# 98 Altima revs high at cold start



## Ponyz (May 31, 2016)

Please help with advice. 
I got a 98 Altima 5 speed that will idle up to 3k in the morning and go down to 2k and spike up and down two or three times before going down to the normal idle of 800. It will usually takes 5 to 10 min to idle normally. There is no codes or check engine light I replaced the Maf, cleaned the throttle body, looked for vacuum leaks and still no luck. Any advice?
Thank you


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## cj1 (Oct 21, 2014)

Cleaned IAC also?


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## Ponyz (May 31, 2016)

Didn't clean iac but I did apply voltage to it and heard it open and close without a problem. Also tested egr with vacuum and worked well. If the car runs and idles well once warm are there any other culprits besides vacuum leaks, iac, and tps.


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## cj1 (Oct 21, 2014)

Best to thoroughly clean IAC and TB passages to IAC, since IAC operates incrementally don't know if applying voltage and listening for a response is a good enough test. 

To better diagnose this observe the engine parameters IAC,ECT,IAT,TPS when idling erratically during warm up.
Try to get a better reading on what engine is doing before replacing additional parts.


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## Ponyz (May 31, 2016)

Thanks cj1 you make a good point I'll work on removing and cleaning the iac tomorow. But before I do that how do I observe the parameters can you do this by hooking up ob2? If so what do you look for?


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## cj1 (Oct 21, 2014)

With an in inexpensive obd2 scan tool( smart phone with app) you can read the engine parameters to help isolate problems. 
Knowing what to look for of course is key. The scan tool app in addition to studying engine diagnostics will help.

You might try McCuistain, Schrodinders or ScannerDanner online. Danner in particular has a good study guide. 
You'll find the why and what to look for there. It will be a good addition to the help available on the forums.

When you get obd2 connected look at the IAT/ECT they both should be approx same on cold start and IAC count should be high maybe around 200.
As ECT increases the IAC count should decrease gradually until reaches a normal 40-60 at idle. 

Is your IAC/TB original, idle problem just started acting up?


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## Ponyz (May 31, 2016)

Alright thanks very helpful information especially since the iac is a pain in the butt to remove in these altimas. The iac and tb are original to the car to the best of my knowledge but it's been doing the same problem since I bought the vehicle a couple months ago.


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## cj1 (Oct 21, 2014)

Since the high idle at cold start was happening when you bought the vehicle and you have no history on what has/hasn't been done, take your time figuring this out. Especially when engine is running well at operating temp. You don't want to start changing parts only to effect the normal operation.
You can record the engine parameters at idle and higher RPMs. Set some bench marks for fuel trims etc. 
Long term fuel trims +-10 across the RPM range at operating temp are what you are looking for.

There is a lot of discussion and sound advise on this forum about cold start idle problems. Just search the Altima 98-2001 forum. 
From what i've read exaggerated RPM flare ups/downs at cold start are common and it may take some tinkering to smooth things out.


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