Rough idle on first start and then dies

[604-Allstar]

Hi,

I did a search and saw lots of peoples post about idle issues but most post were about people having an issue idling once the car had warmed up, my issue is a little different...

My issue only happens on the very first time starting the car that day. When i start the car the engine turns over fine and the engine revs up and idles ok for a few seconds but when the rpm starts to drop towards the normal idle rpm it begins to sputter and couch and the rpm jumps around and some times stalls out completely, while other times it just sputters for 15-20 secs and then idles ok. If I put the car into gear and try to drive away right away it will stall every time. The weather outside doesn't seem to have an effect on if the car will idle better in the morning.

In the past the SES light would come on if I was on the hwy and doing anything over 100 km/h for a decent distance but would go off again after the next time I was in the car, so never really thought much of it. Recently I changed my spark plugs and cleaned my throttle body,while doing this I was listening to music from the car and noticed the black plastic cylinder part of the IACV became very hot, is this normal when power is on?

After finishing the job I started up the car and the SES light came on. I was able to pull the codes with a friends tool and found code P0140 and P0505. With his computer he re-learnt the idle and i had hoped that would solve the issue but it hasn't.

If I understand things correctly, I cant imagine the P0140 error is causing any problems as it's the post cat sensor. is this worth replacing?

Now for the P0505... Before is go and spend money on a new IACV is there any way of checking to see if this is still working? It seems weird that the car only really has issue the very first start up of the day and then is ok.

Things i have checked on or replaced
- Fuel filter (replaces 20km ago)
- Spark plugs (3k ago) - almost all plugs were burning hot and had white tips
- Cleaned throttle body (3k ago)
- Oil Change (3k ago)

Any help or recommendation would be greatly appropriated!

[rgk]

IACV is going bad. Read Buzzman's saga with it frying his ECU.

[Buzzman]

Replace your IACV.....NOW!
Do not pas Go, do not collect $200.
If you're lucky, your ECM is not fried.
If you're unlucky (which I suspect you are at this point, given the 505 code), you're ECM needs a rebuild.
Keep us posted.

[rgk]

Don't worry about the post-cat sensor. It has no bearing on engine function.

Check the IACV connector terminals 1 & 3, then terminals 3 & 6 with an ohmmeter. Each should read 20-24 ohms at 68 degrees F. Resistance increases with temperature.

With the connector facing you, the top left terminal is 1, the top right is 3, the bottom left is 4, and the bottom right is 6. (At least that's the case in my 02 Pathfinder. Refer to your specific FSM for details)

[604-Allstar]

Well i guess that solves that...

Is it best to get a OEM IACV or can i get the Hitachi ABV0043 Idle Air Control Valve?

[rgk]

Just curious: did you check resistance values?

[Buzzman]

Recently I changed my spark plugs and cleaned my throttle body,while doing this I was listening to music from the car and noticed the black plastic cylinder part of the IACV became very hot, is this normal when power is on?

The IACV should not get that hot.
If it's heating up like that, then it means the resistance inside the little motor is too high.
It is this increased resistance which eventually cooks the driver component on the ECM.
Eventually, your truck will not idle at all, and you'll be driving it with your foot on the gas all the time.
Try unplugging it for now and see if it will idle at all.

As for what to buy, it's up to you.
I panicked a bit and just went with an OEM unit. Probably paid more than necessary.
I have seen a few posts on here from guys that have had success with after market parts.

[604-Allstar]

Just curious: did you check resistance values?

I have not had a chance to check the resistance yet, I hope to be able to check it this week. I don't need to remove the value to check it do i?

How would i go about testing what temp the device is at with out an infrared temp gauge?

68F is about 20C i believe... if the weather outside is about 24C could i just test the sensor before I drive the car in the morning and the temp should be close enough to 20C?

[rgk]

Resistance values is just another way of saying resistance numbers.

Yes, 24C is fine. Those numbers are for 20C, and resistance rises with temperature, so at 24C the appropriate resistance numbers will be higher.

You have to unplug the IACV, and probe the terminals (connections) on the IACV with your ohmmeter. Check the resistance between terminals 1 and 3, then check the resistance between terminals 3 and 6. The numbers go left to right, top to bottom.

Report back with what you find, please.

[604-Allstar]

Should be able to get to test the resistance tonight... just in the middle of my training for Fire fighting so things are a little hectic right now.

I think I will probably go ahead and replace the IACV as if its not fried now, I don't want to wait till my ECU is blown(if its not already). Do I need to order anything besides a new throttle body gasket when i replace the IACV?

[atraudes]

Check out my post from when I replaced mine. You'll probably need an impact screwdriver to get the old screws out, and you'll probably want to replace them with something less sucky, like a bolt with a hex head.

