Idle problems on '87 Shelby CSX

[iTurbo]

I'm trying to track down idle problems on an '87 Shelby CSX. The car has the original stock drivetrain and original logic module. I have only added 2.5" FWDP exhaust (no cat and Dynomax Ultraflo muffler), ATP BOV, homemade grainger valve and McMaster-Carr vacuum distribution manifold.

The car had serious issues throwing a ton of codes and I ended up finding out it had the wrong logic module installed ('87 TI L-body). I swapped in the correct LM (from a Shelby Lancer) and that fixed most all of the issues I was having. At first the idle speed was way too high all of the time. I figured the AIS was bad, even though it wasn't giving a code for that. I swapped throttle bodies with another I had lying around and now the idle speed is way too low. It won't idle when it's cold; you have to give it a bit of throttle. It basically stalls out until the car is fully warmed up and even then it idles pretty low.

I did have a code 15 for the speed/distance sensor. I removed and tested the speed sensor using my OTC 4000E and verified there was no signal when turning it by hand with the key to 'on' and engine off. I replaced it with a known/tested good one and the low idle issue didn't change. Still no code for AIS either.

Another strange thing I have noticed is that while the O2 sensor 'works', I only see a maximum output of .48v. While I watch the O2 sensor output with the OTC at warm idle, it will bounce between .00 and .48 volts. It is enough for the OTC scanner show to cycle rich/lean. Even though I know it should get near 1.00v blipping the throttle, I still only see .48v max.

The PCV valve is strangely loud at idle. It is hooked up just like stock. As far as the other vacuum lines, I'm running a very simplified setup using vacuum distribution manifold on the back of the manifold with separate ports for MAP, FPR, BOV, granger valve, and the stock boost gauge. 99% sure I don't have any vacuum leaks going on here. I even zip tied all rubber lines so they wouldn't blow off at WOT.

Any ideas what to check next? I plan on replacing the O2 sensor with a new NTK unit I just got from Rock Auto, and also verify that the coolant temp sensor, incoming air temp sensor, and 'battery' temp sensor are all within a couple degrees of each other with the engine cold in the morning and using the OTC to verify.

[iTurbo]

I just went out and checked the temperatures on my '87 Shelby CSX with the OTC 4000E. I didn't drive it or even start the car today, so the engine is fully cold.

Actual outside temperature: 42'F
Charge temp sensor: 42'F
Battery temp: 42'F
Coolant temp: 41'F

So it looks like there is no problems with the temp sensors. Anybody have an idea on how to check the AIS motor? I'm thinking that if I remove the throttle body I should at least see some movement at the pintle when I turn the key to 'on'. Or I could plug in another AIS motor with the existing throttle body still connected, initiate a large vacuum leak with engine running (pull PCV hose), and see if it even tries to do anything?

Sure wish I could start the car and let it warm up out in the parking lot instead of having to manage the throttle myself while it's freezing outside!

[cordes]

Isn't there a test mode or some such you can do with the scanner to see the AIS function? I thought there was.

[ShelGame]

Which Shelby Lancer computer? There was an auto version (on 0078, I think). Maybe you have an auto LM?

[iTurbo]

Cordes - Thanks, I will give that a try. I knew there was some kind of test mode in the OTC scanner but I've never really tried to use it before. Mostly I just use it to check and erase codes, and set up the 8 line display for realtime viewing of sensors or knock retard. My OTC is starting to become a real PITA to use since the button pad is wearing out...going to have to get another one soon.

Shelgame - I will double check that. I'm 99% sure this LM came out of a manual equipped Shelby Lancer I had bought long ago and then parted out due to severe rust.

[iTurbo]

Which Shelby Lancer computer? There was an auto version (on 0078, I think). Maybe you have an auto LM?

Hi Rob, I looked at it today and the outside of the LM has a sticker that says "CS1" and "079". I removed the lid and the chip has a sticker with "079" hand written on it. Can you confirm the '079' is the manual trans '87 TII code?

I also got a new OTC 4000E setup on eBay. I got it with the "OTC Multi Tester", which is small auxiliary box that plugs into the 4000E along with it's own cartridge and allows you to test idle motors, O2 sensors, relays, and fuel injectors. With this hooked up to my '87 Shelby CSX, I was able to control the idle speed easily by using the buttons on the 4000E to manually extend or retract the AIS motor.

So now that I know my AIS motor works, I can only assume there must be a wiring issue between the LM and AIS. The two additional wires added by Shelby to control the 4-wire AIS seemed fine...guess I will have to get a multimeter with some long probe wires and test for continuity between LM and AIS for all four wires next.

[bgbmxer]

Have u set the base idle?

[iTurbo]

Have u set the base idle?

Not yet, although I have reviewed the procedure on minimopar.net. I've been hoping to correct everything else that is wrong before I resort to messing with the throttle stop screw. The throttle body on the car still has the concealment plug installed, so I'm pretty sure it's never been messed with.

Tomorrow it looks like I'll tackle the base idle "minimum air adjustment" procedure. I'm getting sick to death of this car idling so low and having to baby the throttle when it's cold 'til it warms up. When the car is cold, it won't even start unless you give it a bit of throttle, and even then you have to keep your foot on it just a tad to keep it alive. Major PITA when it's cold outside!

About the only other problem I've noticed the car has is the O2 sensor.....it 'works', but it doesn't output much voltage. It will go into O2 feedback no problem, but the maximum output it rather low. I have the boost controller set to about 14 psi right now, and at WOT I saw only .64v on the OTC. I kinda doubt it has anything to do with the low idle problem though, and I plan to change out the O2 sensor with a new NTK sensor soon. I also plan to check to see if there is fuel in the vacuum line going to the FPR (ruptured diaphragm?) and hook up a fuel pressure gauge to the schrader valve on the fuel rail to check fuel PSI at idle and WOT.

[bgbmxer]

Not yet, although I have reviewed the procedure on minimopar.net. I've been hoping to correct everything else that is wrong before I resort to messing with the throttle stop screw. The throttle body on the car still has the concealment plug installed, so I'm pretty sure it's never been messed with.

Tomorrow it looks like I'll tackle the base idle "minimum air adjustment" procedure. I'm getting sick to death of this car idling so low and having to baby the throttle when it's cold 'til it warms up. When the car is cold, it won't even start unless you give it a bit of throttle, and even then you have to keep your foot on it just a tad to keep it alive. Major PITA when it's cold outside!

About the only other problem I've noticed the car has is the O2 sensor.....it 'works', but it doesn't output much voltage. It will go into O2 feedback no problem, but the maximum output it rather low. I have the boost controller set to about 14 psi right now, and at WOT I saw only .64v on the OTC. I kinda doubt it has anything to do with the low idle problem though, and I plan to change out the O2 sensor with a new NTK sensor soon. I also plan to check to see if there is fuel in the vacuum line going to the FPR (ruptured diaphragm?) and hook up a fuel pressure gauge to the schrader valve on the fuel rail to check fuel PSI at idle and WOT.

Its a super simple procedure to do and I have found that the plug means absolutely nothing. No throttle body seems to stay the same . I had a car that wouldn't idle and it still had the plug in also and the idle was the problem.