Thread: Warm Start Stall

My apologies if this has already been discussed. I'm new to this forum.

I've got a stock 2001 Nissan Sentra SE (183,000 miles, mostly highway) and having an issue with starting my car when the engine is warm.

Car starts fine when the engine is cold. However when the engine is warmed up, it would start, idle drops immediately thereafter and engine stalls. If I rev the engine a little bit, the idle stays and runs fine. I don't have any issues driving around. If I turn off the car and restart, the idle drops immediately and engine stalls. The idle stays only after I rev the engine.

Recently replaced the Mass Air Flow Sensor (because my SES light came on and car had rough idle and stalled, pressing gas didn't do anything) and the Intake Air Temperature Sensor (because my SES light came on again a week later with error code P0110 - intake air temperature malfunction).

Anyways, I don't think it has anything to do with the MAF or IAT senors since I've had this warm start issue sporadically in the past (maybe a year or two ago). The warm start stalling issue went away for a few months, came back, went away, and now it's back again. I'd like to get it fixed because it's really annoying and I'm not sure if it's a bigger problem.

I think I saw somewhere that maybe the idle air control valve could be the issue? I'm not sure since many of these threads involve Sentras that have been modified one way or another. Mine is stock.

Thoughts? Thanks!

Sounds like my car when the MAF sensor was dirty.
Cleaning it fixed this problem 100%.

Did you replace the MAF sensor with a new one, or a used one? The used one could be dirty.

The problem with a dirty one is that the voltage output at idle is *super* intermittent, thus causing the stall.

If the idle air valve was gone, your car would not idle correctly at all, btw. Or you'd have other issues, like hanging revs, a fluctuating idle, etc..

When my car initially died (i.e. I'd start the car, drive 2 feet, idle struggled and eventually stalled while pressing gas). Mechanic said it was the MAF sensor. I replaced it with a "re-manufactured" MAF sensor I purchased from Napa Autoparts ($119). Idle acted a little funny while in Park. The idle would flutter every now and again. Mechanic said it was probably because the ECM had to relearn and suggested I drive it 50-60 miles to see how it behaved. Although the idle flutter never really went away, the car seem to drive ok. A week later, the SES light came on.

Took my car back to the mechanic and he showed me the error code as P0110 (air temperature sensor malfunction). Mechanic said the code was different from the original error code (unfortunately, he didn't recall what the original code was when he replaced the MAF sensor). I thought I got a bad MAF sensor from Napa so I exchanged it for another "re-manufactured" MAF sensor under warranty. This time I installed it myself. Again, a week later, the SES light came on. Brought my car back to the mechanic and got the same code P0110 (air temperature sensor malfunction). Mechanic reset the light and I drove back home.

I remembered that when I re-installed the MAF sensor I never disconnected the battery which I've read that it's suggested but some people said it's not necessary. Anyways, I decided to disconnect the MAF sensor and the battery overnight. Reconnected everything to let the ECM relearn. Started fine cold. Drove around a bit to run errands, returned to the car and tried starting. Car started but then idle drops and stalls. Had to rev the engine a little bit.

Brought my car back to the mechanic and asked him about the P0110 error code and gave him some pages I printed from my Nissan service manual. The P0110 error is related to the Intake Air Temperature Sensor. Left my car overnight, mechanic said he'd take a look at the IAT sensor. Next day, he tells me the IAT sensor was bad. So I just replaced the IAT sensor ($20 from Autozone). We'll see if the SES light comes on again.

With all the above done, I continue to have issue with warm startup. Mechanic is legit since my gf has known him for quite some time. He didn't charge me anything to pull the error codes and while he was trying to figure out the problem.

I would rather not shell out $300 for a new MAF sensor if it could be something else. Ebay sells "new" sensors (no housing) for $50 but not sure how well they work. I also noticed the eBay ones have 4 pin while mine is 5 pin. Not sure if it's compatible.

It's just odd that I have to rev it to get the idle to maintain. It's like it I have to give it a little push.

Those remanufactured MAFs are known to be trouble, man.
Do you have your old one? it's possible that all it needs is a cleaning.

It's not necessary to reset anything at all when changing the maf/iat.

IAT can cause funkiness as it's linked to how the MAF works, but 2001 cars are different than my '96, i imagine.

Anyway, my problem was the same as yours when my MAF was out of whack. I'd start it up at operating temperature, it would fire up, run for maybe a second, then suddenly die.. if i gave it some gas for a second or two it would act fine thereafter.

