94_LT1_TransAm

Hey, I have a 94 LT1 trans am that is stock except for headers and ls1 ram air air box with slp lid and it idles way too low after it warms up. When I start it in the morning before work it will idle fine above 600 to 750 but when it warms up it will idle around 400ish. Also when it is cold started in the mornings, I go to give it a quick throttle burst it acts like its getting too much gas and bogs itself down until it returns back to normal idle. I have replaced and cleaned and checked everything there is to think of on this car and it still idles low. New PCM, new MAF, new TPS, new O2, new opti, new plugs and wires, traded coils with another LT1 (that runs like a champ and idles correctly) for 30 minutes, cleaned iac, new air filter, even had it scanned by my brother who is a professional mechanic and the numbers all check out ok, open to closed loop. i noticed today that only half of the EGR was taken off, the solenoid and vacuum hoses are still attached. Any idea on what it could be causing this low idle??

hrcslam

Have you checked your water pump coolant sensor?

shbox

What readings do you get for IAC? Did you have some reason to replace the PCM, MAF, TPS? What brand opti did you put on it?

94_LT1_TransAm

Yeah the water pump sensor is new, hrcslam. The iac readings im not sure about but the pcm was bad when I bought the car and it wasn't reading an 8th cylinder so i got a new one and fixed that issue right away, the maf and the tps were both bad so when i bought new ones of those the throttle response greatly improved. As for the opti, I bought a new AC Delco one and the idle smoothed out but was still too low.

94_LT1_TransAm

Any other ways I can check why my idle is so low, until I can get the iac readings? When the car runs it sounds like it has a hotcam in it every so often, but it is the stock camshaft.

Supercharged111

iTrader: (1)

If the IAC is shut, the car would either stall or idle way low. It needs to be able to compensate in both directions. Car runs fine off idle?

94_LT1_TransAm

Yeah it will throw you in your seat once the car is rolling. it did stall once a while back but it never did stall after that. I've cleaned the iac once before to where it looked brand new, and the idle never changed.

hrcslam

I think you need a datalog.

94_LT1_TransAm

What does something like that cost? I've never done a datalog before anyway, so how do I read all the information the PCM gives me? Sorry lol, i've never done anything to a pcm except to get a new pcm flashed by a dealership.

hrcslam

Get an ALDL cable (you'll need the OBD1 style) to usb, $60. The programs to Data log are free, Scan9495 and $EE Hack are good ones to use. Add in Tuner Pro RT (also free) and you can tune too.

94_LT1_TransAm

Ok so its not expensive like I thought it would be. Can the datalog be live streamed like a Genesis or a GM TECH2 is? For example, when you hook the car up to the datalog can you see everything from open to closed loop change and throttle position etc,etc? sorry lol ive never used this kind of stuff....

hrcslam

Yup. You can also command things in real time depending on which program you use.

94_LT1_TransAm

Ok so I got my aldl cable in and it shows that my IAC upon warm up is at 0... But the minimum its supposed to be at, according to the PCM on the datalog, is 10 counts. When I checked the car on a cold start, the IAC was ok at around 30-50 counts. I even checked if it was a open or closed loop related problem with the datalog program override features and still no change in the IAC or idle after warm-up, any thoughts? I'm thinking vacuum leak possibly? BTW the minimum idle the PCM wants to be at in park is 550... That's a little low IMO, I can understand that low in drive but not park lol

hrcslam

Whats the idle rpm target?

94_LT1_TransAm

Its supposed to be stock at around 650-700 but the longer it idles on the datalog, the lower the idle target number gets. Strange huh?

kris72079

iTrader: (7)

I think you misunderstood hrcslams question...The PCM should have a idle target programmed in and that value does not change. It is the actual RPM target that the PCM is shooting to maintain at all times and it'll utilize the IAC valve (opening/closing) to maintain that target. If you are seeing 0 IAC counts and the idle is too low, that is where I'd start to look. The only time that you would expect to see 0 is if there is a problem with the idle being too high and the IAC is closing trying to bring it down. IAC should maintain a positive number to give room to open or close to maintain target. Also, what is target AFR?

94_LT1_TransAm

im pretty sure, since the pcm was flashed at a dealership, that the target idle is supposed to be what ever stock is. im not sure what the target afr is but i will do a datalog tonight after work and post it tonight if you guys would like? I use $EE hack to log.

hrcslam

What program are you using? Scan9495? If so, just under "Engine RPM Filt'd" will be "Target idle speed" what does that say? Also, if you can, pull the tune from your car and post it up along with the datalog in a zip file. I'll try and give it a look over when I get a chance (I work night's so it could take a while before I get to it), or someone else will look at it hopefully before I can.

If you are using Scan9495, with the engine running and the program hooked up and running, click on the blue "Actuators" button on the left of the program window. A new window will pop up, on the right side you'll see a bunch of "Idle=" Options. Pick one and see if the idle changes, I'd start with 800 and see what it does. You could've very well gotten a bad load from the dealership. If it's targeting 500RPM, it'll try and idle at 500.

If you are not using Scan9495, download and install Scan9495. This would be free and easy for me to help walk you through things.

94_LT1_TransAm

I have Scan9495 (freescan) and $EEHack, how do I get my pcm tune onto my laptop? I have TunerPro RT also but have no idea how to use it lol, I could only get $EEHack to actually record data unlike Scan9454. I did use the actuator tab in Scan9454 and it seemed like the engine was going to shake out of the car lol. Like I said before, I even switched between open and closed loops with no change in idle.

hrcslam

If EE Hack connected so will Scan9495. You need to tell Scan9495 what Com Port you are using. Also, Scan9495 is not freescan. Two different programs.

I'm not familiar with EE Hack enough to remember if it shows you idle target rpm or not without looking at it and I'm at work right now. Maybe Steveo will chime in.

To load a tune in EE Hack.... That's hard for me to explain step by step without looking at the program. Try PMing Steveo_.