After doing much reading on this site for my rough idle problem, I decided to replace the IACV. Took it for a spin and it seemed a little better. Drove it again and it still idles rough. Now I'm reading to replace the TPS and/or ground the MAF. I have replaced the plugs and checked the coil packs. Car runs fine when driving. What's next?

Joe

 

you replaced the iacv with a brand new one? try checking and adjusting the TPS first. and check the isolator to the MAF if its all cracked up replace that, and spray it with MAF cleaner. also make sure you dont have a KS code, or any other codes for that matter.

 

checked the coil packs? Likely it is the coil packs. I dont think it would be the TPS as you would know if its bad if your revs take a minute to drop once you lift off the gas.

 

said he checked them, but that could mean anything.

 

Had the same problem as you. Tried almost everything but after doing a little research around figured out i had a bad fuel injector with way to high resistance. So check your injectors resistance with a multi meter readings should be between 11.8-12.8ish (well atleast thats what mine read) but everyone is different. If you dont have a multi meter u can try unplugging them and follow the same process as coil packs. Which ever one u unplug and it doesnt change idle is your bad injector.

 

Oh and either high or no resistance means its bad.

 

it's going to be a coil

 

Yup, replaced it with a new one since I've read that a lot of people tried cleaning theirs and it didn't help. No CEL codes showing, but I will check anyway. KS is about a year old. If it was a bad injector, shouldn't I see bad performace at all speeds?? I did check all of the coil packs and they were good. Used the timing light method.

 

I had really bad acceleration in 2nd and 3rd gear plus the rough idle. If your having a rough idle and it sounds like its missfiring then you will always be having bad bad performace and it will most likely end up being coils, plugs, or injectors.

 

It runs great at WOT! Has this issue ever been fixed by replacing the engine mounts? I see a lot of suggestions to replace the mounts.

 

Looks like I may have fixed it. Added an extra ground to the MAF and it seems to be idling better. Will know more tomorrow when I drive it to work.

 

what? you added a ground to the MAF?

 

Yup. Read a post on this forum from a guy who had the same problem as me. Don't ask me how he thought of adding that ground, but I followed his instructions and it worked. I also changed my fuel filter since I couldn't remember when I changed it last.

 

Here's the post:

http://forums.maxima.org/4496448-post1.html

 

UPDATE:

Just drove it to work this morning and idle issue is still not 100%. It has gotten better, but still bucks a little bit if I let off the brakes at a stop. Since adding an extra ground to the MAF changed things a bit, the problem may be with the MAF itself. Will keep monitoring the problem.

Joe

 

did you check your grounds voltage before adding it? or did you just add it? that might not have been your problem at all and might not have fixed anything.

 

Yes I did. They were almost exactly like the voltages in the article. My voltage is now sitting at 8mV.

 

UPDATE:

Drove it home from work and let it idle in the driveway and noticed that the exhaust stunk. Checked the other MAF voltages and they are OK, but I'm not sure if that means the actual sensor is OK. Followed the procedure to set the idle speed, via the black **** on the IACV, in the Chilton manual. Got it to 750 RPMs, but the idle is still rough.

 

maf for sure , make sure to replace with a good one and not a cheap one.

 

Looking into a used oem Nissan MAF.

Drove it to work this morning and at different stops I noticed the RPMs would be either at 800 or 650. The tach never fluctuated, but idle was still rough.

 

UPDATE:

Car still idling rough, gas mileage sucks, I can smell gas from the exhaust while the exhaust is putt, putting.

 

You should check your injectors, spark plugs, and TB. I had similar issues with idle and misfires, turns out problems were 3 injectors, a coil pack, and dirty IACV. have you pulled any codes recently?

 

Spark plugs have recently been replaced. I checked the coil packs using the timing light method, all are good. Just replaced the IACV with a new one. Cleaned TB when I replaced the IACV. CEL is not lit; not sure of hidden codes. Other than idling, the car runs great. No hesitation when accelerating and good power.

 

you egr valve may be slightly clogged to the point where it may not close all the way and wont throw a code, sometimes after the car has started to warm up it will start to idle rough do to the exhaust going into the intake from the egr (the valve is supposed to be closed at idle). i had a problem with it before and after doing coil packs, idle control, maf and grounds for the engine it turned out to be the egr valve. does your car idle nice when you first start it?? symptoms only after it starts to warm up, check your egr valve and the tube going from it to the intake.

 

I just had the egr valve and tube replaced about 1-2 years ago. Yes, when car is first started, it goes into a high idle, like a choke, then comes down. No rough idle.

 

are your injectors testing within spec? maybe try some seafoam? i've had multiple people (as well as myself) use seafoam with good results. My cousin with an A4 used it to cure his idling problem.

 

I used one can of Seafoam so far. Maybe I'll buy a few more. Haven't checked the injectors.

 

Same way you test for coils, just unplug the injectors one at a time and if the car stutters then that injector is fine, the one (or multiple) that dont change the idle is/are your culprits. Only downside is that you cant just unplug cyl 1, 3, 5 injectors cause they are under the upper manifold.

Also with the seafoam which way did you introduce it into the system? (brake booster, gas tank, etc)

 

Maybe I'll try that over the weekend.

I used a half a can of Seafoam thru the brake booster hose and the other half in the tank. Have you ever seen that injector cleaner that looks like an IV bag that hangs and drips cleaner into the injectors??

 

I've never heard of something like the IV bag you are talking about. Normally with injectors any type of cleaner only temporarily fixes the problem (at least in my personal experience). If you have a mutlimeter it makes testing them way easier as well, best 25$ I have ever spent.

 

I have a nice multimeter. What voltages are you checking on the injectors and can you measure all of them even the ones under the manifold??

 

I just unplugged each front injector and I think the center one may be bad. I measured the resistance and the injector on the front pass. side is 12.1 ohms, the center one is 43.6 ohms and the one on the driver side is 12 ohms. Does that high resistance indicate a bad injector? I tried listening to each injector with a screw driver, but since they are all connected to the same fuel rail, the clicking sound is traveling along the fuel rail. So I can't tell if the center injector is clicking.

 

high or no resistance does indicate a bad injector. I never checked the ones under the manifold. i have a buddy who is a mechanic and his scanner (way more advanced than mine) Pinpointed the injectors as my problem. I would have to say replace cyl 4 injector and then go from there, if it still idles rough then maybe a back one is bad.

 

Haven't checked the rear injectors, but I found an article in the forum that states that there is a wire harness that connects to all of the rear injectors. Disconnect the wire harness and it described what pins to measure for each rear injector. I'm guessing that I don't have to remove the fuel rail to replace the injector. I'm surprised that the Maxima shop manual doesn't show how to measure the injector's resistance. I found that here!!

 

Haha the .org is basically a FSM. Good luck with fixing that injector and testing the others!. Let us know if it fixes your idling problem.

 

BTW

shocked no one mentioned this, coils, if they test good, they can still be bad. The only way to know for sure is to get a spare rear and a spare front coil and swap them around until you notice the coil goes out.

I didnt see anything about you saying that the symptoms come and go, but if they do its probably a dying/dead coil pack

 

I did test the coils a little while ago and they were all good. By seeing the high resistance on the front center injector suggests that it's bad.

 

I saw an article on this forum about where to buy good replacement injectors and now I can't find it. I think it said that Autozone sells good replacement injectors. Does Bosch make injectors for the Maxima? Are they any good?

 

I ordered my injectors from car-quest and havent had any problems with them. Bosch may make injectors for the max but you will probably pay a little more with no noticeable difference in quality or the duration for which they last.

 

check the adjustment on the throttle body for the fast idle control solenoid