ssheets

iTrader: (1)

Everytime my wife gets in my car I have a problem. It's been running perfect for a week and I used it to take my wife to her company's Christmas party. We didn't make it a few blocks away and I start getting high idle again. The the SES light comes on with one fault for the high idle and one for a bad O2 sensor. I can swap out the O2, but would that cause high idle in the 2-3k rpm range????

Also, I just took the cats back off yesterday and it drove great all day until last night. We deleted all of the rear O2 sensor codes so swapping then in our out shouldn't have drastic effects on the way the engine runs should it? I know it will change the back pressure and take away a little peak power, but it shouldn't have anything to do with idle speeds etc?

I'm going to swap the O2 sensoor and then plug off my Evap and PCV lines and see how it runs...although it only does this when I want to impress my wife with how well the car runs!

12secSS

iTrader: (30)

You need to get it scanned and see what it is doing. It could possibly be the idle settings (Follower and/or Cracker) that need attention.

ssheets

iTrader: (1)

I'm sooooo pissed off at this thing. I only have a Predator and can't scan the IAC counts, but I'm thinking that's the problem...follow me.

I've unplugged and capped every vacuum line on the mainfold except the brake booster and the little one that attaches right below the brake booster. I've checked these two and sprayed carb cleaner on the rear of the manifold and no signs of leaks. The small vecuum line on the rear I locked on with a tie wrap after I installed it to make sure it didn't come off. I can see it with a mirror and it is all still as it should be.

OK, so I can run with the three vacuum ports near the throttle body capped off. PCV, Evap and ?? It doens't change anything. The car will run alright and then start to idle at 2-3K rpm. I can get out, let it just idle away at 3,000rpm and spray carb cleaner, check everything on the engine and no signs of leaks.

I swapped back to the factory PCM with a predator tune and it runs great. I had to adjust the throttle body set screw a little, but the car runs great with the factory PCM. On the new PCM it will run great for 3-5 days and then start to idle high.

What else can I do to eliminate other potential causes? Do you think it may just be a bad PCM??

How can I test the vacuum or other inputs that may be the culprit???

Thorny

iTrader: (14)

If you move your TB set screw you need to reset your TPS. Your TPS reading the throttle open will add timing and give you a high idle. It may help to put some loctite on the set screw, it can move on it's own if you don't.

Can you pull your TPS voltage with the predator? If not, can you read the ignition timing in real time?

ssheets

iTrader: (1)

I can pull TPS% which is usually 0% when it suffers its high idle episode. Yes I can read the ignition timing in real time...what exactly should I look for?

I wish I would have known then what I know now...I would have bought EFI Live or HP tuners instead wasting my money on the Predator. It's a cool little tool for resetting DTC codes, but it's not a high res scanner and has no logging capability.

I'm setting the TB set screw by turning it just until it increases the idle that is being held by the IAC setting. Then I back it off 1/4 turn so it's still being held by the IAC, but it can't drop far below my where the IAC is holding it. I'm idling in the mid 900 RPM range.

Anybody know much about THESE Looks like I could run it on my laptop and log my data.

ssheets

iTrader: (1)

BTW, I put about 30 miles on it back with the stock (Predator tuned) PCM and it runs fine. Actually, it seem sto make more power with the facotry PCM. I dropped it into 3rd about 45mph, side stepped the clutch and made a nice burnout. I'd love to see how this thing runs at sea level.

I'm going for another drive right now for another 40-50 miles and I bet it drives fine on the old PCM. I just don't know if it's the PCM or if it's an input that has a greater effect on the other tune?

ssheets

iTrader: (1)

Well another 50 mile trip and it runs fine. It does hold the idle when your moving, but it always did that. I beleive all LS1s have that idle hold function...I know my other SS did it too. It is much more noticeable with a louder exhaust though.

I noticed that while coasting and the idl holds at just under 2,000 RPM the timing is about 35* advanced and will drop down to about 21* as it idles down to about 950rpm. This is with the factory PCM with the predator tuning. This seems to run pretty well and my LTFTs are betweem -.78 and +2 while cruising at 70mph in 5th just under 3,000 rpm.

Maybe I'll try the other PCM and watch the timing as it holds the idle up?