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Higher idle problem

Ama83

Ama83

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Location
Southern Finland
I noticed today that sometimes when driving, then stopping and let engine idle rpm´s are at 700-750 and normally 650. This might cause also engine lose some power when this happens and continue driving. Where is problem?
 
Can you explain the actual issue, is it that you want it to stay near 650 all the time, or its low power when its at 650, or is the issue with the higher idle with low power?

Is the SES light on?

If you can look at scanner data I would suggest the CTS on the t-stat x-over could be bad, flucuating between cold idle and cold advance and normal.

You put OPS deleted in your signature, did you mean you did the OPS relay mod or put the LP on ignition power, and how did you wire that?
 
buddy said:
Can you explain the actual issue, is it that you want it to stay near 650 all the time, or its low power when its at 650, or is the issue with the higher idle with low power?

Is the SES light on?

If you can look at scanner data I would suggest the CTS on the t-stat x-over could be bad, flucuating between cold idle and cold advance and normal.

You put OPS deleted in your signature, did you mean you did the OPS relay mod or put the LP on ignition power, and how did you wire that?
Click to expand...

But temp gauge seems normal? Could that still be bad?
LP is at ign power
 
Ama83 said:
But temp gauge seems normal? Could that still be bad?
LP is at ign power
Click to expand...

The temp gauge works off of the ECT sender in the drivers side head, PCM works off the CTS in the t-stat x-over. Unplug it and see how the truck runs, should go to higher cold idle. One way to test it is put a resistor across the engine harness instead of plugging it into the CTS. A 300 ohm resistor should make it think the truck is about 180 degrees and if idle issues go away the CTS was bad.


And you still have the OPS right? Since it feeds the oil pressure gauge. Did you run the LP off ignition power or use a relay to feed it battery power when the ignition is on?
 
buddy said:
The temp gauge works off of the ECT sender in the drivers side head, PCM works off the CTS in the t-stat x-over. Unplug it and see how the truck runs, should go to higher cold idle. One way to test it is put a resistor across the engine harness instead of plugging it into the CTS. A 300 ohm resistor should make it think the truck is about 180 degrees and if idle issues go away the CTS was bad.


And you still have the OPS right? Since it feeds the oil pressure gauge. Did you run the LP off ignition power or use a relay to feed it battery power when the ignition is on?
Click to expand...

Could you find one from Ebay for me, I´m not sure how it looks like?
Yes I have OPS. And I´m really not 100 sure how it´s done, actually my mechanic did the mod same time that we did head job. It has one wire cut and connected to another (from OPS I think) near fuel filter housing.
And SES light is not on, I forgot to write that before :)
 
Last edited:
It still idles after cold start 700-750rpm when engine is warmed up, but only after cold start. When started with warm engine it´s 650, what causes this? Few days it has been ok, no noticeable powerloss as before. Not yet afterall... :D
 
The engine is supposed to idle higher when cold, to warm it up. Are you saying even after driving a while it still idles at 750rpm? Is this with a stock PCM?

What resistance do you have your adjustable FSD resistor set to? And you did remove the internal PMD resistor right?
 
buddy said:
The engine is supposed to idle higher when cold, to warm it up. Are you saying even after driving a while it still idles at 750rpm? Is this with a stock PCM?

What resistance do you have your adjustable FSD resistor set to? And you did remove the internal PMD resistor right?
Click to expand...

Yes, after engine has warmed up it still keeps rpm´s around 750, BUT only when started cold and driven warm. When starting warm eng and driving it´s ok. Before I changed temp sensor it did that same thing any time, not depending anything temp, cold or not start etc. Now or at least for now on it has been just when starting cold and driving it hot.

Res is 82000ohm as #9 should be 79800-81400ohm, couldn´t find anywhere 80000ohm res :/ And ofcourse original res is off :)
 
Whats the temperature there like? And what temperature is the coolant running? Perhaps the Intake Air Temperature sensor is registering cold temps.

The scanner info would be very helpful, I would get an ALDL cable as soon as you can, and then there is a free data software called GMTDScan from Engh Motors, over there in Europe.
 
buddy said:
Whats the temperature there like? And what temperature is the coolant running? Perhaps the Intake Air Temperature sensor is registering cold temps.

The scanner info would be very helpful, I would get an ALDL cable as soon as you can, and then there is a free data software called GMTDScan from Engh Motors, over there in Europe.
Click to expand...

Temperature has been from -15*C to +5*C lately. Coolant temp has been below 210*F. Haven´t set the codes yet for cold intake temp.
I´m going to buy cable and software, but I´m now unemployed so money is the trouble... :(
 
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