Tuning tweaking and swapping PCMs

[ssheets]

This is driving me nuts!

After my H/C swap I left the factory PCM in to get things running. Once things seemed OK, we swapped in a programmed PCM and it seemed to run better, but when trying to drive it the engine started to fast idle first at 2k, then 3 and then onward so I shut it off, tried a few times and it kept doing the same thing. It would start and idle fine, but as soon as you started driving it would just idle away. 0% TPS, 8-15% engine load and 3-4k RPM!!!

I swapped back to the stock PCM and then modified the Diablo performance tune and never had a similar problem, actually no problems on the factory PCM with the Diablo tune other than not wanting to idle on a hot start and I'm sure it could be tuned better.

I swapped the programmed PCM back in and it seemed to run great. No sign of the gremlin until yesterday. It came and then it went. Tonight it came back again with a vengence. I turned down the highway and leaned on it hard while it was doing this and it just laid down and then backfired. I turned for home and it kept trying to idle above 3k!!

I put the factory PCM back in and went for a drive...a hard drive. It runs great. O2 readings are in the +8 at 2800rpm on cruise in 5th gear, but both banks are reading 8.25 exactly. The other PCM gave me readings of +6.24.

To me, it sounds like there may be a hardware issue with the PCM. I don't think it has anything to do with the tune as it is too extreme and random. Tuning would be a consistent difference like the 6.24 reading versus the 8.25 readings.

All of the connectors have been checked, cleaned and greased with dielectric grease. The car is dry (it's never been in rain in its life) and the air is cold, but no no water, snow etc.

Any ideas?

BTW, it's a Wait4me PCM and when this first happened Jesse said he'd send me a new one, but I elected to give it another try which looked like it was going to work until last night. I'll call him Monday, but I'm curious as to what anyone else thinks about it?

One last thing, do O2 readings mean anything under acceleration and deceleration like in traffic and around town? When I log them under constant load (2,800 @10% engine load) I get almost identical readings on the two banks. Driving in traffic on and off the gas sometimes one is way high while the other is real low. They always even out under constant load though???

Here's a cold start and idle http://s238.photobucket.com/albums/ff28 ... art18F.flv

And this is full of pictures of the project.
http://s238.photobucket.com/albums/ff28 ... tor=bottom

[mikel]

I would suggest you contact Jesse before going any further....those guys really know their stuff.

Thanks

[ssheets]

I would suggest you contact Jesse before going any further....those guys really know their stuff.

Thanks

Yep, I think he's go tme on the right track!

[ssheets]

Well I've been running Jesse's tuned PCM all day and with the throttlebody bolted up to the manifold id runs great. Now I can focus on the fine details.

I'm idling at ~970 when standing still. Once the car is rolling it will idle (if I take it out of gear and let it settle) 1180. It will stay at about 1180 until I come to a complete stop. Once stopped it takes about 5-10 seconds and then it will drop back to 970.

Does this sound right or should I talk to Jesse about tuning this more?

I need to get some current LTFTs to. It may be a fe days before I drive it long enough to get a good hot LTFT run though.

Also, if I restore my factory PCM back to the factory program and then swap back to teh tuned PCM (I beleive they have the same VIN) can I use my predator to tweak Jesse's tune? I.E. I think I can drop the idle down 100rpm, but I hate mailing the PCM back in forth for such details.