Surging idle on cold start

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1997

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Tested AC flapper, its working correctly, so it ain't that.
On with the hunt....
 

thinger2

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pic's of the AC with flapper, COLD
Sure enough, mine is totally missing.
Just got the whole assembly from pick n pull for 23 bucks.
I know people sometimes rig them to be always open, but Ive never seen anyone take the time to completely gut one.
I cant believe that Ive never figured that out.
Duh, its a chevy of course it has a flapper.
I havent actually put it on yet so I dont know if it will help but I do know it cant hurt.
 

thinger2

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Good advise! At 71, I’ve come to the same point. We live in Maple Valley and have had several trees come down on our propert. Winter life in the PNW is never dull.
I own a 92 K2500 454, am having the same stumbling on cold start and trying to figure it out - hence, following this thread.
You’re welcome for a cup coffee anytime!

Rich
Even by usual northwest standards the last month has been crappy.
My upslope neighbors retaing wall blew out and cause a mudslide which blew out my retaining wall and washed out the concrete footing for one of my carport posts.
Right about the time I decided that really sucked a tree limb about a foot in diameter and maybe twenty feet long dropped on the corner and snapped a 4x8 beam like a twig.
The whole end of the carport broke.
And all of that water started undercutting the foundation for the garage.
And then flooded across the dirt alley into my downslope neighbors bee hives.
Which really complicated things.
So we all got to spend a few days playing in the mud with shovels.
While getting smacked in the head with random 30 to 50 mile an hour chunks of tree
Somehow, that just isnt a much fun as it was when I was a kid.
The most aggravating part has been trying to find reasonalbly straight lumber.
The 2x8 and 2x10 are so warped I could use them to frame an igloo.
Imagine about twenty guys soaking ass wet and standing in the aisle at home depot while sighting down the length of a board.
All you hear is "Nope, nope, nope, nope...
 

1997

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hooked up my ACTRON CP9690 scanner today, started it up let run, logged live data, but it ran fine today.

not sure what i'm looking at since this is the 1st time i used it. only thing that looked strange to me was o2 sensor reporting rich, then lean continually.
ran open loop, watched it switch to closed.
i'll see if i can figure out how to review and post it up.
 

Schurkey

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only thing that looked strange to me was o2 sensor reporting rich, then lean continually.
Perfect. That's the way the system is intended to work. (As long as it's switching back-and-forth FAST ENOUGH.) Many scan tools offer a feature called "O2 crosscounts" or similar; it's counting the number of rich-lean flip-flops in a given period of time, because the sensor should switch faster than the update speed of the scan tool.
 

1997

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good to know, thx.
what parameter(s) do you think i should focus on? Thx.
 

thinger2

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Thanks for that.

Instant mental image: Professor Snape, as Defense Against the Dark Arts Instructor, giving lessons in proper use of the Torque Wrench Wand, for warding off evil gasket failures.
An old friend of mine coined that term.
He somehow convinced our boss that he knew what he was doing because he had a degree from the "Le Institute de Combustion" in Paris
Then he rattled of various words in french which made no sense at all.
I think he called him a stupid root beet.
All while he was using a pallet bander to repair a broken leaf spring pack on the company truck.
 

Sabinoerc

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good to know, thx.
what parameter(s) do you think i should focus on? Thx.
I’m a newbie on this so assume some may be wrong or not the most efficient but it’s what Id do in your case.
I think I’d first see if the surging is happening during open loop or starts surging when going into closed loop.
If during open loop I’d be thinking fuel pressure, air leaks, and be looking for some error flag like stall prevention which occurs at same time as surging.
if it starts when going into closed loop, I’d be looking at temp, tps, O2, trim (I forget now what it’s called Integrator and long term, I think), and again, any potential error conditions which are in sync with the surge. Perhaps also see if it’s bouncing between A/F maps (i think its called blm cell or something like that on tunerpro) if bouncing between cells when it’s supposed to just be stable idle one of the sensor inputs to ECM may be flakey?
good luck, once you go down this path it can be frustrating even though probably only way to figure out what going on in your case,
 

1997

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here's readings from scanner, Frame 0 there are 11 frames.
i suspect issue occurs when going from OPEN to CLOSE loop.

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Bodageta1995

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here's readings from scanner, Frame 0 there are 11 frames.
i suspect issue occurs when going from OPEN to CLOSE loop.

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It’s interesting to see that your trim cell at idle is No 18. I’m showing a lean condition and code 44. I’m showing an 18 too which I thought might be a problem as the factory service manual showed it to be zero as normal? Maybe that’s an error in the manual since we are both 18. 1995 K1500 350 engine here. This forum is helpful
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