02 Pathfinder Idle Issues

[Buzzman]

Oh wow $80, much better than the $250 I just seen on ecu medics. I would greatly appreciate there name/link, I can take a few days downtime and get rides to work, but Im also in canada which would surely add a week to shipping times.

My 2001.5 seems to have a funny idle, and sometimes on initial startup it will stutter/bog until it has warmed up. I believe my IACV is bad though, as it seems seized when I had it out last ( this ecm problem is the first Im hearing ) Sounds like I need to replace both

This IACV blowing the ECM thing has been discussed before. There's a whole earlier thread on this subject.
I know because I went through it last winter and documented my experiences.
I'm also in Canada (Ottawa), and the price quotes for parts from the dealer here were ridiculous.
A new ECM was $1200, and the IACV was close to $500..
I went to Florida for a few weeks last winter, so I took my ECM with me and had it repaired while I was down there.
I used the circuit board medics ($250.00). Too bad I didn't know about the cheaper alternative.
Their turnaround time was fast though.
I also bought a new IACv down there.

I can't stress this enough: don't fix your ECM without replacing the IACV. It's the bad valve that takes out the ECM.
You will also have to do a relearn after the repairs.

[CanuckQx4]

I am just wonderring if I need to buy a new iacv as I have about 3 from the junkyard sitting in my "used" parts box, I swapped them in but nothing changed, obviously because I didnt know the ecm was fried, so Im not sure if they are useable, a tps I do not have though, only the one that came installed on the jdm engine I swapped in

[Buzzman]

I am just wondering if I need to buy a new iacv as I have about 3 from the junkyard sitting in my "used" parts box. A tps I do not have though, only the one that came installed on the jdm engine I swapped in

Considering the hassles of getting an ECM repaired, I would not risk installing a used IACV from a junker.
If you think about it, the junker IACV's are just as old (or older) than the one you are replacing in your truck.
Even if the junker works, you have to as yourself, how long will it last?
I would be constantly worrying about it if I installed an old used one in my truck.
Buy a new OEM unit. You'll have peace of mind.

As for the TPS, if it works, leave it. A bad TPS will not kill your ECM.

[CanuckQx4]

Well if I can get one for $100 I would buy a new IACV, but $230 is just overkill

[skibum05]

So while talking to a company that repairs ecm i was told : Attention!!!
You will need to replace idle control valve (IACV-AAC) and throttle position sensor before installing your rebuilt computer, or computer will be damaged again"

W

I have been told by 2 different certified Nissan techs that there is NO reason to replace the TPS. It's on a completely different circuit from the IACV, and the IACV solenoid that blows, thereby allowing higher than normal voltage to the ECU, doesn't have any affect on the TPS. You will just be throwing good money after bad if you replace the TPS.

Also... if you stop driving your Pathy immediately (or as soon as you can get it safely parked somewhere) upon first noticing that it won't idle without giving it gas (i.e., keeping the throttle plate open just a tad), then it is VERY unlikely that the ECU will have suffered any damage. The problem is, most people keep driving the vehicle for a while with the failed IACV, by giving it gas to prevent it from stalling, and this is what causes the ECU MOSFET/IC to fry - prolonged periods of higher than normal voltage.

And if your ECU does get fried, and after you either have it repaired or replaced, along with a new IACV-AAC valve, and the vehicle won't start, before you start pulling out hair trying to figure out why it cranks but won't start, be sure to check for a blown fuse in the passenger side fuse block in the engine bay. It's not uncommon for either Fuse # 62 (7.5A) and/or #63 (10A) to be blown. I don't recall what the exact labeling of these two fuses are, but it's something like ECCx. The diagram of this circuit can be found on page 446 of the DTC P0505 ISC SYSTEM section in the EC chapter of the factory service manual: http://www.nicoclub.com/FSM/Pathfinder/ ... der/ec.pdf

[CanuckQx4]

Is there any links to what the ecu looks like inside and if it is a possible DIY job at all? Im not to huge on the week plus downtime. I found some iacv's for about $125 shipped which isnt horrible, but thats something I can swap in an hour or two.

And if I were to buy a spare off ebay or from a junkyard to send to the ecu medic to save downtime, would it simply swap in once replaced, or would it need some sort of procedure at the dealership to make it work?

[donald]

...
Also... if you stop driving your Pathy immediately (or as soon as you can get it safely parked somewhere) upon first noticing that it won't idle without giving it gas (i.e., keeping the throttle plate open just a tad), then it is VERY unlikely that the ECU will have suffered any damage. The problem is, most people keep driving the vehicle for a while with the failed IACV, by giving it gas to prevent it from stalling, and this is what causes the ECU MOSFET/IC to fry - prolonged periods of higher than normal voltage.
...

at what point, in your opinion, would the ECU reach the point of no return if one were to experience intermittent engine stumble?

[skibum05]

...
Also... if you stop driving your Pathy immediately (or as soon as you can get it safely parked somewhere) upon first noticing that it won't idle without giving it gas (i.e., keeping the throttle plate open just a tad), then it is VERY unlikely that the ECU will have suffered any damage. The problem is, most people keep driving the vehicle for a while with the failed IACV, by giving it gas to prevent it from stalling, and this is what causes the ECU MOSFET/IC to fry - prolonged periods of higher than normal voltage.
...

at what point, in your opinion, would the ECU reach the point of no return if one were to experience intermittent engine stumble?

