section8

I have an LS6 stuffed into a 93 RX7 and I've been fighting with a high idle issue ever since i got my base tune PCM hooked up to the car. tach isn't working just yet so I don't know exact RPMs but it is pretty high.

Yesterday I thought I had it fixed when i reset the TPS (my previous attempts to reset it failed because i'm an idiot and was unplugging the IAC instead)

I fired up the engine cold and it immediately settle down into a proper idle.



well this morning i go out to fire up the car and just drive it around the block, and it is back to the high idle again, i'm thinking it has to be 2000rpm. If i blip the throttle it goes up and does not come back down.

I didn't touch the car after last night, i turned it off and closed the garage.

Any ideas what could be the issue? My best guess is that somehow after resetting the TPS last night after the engine cooled down something cracked and i developed a vacuum leak but I really don't know. I'm pretty new to LSx troubleshooting coming from the rotary world. Could the TPS or IAC have gone bad just like that?

99Bluz28

iTrader: (35)

I doubt the tps or iac just went bad if there fairly new, but the iac would be more likely to be the issue then the tps, unless the TB blade has be adjusted open at or beyond 3% throttle position.

section8

I'm not sure the percentage of the TB open, but it isn't much at all. I've backed the set screw down flush then raised it just to the point where the blade doesn't hang before i reset the TPS last night. It just seems so odd to me that it would run fine last night and not today.

section8

So i'm back to bumping this thread because I'm pulling my hair out over this.

I had the car running great, but it wasn't charging the alternator. After some troubleshooting I got the alternator wired to the mazda harness so it is charging the battery. As soon as I got that fixed, the car decided to start doing this ridiculously high idle again.

I pulled these codes off the PCM with an old diablosport tuner for a duramax i no longer own:

P0102
P0118
P0122
P0650

The MAF and TPS codes are kind of in line with what the car is doing - in the past I have been able to reset the TPS and IAC and get the car running - but I have swapped those out with known good units from a neighbor's car so I'm worried now that my PCM is actually bad - reading the fault code data on 3 of these codes it lists "faulty PCM" as a rare but possible explanation.

Any other ideas?

trans_am7935

iTrader: (15)

i would say clean the MAF as it sounds like it is not reading the airflow right, as you stated the idle would stay after a quick rev or take a long time to come down.

did you unplug the maf and start it up yet?

section8

So last night I pulled the MAF off and cleaned it, still had high idle. Then i unplugged it and started the car - it immediately starts running normally. ugh.

So I guess the MAF is bad or going bad? it came with the engine and has been descreened already.

section8

I got a new MAF and put it on the car, still getting same results and same codes.

section8

I emailed my PCM tuner and he told me to make sure i had done the IAC setup properly. This requires a scan tool which i don't have

"TPS voltage at the PCM (must check with scan tool) has to be under .600 VDC as well at closed throttle and the TPS must read 0.00% ALWAYS (not 0.8% or more; many scan tools will not show the decimal place though).

The worksheet that came back with the TB setup goes over things. If you had used it and a tool to setup the TB you would surely see zero IAC counts (it's fully closed trying to limit idle speed but is unable to). That IAC range specified HAS to be setup, that's why I send the sheet out. Assuming it was attempted, then it only leaves a giant leak, incorrect arm, etc as the culprit. "

So I started by testing voltage to the maf and tps wires, all looked good - so i cleaned out the TB and IAC and opened the idle screw some. No change. Opened a bit more. No change. I cranked it all the way, no change. Closed it back down, no change. (i was resetting TPS each time)

Then my brother called and he walked me through some electrical tests - specifically current and resistance. I'm seeing some odd stuff on the resistance to one of the wires on the maf connector. on DC it reads 11V, but on 2000ohm resistance test my meter is beeping and telling me 005. My brother says that is an indicator of a ground short. Other wires show normal resistance on that harness connector.

SOoooo, I need to pull up an LSx wiring harness schematic and figure out which of these MAF connector wires does what, and what current should be going through it, but i'm thinking I have a ground short somewhere on the harness.

section8

ok another interesting discovery - this could be my problem. i started looking at the wires on the LS6 harness to the maf, it is a 3 wire pin out. reference link here:

https://ls1tech.com/forums/pcm-diagno...g-diagram.html

My harness is configured like the 98 harness.

