Cruise Control Surging

[ViciousKnid]

I get a bit of surging between 65-70 usually. Seems to only happen when My cruise control is on. If i shut it off and keep the throttle about the same it does not happen. It's only when it needs to let off the throttle on slight downgrades.

It acts like the converter unlocked and that i floored it for a fraction of a second and then backed out and locked again.

If you need more pids let me know which ones

BTW the AFR is richer than this shows. For some reason the logs show a bit leaner than the gauge.

You can see it clearly in frames 298, 342, 913, 926
This is a DBW 5.3 with mods in sig

Edit: I bet it helps to load the log huh?

[ViciousKnid]

bump. This happens both with DFCO on and off.
Not really sure what to make of it. If there's a strong head wind it will cause enough of a load on the engine where it won't do it but in normal conditions it really doesn't like it when there is no load.

[ViciousKnid]

bump Deux


ANYTHING at all? Open to guesses.

[nathans1987]

surging? i didnt notice anything

[WeathermanShawn]

Yea, I see your TPS% go up, and all of a sudden your MAP jumps, etc..

I do not think wind would cause that much of a load to cause a car under cruise control to react like that.

I am guessing it is your transmission slipping, or perhaps an electrical short in your cruise control.

I would start eliminating any possible mechanical reasons.

[chevy052500hd]

I noticed in your log you have a P0102 set, could possibly be a maf problem, unless your running a cos and have elimated the maf, then forget what I said. I would be looking into the maf being the culprit, whether it is dirty with oil from a k&n filter or is taking a shiat. Try cleaning it with maf cleaner and see if you get the same surging. Good luck.

[ViciousKnid]

Running COS3 so no MAF, Stock filter, FLT4 transmission that shifts like a dream. p0102 is likely because the MAF is unhooked.
In frames 298, 342, 913, 926 when you see the TP% change and the MAP jump that is what I'm talking about. the truck JOLTS like it went WOT for a fraction of a second. it's the worst going down hill. It will do it repeatedly then.

I"ll try to get a better log of when it does it real bad.

It's DBW so I think I'm going to clean the TP sensor and see if maybe it's messing up. That's the only thing mechanical I can think of that would do this. That would also explain why It threw c0237 as I don't have traction control.

[chevy052500hd]

Or the throttle body could be sticking with carbon build up, might be a possible issue, but if it surged to wot then seems like a electrical prob, faulty sensor.

[Mr. P.]

... the truck JOLTS like it went WOT for a fraction of a second. it's the worst going down hill. It will do it repeatedly then...

??? Torque Converter Clutch issue ???

[ViciousKnid]

VSS was going bad. It finally started affecting the speedometer a couple weeks ago. Replaced the VSS and everything cleared up.

Thanks for the suggestions. FYI for anyone else with the symptom.