Did a quick search. Didn't see anything that seemed to match what I'm experiencing, put could have overlooked it. If so, I apologize.

'89 L98 6-speed with 21K miles. Car has the common "cold start" issue, but has now developed an intermittent stalling problem.

To address the cold start issue, I:
- replaced the factory injectors with 22# Delphi units from FIC
- replaced the MAF sensor
- replaced the MAF power and burn-off relays (burn-off relay was replaced twice)

Also replaced the battery, as the effort to get the car started again after a stall had taken its toll and the battery was 6+ years old.

Only code I've ever been able to pull from the ECM is a "36" ("MAF sensor burn-off voltage was missing").

Can't seem to find a pattern with the stalling. Engine temp doesn't seem to be a factor. Sometimes occurs when I'm approaching a red light. Sometimes occurs when I'm sitting at that red light. Have occasionally noticed episodes where I'm cruising at 45-50 MPH and the car suddenly (and abruptly) slows down momentarily then resumes (like someone flipped an on/off switch). Idle is overall smooth except during these episodes.

Leaning towards replacing the fuel pump, but thought I'd throw this out here for the experts to chime in first.

Any help is greatly appreciated! Thank you in advance!

 

21K miles is scary....car just sitting too much ... alot of possibles...trash in fuel - change fuel filter shake it out to see if there is debris present. What is fuel pressure? Was car stored inside away from wire eating mice? Does car restart easily?

 

don't overlook the obvious. the IAC just might need to be replaced.

John

 

Will try a new fuel filter.

Haven't tested fuel pressure yet. Have read here about folks "taping a gauge to their windshield".

Car was never properly stored. Previous owner claims car was "used occasionally to go to the corner market for milk or bread."

Car does restart easily.

Considered the IAC, but figured the "episodes" I've experienced while at cruising speeds were related to the stalling, and that the IAC wouldn't be playing a part beyond idle. Again, I'm no expert.

 

Almost sounds like the ecm may not be receiving the correct vss signal. Can you scan the ecm while driving and confirm vss is present?

 

... which brings me to another issue. I purchased TunerPro RT and a "ALDL to USB" cable, thinking I could use the software to "see" what was going on in the ECM.

I have the software installed on my laptop. I have the cable plugged into the car's ALDL and a USB port on the laptop. And ... well ... now I'm clueless what to do next. If I understand correctly, I have to download a few files, including the proper mask(???) for my car's ECM.

Sure wish I could find TunerPro instructions written in layman's terms.

 

Download this software here:
http://www.ttspowersystems.com/DataM...ownloads2.html
You may make 20 logs for free.

Learn to use it here:
http://www.scotthansen.net/data.html
Post up if you need further assistance.

 

I'm getting closer with TunerPro. I went to the website and downloaded the $6E ADS (V4?) file, then imported it into TP which forced me to save it as an ADX (v5?) file.

But my computer isn't seeing the car. When I do the test (under tools/preferences), half of the time I get "CABLE FOUND AND FUNCTIONAL" and the other half of the time I get "CABLE NOT FOUND OR NOT FUNCTIONING (TESTED AT 8192 BAUD)".

 

Please tell me who you bought the cable from?

 

OBD Diagnostics, Inc.

http://www.aldlcable.com/sc/details.asp?item=aldlobd1u

 

Never heard of them, try Datamaster and see if it works. Tunerpro is very difficult to figure out.

 

You need a driver for the chip inside the cable that converts USB to serial data. See this web site (they make the chip):

http://www.ftdichip.com/index.html

 

If the VSS signal is not getting to the ECM it will set an error code 24.

I'm very familiar with that guy since I've been driving my car without the cluster.

 

I saw that driver topic in another thread, so I went ahead and tried it. It made no change.

One thing to note ... after I hit the "Acquire Data" button in TunerPro, I hear clicking noises coming from under the hood, and the fans will randomly turn on and off. That doesn't seem normal.

 

I download DataMaster and fired it up. It doesn't recognize the car either. And I saw the note where it said I had to have the jumper in place on the cable for the 10K resistor modification.

 

Now I've started getting a code "42" ("The EST signal did not change when the ECM applied bypass voltage to the ignition module").

Good grief! Have I fried something now!?

 

The ECM will store code 42 if you disconnect the EST connector to set the timing. That is next to the windshield wiper motor and has a tan wire with a black stripe.

Clear the codes and it should go away.

If it doesn't then you need to look at the distributor wiring and connectors. That would be the 4 wire harness that comes out of the back of the distributor (the EST connector is part of this harness). A bad ignition module could cause this, but that is unlikely.

 

You should see the FTDI driver in the Windows Device Manager under USB devices. I believe it only shows up if the cable is connected.