940 Wagon, 8V engine, auto trans

Car will start without trouble, but hesitate at low RPMs (less then 2200) under load. It will generally idle fine, but does stumble a little at times. After about 5 minutes, the car runs fine. Also, it only seems to occur the first time it is started in the morning. It runs fine when started after work.

I have cleaned the throttle body and the IAV. I found a vacuum hose with a crack in it and did a temp fix on that (the hose comes from something just behind the driver side front light, near the battery, not sure what the device is). Also tried starting with the AMM disconnected to see if that was potentially defective and it ran terrible, so the AMM should be OK.

The problem seems to be getting a little worse over time, with some hesitation at higher RPMs and for a little longer in the morning.

The next thing I think I need to check is the temp sensor and maybe the knock sensor. Is there anything else anyone could suggest? I am leaning torward a sensor issue since it is not a persistent problem, only in the morning. I would assume if it was fuel pressure related, it wouldn't disappear after a few minutes. Also the fuel pump and relay are about 1 year old.

Thanks in advance.

Seems to have been a loose connection somewhere, probably the RPM sensor. I checked the codes and got the RPM sensor code (don't know how I missed it last time I checked) and the AMM sensor code (I think this is from the time I disconnected the AMM to see how the car would run).

The temp sensor connection looked fine, but I did disconnect and reconnect to ensure it fit snugly. The RPM sensor connections were also snugged up. I then snugged up all other connections under the hood just to make sure.

Car started up fine this morning with no signs of any problems. Hopefully it was just a loose connection somewhere and it will be behind me. The RPM sensor is only about a year old, so I hope it has not gone bad this quickly.

Thanks for your help and suggestions.

I had a similar problem with a 92 turbo. I believe it was caused by a poor connection at the EFI temp sensor. That sensor is under the intake just past midway toward the firewall. I removed the connector (a tight fit), took the spring clip off and squirted some contact cleaner on the connector. I cleaned it by plugging it in and removing it about twenty times. It seems to have taken care of the problem. If this helps, I would suggest that you clean all your EFI connectors the same way.

I usually put a drop of tuneup grease on the connectors to keep the corrosion down. The FAQ has a pretty good write-up. Do not use the tuneup grease on the O2 sensor, the voltage is too low and the grease will interfere with the signal.

My symptoms were poor running for the first minute and then everything was fine.

I would also suggest checking for diagnostic codes.

Good luck!

The first thing I would check are plug wires and distributor cap. When is the last time they were replaced?

The second thing I would check are the electrical connectors on the fuel injectors (disconnect them and look for corrosion - both inside the connector and on the fuel injector terminals).

I would also look at the wire harness on the crank position sensor, if the insulation is shredding or badly cracked, get another one.

Have you checked for trouble codes? http://www.brickboard.com/FAQ/700-900/EngineOBDCodes.htm

Good luck!

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Matt L. -- Cary, NC -- '91 740 wagon