As so many posts here deal with, I have a starting problem which causes me to need to give it gas to get it started and it nearly stalls at stop lights with any accessories on (even with none on). I know this is typically an IACV issue, however through extensive reading here I now realize the problem could be further down the line starting in the motor mounts. My question is how can I tell if the problem is the mounts? I don't have any of the clunking sound when turning the car off, so I don't know how else to diagnose the mounts. I also don't really want to pull the computer out if I don't have to. I am not equipped to repair it even if I do find an issue there. I would have to send it out. So how do I test the mounts?

 

You can unplug the mounts, but do it with the rpm's over 1000 if you are going to drive the car with the mounts unplugged. But I don't know if the motor mounts could create the hard starting problem that you have.

 

I think I only asked the question half right. I didn't know how to test the motor mounts, but I realize now that I also don't know how to test the computer either. I'm just trying to go through a process of elimination to figure out at which point I have a problem.

If I unplug the mounts what should I expect to happen? If the mounts did cause an electrical problem through the computer to the IACV then the damage is done, right? So by unplugging them I won't actually see any difference...?

 

I don't ever recall reading any posts relating bad motor mounts to hard starting or bad idle. If the motor mounts go bad, they have a tendency to burn up the driver transistors in the ECU. If the motor mounts are going bad, you will usually hear a buzzing type sound coming from the engine compartment after the engine has been turned off. If the mount is bad and not making any noise, unplugging it won't make any difference.

The testing of the motor mounts is kind of non scientific. here is the procedure from the service manual:

1. After warming up engine, run it at idle speed.
2. Shift selector lever to “D” range while depressing the brake pedal and pulling the parking brake control lever.
3. Disconnect front or rear electronic controlled engine mount harness connector when engine speed is more than 1,000 rpm.
4. When returning engine speed to idle speed, check that the body vibration increases, compared with the condition of the above step 2 (With vehicle stopped).

The IACV can be directly responsible for bad idle. It has engine coolant flowing through it and has been known to leak internally, which causes driver transistors in the ECU to burn up.

I would suggest you focus you attention to the IAVC, as I don't believe that motor mounts would be the cause of your problem.

 

DennisMik,
I don't mean to say that bad motor mounts are causing a hard starting or rough idle. I may not know much, but I know that doesn't make any sense. In another thread many were talking about the mounts going bad and causing a short in or burning up a section of the computer. How this related to the IACV I'm not sure, I'm assuming that the fried section might be in close proximity to the IACV control within the ECC. My whole point is that I'm trying to figure out how to narrow the issue down to pinpoint what is causing my starting and idling problems. I would like to go ahead and disconnect my motor mounts even if they are not an issue, just to be on the safe side, but I see two brown connections on the right side of the engine under the radiator tube, so I don't know which one to disconnect. Your point about being over 1000 rpm is well taken, and I will make sure I do that.

 

If either the motor mounts or the IACV cause the ECU to fry any of the driver transistors, The car probably will not start and the fuse that runs the ECU will blow. Maybe you should read this longgggg thread about the ECU.

http://forums.maxima.org/5th-generat...d-seconds.html

As far as unplugging the motor mounts, here are pictures of the connectors on my 2000, which I think is the same as your 2001.



This picture of the rear connector is taken while looking over the driver's side fender.

 

Ok, great and thanks! I knew where the front one was, but the rear was the mystery as there are two brown connectors in the same area. I will use this picture to compare to my engine, but I think you are right in them being the same. I saw someone else say they just cut the wires and taped them off - is that an ok idea, or should I just disconnect them and tape over the ends?

 

Always better to simply unplug them and tape them off, when you cut them its almost like no going back. I have ES Poly mounts on my 5.5 gen and just unplugged the front mount as I only have one (had) electric mount to deal with.

 

hello, i am new and need some help with my car. i have a 2001 nissan maxima. it starts up fine and runs great, but recently the ses light came on. i took it to a mechanic and he told me the light was on because of the oxygen sensor. the problem that i am having is when i stop at a light the car just shuts of and the dash lights come on. this doesn't happen every time i drive the car and it never shuts off when i am in drive with my foot on the gas. somebody please help.

 

Post your question here...

5th Gen "I AM NEW HERE BUT HAVE A QUESTION" thread

 

DennisMik,
OK, your pics did the trick. Got my motor mounts disconnected while over 1000 rpm with no problem. Also took my IACV out to do an ohms check on it and found it lacking. The book says there should be approximately 30 ohms between each connection point - I had 10 on one, 8 something on another and it just read 1 on the other two. I also could not manually screw in or plunge the actuator, so I'm assuming these two things mean it is bad. I am going to order one from ebay for $103. My local Auto Zone is like $230. NEW QUESTION: I discovered some congealed sticky stuff inside the connection, so its on the plug and also the harness side of the connector. What do I do about it? Is there a way to clean an electrical connection? I'm assuming also that this is refrigerant that made it through the valve. There's not much, but I would like to get it out of there - and I'm hopeful it hasn't caused more damage than I am able to handle repairing.

