# 97 Nissan Pickup 2wd A/T Idle issues



## cacostar (Dec 5, 2005)

Hope you guys can help. So i been trying to chase this problem of High idle (1500 in Park) and then after a few minutes it will go down to 800-900 and stumble for a minute or two and then back up to 1500. So I installed a new IAC valve which made it worst so installed the old one back on. I check the TPS and adjusted it by the NTB99-053b and still the same. I check the EGR and it seems fine. The truck runs like a bat out of hell great other than the idle. I check all the vacuum lines and even sprayed WD40 around the TBI base and intake no vacuum leaks. I also do not get any codes at all. 

About a year ago I installed a new MAF which I got from Courtesy Nissan so it original Nissan, Converter, and both Oxygen sensors. 

So I am kind of stump here any suggestions would be great.

Thanks

Chris


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## otto888man (Dec 30, 2013)

Does it only idle high when its cold? Does it do it all the time?


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## cacostar (Dec 5, 2005)

It does it all the time.


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## otto888man (Dec 30, 2013)

Was anything done before this happened? Is there any coolant lines going to the throttle body? If so, check it if its plugged up or corroded.


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## fsglover (Jan 14, 2011)

I had a similar problem with my 93. changed some parts with no helping. I started moving stuff around will it was running (wires, hoses, etc. ) and found that the fuel injector wire bundle that comes around the back of the valve cover must of had a short or something. I moved it over the engine pull out location hook and zip tied it up. Never had problem again.


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## cacostar (Dec 5, 2005)

Thanks I did that also, I am thinking that the EGR valve is not completely sealing. If I put vacuum on it will hold it also stall the truck out. I may try to use propane to see if I have a vacuum leak even though it runs great. I also thought about pulling those allen plugs and clean the EGR passages. 

Thanks

Chris


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## otto888man (Dec 30, 2013)

Try this completely seal out the EGR ports & then start the engine see if it gives you a rough idle or it smoothes out. Let me know how it turned out.


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## cacostar (Dec 5, 2005)

What is good to use for finding a vacuum leak? Carb cleaner or propane? Also is it possible for the EGR valve to not seat all the way close? If so how can I check that? I did use a hand pump and applied vacuum to EGR and truck stalled out, it also held vacuum leading me to believe the EGR is OK. Can a MAF sensor do this also?

Thank You


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## rogoman (Dec 16, 2004)

cacostar said:


> What is good to use for finding a vacuum leak? Carb cleaner or propane? Also is it possible for the EGR valve to not seat all the way close? If so how can I check that? I did use a hand pump and applied vacuum to EGR and truck stalled out, it also held vacuum leading me to believe the EGR is OK.


The best way to check the intake system for a vacuum leak, is to attach a vacuum gauge to a full vacuum source. With the engine fully warmed up, the reading at idle should be 18 - 20 InHg. At 3,000 RPM, it should be around 21 InHg.

If readings are under 18 InHg, check the intake manifold nuts to make sure they are tight. The gasket may have failed; spray a water mist at the gasket to see if the gauge reading changes. Also check the intake plenum bellows at the throttle valve and at the MAF for cracks or loose clamps.


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## cacostar (Dec 5, 2005)

Ok I will try that out.

Thanks


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## cacostar (Dec 5, 2005)

Well I decide to do the check of the FIC (Fast Idle Cam)Inspection and Adjustment and it was way off. So I adjusted till the A/T mark was center with the roll pin. Then started truck and warmed up and adjusted the lever roller and top of FIC to 0.83 for Automatic. It now idles down still stumbles after a few minutes. I know i did mess with idel stop screw which your not suppose to mess with. How do I set it back? Should I adjust it to when it just start opening the throttle valve? Also should I do the TPS again.

Thanks


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## cacostar (Dec 5, 2005)

Ok hook up vacuum gauge. When it idles and its good it reads 19 at 1000 rpm when it starts erratic idle it drops down to 15. If I hold to 2500 rpm it reads 20. So took it for drive at 55 mph when it good it reads 20, but when it starts to stumble it goes to 15. The needle seems to move smooth. It feels like when a carburetor is way out of adjustment. It runs great when you are on the gas it just when you try to maintain the speed it is good for a while and then starts to stumble and I can see the vacuum gauge go from 20 down to 13-15. Any ideas?


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## cacostar (Dec 5, 2005)

Well *Fixed* the Truck today!! I replaced both gaskets where the TBI bolt on to the intake. The gaskets did not look bad since their the metal type gaskets installed new ones and everything seems fine. I had to adjust the idle screw in all the way closed but it idles at 900rpms in Park and in drive it is 700rpms. I wanted to thank you for all your inputs it definitely help me narrow it down. Truck idles and runs great.

Thanks

Chris


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## otto888man (Dec 30, 2013)

Glad you had fixed the problem. Thanks for letting us know.


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