OIL causing high idle?

[suprasick]

My idle is most of the time at 800rpm when fully warm. Every once and awhile I will see it drop to the 650rpm I am looking for.

From my understanding the following signals effect idle: NE, IDL, SPD, THW, NSW, STA, A/C, ELS (DEF & LP)

I remember looking at a post from JJ or 3p regarding OIL but cant remember if he said it had anything to do with idle.


I took a voltage reading from the ECU and all of the above that I can measure with voltage and resistance was within spec. I did not see in the TSRM anything about proper voltage or resistance for OIL.

My readings:

OIL probed at the ecu showed 13 Volts @idle. When I accelerated it showed a linear relationship 13v to 11v to 9v etc down to 6 volts. My understanding was that the ECU only saw ON/OFF? Hence the name oil pressure switch? Though the gauge on the dash reads fine. (5ish PSI @idle up to 40PSI @3K)

I also thought maybe the wires to NE were degrading but a resistance check shows NE to G- @180 (within spec of 180)

THW also when warm is .28v

ISC clicks when car is turned off




Is there anything I'm missing here? (obviously there is ha!)

Mods: 87 GE->GTE with all GTE Electronics KNK1&2 Rewire with sheilded cable and grounded @ecu side

NO piggybacks ALL stock TCCS




Thanks for your help my wife thinks I'm crazy that 150 rpm would bug me this much!


I do have these plugs at the ECU not sure if there relevant I just thought they were ABS or TEMS

 

[CyFi6]

I believe the oil pressure reading does have an impact on idle speed albeit very little. The oil pressure sensor puts out a frequency signal so you will want to measure it in hertz. You can also use a test light to verify the sensors operation, but since your gauge is working it seems unlikely that it is the problem. Someone else will have to give you an idea of an acceptable range I am not quite sure.
Have you checked all your throttle body adjustments including the TPS, stop screws and dashpot settings?
Do you have an automatic or manual transmission? I assume you have checked and have no stored codes.

 

[3p141592654]

The logic in the ECU raises the idle speed 100 rpm to 750rpm if OILP is low. On my car, I have datalogged it and it never triggers, even when the engine if off, so its a bit of a mystery to me. On the bench, I can definitely get it to trigger by making the OILP input low or high, but on the car its a different matter it seems. A bit more info to be found here....

http://www.supramania.com/forums/sh...bly-Analysis&p=1903522&viewfull=1#post1903522

 

[suprasick]

Have you checked all your throttle body adjustments including the TPS, stop screws and dashpot settings?
Do you have an automatic or manual transmission? I assume you have checked and have no stored codes.

Yes on throttle body adjustments, TPS and dashpot all set to TSRM specs. Car has a W58. And only code is 34 for fuel cut

The logic in the ECU raises the idle speed 100 rpm to 750rpm if OILP is low. On my car, I have datalogged it and it never triggers, even when the engine if off, so its a bit of a mystery to me. On the bench, I can definitely get it to trigger by making the OILP input low or high, but on the car its a different matter it seems. A bit more info to be found here....

http://www.supramania.com/forums/sh...bly-Analysis&p=1903522&viewfull=1#post1903522

After reading that post, would you mind to elaborate on "high average load over the current drive cycle" and how I would go about testing? (if possible)


Here is a video of OIL hooked up to HZ. Notice rpm at idle and how long it takes for the signal to resume. Is this normal?

[video=youtube;IEmoJ1eEk4s]https://www.youtube.com/watch?v=IEmoJ1eEk4s&feature=youtu.be[/video]

Thanks again for all your help.

 

[3p141592654]

The ECU computes a number that is incremented when VE>30% and rpm>2500 and decremented otherwise every 64ms. If the number exceeds 55040 then a high average load condition is flagged. Higher rpms cause it to go up faster.

For example, high load is continuous VE>30% and rpm> 2500 for about 7.4 minutes, or VE>30% and rpm> 4000 for 3.7min, or VE>30% and rpm> 6000 for 1.5min.

This number is remembered over drive cycles. It takes about 14 minutes of low load driving to reset the counter to 0.