Jason

 

That goo in the connector may be a water proofing goo. It is used in a few connectors that Nissan deems important. But I don't know aboit the IACV connector. I'll try to remember to pull mine off tomorrow and check it.

You can go to most auto parts stores and get "bulb grease". It is a water proofing goo (or grease) that was originally put in the light bulb sockets to waterproof them and prevent corrosion. I use the stuff on my battery terminals to keep them from corroding and growing that white fuzz stuff.

 

Thanks for the info. I hadn't heard of bulb grease. I could maybe use that, but this is not uniform, its only around/in one of the blade recepticals, and its on the same spot on the IACV unit itself. I have heard that refrigerant could get through the unit, so I'm guessing that is what it is. I took a pic but don't know how to upload it - it asks for an http site to read the pic from. What I need is a way to clean the harness side of the plug internally.

 

I pulled the connector off of my car and there was no goo in it, so you are dealing with something that's not supposed to be there. You can try cleaning it with a baking soda/water solution, But I really don't know of any specific thing for that.

You said "I have heard that refrigerant could get through the unit. It is engine coolant (antifreeze), not refrigerant. Refrigerant is used in the air conditioning. But coolant can leak into the IACV. Thats when the ECU gets shorted out, the antifreeze gets into the IACV motor windings.

 

SE01MAX
If you have found coolant on any of the IACV pins-it is toast. You made a good call testing the pins for continuity and 23 ohms is the perfect target I think. Replace it, disconnect both ec motor mounts, and bypass coolant on both sides of the IACV. There is no fuse protection between ECM and the IACV, EC mounts, and some other stuff. That being said DennisMik nailed the right thread for you to review and you will get a better understanding of what happens next if you allow the "cold start idle" issue to continue. Check out the New ecu, fried in seconds....

 

DennisMik,
You are right, I just slipped up and said refrigerant. I know its coolant.

Darkrock,
How do I bypass both sides of the IACV, and why should I need to if I replace it? I have already disconnected the motor mounts thanks to DennisMik (you sure can tell the difference at idle). Do you have any suggestions on how to clean the harness side of the plug? I think I have heard of electrical cleaner before.

Thanks.

 

I don't think that Darkrock meant bypass the IACV permanently, just until you get the new IACV.

There is contact cleaner that is used in electronics. I think that Radio Shack wants over $10 for a spray can of the stuff. You could try using a tooth brush and probably just water, but I can't say for sure if it will work. The space inside the connector my be too tight. I already forgot how the connector looks.

Interestingly enough, my front motor mount crapped out on me. It's always something.

http://forums.maxima.org/5th-generat...tor-mount.html

 

Wow, that's a bummer. How many miles do you have? Are hyou going to replace it or just disconnect it? The funny thing about mine is I don't know if they were shot or not, I just disconnected them.

I went and reread the post you mentioned about the ECU. If I understand it correctly, should I be concerned that it might be fried and would then fry my new IACV? Darkrock said that the goop is antifreeze, so would it have necessarily shorted out my ECU just because it was inside the plug? Is there a way that I can test the ECU from the harness side of the IACV plug? Keep in mind I barely made it through the continuity test on the IACV itself. I unfortunately don't have a good working knowledge of electricity or my multimeter. I ask because I really don't want to pull the ECU out; I've heard its a real nightmare.

Thanks

 

My car has 90.7K on it. I unplugged the mount when I saw that it was puking its guts out to prevent any damage to the ECU. I will replace replace it in the spring when the weather warms up but I have not decided with what. My choices are ES type bushings, a stock mount for a manual trans car or another electronic mount.

Your mounts, or at least one of them, are good because you said the idle feels rough now. That's the test from the service manual.

The IACV and the motor mounts are not linked in any way and so one going bad will not affect the other. But each can destroy the ECU if it goes bad.

The IACV's purpose is to compensate the fuel/air mixture when the engine is cold. Cold engines need a richer fuel mixture. The IACV has engine coolant flowing through it to help the gas vaporize better. Goo in the connector wouldn't damage the IACV motor windings but could theoretically short out the ECU. The seals in the IACV leak, allowing coolant to get into the motor windings. This is probably why you got the low resistance readings. But the engine coolant eventually causes the motor windings to short and this is when the ECU gets damaged. When the ECU blows out the driver transistors for the IACV (or motor mounts or any of the other things it controls) you won't be able to start and drive the car.