[604-Allstar]

Resistance values is just another way of saying resistance numbers.

Yes, 24C is fine. Those numbers are for 20C, and resistance rises with temperature, so at 24C the appropriate resistance numbers will be higher.

You have to unplug the IACV, and probe the terminals (connections) on the IACV with your ohmmeter. Check the resistance between terminals 1 and 3, then check the resistance between terminals 3 and 6. The numbers go left to right, top to bottom.

Report back with what you find, please.

So i followed the FSM guide last night and checked the terminals for resistance.

"Check resistance between IACV-AAC valve terminal 2 and terminals 1, 3, terminal 5 and terminals 4, 6."

Terminal (2,1) - 24.3 ohms *
Terminal (2,3) - 24.3 ohms *
Terminal (5,4) - 24.3 ohms *
Terminal (5,6) - 24.3 ohms*

*I let the car sit for an hr after I drove it home but the valve was still warm when i tested the resistance.

I noticed after i finished putting things back together that you mentioned I should check different terminals (terminals 1 and 3, then check the resistance between terminals 3 and 6.)

Did I check the wrong thing?

Thanks for everyone's help with this

[rgk]

You did the right thing. Follow the rest of the FSM's instructions on troubleshooting P0505. It will want you to check battery voltage, maybe voltage from the ECU, and maybe even resistance between the IACV and the ECU.

To check voltage, unplug the IACV, put the key in the ignition, turn it to "ON", and probe the harness end of the wire that plugs in to the IACV (instead of the IACV end). One of the terminals will be your positive voltage. Probe this with your positive wire on your voltmeter (The FSM will tell you which terminal). Press your negative voltmeter wire to a good ground (such as a heavy bolt in a main part of the engine). You should have around 12 volts (or whatever your FSM says).

Checking IACV/ECU resistance is like checking the resistance of just the IACV, but you will probe the harness end of the IACV connection with one ohmmeter wire (like checking voltage to the IACV), and the ECU with the other. To gain access to the ECU, you will have to unscrew it and pull it down. Make sure to disconnect the battery before attempting this. See all the wires going into the ECU? This is what you will want to backprobe with your little wire.

Needless to say, you may need to extend your voltmeter wire with a piece of wire. You may also need to wrap a smaller gauge piece of wire around your voltmeter wire to backprobe that wire. The FSM will tell you which one. There should be a way of probing the ECU itself to check whether it is fried, but I don't know it.

Never use an ECU ground when checking voltage at your ECU. Only use a bare ground, such as a bolt that is not connected to the ECU.

Also, never have battery voltage flowing through something when you are checking resistance.

[604-Allstar]

Thanks for a great description of what to check on next. Unfortunately, I wont have a chance to get back under the hood till next monday.

Even thought the IACV resistance # came back in line with what the manual called for do you think I should just go ahead and replace the whole unit any ways as they commonly fail?

When I removed the black solenoid to test the resistance, i notice a lot of carbon build up on the IACV, is it safe to clean that with some throttle body cleaner and a rag?

I also feel like the engine bay has been extremely hot but my temp gauge never shows a problem. When I start the car in the morning the temp starts out cold and slowly moves up to normal temp and never runs hot of the gauge. Now we are going through a heat wave here right now and my truck is black so not sure if that's why it seems hotter. Weather is around 29C ~85F

[Buzzman]

do you think I should just go ahead and replace the whole unit any ways as they commonly fail?

I'm going to risk getting flamed or pissing you off, but this thread has been going for a week now, and you have asked several times already whether you should change the IACV or not.
I wrote 5 days ago that you should replace it ASAP, or risk frying the ECM.
I speak from personal experience on this matter.
Now you're wasting more of your time and effort checking resistances, voltages, etc., and then asking again whether you should just replace the whole unit anyways.
The answer is YES!! Quit messin' around and replace the freakin' thing already.
You've probably fried the ECM by now too, given the P0505 code you're getting. Sheesh.

[604-Allstar]

Lol, All good. I placed the order for IACV, Throttle body gasket and IACV gasket this morning. I was mostly just waiting to see if there was any other parts that I was going to need before I placed my order.

[604-Allstar]

Well, I had a chance to replace the IACV on the weekend and unfortunately still have the same problem as before. I guess it's time to get back to testing things again

[Buzzman]

Couple of things: Are you getting an SES light, and if so, can you pull the code(s)?
Did you do a relearn?
As I said earlier, you also may have fried the ECM. That's what usually happens.

[604-Allstar]

Couple of things: Are you getting an SES light, and if so, can you pull the code(s)?
Did you do a relearn?
As I said earlier, you also may have fried the ECM. That's what usually happens.

I was getting a SES light and pulled the codes which came back as P0140 and P0505.

