# Dire Straits "High and surging idle"



## Eztiger12 (Feb 10, 2008)

2000 Nissan Pathfinder LE. 3.3L. 4x4, automatic, 109km. 

Problem started about a week ago after the truck stalled at a red light and service engine soon light went on. The truck did start up right away but was shifting gears at higher rpm's and idling high.

A couple of days latter I got the codes read but only remember the knock sensor P0325 amongst others I did not note down. The mechanic erased the codes and said he would read the codes again if the light would come back on. As you would guess it, the light did come back on and the knock sensor was the code on the scanner.

The light never came back on but no improvement on the condition, when the codes are read the knock sensor always appears.

At cold start the truck will rev as high as 3000 rpm and the transmission will shift at very high rpm. I also have to help the shifting by jerking the gas pedal so can shift sooner. Once the engine is warm it shifts a little better but still rough also the idle never goes below 1200 and surges up to 1600 while in park or neutral.

What I've done so far....

Removed and cleaned the throttle body and replaced the gasket.
Put a new air filter
Cleaned ground connection on the plenium
Cleaned battery connection.
Check connections on the TPS, MAF
Check coolant level
Attempt to find rhe knock sensor but to no avail

Would this be caused by the knock sensor alone? 
Is there any test I can perform to isolate the problem?
Has anyone ever encounted this problem?

I've never had a problem with the truck until about a week ago.........

I would really appreciate some feedback ...
Thanks for your time in advance......


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## NPath (Dec 12, 2004)

Eztiger12 said:


> At cold start the truck will rev as high as 3000 rpm and the transmission will shift at very high rpm. I also have to help the shifting by jerking the gas pedal so can shift sooner. Once the engine is warm it shifts a little better but still rough also the idle never goes below 1200 and surges up to 1600 while in park or neutral.


with this part here, it could be a broken or disconnected vacuum line. I've had a similar problem before. Other than that, I can't think of anything else.


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## Eztiger12 (Feb 10, 2008)

I've checked the vacuum line but quickly, looks fine. I'll do an in depth check on the line this weekend, but do you think that a vacuum leak in the line would cause all that behavior.


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## NPath (Dec 12, 2004)

Eztiger12 said:


> I've checked the vacuum line but quickly, looks fine. I'll do an in depth check on the line this weekend, but do you think that a vacuum leak in the line would cause all that behavior.


I had a broken line and it was idling at 1000 in gear at a complete stop. In "P" or "N" at a complete stop, it'd idle at 1600RPM. It wasn't disconnected, it was broken. Line was replaced for free and ran normally after that. 

Believe it or not, a really small problem that can be fixed in 5 minutes can turn into a headache. 

On a different topic, I had a carbureted 5.7L in my Jeep, failed emissions testing and turned out to be a disconnected line after working on the engine previously


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## Eztiger12 (Feb 10, 2008)

Well thanks a lot for the input NPath,

I sure hope I have the same problem, It would make me a happy man.

If anyone has any other input to offer it would be appreciated.


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## Eztiger12 (Feb 10, 2008)

Well as you can all see, I have not yet found the solution to my problem........It's a little less problematic when the out door temperature is warmer but on colder days it still behaves as mentioned on the opening thread........
Does anyone have any other ideas........
I bought a CTS sensor (Coolant temperature sensor) and will most probably be changing it this week end. Don't know if that will change anything.
Thanks


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## Eztiger12 (Feb 10, 2008)

Can anyone out there help..........It would really be appreciated......any suggestions


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## 88pathoffroad (Jun 6, 2004)

Knock sensor will not cause the problem described. It is under the intake in the middle of the engine block.

I'd look for leaks in the intake tract after the MAF sensor. Perhaps a hose clamp is loose or there is a crack in the rubber tubing underneath where you can't easily see it.


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## b67 (Apr 21, 2004)

88pathoffroad said:


> Knock sensor will not cause the problem described. It is under the intake in the middle of the engine block.
> 
> I'd look for leaks in the intake tract after the MAF sensor. Perhaps a hose clamp is loose or there is a crack in the rubber tubing underneath where you can't easily see it.


I second that, I had the intake hose come loose once and similar symptoms as you describe


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## Eztiger12 (Feb 10, 2008)

Hey Guy thanks to you both........88pathoffraod and B67...

