Surging at idle

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MightyP

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I've noticed that on occasion I get some surging and high idle (1k) if I goose the throttle a bit and then come to a stop. It seems to last for a minute or more and then clears up.

It's an 05 QC with about 21k miles, stock motor AFAIK with exception of a K&N filter.

No engine codes or any other items going on but it's fairly reproducible and I'm pretty sure not a standard feature of the motor.

Anyone have any troubleshooting tips to start with?
 
MightyP said:
I've noticed that on occasion I get some surging and high idle (1k) if I goose the throttle a bit and then come to a stop. It seems to last for a minute or more and then clears up.

It's an 05 QC with about 21k miles, stock motor AFAIK with exception of a K&N filter.

No engine codes or any other items going on but it's fairly reproducible and I'm pretty sure not a standard feature of the motor.

Anyone have any troubleshooting tips to start with?
Click to expand...

Make sure hose from idle air control valve on pass side of intake to K&N is not kinked. Otherwise TPS or IAC needs replacement.
 
I experience the same thing. I've replaced both the iac and tps and still no change. Another guy told me he had the same issue and it ended up being the solenoids and governor in the trans causing the torque convertor of go wacky. I haven't replaced those yet due to winter coming but will update once I do.
 
You could also check your tb to make sure its clean and the blades are not getting stuck. Also if its an aftermarket tb try loosening the bolts and re tighten them
 
MightyP said:
Awesome! Thanks for the data, I'll order them and post back with the results.:rock:
Click to expand...

The TPS was available off the shelf so I just changed that, no change. So now I'm waiting on the IAC valve to show up.

When I do the IAC I'll check the butterflies to see if there is anything going on in there but from and external glance check everything seems "snappy", no indications of it being hung up on anything.

If I did end up swapping the throttle body are the 67mm aftermarket ones worth it or is that more of "make it pretty" mod? No other mods on the motor except for air intake.
 
Do you have access to a scan tool or code reader with data display? See where your voltages are at for the tps and see how many steps your iac is using. Could also be a vacuum leak and the computer is trying to compensate.
 
rbabody said:
Do you have access to a scan tool or code reader with data display? See where your voltages are at for the tps and see how many steps your iac is using. Could also be a vacuum leak and the computer is trying to compensate.
Click to expand...

I've got a bluetooth ODBII scanner, I've only ever used it to pull codes on a few other cars and to see if anything obvious showed up on this. I'll check it out on this guy and see if I can find the readings you mention.

The high idle seems to act like something is a little sticky, if I blip the throttle and let go quickly the revs drop to normal. If I run it up a bit a bit and then release the throttle a little slower it seems like it hangs around 1k and then drops after a bit.

I should see the IAC by the weekend and after I put that in I'll test it out and then document the exact symptom, if it's still happening.
 
MightyP said:
I've got a bluetooth ODBII scanner, I've only ever used it to pull codes on a few other cars and to see if anything obvious showed up on this. I'll check it out on this guy and see if I can find the readings you mention.

The high idle seems to act like something is a little sticky, if I blip the throttle and let go quickly the revs drop to normal. If I run it up a bit a bit and then release the throttle a little slower it seems like it hangs around 1k and then drops after a bit.

I should see the IAC by the weekend and after I put that in I'll test it out and then document the exact symptom, if it's still happening.
Click to expand...

Have you pulled out the iac motor and cleaned it and its passage?
 
You said you have a k&n filter do you oil it? That oil and stuff can reach your tb and gum up the blades to where they dont close all the way thats what happened to mine awhile back
 
the stock throttle body has no provision for adjustment. Check for vacuum leaks. Cpu is trying to set fuel to idle but Map sensor voltage is incorrect. The computer is confused ......
 
Update

Ok, I've replaced the TPS and IAC, cleaning the IAC body as I did it and the problem seems to be about the same. I don't see "surging" so much as a general lag in returning to normal idle. This weekend I'll clean the throttle body and see if that makes a difference.

I've made video you so ya'll can see what I'm talking about. The first blips are minor taps on the throttle, then the 3rd and 5th are slightly longer blips where I let it get up a bit higher. In all cases I hit and released, so the creeping down is happening on it's own.

https://drive.google.com/file/d/0B89_OseJtpW9cHh5VDNiM2tDLVU/view?usp=sharing
 
Cudawrestler said:
I experience the same thing. I've replaced both the iac and tps and still no change. Another guy told me he had the same issue and it ended up being the solenoids and governor in the trans causing the torque convertor of go wacky. I haven't replaced those yet due to winter coming but will update once I do.
Click to expand...

This is an interesting theory, I too, have the exact same issue as seen in the video. I had it with the factory throttle body, and after with the New throttle body and all new sensors, I also did the reset of the adaptive memory with no change. I also have the Occasional 2to1to2 shift at just off idle acceleration. I sure would like to solve this issue, I have no surging, just the hanging and slow return to correct Idle. This only happens in Park. No idle issues driving.

MightyP said:
Ok, I've replaced the TPS and IAC, cleaning the IAC body as I did it and the problem seems to be about the same. I don't see "surging" so much as a general lag in returning to normal idle. This weekend I'll clean the throttle body and see if that makes a difference.

I've made video you so ya'll can see what I'm talking about. The first blips are minor taps on the throttle, then the 3rd and 5th are slightly longer blips where I let it get up a bit higher. In all cases I hit and released, so the creeping down is happening on it's own.

https://drive.google.com/file/d/0B89_OseJtpW9cHh5VDNiM2tDLVU/view?usp=sharing
Click to expand...

This is exactly what mine does. It would be nice to goose the throttle every now and then. especially after installing the full B&B header and exhaust system. Try and reset the adaptive systems, This seem to have worked for others. There is a procedure on here to do it correctly. I believe it was posted by Arska2
 
MightyP said:
Ok, I've replaced the TPS and IAC, cleaning the IAC body as I did it and the problem seems to be about the same. I don't see "surging" so much as a general lag in returning to normal idle. This weekend I'll clean the throttle body and see if that makes a difference.

I've made video you so ya'll can see what I'm talking about. The first blips are minor taps on the throttle, then the 3rd and 5th are slightly longer blips where I let it get up a bit higher. In all cases I hit and released, so the creeping down is happening on it's own.

https://drive.google.com/file/d/0B89_OseJtpW9cHh5VDNiM2tDLVU/view?usp=sharing
Click to expand...
Exactly what mine is doing. I have replaced iac, tps and cleaned tb with no change. Also reset the ecu by touching the battery cables together. Mine is actually staring to get worse. On initial startup it will surge and seems like it has a miss but I never get any codes. After it warms up it still has the hesitation like there is a miss but all plugs and cables are good. I was also told by the dealer that the torque convertor could be causing these issues as well. But like I said before, another guy with a QC here in Canada was having the same issue and he changed his solenoids and the governor in the trans and that fixed it until he blew the trans cooler lines. But that's my next step. It needs to be done anyways so I might as well just do it now and see if it helps.

Sent from my SM-G935T using Tapatalk
 
The slow drop in idle is normal if you can get some data and watch your iac you can watch it step down . Every time you do a battery disconnect mopars have to relearn everything . I hope you fixed the surging problem if not need more info.
 
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