91 740 just won't run correctly

Bdubs · Post by **Bdubs** » 13 Jan 2009, 15:08

91 740 wagon, 200K miles, AT

Okay, so I'm back! No offense, but unfortunately, I might add.

Thanks to Billofdurham I replaced the kickdown cable successfully, and also cleaned the TB and adjusted the idle accordingly. Hoping this would cure the erratic idling/running of the car.

Well, unfortunately I have come full circle with this issue. It still runs terrible. I actually got the car to run decent enough so it doesn't idle like crazy, but it seems like it is only idling at ~900rpms, and won't die, but sounds as if it wants to.

In Park I can rev it up to 3krpms with no problems, it has excellent power. But, in any other gear, the car stumbles.
My garage is down a hill, so I go to take the car up the hill to the road, and once it hits about 3krpms, bang, it dies. As if it hits fuel cutoff. A CEL then comes on (there are no lights up until this point) a 1-2-1 and a 1-2-2. At first I thought it was the MAF temp sensor, but I got another one, and I have the same exact issues and same codes. Also, the car runs the same whether the harness is plugged in or not, is this a sign of a bad sensor?

I've replaced the fuel relay a couple months ago, but I have recently noticed the fuel gauge stuck on 1/4 of a tank no matter what (I know it is operational, it turns off when the car is off) So I'm wondering if the fuel sender or the pump is causing this issue?

I'm getting no fuel delivery codes, but could it be fooling the ECU thinking its an intake issue once it totally stalls?

I'm at a loss, the only thing I haven't touched is the fuel pump yet. That may be my next step, I just need some more guidance before I go buy something I may not even need once again.

Post by **billofdurham** » 13 Jan 2009, 15:19

Good to know you managed the kickdown cable.

I am wondering how you get a code 1-2-2 as I can't find it on the code lists. Can you confirm this one?

Bill.

Bdubs · Post by **Bdubs** » 13 Jan 2009, 15:39

Using port 2, on the Regina system it is defined as "Signal missing or faulty to/from air temperature sensor."

The car idling and revving in Park does not throw these codes. Only until the car dies do I receive these.

Post by **billofdurham** » 14 Jan 2009, 12:46

I was having a bad day that day and forgot about the Regina.

1-2-2 is Intake Air Temperature sensor signal missing or defective.

Possible causes are: A short circuit to earth (ground) in the cable, connectors or sensors.
Contact resistance in the terminals.
Poor earth (ground) for the signal earth.

Check all the earth contacts around the MAF and IAT and check the terminal contacts for corrosion/oxidization. Also, whilst you are busy at the plug test for voltage between terminal 1 and earth. Switch ignition on, disconnect the plug and connect a voltmeter between terminal 1 and earth. Reading should be approximately 5 volts.

: IAT plug.jpg (36.99 KiB) Viewed 303 times

I thought I'd better show which is terminal 1.

Bill.