I have an adaptor to go from the 3 pin to the 5 pin 2001 MAF style plug.

Well the 3 pin part of my harness which is SUPPOSED to be YEL/BLK/PINK is actually YEL/PNK/BLK - which means when it goes through the adaptor to the MAF the power and ground are switched.

So before I go cutting up my harness, can someone confirm that I am right and these wires should not be swapped?

section8

VICTORY IS MINE! I swapped the pink and black wires on my 3 to 5 pin harness adaptor, checked the pinouts for correct voltage and then hooked it up. Since I discovered the mistake in the harness, i looked at the coolant temp connector too since I'm getting a code on that. Well god damn it, the wrong connector was plugged in! The correct connector was tucked up somewhere, too short to reach so we thought it wasn't used. I cut back the wrapping for that and got it to reach the ECT.

Cleared the codes, and fired her up. WOW perfect on first fire.

section8

Well I guess my self congratulations were a bit premature. The car started throwing ECT codes again and idling high, so i looked into the wires for the sensor since the sensor itself is brand new and showing good resistance.


I found that the yellow 5v wire going to the sender was connected to the wrong pin on the PCM harness side. I moved that to pin 74 where it should be, checked voltage at the plug and all was good. Plugged it in, and it fires up with no more ECT codes, but now the god damn car is idling high again.


I'm back to basically where I started now, except now I have no codes being thrown to tell me why. When I start it up from cold, it will fire up to 1100 rpm, then rise to 1800, then 2200, then 2800. I let it run until warmed to around 180F then I shut it down.


I reset the TPS, started it again, it now fires up to around 2800 or 3000, and starts climbing, so I shut it down again.


I guess tomorrow when there is more light i will go through each wire on the PCM harness connection and compare to the schematic and verify everything is where it should be, but I really don't know what could be causing it to not idle properly now.

Eturtle

This may be something you already tried, but I made the mistake of taking out the IAC and putting the o-ring on the larger part of the IAC instead of on the land provided.
I started it and the idle shot up from 150 to just short of 3k and stayed there.

section8

Never got back to updating this thread, but the problem ended up being the actual harness connector to my IAC. It has to be really jammed on tight to work the IAC unit. I've ordered a replacement pig tail, eventually will put that on it, but the car has been starting and running normally since i figured that out and just got that thing really pushed on hard to the IAC connector.

section8

squeeking is from solid delrin bushings in the suspension.

TransAmBlue

Sounds like a old chuck wagon ran into a popcorn machine

AmDWs6

P0650 Malfunction Indicator Lamp (MIL) Control Circuit Malfunction
P0118 Engine Coolant Temperature Circuit High Input
P0122 Throttle/Petal Position Sensor/Switch A Circuit Low Input
Now this is where your problem is at (in those 3 codes), some will pop up soon just keep driving it and you'll know which one's of those are left but my expectations are on the 122 and 650 ... no info on the 118 but might be wrong wiring just like the 102 same as for the 122

p650
Possible causes
- Harness or connectors for the MIL circuit is open or shorted
- MIL bulb may be faulty
- Faulty ECM
When is the code detected?
-An excessively high voltage is sent to ECM through the MIL circuit under the condition that calls for MIL light up.
-An excessively low voltage is sent to ECM through the MIL circuit under the condition that calls for MIL not to light up.

for the 122 check the voltage it's getting, when very low voltage is sent to the ecm it triggers the DTC
Possible causes
- Faulty throttle position sensor.
- Throttle position sensor harness is open or shorted
- Throttle position sensor circuit poor electrical connection
p118
Possible causes
- Low engine coolant level
- Faulty Engine Coolant Temperature (ECT) sensor
- Faulty engine coolant thermostat
- Engine Coolant Temperature (ECT) sensor harness is open or shorted
- Engine Coolant Temperature (ECT) sensor electrical circuit poor connection

DTC is triggered when An excessively high voltage from the sensor is sent to ECM

some good info found in a quick search that might help

gl

section8

LOL yeah it is pretty annoying, but it is a track only car so i don't care. No carpet inside too, so you hear every pebble thrown up by the tires.