As for the goo in the connector, I doubt if it is engine coolant that came from inside of the IACV. It could have come from some other leak somewhere, somehow. And then the goo may not even be engine coolant. Even if I was looking at the connector, I don't know if I could tell you if it was engine coolant or not. I suggested using a tooth brush to clean it, but you could also try water pressure, blast it with a hose or something. You got a dental water pick?

 

So have you any idea if my ECU has been compromised, or is that what you mean by frying the driver transistors? Are the driver transistors the STA509A chip that the other thread you mentioned was talking about replacing? So if my car is still starting (which it is) then my ECU is fine? I just don't want to replace the IACV only to have it fry because the ECU somehow damages it on start up because it itself is fried. Does that make sense? What I took away from the other thread was don't replace your IACV w/o knowing that your ECU is OK, or you will then be replacing/repairing the ECU and again replacing the IACV. That's a lot of money that I can't spend right now. I'm waiting on ordering the IACV in case I first have to do something with the ECU.

Thanks for all your help - this forum is awesome because of guys like you.

 

The STA509A are the driver transistors I have been referring to. When a transistor sends electricity to something that is shorted out, more electrical current flows then what is normal. This creates heat and the transistor literally burns up. If you read through that link (post # 4) there are photos of fried/burned up STA509A driver transistors.

The big question for you is "Is my ECU ok?" I really don't know. I think it is because you still had resistance when you measured the IACV windings. There is still the possibility it could be bad. I can't remember if that link gave any way of testing the ECU without removing it.

 

I just went through all of this on my 01 SE. Mine would stall when I pushed the clutch in and I had to give it gas when I started it from a cold start.

My car has 111,000 on it. I replaced the MAF and also the IACV. I tested the old IACV and it was dead. I put the new one in and then did the manual idle relearn and everything worked. The car now idles at ~650.

As soon as my SES light came on and I saw the code P0505, I stopped driving the car until I could get the part and install it. I did not want to fry the computer.

I would replace the IACV, then do the idle relearn.

Good luck

 

Dennis,
Not sure if I measured resistance or not. I was able to obtain a couple of very low ohm readings, the other two just showed '1'. I wish I could probe the harness side of the plug somehow and be able to tell if the driver transistor is ok or not. Not sure if that would work, and I don't know how to do it anyway.

Bryan,
Thanks for the input. I've got about 70k miles on you. Sounds like a similar issue. Did coolant get through your IACV to the plug?

Jason

 

Jason, I had a few drops of coolant but that was all. I only drove the car about 3 miles from when the SES light came on. I had heard stories of it killing the computer..so I played it safe and drove other cars till I could it fixed.

 

The IACV plug has 6 pins arranged in 2 rows of 3. Row 1 would be underneath the connector lock clip and have pin numbers 1 2 3. Row 2 is numbered 4 5 6. You would measure on the IACV, not the wire harness, from the center pin of each row to each of the ones along side of it -
pin 2 to 1
pin 2 to 3
pin 5 to 4
pin 5 to 6

This gives you 4 readings. Each reading should be 22 ohms on a good IACV.

Pins 2 and 5 will be 12 volts when the ignition key is on, engine does not have to be running, unless you have a blown fuse # 58 (next to battery labeled "ENG CONT 1".)

 

Coolant Bypass is the indicated fix for the 2001 Max IACV fryup of ECMs. I have replaced a number of IACVs and feel the fix is as I indicate here...."IACV-ECM-TSP
This is a copy of an email I sent to NAKIS-you need to read his post carefully! Otherwise you will continue to fry IACVs and ECMs! The most critical step other than the obvious part replacement are the directions on page EC-111. YOU MUST HAVE THE TECH DO THIS PRIOR TO REKEYING AND STARTING THE ENGINE. Here it is.....To NAKIS:
Thank you!
I have a 4/2001 with continuous IACV valves replacement for years and a couple ECM's and my last "fix" with this issue was to close out the throttle with the idle screw and it worked for a couple years. Finally stumbled on your thread or odyssey with the ECM short and your thoughts about TSP and coolant problems in conjunction with the IACV. A week ago the Maxima fried the ECM and IACV. OBD codes 505 and 612 (dead ECM lots of carbon on the cover plate and at least 4 circuits burned through the 509 was melted) and another for the fuel regulator. I replaced the IACV, disconnected both EC motor mounts and bought a used matching ECM (EBAY which looked totally rebuilt on the inside) took it the dealer for rekeying with instructions.-----> top of the list requiring the TECH to follow instructions on EC-111 before reprogramming. Had a 21 year TECH on it and it took him an hour or less to close the throttle, rekey, and perform idle relearn. Good to go!
Thank you

Hats off to Nakis, et al"

