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Tim Mohr
Category: Nissan
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When the truck starts the idle goes to around 1500 then

Customer Question

when the truck starts the idle goes to around 1500 then quickly setles down but fluctuates between 900 and 1200 rpm. Never settles down to a steady 800? No check engine light is on? THe t/body has been cleaned and the idle air motor seems to be good. could I have a vacuum leak?
JA: Does the light stay on, or does it blink?
Customer: The check engine light is not on at all
JA: What is the model/year of your Nissan?
Customer: 1997 D21 hardbody 4x4 pick up. 2.4L, 5 sped manual
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: yes. I have been o several forums and am seeing a lot of suggestions indicating vacuum leaks at or near egr valve. I want to get as much info as I can before tearing into it.
Submitted: 3 months ago.
Category: Nissan
Expert:  Jay replied 3 months ago.

Hello my name is ***** ***** thank you for your question.

If you remove the throttle cable from the throttle chamber, see if the idle settles and let me know..

Customer: replied 3 months ago.
No the idle stays the same. the cable actually has a little slack when connected
and setting on the stop that is on a cam that is controlled by a plunger.The plunger is extended.
when engine at operating temp.
Expert:  Jay replied 3 months ago.

the cable should have a little slack. That is normal. Did you try cleaning the throttle chamber? Did you replace a TPS or anything?

Customer: replied 3 months ago.
I bought the truck used, It was doing this when I got it. I cleaned the throttle. It looked like a used replacement, the idle air motor looks new. I had to put a t/stat in because it had been removed. The truck runs beautifully down the highway, doesn't use oil. I havn't checked or set timing yet. I don't know if the TPS was replaced or not.
Expert:  Jay replied 3 months ago.

Do you have a scanner to check TPS voltage with key ON?

Customer: replied 3 months ago.
I work at a shop I can use one
Expert:  Jay replied 3 months ago.

Perfect.. Let me know what the tps voltage is with key in the ON Position!

Customer: replied 3 months ago.
without engine running?
Expert:  Jay replied 3 months ago.


Customer: replied 3 months ago.
Problem with scanning. neither of our scanners will read or connect thru the 14 pin port.
I did pull 2 old memory codes thru the OBD II port: P0400 EGR and P0180 fuel temp sensor A
Cleared both and they have not returned.
Expert:  Jay replied 3 months ago.

You have to use the Gray diagnostic connector by the fuse box

Customer: replied 3 months ago.
I did notice the the plunger I had mentioned earlier does not move at all during the warm up stays in one position fully cold or at operating temp. It looks like it should move.
Customer: replied 3 months ago.
thank you
Expert:  Jay replied 3 months ago.

The IAC plunger?

Customer: replied 3 months ago.
Actually ,that is the one I hooked the diagnostic scanner to.
I only used the OBD port to pull codes with a code scanner tool.
Customer: replied 3 months ago.
I was using a snap-on Versus.
I am going to try our Matco Maximus 2.0 diag tool as soon as I find the 14 pin adapter.
It seems to work better on the older cars than the Versus
Customer: replied 3 months ago.
I think so. It points up from what looks like an eye shaped mount with 2 screws. It is right next to the passenger rear corner of throttle assy base plate
Customer: replied 3 months ago.
The maximus scanner is being used by one of the techs right now.
Expert:  Jay replied 3 months ago.


Customer: replied 3 months ago.
may have to pick back up on this on Tuesday, We are getting ready to close down for the weekend, your help is great!!!! While looking at the stuff you suggested I also foundthe vacuum hose that hooks from egr sensor to egr valve was completely rotted out and have replaced it.
Expert:  Jay replied 3 months ago.

ok, Let me know.

Customer: replied 3 months ago.
sorry about the delay, had to take a few days to rewire my house, blew a main circuit!!!
Expert:  Jay replied 3 months ago.

Got ya.. Hope you made out ok with the house.

So where are we at now with the car?

Customer: replied 3 months ago.
To check TPS voltage.
Expert:  Jay replied 3 months ago.

Ok.. So what is that TPS voltage with the key in the ON position?

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