engine surge

[ohgary]

I have an issue I am trying to diagnose.. 02 AV, 265K miles..

Between 45 and 55 mph there are several spots where the engine will surge, Keep a steady speed and the engine RPM will go up and down 300-500 rpm.. Makes the vehicle surge back and forth..  Leave it at those speeds and the issue doesn't stop, go below or above and everything is fine. If I am powering through those speeds I feel no surge or lack of power.

At first I thought it was due to a non related transmission issue  I was having, but replaced the transmission and the problem is still around. thought maybe I had some bad gas but only at certain speeds seemed odd, but did run that tank out and filled it with high test and ran that tank out, still have the issue.

Any suggestion? what can cause a engine issue withing such a small speed range?

 

[Intimidatoruag]

I wonder if you computer is having issues ... but that would be weird to only be at certain speeds ...

could your fuel pump have issue? ... did you try changing the fuel filter? ....

bad injector(s)? ....

just guesses at this point ....

John

 

[enoniam]

May have a small air leak in the intake manifold gaskets that comes and goes.  There was a TSB for early year AVs on a redesign for the gaskets.  If yours are the original they have design issues that have been corrected by GM and other gasket makers.

 

[MS03 2500]

When was the last time you changed spark plugs and wires.
Maybe clean MAF

 

[raiderron]

So, any CEL? Leaning toward a TPS problem or the MAF needing cleaned, like MS03 2500 said, or replaced. Did this come on all of a sudden or a little bit at a time? 

 

[AvyOwner23]

Mine does that... It feels like it's in over drive then goes into 4th and just switches back and forth... mine has done that since i got it.. just thought it was a tranny problem didn't know it could be something else.. i tend to just run tow haul if i'm inbetween 45-55.. it runs just fine then.

 

[ohgary]

So, any CEL? Leaning toward a TPS problem or the MAF needing cleaned, like MS03 2500 said, or replaced. Did this come on all of a sudden or a little bit at a time? 

No check engine light. Hard to tell how fast it came on, I  noticed it more when I was having transmission issues, Its in a speed range that I dont normally operate in. It might have had some issues in the past but recently become more noticeable.  Ill look at cleaning the MAF and see what that does.

thanks guys.

 

[raiderron]

Like AvyOwner23 said, did you try the tow/haul mode to see if anything changed?

 

[LornesAV]

Mine does this as well but also down to 35. Manual says fuel pressure regulator, my 08 is built into the fuel pump assembly. I am running at 42psi. The term is chuggle if I remember right. I have been searching for a long time to figure it out. I can check the manual again when I get back home later this week, I don't think there was another suggested problem.

 

[ohgary]

Like AvyOwner23 said, did you try the tow/haul mode to see if anything changed?

Kicking the tow/haul button does stop the surges.

 

[raiderron]

Kicking the tow/haul button does stop the surges.

That makes it sound like the problem you experience is definitely related to the trans. Now that could be something that the dealer will say is normal but I would take to a reputable trans shop. I googled the problem and several techs recommended replacing TPS but the OP would then say that it still had the problem after TPS replacement. One tech did say that if it is happening and you just tap the brake pedal and the problem stops then it is related to the torque convertor solenoid and some techs said a qualified shop could reprogram computer.

 

[mja]

Has anyone figured out what would cause this/how to resolve this? My 06 does the exact same thing around 45ish mph. Thanks.