Idle jumps to 2,000 RPM

[camarokidd]

Hey guys, I'll try to make this short, but I can't seem to find anyone else with this issue on a fifth gen.

Yesterday night I decided to take off the throttle body and clean it. My car has 65k miles on it, it's a 2015 1SS M6 with an Air Raid CAI, and Speed Engineering LTH. I live in Cali so this isn't exactly legal, lol.

Anyway, I removed the throttle body and disconnected the TPS module. I cleaned the throttle body with throttle body cleaner, and I WAS pushing on the blades to open them and clean every ounce of it. I reinstalled it and my dumbass started and revved it without the MAF or Vacuum hose connection that goes to the intake elbow. I shut it off after a rev.

I know I know, two rookie mistakes already. I didn't realize that pushing on the blades would affect anything since I've worked on my 1994 TA so much and the blade on there is spring loaded with an idle air screw.

After install I reinstalled everything, I started the car and it ran normal, but as soon I coasted down my driveway (which is pretty steep) the RPM's shot up to about 1500 and then dropped again.

I took it for a drive and it seems the RPM's rise to 2,000 RPM's when coasting in neutral with the clutch disengaged. As soon as I depress the clutch, the engine drops down to around 800 RPM's, and it only goes down to what seems to be normal (around 550 RPM's) when I come to a complete stop. It also seems to accelerate on its own up to 2,000 RPM's in 1st, 2nd, and 3rd gear.

My question is, would it be something wrong with the TPS module or could it be something worse since I revved it without the MAF or vacuum hose hooked up. I made sure to clean the MAF, I tried doing the Idle re-learn with and without resetting the codes. I drove it to work today but it acted this way all the way here.

Note: The only codes it has are for the rear O2 sensors and the IAT. Not sure if the IAT would have something to do with it.

I'd appreciate any feedback you'd have. I also ran a diagnostic check with OBD Auto Doctor, I can attach it later today, it's on my personal computer.

Thanks!

[JerTM]

Clear the dtcs and drive it around, then let it idle for a while. It's just trying to learn the idle since the cleaning of the TB.

[LETHAL2SS]

Mine started this after porting the TB...still haven't found a fix.

[camarokidd]

Update:

After going crazy in the office I went out to unhook the battery as I read on a forum from a G8 owner who had this issue. Click here to see it. Before I did so, I hooked up my laptop and good ol' OBD Auto Doctor to scan it. It came up with P0122 and P0223 codes. I drove it around after clearing the codes and same issue. Unhooked the negative cable and left it unhooked for about two hours.

I took my lunch and decided to do the Idle relearn again. Took an hour lunch at In N Out and decided to eat in my car while it idled, about 45 minutes to be exact. ITS STILL THE SAME. What's weird is the RPM's drop to around 800 RPM's when I put the clutch in at cruising speeds, but not what was previously normal (around 550). The problem is only there when the clutch is not depressed and if the car is rolling in or out of gear. Could I have damaged the TPS sensor whilst cleaning it?

[Avenging Orange]

Start with basics. Make sure everything is matching up...no vac leaks. Clean the maf sensor. Check electrical connections. Then leave it alone for awhile and just drive it. Give it time to learn. Every time you disconnect battery, it starts the process over again. Good luck.

[Russell James]

Idling, use a propane torch (not lit) to flow propane around all the intake joints. If the engine speeds up, you found a leak. Start with everything you touched making sure all the intake joints are tight.

Starting and revving with the MAF and vac hose off is not a problem. With the MAF off-line, the ecm runs on a base speed density map. Causes no issues, just not as efficient - the ecm calcs the air weight instead of measuring it.

After making sure there are no intake vac leaks:
Also make sure the MAF is not in backwards.
Try unplugging the MAF again. Let it idle, drive it with the MAF unplugged. Idle back to normal? Then there is a MAF issue. That is actually an easy MAF sensor test. If a car is screwing up with the MAF plugged in, but runs smoothly and idles proper with it unplugged...something is whacked with the MAF. Like it may be in backwards or dead.

Pushing on the throttle blade though...yikes. If there is no vacuum leak found with the propane torch...the guts of the TB may be forked. When things are working properly, it should learn the idle pretty quick.

My leading guesses are:

MAF is backwards
Intake leak
TB guts are wonky

[Juiced1]

It seems to be hanging open more then it should.

Give Russell James ideas a shot and if that doesn't work you might need to replace it. We have ported systems available that you can buy outright without a core charge.