It's also possible that you have an intake hose leak before the throttle body. If that's the case, the car isn't seeing all the air that's going on.. which can be a problem..

Thanks for your reply. Unfortunately, I turned in my original MAF sensor to get the core deposit $50 credit ($119 after turning in my old MAF sensor).

I found my old work order prior to the mechanic changing my MAF sensor. The error codes he pulled were P0100 (MAF Circuit Malfunction) and P0171 (System Too Lean (Bank 1)).

I read on a Infiniti G35 forum, that the symptoms I'm experiencing could be related to the Throttle Body being dirty (carbon build-up) and needing to be cleaned. Other forums say it could be the Throttle Position Sensor, Idle Air Control Valve, or Fuel Injector Pressure Regulator. Least expensive option is to get the Throttle Body inspected/cleaned so that'll be my first step. Just ordered a Throttle Body Gasket from Kragen/Checks for $2.60.

Hopefully, that'll solve it otherwise back to square one.

You shouldn't need to pull the TB to clean it, so you will probably not need the gasket (keep your receipt).
Not exactly what you are describing, but I was having stalling issues once the car was warm when coming to a stop. My issue was a combo of TB being dirty and the engine not being grounded well. Are you in a rust-beltish area? If you are, throwing some new ground cables on might be a cheap and easy stab at it.

I'm east of the SF Bay Area, CA mostly dry so I guess I wouldn't classify it as a rust-beltish area. I may ask my mechanic to look at the idle air control valve as well. How do you clean the IACV? Does it need to be removed? How many gaskets are there? I could only find one looks like it fits between the electrical connection and IACV (3 holes, 2 for the screw, 1 for the valve but noticed if you buy a new IACV there seems to be a gasket that goes between the IACV and the throttle body (the IACV connects to the throttle body right?). In any case, I can't seem to find this 2nd gasket by itself.

What you want to clean is the IACV AAC, which has a squarish gasket with two main holes and 4 bolt holes. Now I'm talking about my engine, which is a '91 DE. I don't know if this link is going to work, but let's see as it has a pic of the part I pulled off my car:

Duralast/Idle Air Control Valve | Idle Air Control Valve | 1991 Nissan/Datsun Sentra 4 Cylinders G 2.0L SFI DOHC | AutoZone.com

You have you pull it off to clean it, hence the need for a gasket. I removed all the sensor bits off of it and then attacked the spring and passageways with carb cleaner until it was nice and shiny inside. Carb cleaner is pretty strong stuff, so I tried to avoid any area I though might be sensitive to such a harsh substance. On my car it is located near the oil filter. Getting it back on with the gasket all lined up was the major pain in the butt, which is why I suggest looking for vacuum leaks first. I cleaned mine but it didn't solve my problem, which was slightly different from your problem. Personally, if I had your problem, from a cost and ease of labor standpoint, here's what I'd do:

1) get some jumper cables and when it is doing it use the jumper cables between metal spots on your engine and chassis to act as grounds. See if that reduces the issue/stops it. The jumper cables were not as effective as 4 brand new ground wires, but if you see a bit of a difference, you can go the extra step of building new ground wires/cleaning your existing ground wires and see if that solves it.

2) check all of your vacuum lines for cracks and/or build a vacuum leak tester for a bike pump (here's a pic of the one I built:http://www.sr20-forum.com/308502-post23.html)

3) Clean throttle body. Cheap, and even if it doesn't fix it cleaning it will likely help other things.

4) Clean IACV AAC and put on new gasket.

5) Bang head against the wall.

Maybe it is the IACV Air Regulator? There was a lot of discussion on this forum about what it does/is it needed. Search and maybe you can find a thread that discusses what it does. Obviously you are looking for something that changes purposes once the car warms up if it is not an electrical/vacuum issue. The two IACV pieces and thermostat are the only things I'm aware of that affect that (besides ECU, of course). But I'm a mechanical newbie. Good luck, and report back!

Btw, where east of the bay are you?

I'm in Livermore. I plan on bringing in my car to the mechanic this weekend. Will see what happens afterward.

Just wanted to give an update. So the mechanic cleaned the throttle body and idle air control valve and replaced their gaskets. I picked up my car tonight, drove it back home. Turned off the car and it restarted no problem without stalling. Idle seemed fine and stayed put. I'll give it another week or two and see how it goes. I'll provide a final update in a couple of weeks if all goes well.