**Posted on the "coolant bypass thread"---->Just completed it today and I live in a fairly cold clime in N. IL and will report if any issues. But I view this as additional insurance against coolant contacting IACV. I have found corrosion at the pin base of at least 2 IACVs that have faulted and possibly a third to not closing TSP before starting.
Procedure: Purchased 5/16" brass split hose mender with the claw backs. Disconnected each hose from each side of the IACV/TB and joined each to the brass mender and clamped with existing. Capped each IACV port with 3/8" ID black chair tips and these aren't as snug as I would have liked but not certain I even need any but it looks more finished. Fired up with no issues. Maybe $3.00 with Cook County tax and might have saved me real money if done sooner. Ignorance isn't bliss! It's expensive!
Last edited by Darkrock; 11-02-2011 at 10:32 PM.

The above came from a post on the link Dennis put up earlier... http://forums.maxima.org/5th-generat...d-seconds.html

 

The coolant by pass is a must if you live in the south. Up north shouldnt be an issue but I have no experience with it. Bypassing it completely eliminates the chance of the ICV shorting out due to coolant.

I have done the Bypass and unplug the Motor Mounts and have no worries.

I have also done the Bypass on my qr25 in my sentra. Its been done for about 7 years with no issues. I do live in florida.

 

Hi Bryan, did any other codes come up along with P0505? I believe I have the same problem you had. I have 01 Max 20th Anniv with 5sp. I started my car and everything was normal, went to move it and car stalled out on me (hadn't driven my car in almost 3 months) when I went to restart it, it just cranked over. I was able to start it by gasing it as well, but if I let of the gas it shuts off and the ses light came on. Autozone checked for codes and got P0100, P0134, P0505. I checked the MAF(P0100) and its fine. P0134(oxygen sensor) don't know how this sensor wouldn't allow my car to start. so that leaves me with P0505. Any help appriciated. Thanks

 

We can understand that you want an answer as quickly as possible so that you can get your car fixed, but please don't be posting the same problem in multiple threads.

P0505 is the IACV (Idle Air Control Valve)
P0134 is an oxygen sensor, sensor 1 bank 2

The P0505 is your won't stay running problem. Take care of this and see if the other codes go away.

 

Hello,
Background:
2000 Maxima with 99,000 miles. I was driving the car and when I stopped at a red light the car stalled and die. I tried to start it again and after some attempts it did start and was able to move it to the side of the road. Friend came and gave me a battery boost ( I thought it was the battery) and was able to drive it to a nearby mechanic.
Mechanic said code P0505 came up and that the IACV had to be replaced. He replaced the IACV and car has been starting normally. I did not have any idle issues prior to the car stalling and dying on me.
Car has been driven for 100+ miles now and it is working and idling fine.
Qustions: Does this mean the ECU was not affected? How can I know for sure the ECU is fine? I have read that if it was fried then car will not start or will not idle properly.
I started reading here about the IACV and came across the suggestion to disconnect the electric motor mounts. I disconnected them (without unplugging the battery) and with the car off. Turned car on and drove around the block fine. When I parked and tried to start it again it did not. The battery die. I reconnected the mounts and gave a battery boost. Drove to autozone and tested battery and they said battery was dead. I installed a new battery in the car.
My mounts are not making the whuzzing sound after I turn off the car. However I want to make sure if something happened to them that my ECU is not damaged.
Questions: Why did my battery die? Is it safe to unplug the mounts? If so, should I unplug the battery, unplug the mounts and then plug in the battery again and start the car? Can unplugging the mounts cause any damage to the car?
I am not very mechanically inclined but I have spent hours reading posts here so your input would be greatly appreciated.

Thank you.

 

This sounds so crazy i cannot imagine disconnecting the mounts had anything to do with the battery dying, i dont have an automatic but i would do exactly what you did and not expect a problem. Someone who has done this pls chime in

 

ECU was not affected otherwise car wouldn't start.
They are 2 independent and unrelated parts. The only thing which 'connects' them is that when going bad each is capable to prevent engine from starting but for completely different reasons.
This either freak (very rare) coincidence or you simply had bad battery contact.
Sounds strange to me - usually batteries don't die suddenly and go through some process of giving you starting problems first and then eventually quitting. My bet it was just bad post contact but I digress.
I don't recall confirmed case of this happening. What happens is that bad mount(s) causes fuse #59 to blow and this very fuse happens to power ECU as well so overall impression is 'ECU is dead'. If you unplug the mounts at that point and replace the fuse everything would be back to normal.
- most likely it didn't
- yes
- you can do it on the running engine
- no
Take it easy, seriously .

 

Sorry for resurrecting an old thread but....

I have been working on cars for a good while now but I'm stumped.

Will a bad IACV always throw a code?

The car in question is my wife's 01 GLE 86k miles.