rough Idle when cold and P0171

[amir1234]

hi,

I had my check engin light on a while ago ( six months) but the car was running fine. recently the car stalled when come to stop.
I checked the codes ant it was both P0171 and P0174

I checked many websites to track done this problem and end up cleaning MAF with a MAF cleaner.
After that the car was running too bad (rpm caoulnet go higher than 2000) for a few kilometers but then it was fine.

i cleared the code again and again CEL came up this time the code was P0171.

Now I got this problem, when the engin is code and I start it goes up to 2000rpm and after 5 secends it drops and engine idle roughly and stall.
It will be fine if the engine warm up just a little bite and no problem runs just fine after warm up. but again after few kilometers (say 20 km) the light come up again - checking the code , this time is only P0171.

Please help what is the problem

[amir1234]

well, after i cleaned up MAF the stalling when car come to stop is resolved and never happened again.

Now the only problem is engine idles rough for few second when first start in morning (cold start) after about 1 minute every thing is fine and no more rough idle or stalling.
I confirm when engine is warm everything is perfect as far as car performance and I even have very good gas millage.

when I clear the code P0171 will be registered after I drive the car for some kilometers , let's say 20 to 50 km.

[NissanTech]

The engine is running too lean. You should start by adjusting the idle speed.
The information is the "Engine Control" section of the service manual. You can download the section free from here: Knowledgebase - 2001 Sentra - Nissanhelp.com

[amir1234]

rough idle only happens for about 20 seconds when I do a cold start.
after that car runs perfect and idles normal.
any suggestions?

thanks for your help in advance.

[NissanTech]

Adjusting the base idle is adjusting the AAC valve, the AAC valve controls the air flow to the engine when the engine is cold and when the engine is idling. Properly adjusting the idle may or may not resolve your problem, but you can't start replacing any parts or moving to inspect another items until that possibility is rule out.

[amir1234]

I did the exact procedure as it is in service manual (EC - 82 page 83) but nothing has changed - when engine is warm I checked the RPM and ignition timing and ever this is normal.

here is what happens exactly:
when I start the engine when it is cold rpm goes to around 1500 (which is normal) but after 5 seconds it drops below 500 and engine stalls.
I start again and this happens exactly the same
the third time that I start rmp goes to 1500 and drops around 800 but engine is shaking and after about 10 - 20 second rmp goes up agin and every this will be all right.

I should mention again this is happening exactly after I cleaned MAF with MAF cleaner.
After I cleaned MAF engine didn't go above 2500 - 3000 for about 30 kilometers but it was resolved by itself after 30k-I assume it was in fail safe mode.

in cold start when rpm drops and i try to gas, it wouldn't go up at all.

Please help

[tech22]

After you cleaned the system did you clean the throttle body? sounds like you need to preform the idle air/volume learn proceedure and if you cleaned the throttle body you need to reset the throttle position all of which you can find within this web site.

[amir1234]

As I mentioned in my previous post, I did the procedure but nothing changed and problem still exists