# Runs rough/stalls when almost warm, No Codes



## ajnbf (Mar 7, 2009)

Good morning,
1997 Altima 90K miles

I just bought this car two weeks ago and like it. Funny thing was I bought one in 97 and paid a lot more for it then 

The problem it is having is that when you start off first thing, no problems. After about 2 miles, it will start idling way low and stalling at light or if going real slow (school zone). Usually after 2 minutes like this, it runs like a champ rest of day. No service lights or codes. Yesterday, it did its routine but this time did not return to "normal". Had to turn around and keep RPM's above 1500 to get it home.

Has a mechanic buddy look at it. No codes in system and off course did not stall  during test drive. Got it to the shop and let it idle, got out and it died. Started and died. Started and ran fine. His opinion was to wait until it doesn't run at all...

Anyone have similar issue? The computer said everything is running perfectly. This is very confusing. Any suggestions would be of help. I looked through the forums and found a few like the O2 sensor but if it is that, wouldn't it throw codes? And being this car has 2 O2 sensors, which would ti be? Thanks for any advice! :givebeer:


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## bassman1984 (Mar 18, 2009)

my advice is to ohm your injectors when the engine is warm or when you notice the low idle, they should be around 11-12 ohms. they normally fail due to the injectors coil shorting out when the engine gets warm or to running temp.
I had a problem like yours and it was my injectors, I bought a set from Motor Man Fuel Injection for $34.99 each, thats the best price I found anywhere.


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## glacierlodge (Mar 7, 2009)

*Warm Engine Stall / Rough Idle*

This warm engine stall and rough idle problem is affecting my 1997.5 Altima which had 100K on it. Once the engine is fully up to temp, the car drives with no stalling. I've been working on this for a couple weekends and here's what I've tried. 

I cleaned the throttle body, cleaned the MAFS, replaced plugs, wires, cap and rotor, fuel filter, air filter. Checked vacuum lines and cleaned the EGR valve. Checked fuel pressure and temp sensors, MAFS voltage...all fine. 

After cleaning the throttle body, the idle speed improved but the stalling problem returned the next cold morning. After cleaning the IACV and replacing the PCV valve, the problem seemed to go away for four days, but the problem has returned with a vengence and now runs rough at all temperatures...hot or cold. 

Then I noticed today that there was fluid coming out of the radiator cap, so I installed a new cap. I drove the car for an hour and it ran great. In hindsight, I wish I had replaced the radiator cap first ($7.59 at NAPA) for all my time and cost of trying other things. I'll give updates on whether the probelm resurfaces or not in the next few days.


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## ajnbf (Mar 7, 2009)

I really have a hard time believing that it might be the radiator cap though I suppose anything is possible.

Bassman, how do you test the injectors? I have never done this and am really getting fed up with this car. I barely made it home from work today. What ever it is, it is getting worse and lots more frequent, not just for a few minutes after it's half way warm. I can not find any vac hoses off, nothing. I replaced the fuel filter. The only thing that i can figure it is pointing to is the EGR or EGR controller. IF anyone knows how to test injectors, please reply. Thank you.


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## rogoman (Dec 16, 2004)

ajnbf said:


> I really have a hard time believing that it might be the radiator cap though I suppose anything is possible.
> 
> Bassman, how do you test the injectors? I have never done this and am really getting fed up with this car. I barely made it home from work today. What ever it is, it is getting worse and lots more frequent, not just for a few minutes after it's half way warm. I can not find any vac hoses off, nothing. I replaced the fuel filter. The only thing that i can figure it is pointing to is the EGR or EGR controller. IF anyone knows how to test injectors, please reply. Thank you.


To test fuel injectors, use a multimeter and set it to ohms. Disconnect the harness connector from the injector and measure the resistance at the two pins of the injector. It should be around 10 to 12 ohms.

If the injectors read OK, then here are some other possibilities:
- Weak spark.
- Bad fuel pressure regulator.
- Major vacuum leak.


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## ajnbf (Mar 7, 2009)

I know I may sound naive but does the car need to be on to check the ohms? Does it need to be warm? WHat exactly should be the procedure. Sorry but thanks again.


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## glacierlodge (Mar 7, 2009)

*Not Radiator Cap*

Tried the car out this morning and the problem came back, still no codes popping up.  Radiator cap did not do the trick. I knew it was too good to be true. But at least now I have a shiny new cap 

I took the car into a shop specializing in imports for a basic diagnostic. (more than a code reader) They said that my MAF sensor was reading about 3-4 times higher than it should at idle. The computer thought that a lot more air was entering the engine and was then dumping fuel into the engine making the engine rev. The ECM would then try to reduce the idle speed and the car would stall.

They offered to replace it for about $450, but I said I could manage replacing it myself. I should have the new (rebuilt $217 at Shuck's) MAF tomorrow morning to try out.

I sure wish it was the Radiator Cap. Oh well, I will let you know tomorrow if the MAF does the trick.


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## ajnbf (Mar 7, 2009)

Alright, I tested the injectors with the ohm meter both cold and hot. The results (drum roll please): From left to right: COld - 21.5, 21.5, 21.8, 22.8 - Hot - 12.2, 11.6, 12.1, 12.3. So if I am reading the results correctly, the injectors are fine. I am attempting to find a fuel pressure tester to check the pump and pressure regulator.


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## glacierlodge (Mar 7, 2009)

*New Rebuilt MAF Fixed it, so far...*

Just an update on my 97 Altima with same stalling problem.

I installed the rebuilt MAF (took all of 10 minutes) and the car runs very smooth. I adjusted the Idle speed back down to 750 and it does not stall or stumble. When I had checked the old MAF sensor with my volt meter it appeared to work fine according to Chiltons testing procedure, but obviously it was bad.

My recommendation: Find a shop that can hook your car up to a computer, not just a code scanner, to run a full diagnostics. You can always do the work yourself. Better than throwing parts at it. The shop I went to (Clarke's Discount in Oregon) gave me a full printout of the diagnostics on the problem for $75.

Most likely, from your description, the problem is a "closed loop" issue. When the car is cold, it operates under "open loop" which is a set of predefined conditions and ignores feedback from the MAF, and other sensors. After the engine reaches operating temperature, the ECM switches over to "closed-loop" control and adjusts the Engine based on sensor input. The "closed-loop" condition is where your problems are so look closely at the sensors. (TPS, MAF, Air intake temperature, Engine Temperature)


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## rogoman (Dec 16, 2004)

ajnbf said:


> Alright, I tested the injectors with the ohm meter both cold and hot. The results (drum roll please): From left to right: COld - 21.5, 21.5, 21.8, 22.8 - Hot - 12.2, 11.6, 12.1, 12.3. So if I am reading the results correctly, the injectors are fine. I am attempting to find a fuel pressure tester to check the pump and pressure regulator.


The injectors are OK. Tee in the fuel pressure gauge at the fuel filter outlet.


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