[JLGO]

Pushing the blades on an electronic throttle body is a bad thing to do. It happened to me before I even own a 5th gen. I didn't have a spike on the rpm like you, but the car randomly turned off and for that reason I had to buy an electronic throttle. This situation happen to a customer that walk in to my work place. The customer told me that his 350z was turning off randomly and that his check engine line or MIL was on. I when and checked it, I do not remember what was the code but it had to do with the throttle body. I asked him if he clean out the cars throttle and if he did moved the blade with his hand. He said yes.

I think when a electronic throttle's blade is move by hand it comes off timing or something breaks. You might need to swap out throttles to see if that fixes the problem.

[xc_SS/RS]

i've pushed the throttle blade on my tb plenty of times, and i've had the blade out to port it (twice now on the same TB). my car will have the idle jump up a bit but not this extreme so i'd check for leaks around the TB.

i would check the tightness on the bolts that hold the TB in after a drive or two if you remove it to clean, port, etc.

[cypressh]

I had this same problem, You will need to have your mechanic do what is called a "crank Relearn" procedure, it can be accessed by GM techs or if you have any friends with a Snap on computer.

[camarokidd]

Another Update:

I did what Russell James recommended, and tried to narrow down the problem.

I disconnected the MAF and drove around with it disconnected, then let it idle. It did not change the way the car was driving. It still had the high RPM problem when coasting and the idle would not settle until I was completely stopped. Could this mean the MAF is bad?

After doing so, I removed the intake manifold, checked for leaks (there were none) and replaced the gaskets with new ones (I thought it wouldn't hurt to replace them). I reassembled and it is still behaving the same. Drove it around a bit but to no avail, it's not fixed.

Note: Before you ask, I triple checked every pug, vacuum hose, and made sure the MAF was facing the right way. Everything was plugged in and functioning properly.

The only thing left would be that I messed up the throttle body somehow, or it just needs more time to learn itself. I drive 45 miles to work one way, so after almost 200 miles it should have re-learned right?

Also, it's no longer throwing the codes for the TPS sensor, but it's still throwing a code for the IAT sensor.

Thoughts?

[xc_SS/RS]

when you say you removed the TPS sensor, what sensor are you talking about exactly? i was under the impression that sensor is in the TB itself...

get a new TB and swap them to see if the issue is still there with a new one.

to me if the problem was still there with the maf disconnected you've either got a TB issue or a leak. check the TB bolts that hold it to the intake manifold and snug them down slowly and evenly. they might be loose after a few heat cycles

[Russell James]

Originally Posted by camarokidd

Another Update:

I did what Russell James recommended, and tried to narrow down the problem.

I disconnected the MAF and drove around with it disconnected, then let it idle. It did not change the way the car was driving. It still had the high RPM problem when coasting and the idle would not settle until I was completely stopped. Could this mean the MAF is bad?

After doing so, I removed the intake manifold, checked for leaks (there were none) and replaced the gaskets with new ones (I thought it wouldn't hurt to replace them). I reassembled and it is still behaving the same. Drove it around a bit but to no avail, it's not fixed.

Note: Before you ask, I triple checked every pug, vacuum hose, and made sure the MAF was facing the right way. Everything was plugged in and functioning properly.

The only thing left would be that I messed up the throttle body somehow, or it just needs more time to learn itself. I drive 45 miles to work one way, so after almost 200 miles it should have re-learned right?

Also, it's no longer throwing the codes for the TPS sensor, but it's still throwing a code for the IAT sensor.

Thoughts?

Use a scan tool and see what the IAT sensor is reading. Should be a bit higher than ambient. If it's reading like -20F, there is your problem.

A big change when disconnecting the MAF, would have meant a MAF problem. The car should idle relatively the same with the MAF plugged in or out. With the MAF unplugged, the ECM uses an air weight grams per second calculation instead of the actual measurement off the hot wire. The calc is ofter very close to actual, whichiswhy there shouldn't be much change. Often when someone has a bad MAF...it won't idle or won't start... then when unplugging the MAF it starts and idles fine...but with a MAF DTC.

[camarokidd]

Originally Posted by xc_SS/RS

when you say you removed the TPS sensor, what sensor are you talking about exactly? i was under the impression that sensor is in the TB itself...

get a new TB and swap them to see if the issue is still there with a new one.

to me if the problem was still there with the maf disconnected you've either got a TB issue or a leak. check the TB bolts that hold it to the intake manifold and snug them down slowly and evenly. they might be loose after a few heat cycles

Sorry if I misled, I didn't remove the TPS sensor, but when I was cleaning the throttle body perhaps some of the cleaner could've worked its way into the sensor. I read on another forum to be careful spraying cleaner into the throttle body directly when cleaning it, as this could happen.

To clarify I didn't remove the sensor just the throttle body. And to my knowledge, the sensor is in the throttle body. I've rechecked those bolts a few times, tightening them to spec. I also checked the gasket and it looked okay.