jspecteggy

iTrader: (13)

I do not know what else to look for, perhaps I am overlooking something? I recently got my IX tuned at a reputable local shop here in Texas. However, since the tune the car has been idling like crap. Not sure if it is a result of the tune or perhaps a sensor has gone bad? The idle is intermittently erratic. It will idle fine at the desired RPM of 1200, however if you come to a light and idle for a second it will hunt, drop to approximately 400 RPM and sometimes die. Other times it will bump the RPM up to ~1900-2k and will sit there for a second before settling down to the desired RPM. The AFR move along with the RPM fluctuation, sometimes going full lean, other times dumping to 10.5.

The car is a built 2.4LR with GSC R2's, S90 TB, SpoolinUp COP, and running a PTE 6466 on Speed Density.

I have attempted to rule out all the usual suspects, coils, injectors, ISCV, TPS, etc. I am continuously getting a P0121 code which is for the TPS sensos/switch circuit range/performance. When I check the output voltage at idle it reads ~0.667v with a 5v input signal. With the throttle plate fully open it is reading ~4.71v. I tried checking via EvoScan as well and it is reading 13.333 - 13.67% at idle and 95% at WOT. I did not see any spike in voltage throughout the range in pedal movement, but I was also using a digital multimeter like most people do. The digital multimeter makes it difficult to see any sort of brief voltage or ohm spike or drop. I also tried adjusting the TPS bumping the voltage up and down, I have left it all the way down at around 0.63v and that is where it is reading 13%. When I bumped it up, anywhere past 0.75 it was not happy and wanted to die rather quickly.

The idle speed/air control motor I thought might be going so I took it out to see what happens when I switch the key ON. The ISC does its self test procedure on a fresh ignition, so if the battery has been disconnected, and will cycle fully and do its little .5 second rattle or whatever you want to call that noise. The ISC however does not do this self test procedure after the ignition has been turned on more than once since the battery was disconnected. I am not sure if that is because it has "learned" the position of the throttle plate or if that is not supposed to occur? The car idles fine until I give it some throttle where its a roll of the dice whether it returns to the desired idle or if it decides to have one of its episodes.

Any and all help with this would be greatly appreciated. I am ready to continue to upgrade my fuel system and get a re-tune.

hutch959

iTrader: (18)

check for boost leak.

if no boost leak, your tuner should be able to help with the diagnosis by looking at the logs.

if they cant, i would get a new tuner

evo8vz

youd be amazed what a clogged injector does to idle or a dirty fuel tank

but check for leaks and vacuum first....if not get your injectors cleaned and check

butte

You've got poor drivability and a TPS voltage-out-of-range error code, this doesn't exactly seem like a mystery to me. The first effort should be to replace the faulty TPS before you start chasing phantoms.

jspecteggy

iTrader: (13)

They performed a boost leak, and compression test, as well as a leak down. They are unable to explain the erratic idle. He changed ISC stepper and TPS settings, nothing came of it.

jspecteggy

iTrader: (13)

Injectors were cleaned out when before the tune. And any boost leaks were corrected before hand. Even with a minor boost leak though, the car should idle normally though. Am I wrong?

Would the sensor be displaying proper voltage and ohm readings if it were bad? I've purchased a sensor and it is in the mail, just waiting to install it. But I wouldn't think that it would be reading properly on a multimeter and in EvoScan if it was bad.

J_Striker

iTrader: (4)

In all areas that were touched for the pre tune inspection, check for anything out of the ordinary. Disconnect anything they might have disconnected and check that all pins are still in there connectors nicely. No pins pushed out or bent. Check to see if the ground strap on the top of the intake is still functioning correctly.

A free thing to try is to download another rom, and copy and paste all of your tables to the new rom. I know that doesn't sound right, but I had an AC issue that I could not get to go away, (that only occurred after i was tuned) until that was done. Again it's free and worth a shot.

butte

Yes sir, it's not that uncommon to have trouble reproducing issues with potentiometers especially with a digital multimeter.

Biggiesacks

adjust B.I.S.S. (Open it up) and/or adjust ISCV tables. I would probably start with "ISCV Demand Below 500 RPM Idle Recovery Adder" and "Desired ISCV initial step position with AC off-Neutral". So you can either adjust the B.I.S.S. until your logged steps at your desired idle RPM match whats in that 2nd table, or you can adjust that 2nd table to match how ever many steps you log at your desired idle rpm. Chances are it has to "learn" how many steps are needed to keep the engine idling at your set value, and when it falls back to the programmed table its stumbling. So you need to adjust that table so the values are closer to the learned values, or adjust the B.I.S.S. until they match. Thats my guess anyway.

jspecteggy

iTrader: (13)

Well, $200 later... The issue continues, so it was not the sensor... Also I now have a spare TPS... thanks.

This is along the lines of what i was looking for. I figure the BISS wasn't messed with as I didn't see them adjust the screw at all. I do have my suspicions about the ISCV tables since I know he messed with the stepper and idle settings. Do you have a pic of what your tables look like? I appreciate your help here Biggie!

butte

Man you posted a thread about poor idle conditions with a TPS out of range CEL...