Rough Cold-Start Idle

[PonyCAR]

Hello,

My ride is a 01 Trans AM WS6 with 75k miles. It sits in the garage and gets started 1-2 times a month just to circulate some oil through the block. It was built in CAN and resides in AZ (Hot Weather). First owner.

The Problem:
In the passed 3 months, when I start the car, it struggles to hold a steady operating idle. It chokes for about a minute before exhibiting signs of a steady idle. Then, it struggles to hold the idle as if it is not getting enough air or fuel.

When I put it into Drive or Reverse, the rpm's drop really low as if the car is about to die (Has died once or twice). Almost feels like it has no torque to turn the rear wheels.

Now after the car has warmed up (10+mins), I can take it for a spin and drives fine. But, I am hesitant and reserved during the drive with this issue that is reoccurring.

My Troubleshooting Attempts

1. Driving the car
2. Adding ZMAX Engine Lub
3. Gas Treatment
4. Oil still looks/smells new

MODS

• DS Tune
• Cat-back
• SLP Airlid

I appreciate the help. Hopefully we can troubleshoot what's going on here.

[cammed goat]

I would check your IAC valve first. I assume your DS tune is speed density/MAF delete? You could possibly have a dirty/stuck IAC valve that is causing your issue. Start with the IAC and keep us posted if you have any other issues.

[pajeff02]

Carefully remove your lid and MAF and then using a suitable spray throttle body cleaner clean the throttle body. Liberally spray it with cleaner and then wipe it down with a lint free towel. You can use Q-tips to get into tight areas. Verify that your air filter is clean and while you have everything apart you may as well grab some CRC MAF cleaner and take care of that as well. Do not wipe down the MAP or touch the wires though. Just liberally spray it and let it dry.

If cleaning the throttle body does not remedy the issue, as posted, your Idle Air Control Valve (IAC) may be acting up. I take it that the SES light is not on?

[1998 T/A]

I would check fuel pressure first.

[pajeff02]

Agree -- usually if the fuel pressure is down the engine will crank a bit before starting. Although a fuel pressure issue is not likely to go away when the PCM goes into closed loop.

[1998 T/A]

I wouldn't say going into close loop as much as the fuel pump probably warms up and starts functioning properly...

[PonyCAR]

Hey Guys,

Thanks for the leads. I think it might be a vacuum leak somewhere or a bad sensor. How would I check the IAC/MF sensor?

[pajeff02]

Most faulty sensors will set a code. Did you check fuel pressure?

[PonyCAR]

Yeah, no codes show up unfortunately. I did, fuel pressure is good.