LS6 idling high

[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. I've pulled the intake manifold off, replaced all the gaskets, cleaned the MAF, swapped the IAC and TPS with a neighbor's car parts. After the new gaskets and MAF cleaning, the car settled down and has been running great unless the battery was disconnected for a long time, then I just had to reset the TPS/IAC when i hooked the battery back up

I then realized the car wasn't charging the battery 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? I'm really getting to my wit's end here.

[garys 68]

Any other possible intake leaks? How's your PCV hooked up. Is the TB clean?

[Section8]

I can't find any other intake leaks, the TB is clean, it has fresh intank manifold gaskets.

I put a new MAF on the car tonight, battery has been disconnected for two days, so I hooked it up, did a TPS reset, fired it up and it immediately fires up to a 3k rpm idle, then will climb from there if you let it sit.

If i disconnect the MAF it doesn't even start - which I thought it should do, just not run exactly well.

I cleared the codes and it is still throwing the MAF code too.

I'm about to burn this thing to the ground I am so fed up at this point, been fighting with this for way too long.

[Section8]

I'd have to get a pic of the PCV routing, but I've checked that via a standard LS6 PCV diagram and it is connected properly I believe.

[garys 68]

Do you have the capability to read the sensor values? With all those codes, sounds like a wiring problem. Did the engine ever run correctly or is this the first startup?

[Section8]

all i have to plug in is this diablo sport duramax tuner which will read the OBD2 codes and some live data. It has run properly before, but not what I would call consistently.

[garys 68]

With the temp sensor code, that should be easy to determine if it's reading or not. Try unplugging the temp sensor and see if it changes.
You also might want to post over at LS1tech conversion board.

[Section8]

Thanks man, I will try that too. Yeah I have a thread over at LS1 tech as well, and on the norotors v8 rx7 swap forum - casting as wide a net as I can on this.

[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:

http://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?

[garys 68]

The 98 harness and ecu was the red headed stepchild of LS motors. You might want to recheck youor ecu, harness, and sensors for compatibility.

[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.

[sjaroslo]

Congrats!

[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.

[Section8]

Started the car with intake off to observe the IAC in action. Well it isn't in action. Plugged the hole with my finger and car idles normally.

I started the car and watched the IAC - it stayed open, didn't move at all. Putting my finger in causes the car to drop to approximate normal idle.

I double checked the pinout on the plug since I have a custom made harness, and they look correct according to the PCM pinout here:
http://www.ls2.com/boggs/torques/2002pcm.htm

I then tested the wires for voltage with key on, engine off. I get 10v on pin A, but nothing on the other pins.
I tested the IAC for resistance and i get 45ohms resistance on coil A and B. I can't find specs on the IAC to determine if those are correct or not.

Before I go out and buy a new IAC, is there anything else I should look at?