out more than one and that it doesn't seem to be all that uncommon. Also gave the advice that the auto parts store brand NOT be used and to just bite the bullet and get a factory replacement.

    So!... I may just have to do that. Ugh!

    To be continued.....

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