Alright guys I'll check for a loose clamp.....but if one of you con clarify for me where the intake hose can be located....
I gather it will be very close to the intake.......

Thanks once again


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## b67 (Apr 21, 2004)

just start from the air box (where your air filter is) and work towards the engine. check all the clamps and hoses. if air is bypassing your MAF then your engine would run like you describe - since the ECU can't tell how much air the engine is getting.

If you don't find anything there check the vaccuum hoses.

If nothing there then I you should check the MAF impedence

I would not think the knock sensor would cause this problem

Just some ideas - are you getting any new codes after clearing them out?


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## Eztiger12 (Feb 10, 2008)

Thanks B67

I'll do what you suggested....I've done it a couple of times but I'll really take my time and check it out.
Just in case it's not clear....the idle does not fluctuate non stop but spuratic....
and cold starts are crazy high revving

No new codes come up and the light doesn't come on.....when codes are read the only thing that comes up is the knock sensor.

Would unplugging the MAF tell me if it's defective or not?
Is there a way of testing it?

When 88Pathoffraod mentions the "intake tract" I guess he's talking about the samething...from the air box to the throttle body...(right?)


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## b67 (Apr 21, 2004)

Is the check engine light on? If the ECU is getting a very low voltage signal from the MAF sensor The MIL should come on and the engine will go into fuel cut mode - you should not be able to rev more than 2400rpm

if the ecu is getting a high voltage from the MAF under light engine load then it gets more involved 

the spec on ecu pin 54 is 1-1.7v at idle and 1.7-2.4v at 2500RPM

I guess it would not hurt to disconnect the maf and see if the car behaves the same way or changes

it could also be a bad engine ground - loosen and tighten the main cable ground screws - (don't hurt to try)

see if you can get more codes


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## Eztiger12 (Feb 10, 2008)

B67 just to answer some of your questions...........
The service engine light is not on or flashing.

I don't think it's in the fuel cut mode, because it revs more than 2400rpm on cold start and while driving.

Concerning the engine ground that might be dirty or loose....is that the ground(s) found on the plenium?
If not, can you please indicate where it may be found.

I also bought a CTS (coolant temperature sensor) but I can't local it on the engine to replace it....do you have any idea where it might be found?


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## b67 (Apr 21, 2004)

The temp senso is almost right in the middle of you engine compartment. stand in front of the car with the hood open, look at the distributor, from the left edge it is a couple inches back - the resistance @ 20C should be between 2.1 to 2.9 K ohms & drops the hotter it gets

Check if you maf is 1 to 1.7 volts when the engine is warmed up

as for the gounds there are 2 connections to the left of the one where one of the (middle?) spark plug is - thay are coming from the bundle of wiring


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## b67 (Apr 21, 2004)

try to get some more codes if you can


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## Eztiger12 (Feb 10, 2008)

Thanks for the info "b67"

I located the CTS.......I'll probably change that tomorrow since I already have a new one.
I didn't get a chance to have more code read but should get that done at the beginning
of the week.

Meanwhile if you have any other suggestions I'm all ears.......................

Thanks


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## Eztiger12 (Feb 10, 2008)

Just an up date

B67...if your still out there.....or anyone else that can help....

I changed the CTS, 
checked for vacuum leaks but didn't find any...
Changed the air filter...
Cleaned the grounds again......
Checked the throttle body, still clean......
Cleaned MAF with compressed air.....and checked the connections..ok

On cold start, it still revvs high until it warms up (revvs higher then normal).....
Once warm, revvs at about 800 rpm in drive and 1000 in neutral.
When left idling ....it will sometimes (not often) fluctuate (goes up to about 1500 for a while and then back down) few seconds,

Even once the engine is warm, it will sometimes revv at 1500 in neutral and 1000 in drive.

The exterior temperature does have an influence on the trucks behavior......
Re check codes.....the only thing that comes up is the knock sensor.......

Do you think I need a more suffisticated machine to read my codes?....

I'm trying to avoid going to the Stealership if I could.....


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## Eztiger12 (Feb 10, 2008)

Is anyone willing to give it a shot......


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## Eztiger12 (Feb 10, 2008)

Tps replacement did the trick


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