I did a relearn before i changed the IACV but not since. I'm going to take the truck to my cousins shop today hopefully and get him to do the relearn.

My only hesitation on sending the ECM out to be repaired is that my car idles the rest of the day more or less fine, its just the very first start of the day and then things are ok. Doesn't the car die at idle when the ECM is fried?

[Buzzman]

The p0505 code is usually the nail in the coffin for the ECM.
Try the relearn first, but my gut tells me it's the ECM.

The engine will still idle if the IACV is not fully closed. It might be stuck in a slightly open position, and that would allow the truck to idle, more or less.
The truck will die if the IACV fails in the closed position.

[604-Allstar]

So the saga continuous....

I replaced the ECM and still have the same issues.

The CEL codes seem to keep changing too which makes things even harder to figure out... Now i get P0700(random misfire) and P0171 (fuel system too Lean bank one)

I checked my MAF sensor by following this article
http://easyautodiagnostics.com/nissan/3 ... f-sensor-1

Everything came back ok except that on the final test "TEST 4: Testing the MAF Signal" the volts on wire 4 went from 1.4v at idle to 1.8v at 2500rpm. The current increased smoothly as i increased the rpm but didn't reach anything near the 2.5v that the test referenced. is that an issue or are you mostly looking to see that the current increases and drops smoothly relating to RPM?

Im kinda lost with where to go next with this issue as I feel like im just throwing parts at the car now and wasting money.

[Buzzman]

So the saga continuous....

I replaced the ECM and still have the same issues.

Did you keep the same IACV, or did you replace it again?

[rgk]

It sounded like he replaced it:

Well, I had a chance to replace the IACV on the weekend and unfortunately still have the same problem as before. I guess it's time to get back to testing things again

[604-Allstar]

So the saga continuous....

I replaced the ECM and still have the same issues.

Did you keep the same IACV, or did you replace it again?

Yes, Replaced both the IACV and the ECM

[604-Allstar]

I ended up buying Torq Pro and a Bluetooth adaptor in hopes that some of the info it can read will shed some light on things...

Car warmed up and idling fine readings
Coolant - 83.0c
MAF - 2.9g/s
STFT1 - 25.0%
intake: 34.0c
Timing Adv - 10.0
F/T 1x1 - 25%
F/T 2x1 - 25%
LTFT1 - 9.4%
LTFT2 - 9.4%
STFT2 - 0.8%
Vacuum - 26.5

[rgk]

Hey, look at it this way: you're getting a priceless education.

The CEL codes seem to keep changing too which makes things even harder to figure out... Now i get P0700(random misfire) and P0171 (fuel system too Lean bank one)

This is actually a good thing, it means that your IACV and ECU are probably good. Are you still getting P0505?

Everything came back ok except that on the final test "TEST 4: Testing the MAF Signal" the volts on wire 4 went from 1.4v at idle to 1.8v at 2500rpm. The current increased smoothly as i increased the rpm but didn't reach anything near the 2.5v that the test referenced. is that an issue or are you mostly looking to see that the current increases and drops smoothly relating to RPM?

Not too sure there, but I can attest that when my MAF was bad, the car idled fine but wouldn't rev over 2500 RPM. This was a well-documented issue.

Does your code reader have a throttle % open value?

[604-Allstar]

Does your code reader have a throttle % open value?

Yes, reading at idle
Throttle: 0.0%

The only codes that showed up the last time I checked were P1320 and P0171. P1320 is a new code that just showed up and is the first time I have seen it, so i will keep clearing the codes and see if it routinely comes back.

[rgk]

Hold the gas pedal down for about five seconds while the car is running. Does the throttle open % value rise?

P1320

Start testing ignition coil resistances. Do them all cold, then warm up the car and carefully do them all warm. Don't burn yourself. A random misfire code is also often associated with a bad coil or coils. Double-check all your coil connections.

[604-Allstar]

When testing the ignition coil which prongs should I be testing? I see on the coil there are 3 markings "IB", "G", and "+". Do you test IB and G?

also is there a range the the resistance should come between?

[rgk]

The diagnostic procedure begins on page 508 of the Engine Control portion of your factory service manual.

Page 509 shows you are supposed to test terminals 2 and 3, and as long as you don't have an open circuit (resistance of 0), you are good.

There is a drawing which shows the location of terminals 2 and 3.

However, it would be wise to go through the entire diagnostic procedure. The resistance value test is the final one.

A bad coil or coils can cause all sorts of funky issues, and sometimes the coils can be bad even though the resistances read OK.

Another thing I am wondering is whether you replaced the ECU with the EXACT same model as your original, and whether it was new or used.

Do you get a throttle value when holding the throttle open?