I would say before the higher voltage causes irreparable damage to the IC or anything else related to the IACV circuit on the ECM. The short answer is: ASAP. As someone else (Buzzman I think) wrote, the important thing is to replace the IACV-AAC module ASAP. It is the failed IACV valve which damages components on the ECM. If the ECM does turn out to be bad, and you've replaced the IACV-AAC valve, it won't damage your new IACV.

[donald]

Finished the IACV R/R 2weeks ago, but I still get the occasional engine stutter (no stall... yet ). I wanted to give it sometime to be sure nothing else was affected after the replacement.
Just heads up to those that do decide to do this - most likely you will need a throttlebody gasket, so have one of those ready . Luckily the local parts store (O'Reilly Auto) had it in stock. Removing the TB was necessary for me to gain access to the IACV bolts.

Regarding the relearn (not to make this a pissing contest, just FYI to others)

...
Once you have all the new parts installed, you'll still have to do the relearn process.
After I installed the new parts in my truck, my idle was too high, and it generated a fault code (SES light on) for (you guessed it) idle to high.
I had a hard time trying to do the relearn like in the FSM.
I finally took it to my mechanic at the dealership, and he did the relearn for free in less than 5 minutes.
He cheated though....lol...he used his scan tool through the OBD port.
My engine has run like new ever since.

I found it a little "not-so-easy" at first. The pre-relearn idle ran at about 1000RPM.
My first 2 tries were unsuccessful. On my 3rd (and "a little frustrated") attempt. This had to do with the part in the FSM where it says
"Disconnect throttle position sensor harness connector (brown), and reconnect it within 5 seconds"

My first 2 attempts, I had just unplugged it, counted to 2 and plugged it back in - a total of 2-3sec of disconnect. Both unsucessful, as mentioned earlier.
On my 3rd attempt, I unplugged it and counted to exactly 5 and then reconnected, then went to check the tach, and it slowly reduced the RPMs to 750 and held there. I rev'd the engine a few times (per FSM) to confirm idle held at 750.
Worthwhile observation: while I had it unplugged for the 5-seconds, I noticed the RPMs increasing up to perhaps 1800-2000 before I reconnected. Perhaps that is part of the relarn?

Anyway - since I still get the occasional engine stutters (at stops and cold start ups while backing out of garage) I'll consider when to send in the ECU. I'll have to wait for more drier weather, so that I can at least get to work dry

[atraudes]

So, I just replaced mine and except for the screws, didn't have any problems. I bought a Hitachi ABV0043 as a replacement for about $90 on Amazon. It came as pictured below, sadly without screws or gasket.

I tried using a screwdriver to remove the 5 screws attaching it to the bottom of the throttle body, but only succeeded in badly stripping one of them. Fortunately I also bought an impact driver set which worked like a charm and even got the stripped one out. A few heavy whacks of the hammer was all it took. I replaced the stripped screw with one of the screws holding the old sensor on. I probably could have just swapped the sensor out and left the old aluminum piece in place, but the shiny clean metal was really tempting

Once I got everything reconnected the car started right up and has no problem idling. Once warmed up and in drive, the tachometer needle stays steady on the second blue tick below 1k. I'm assming I didn't have to do the idle relearn because the ECU hadn't been repaired. It may just be me, but it seems to run a little better overall, too

[pf2130]

I just got my ECM repaired and back in place. I am going to replace the idle air control valve. It is late and dark so this will wait until tomorrow but this looks like a monster of a job! What is the easiest way to get the IACV out and replaced? Do you have to pull the Throttle body? Is it easier to take off the whole intake manifold? Any advice is greatly appreciated.

[atraudes]

Whoa, just went back to this thread to post an update and saw you didn't get a reply; sorry about that! The easiest way is to pull the throttle body off. Disconnect the air intake tubing from it enough to give yourself some room, put a rag below the hose on the bottom left of it and disconnect the hose (a bit of coolant will come out). Disconnect the three plugs from the throttle body and use an allen wrench to loosen and remove the four bolt/screws. Once it's loose you'll be able to access and remove the other coolant hose, which should be empty at this point.

My update was that instead of using the same mashed screws again, I went back and replaced them with bolts I bought from the hardware store. I used 4 "5MM-.8 ×16MM" bolts and one "5MM-.8 × 40MM" and some split-lock washers. It looks a lot sharper and I was able to torque them down without worrying about damaging the heads.

[donald]

I also have an interim update

... I still get the occasional engine stutters (at stops and cold start ups while backing out of garage) I'll consider when to send in the ECU. I'll have to wait for more drier weather, so that I can at least get to work dry

Even after the IACV replacement (also checking no leaks around any parts that were recently removed/re-installed), I was getting the occasionally engine-stall.
The main/easiest wayin which I could cause a stumble or stall was on cold-starts (>2hour sitting), by moderately stopping hard (eg. backing out of driveway on to street, at stop sign/light, etc).

I took the truck in to have it looked at (diganostic was free!) and in regards to the idle issue, the only thing mechanic noticed that could be related is that my ATF was low by 2-3quarts (per mechanic)
I suppose all this idle stuff had started when I last did a drain/refill on my ATF - but I always put back in what came out, so I'm not sure how I had measured wrong

Anyway, I can no longer force an idle-stumble or engine-stall by moderately stopping hard on cold starts. Although, now is the "summer" time around my parts, and weather has been generally warm. But I suppose another check for those experiencing an idle-stumble or engine-stall, especially at stopping speed, check the ATF levels and condition.

1 other thing my mechanic found... possible headgasket leaking coolant