Rough idle with thrasher chips???

[sick GN]

I just fixed a couple of problems that were with my car. Replaced MAF, IAC, Fuel filter, and checked all Vacuum hoses. Well got everything all set and the car seems to run fine when I set everything with the stock chip, but when I put in a Thrasher 97 or the 108 the car starts to idle really rough (kinda like the IAC isn't plugged in) and wants to die out. Also sometimes when I rev it it slows down in rpm's slower than normal. What else could I check?? Thanks

 

[Ken Cunningham]

Are your MAF screens both still in? Even with only 1 screen removed, I found my car would not idle right with the Thrasher.

 

[sick GN]

Yes, both of the screens are in. I ran these chips before I changed this stuff and they worked fine but now when I put them in the car idles really rough.

 

[TurboDave]

Originally posted by sick GN
I just fixed a couple of problems that were with my car. Replaced MAF, IAC, Fuel filter, and checked all Vacuum hoses. Well got everything all set and the car seems to run fine when I set everything with the stock chip, but when I put in a Thrasher 97 or the 108 the car starts to idle really rough (kinda like the IAC isn't plugged in) and wants to die out. Also sometimes when I rev it it slows down in rpm's slower than normal. What else could I check?? Thanks

Since you changed your IAC, what are the IAC numbers at idle, warm in park?

 

[sick GN]

I lent my OTC to a friend and can't get ahold of him. So now I can't get any numbers off of the car. Is there any other way I can check this stuff??

 

[sick GN]

OK I switched the stock chip back and it ran fine. So I unplugged the computer and put the Thrasher 108 in it. Again it ran really rough, and when I would rev it it would stay revved for a sec or two after I let off. Also I decided to totally unplug the IAC while the car was running and it made no difference at all. The car didn't change a bit. What does this mean?? Thanks

 

[blackbuick87]

Wouldnt that be normal with the Thrasher's open loop idle?

 

[Scott231]

First of all,

Is this a correct MAF sensor for the LC2 motor?
Did you do the IAC reset procedure?
Did you set the static fuel pressure to 43.5-45psi?
Is there a catalytic converter on the car? If so, you need to remove it with the Thrasher chips.

Get that Scantool and give us some #s!

 

[Scott231]

Originally posted by blackbuick87
Wouldnt that be normal with the Thrasher's open loop idle?

Unplugging the IAC motor simply locks the pintle in place...and if the chip has already placed the IAC pintle where it wants it, unplugging the IAC isn't going to do anything.

Kinda sounds like you are in Limp Home mode. Is the Service Engine Soon lamp blinking? Check the diagnostics if it is. Code Five One would explain that the chip is bad (i.e. zapped).

 

[sick GN]

Yes it is the correct MAF sensor, same numbers, The fuel pressure is set at 44psi, I did the IAC reset procedure a ton of times. And there is no cat on my car. It doesn't seem like u can reset the IAC witht he Thrasher chips in the car so I set it with the stock chip and then switch over chips. And then it starts to idle rough. I don't think that it is in limp home mode cuz it really hauls A$$ when you get on it. It just has a rough idle at stop lights and stuff.

 

[tes87gn]

same problem

i just posted a thread myself i have the exact same problem car idles fine with old chip but idles like crap with thrasher chip but the car runs great at WOT with thrasher chip. if you come across any solutions let me know thanks

 

[Scott231]

Without thinking hard about this matter...you guys may want to clean your injectors and/or run a can of GM's Top Engine Cleaner through the motor to clean things up.

 

[TurboDave]

sick GN
tes87gn

Are you both running a check valve in place of the correct PCV by chance??

If you are, get the correct PCV in place and ditch the check valve.
When I was running Thrashers, and was dupped into getting a check valve in place of the PCV, I suffered the same fate. Car ran great, except the idle sucked (which is contrary to what the Thrasher should do).

Problem ended up being the check valve. You see, the PCV valve is a "metered" vacuum and the check valve is not metered correctly, so the engine sees a HUGE vacuum leak there, instead of the metered vacuum that is normal. My idle O2's were generally less than 100 mv

Dumped the stupid check valve and put in the proper 893 PCV valve and all went back to normal.

 

[tes87gn]

turbo dave your the man. i've got that valve and i've had problem since and didn't realize it until you said something. the problems you describe are idenical to mine. thanks dave you da' man

 

[sick GN]

Could a bad PCV valve cause this also??

 

[TurboDave]

Originally posted by sick GN
Could a bad PCV valve cause this also??

I suppose it's possible, but not very likely. A wrong PCV valve will however, definately cause it!

 

[granitestategn]

I'm working through a problem on my car, too. I've got a Thrasher 92 on mine. I've got the correct AC PCV valve and the Kirban's check valve. I can't see that harming anything. What do you guys think? I still need to gut my cat. Running stock exhaust. I'm going home to see if I can find any other problems with it while I'm at it. Running real rich at idle. I'm going to check out my MAF #'s also.

 

[Scott231]

Gregg,

GUT the cat and fix the header! End of story...

 

[granitestategn]

Scott,

Hosed the cat bolts down with PB Nutblaster last night. The cat comes off tonight. The bolts are really in bad shape. I will then procede to beat the guts out of it!

 

[Scott231]

The nuts are the easy part. Getting the cat to let loose of the downpipe is where you will have the most fun.

Hint: If a BFH doesn't work, use a cut-off wheel. Once gutted, have the sleeve welded back together/on. Much faster. (Experience talking.)