Running lean in open loop, STOCK ECU

[snakeyes711]

man, I just had time to go through, and test all the engine sensors, they are all in spec?...Is there a way to test the CAS?

 

[Spoolin92GSX]

The only way I've found to test the operation of the CAS is with an oscilloscope and a dealer-only connector, otherwise it's trial and error swapping other units in and out. Sorry I didn't see your other post, I haven't used MMCd in quite a while so I'm not much help there. A bad CAS, though, should show up on a log as erratic engine speed jumps/spikes. The MAF reading definitely sounds out of whack though, the sensor or wiring may be bad/loose connections.

 

[snakeyes711]

Well I read it either works or it does not work. I also found that one of the pins reads 478ohms when testing continuity. Other then that, all the engine sensors had good checks.

Could someone check the same, and see if their CAS wiring harness side reads that similar resistance? also the only ECU Pinout picture I can find says pre 91. I want to check all the sensor wiring right at the ecu connector to the sensor connector. Somethings gotta give.

The thing that gets me is if a sensor was bad, or a connection, it would kick the CEL. Would it even with a broken wire?

 

[Spoolin92GSX]

Honestly the CEL is not much help in diagnosing a 1G, it only comes on for major emissions related failures (o2 sensor, EGR, spark misfires, etc). Have you checked VFAQ? I'm almost positive they have a full ECU pinout for every DSM ECU. The CAS could have an intermittent output issue, but the only way you would see that is with an oscilloscope like I mentioned earlier.

 

[snakeyes711]

Right on, Thanks for your help my friend. I'm just clueless at this point. Can you do me that favor? When you get time maybe unplug the TPS,a nd measure resistance? One came back like 7 ohms the other I had tested was 479 ohms. Thats a ways from being zero. This was on the harness side connector.

Thanks again.

 

[snakeyes711]

Nobody?

Yesterday I got a chance, and printed out the ECU pinout, and went through EVERY WIRE on the ecu to its corresponding sensor.....All tested good............................................

 

[Spoolin92GSX]

If you're measuring resistance on the harness plug, that's just going to give you resistance through the ECU. For the TPS you need to measure resistance at closed and full throttle positions, on the sensor pins themselves. As far as the CAS, though, there is no resistance test that I'm aware of aside from making sure the sensor itself isn't shorted out or open circuited somehow.

 

[snakeyes711]

damn long time, I still have this problem. I tested the TPS as said. So I'm about to just get a CAS and swap it out just to see.

 

[92tsifwd]

I am having the same problem on my car and mine just started random misfire when cruising on my 90 Talon. I have swaped out everything but the cas. Mine is going so lean that it closes the gaps on the # 1 and #2 spark plugs. It is fine until I under wot and about 5500 it breaks up and the exhaust tone changes and the wideband goes lean to 12.0.1 and sometimes it will close the gaps on the plugs and show damage oon the base of the plug confirming it is lean. I am trying to find out how to wire in a 91 cas on a 90. Here is the link of my thread.http://www.dsmtuners.com/forums/tuning-engine-management/466019-running-lean-under-boost.html