Why the rough idle?

[Hyboost]

Driving me crazy. Idles like crap warm, only in Neutral or park. My o2's drop to double digits, Ex 019-031 and even 0. But as soon as I put it into drive, the idle smooths out and the o2's pick up and return to normal.

I tried pressing the "TEST" button on my alchy system, and the o2 jump and it smooths out for a few seconds before dropping again.

I tried adjusting the f.p. all over the board, from 29 lbs to 50 lbs vacuum hose off & plugged.
I have the tps at .44v. Tried it at .38 to 46. No real change. I tried adjusting the "Idle screw" in and out but no help there.

My BL & INT are always right around 128. Maybe a little low, at 125, but I figured that was b.c. my fuel pressure was a bit high at 48 lbs static.

I did notice my cross counts lock on whatever # they are at when I shift into p or n. When in gear they are constantly moving like they should.

Other than the idle problem, the car runs great, no misses, or surges. When going over data on power logger, my o2's are highest 700's or low 800 at wot.

I checked for vacuum leaks, couldn't find any. But wouldn't it idle lousy in drive also if it was a vacuum problem?

Any ideas would be greatly appreciated. Thanks Ken.

 

[Emiliano Lago]

Yes if it was a vaccuum leack the idle would be rough at park idle and in drive also,could be the chip.I had similar problem with the idle ,changed all vacuum houses nothing same thing,tried a different chip problem solved.Hope you solve the problem good luck

 

[DavidM]

What chip? Is it in close loop or open loop at idle? If it is open loop the dot in the knock retard on the Scanmaster will blink.

 

[Shawn N]

Have you cleaned out and reset the IAC? What are your idle IAC counts at idle? He has a TT chip DavidM according to his signature.

 

[Lil Truck]

Have you tried MAF cleaner ?

 

[Hyboost]

What chip? Is it in close loop or open loop at idle? If it is open loop the dot in the knock retard on the Scanmaster will blink.

It is one of Erics chips. I got to see if it's going back into closed loop. I assumed (dumb) it was closed, b.c. the car was totally warmed up.

I totally forgot about the little lite on my scanmaster.

I'll try and see today.

Thanks.

 

[Hyboost]

Have you cleaned out and reset the IAC? What are your idle IAC counts at idle? He has a TT chip DavidM according to his signature.

I didn't b.c. the iac was showing around 32-37 in Park, and jumps up when I turn the a/c on. And jumps to mid 50's in D. I'll pull it out and clean it, but if it wasn't working, it shouldn't idle fine in gear. Or cause the o2's to drop to near 0 only in P/N, fine in D.

 

[Hyboost]

Have you tried MAF cleaner ?

No, my a/f is good in P/N and in D. I compared it to my buddies TR and we were almost exactly the same in P and D. So I thought that wasn't the problem. But I'll buy some and try that. Is there MAF cleaner or do I use carb / f.i. cleaner?

 

[Lil Truck]

No, my a/f is good in P/N and in D. I compared it to my buddies TR and we were almost exactly the same in P and D. So I thought that wasn't the problem. But I'll buy some and try that. Is there MAF cleaner or do I use carb / f.i. cleaner?

There is MAF cleaner, I believe CRC is the one I used. I had a similar problem after warm up, my wide band showed 16.0 + AFR, when I drop into gear it calmed down to 13-14 AFR and ran smooth.
The cleaner seems to have fix that problem.

If you are still running a stock MAF tube check for small pin hole leaks.

 

[Hyboost]

I'll try cleaning my MAF. I have a newer polished aluminum maf pipe, but I'll double check the hole where the alcohol line goes in.

Is the open loop indicator the little blinking lite (see pic) on the main scan master screen where it reads "spark retard" and the lite is between the 2 zero's? If it is, it is on when in park @ idle when car is idling rough, and o2's are between 25-65 m.v.

So that is telling me I'm very rich (no me, my engine) and it's trying to lean it out?

Then I put into drive, and idle smooths out at 850 rpm, o2 mv starts to go back to normal, and cross counts start to move also.

Thanks, I'm going to clean MAF and IAC first, then see if anyone has any more suggestions.

 

[Shawn N]

Anytime you jack with that idle air screw it will throw off the tps and iac in my past experience with it.

 

[DavidM]

Yes, the blinking light between the two zeros will let you know you are in Open Loop.

Open Loop refers back to your Fuel Tables to modify AFR at Idle. The ECM does not gather data from the O2 Sensor to adjust AFR until after the ECM is in Closed Loop.

I know this will sound crazy, unplug/reset the ECM and see what happens. Sometimes they just need a reboot especially after tinkering and adjusting with it for a while.

Can you try swapping your buddy's MAF sensor in to yours? Sometimes they will act wacky without throwing a code or showing any real problems.

 

[Hyboost]

Yes, the blinking light between the two zeros will let you know you are in Open Loop.

Open Loop refers back to your Fuel Tables to modify AFR at Idle. The ECM does not gather data from the O2 Sensor to adjust AFR until after the ECM is in Closed Loop.

I know this will sound crazy, unplug/reset the ECM and see what happens. Sometimes they just need a reboot especially after tinkering and adjusting with it for a while.

Can you try swapping your buddy's MAF sensor in to yours? Sometimes they will act wacky without throwing a code or showing any real problems.

Thanks to everyone for all the ideas.

I'm going to clean everything you guys mentioned, & reboot my ECM.
I wish I could, but I can't swap MAFs b.c. I have an LS style and he's still running the stock type.
I'll report if doing the above repairs fixes my problems.
Thanx again. T.B.C.

 

[Shawn N]

What chip? Is it in close loop or open loop at idle? If it is open loop the dot in the knock retard on the Scanmaster will blink.

I wondered why it flashed and then stopped. Good to know!