I hate this lumpy idle that my car seems to exhibit lately! Here's the list of stuff I've done;

- Cleaned IACV mutiple times, put on new gasket also.
- Cleaned MAF & throttle body
- Cleaned K&N drop-in filter
- replaced EGR valve (bought online from autopartsonline, great service since I got my Made in Japan valve next day + plus free shipping since it cost $75CAD. Dealer wanted twice that)
- ran redline SL 1 cleaner
- ran CRC Guaranteed to Pass
- plugs new, Z32 fuel filter

When I cold start it, it will rev to abt 1300rpm, but I can tell it's not smooth. As the car warms up, the idle will drop to 700rpm (good for manual), and idle pretty good. As I drive around, it will will eventually do the thud thud thud idle as if I have high lift cams. It doesn't ever cut out or drop lower than 650rpms.
I can hear the IACV valve clicking, but not sure if it's functioning as designed. I'd love to change it out, but don't want to keep throwing parts at it.
Oh, there are no vaccum leaks than I can hear, I've also spray TB cleaner around various parts as the car idled, but no change is noticed.

 

You can check your Air Filter, your PCV Valve, ECTS, but what I'd recommend is finding a friend with a 4th gen and just swapping MAF's for a test drive.

 

especially the PCV. it's a cheap part and should take you no more than 15-20 minutes to replace. i still have a similar problem, but the PCV replacement definately helped a lot.

EDIT: did you just replace the EGR valve or did you clean the EGR Pipe? EGR's generally don't go bad, the problem is the carbon buildup in the pipe. EGR and PCV problems are pretty common, especially in higher mileage cars. stupid emmissions BS

 

check your codes, sometimes EGR will throw a code and sometimes it won't even though it's very badly clogged. I might take a look at the EGR pipe and make sure it isn't clogged I had to clean mine out last fall and I have reason to believe I'm gonna need to clean it out again now.

 

I forgot to mention that I DID get the EGR temp code (forgot what it was), and I cleaned the EGR inlet with a coat hanger contraption. This got rid of the code, but the idle issue remains. Remember, the EGR only operates between 2000 to 4000rpms, so that inlet tube being clogged will not affect idle. Before replacing the EGR, I took it off and gave it a good cleaning before replacing. Funny thing is my idle seemed fine after this for a day or 2, then the issue returned. I replaced the EGR valve partly because I somehow caused the big nut to crossthread the EGR threads . It would only go one part way, so I bit the bullet & replaced it & the rubber hose to the BPT(?) valve.

I went to purchase a PCV valve from the dealership & the parts guy wanted to know why since it's never replaced according to him. So I bought an aftermarket one & installed it. No changes so this morning I replaced the K&N with my old Nissan filter as a test, same issue. I've thoroughly cleaned the K&N and will carefully oil it & let it sit for awhile before putting it back in.

I have a bad MAF (was causing stumbling), thinking of throwing it on to see if there's a diff in the idling.

I'm stumped, I'm wondering if one of my injectors is not flowing properly at low rpms? or a flaky coil pack? As stated before, at h/way speeds, she runs pretty good.
Some other suggestions I've gotten are:
- check compression due to my high mileage
- check crank position sensor

I'll do that when time permits.

Oh..almost forgot...the only code that popped up during all of this was 0806 (P0173), which is Fuel system function (Left bank). I cleared it and it hasn't returned. The FSM suggests a ton of stuff to check:

- Air like
- Front O2 sensor (left bank)
- Injectors (left bank)
- Incorrect fuel pressure
- Exhaust leak
-Lack of fuel
-MAF
I think this was caused by the EGR leaking (when I had the big nut partially on since I used to hear a slight hiss when I accelerated).

 

Change the coolant sensor part #22630-44B20. It's only $25 at the dealer. Service manual doesn't tell you but you are suppose to change those every 40g miles. I thought it was a lot of stuff but my dad has been a mechanic for 30+ years and he said to change it b/c it also controls fuel. So try that. I had the same symptoms as you and now it's all good.

 

change coolant sensor

 

i duno as far as ur problem, but dont listen to the parts guy over the counter at the dealer, if u need something just tell him u need it.

I only buy nissan genuine parts, no after-market for my VQ

 

Well against my better judgement, I replaced the ECTS & the problem remains. I had checked the resistance on the old & it measured a little higher (around 2K-ohms at cold) than what the FSM stated, so I gambled $45CAD & lost. Now I'm really stumped, the only major sensor left is the MAF...

 

Seriously try the coolant sensor....

 

where is the coolant sensor?

 

Right by the upper radiator hose engine side. It is the second sensor with two wires, when you take the connection off it should be a blueish color connection.

 

Umm ECTS is the coolant sensor. Anyway, found out it's my #1 injector, going to get the on-car flush done.