Hey guys, I have an '87 that ran great. Drove the car 100 miles round trip on xmas. Got stuck in stop and go traffic for an hour but the car ran great the whole trip - perfect idle. Started the car a few days later, it started up immediately, then began searching for idle. Surging and then dying. The car starts immediately every time but if I don't have my foot on the gas, it'll search for idle and then die. I tried the WD-40 trick on the ISV (ISV was replaced about 12 years ago). Took off the MAF and sprayed it with CRC MAF cleaner. While the MAF was out, I ran a 1/4" tube to the ISV and sprayed WD-40 in and blew it toward the ISV. I reinstalled everything and same problem. What should I try next?

 

Has the MAF ever been rebuilt? Does it idle steady with the MAF disconnected?

Mike

 

As far as I know the MAF is original but I was surprised when I took it out that it was as clean as it was compared to pics of others I've seen. I'll try running the car with it disconnected tomorrow. Should I just start it and let it idle with the MAF disconnected or try and drive the car a short distance with the MAF disconnected? How should it run with the MAF disconnected? Thanks.

 

Remember that the MAF base settings only control the fuel mixture for the first minute or so. At that point, the O2 sensor takes over and modifies the MAF signal with the O2 sensor's correction factor.

If your problem only lasts for the first minute and then is normal, you need to consider that the MAF can be defective, the engine could have an intake leak, the idle stabilizer may not be working, you are getting improper information from Temperature Sender 2, etc.

If the surge continues after a couple of minutes, you need to take a look at the voltage output from the O2 sender (when hooked up to the brain) to see what the O2 sensor is actually telling the brain to do, once the O2 sensor is warmed up.

 

The idle problem lasts for more than a few minutes. I drove the car around the neighborhood repeatedly for at least 15 minutes and the idle problem continued. So we can rule out a bad MAF? That's good. I'll look into the O2 sensor.

 

could also be faulty TB idle switch.

 

Check the Temp II sensor. I had same symptoms and did same operations as you described. ISV was partial culprit but WD-40 made things better or at least I wanted to think it did. Idle was totally fixed with new Temp II sensor.

 

Hey Dave, do you have the part number for the TB idle switch? Thanks.

 

I was just about to order a new Temp II sensor and I hope that's the problem since it's an easy cheap fix. Fingers crossed!

 

TPS is not a trifle swap out on the S4 it usually requires intake removal.
so testing the switch at the computer connectors is the way to go,
NOTE test for the idle and WOT setting function.

also make sure the click can be heard just as the cable begins moving the throttle plate

 

Yes, I can hear the click just as the cable begins moving the throttle plate. Thanks for the tips. I'll try and do the easy checks first and work my way up.

 

Got my Temp II sensor today. What is the torque value I should install it with?

 

9 ft lbs.

 

Thanks Steve!

 

Just an update: No change in the car but haven't had any time to do anything to it since I changed the temp II sensor a few weeks ago. I'd like to swap out the brain to see if that's the problem before digging any deeper into it. Not really sure what I'm going to do. I don't have the room or time to do any major repairs on it right now.