On my way to work yesterday the rpm's started to bounce a few blocks from home. From 800 to1200 without me pushing the pedal, then it stalled. The SES light came on, but no codes were thrown. I restarted and it was fine after that, and again coming home.

I don't think it is the CPA as I have battled that and it never acted like this.

What do you guys think? Maybe the idle air control valve sticking

 

I'd certainly check the IAC as they can get pretty nasty.

 

No codes at all? How soon after starting up did this flame-out occur? I ask because I've seen two different causes on other German and Swedish cars with Bosch Motronic that resulted in behavior like this:

1. The battery may be tired, and the voltage droops after starting the car. This resulted in my Saab and my BMW having rough running for up to a minute after starting, but the rough running started about two minutes after startup. I diagnosed this problem with a battery tester. Voltage was dropping below 9V, and the Motronic was browning out, losing its mind. I had a similar problem like this on an old Contour, but it recorded lots of codes and made the problem a snap to diagnose a bad battery.

2. After high revs during acceleration, a worn fuel pump in my BMW couldn't feed the injectors so just as I reached highway speed the car would run very rough until the fuel pump gradually rebuilt fuel pressure, and the fuel pressure regulators (two of them on my V-12) closed with higher vacuum. Since this car was before the age of OBD, I had to rig up a pressure gauge on one of the fuel rails and watch as I did full-throttle acceleration. Our Discos should throw codes in this case that should make it obvious of the fuel pumps aren't generating enough pressure.

Anyway, those are a couple of testable hypotheses, and maybe my ideas will inspire some things for you to check that I didn't think of. Good luck.

Scott

 

my Idle Air Control Module started causing that soon after I bought mine; I ordered a new one. When I went to replace it I found out that the lock tabs on the plug were broken and it had vibrated free from the connector. Plugged it back in tight and it stopped.

so now I have a spare for future issues....

hope that information helps.

Doc

 

Thanks guys. It did throw a P1834 Code which is a transmission fault.

I cleaned up the battery terminals took a small test drive and so far so good. Will test again tomorrow.

 

RPM's bounced a little today when it was cold. Did not stall. Once warm it ran perfectly fine.

A little puzzled.

 

From my experience the only time I had the engine rev up for no apparent reason in traffic (luckily I had my foot on the brake) was due to a bad new Duralast Cpk sensor. I really couldn't explain why the engine reved up. The Cpk sensor was the only part I had changed on my engine after the older Cpk died and left me stranded in Atlanta traffic.
I returned the new Cpk back to Auto Zone, got a Bosch from online, installed it and no more surges. Weird...

 

I am going to charge the battery this weekend, and if that doesn't solve it I will likely order a new CPS. I leak oil back there and it could be fouling it.