some of u may have seen my previous threads, what happens is when i rev above like 2500 in gear and put it in nuetral (or just rev in nuetral) when rpms come back down they go below idle, to like 400, car shakes and they go back to 550. sometimes car idles ok (650) sometimes very low (500). also when car starts they jump to 2000, then dip to like 900 and back up.

checked for codes, none. checked for air leaks, none. even went freind at nissan he pluged in Consult II and said everything looks fine. also did idle relearn, and i still have all the problems!!!!!!!!!!!!

i noticed when heat or AC is on it idles better (higher) and doesnt dip the rpms below norman range (which makes me think its not a vacume leak). PLEASE HELP!!!

 

IACV cleaning, I had that problem on my 4th Gen and a cleaning of the IAC valve cured it, I'm just not sure if they are on your particular year???

How to clean IAC valve

Tools needed:
10 and 12 mm sockets
3 inch socket extension
universal joint (swivel pivot socket thing)
12-inch rachet (a short rachet may not work - need something to apply a lot of torque to loosen the bolts
Philip's screwdriver
rag
throttle body cleaner

1. Unplug the 4 connectors from the IAC assembly. Undo the hose that connects teh IAC to the intake assembly.

2. The metal bracket holding up the gray-colored connector is blocking one of the IAC mounting bolts. Using a 10mm socket, remove the bolt that holds the metal bracket. The bolt is just below the purple connector - you have to twist your head and crane your neck around to see the bolt.

3. Remove the 3 mounting bolts using the 12mm socket. The lowest bolt may require the Universal joint.

4. Pull out your IAC valve and clean it w/throttle body cleaner, rag, and old toothbrush.

You may even want to separate the plastic valve to clean it more thoroughly. Use a philip's head screwdriver, but make sure it is a snug fight. It's on there tight and if you don't have a good fitting screwdriver, you could ruin the screw head.

Reinstallation is just the reverse of these steps. It may be easier access to the IAC if you remove the whole air intake assembly, but it's not necessary.

How to adjust IACV -

Warm the engine up to operating temp.
Turn off the engine.
Disconnect the TPS.
Start the engine and adjust the idle speed using the stop screw on the throttle body to 650 RPM's.
Turn off the engine.
Reconnect the TPS and restart the engine.

If the IACV is working correctly your idle should be correct. If it's a bit low, try adjusting the screw on the IACV bypass to get your idle speed to ~700 in neutral with no load. (no load means no lights or A/C)



Item #11

 

i cleaned the iacv about a year ago, but will try again, if i need a new one, is it true that if u replace IACV u have to replace the ECU? doesnt seem right, but ive heard that a few times.

 

I had the same thing.
I cleaned the TB and then changed the MAF and everything was fixed.

 

oh by the way, i changed the MAF, didnt fix it either.

 

ok, now i changed the iacv, and still nothing, in fact it seems the problem has gotten worse!!! what to do?????????

 

Try a new mass air flow sensor sound like some off the symptoms of a maf failure also, just for shts and giggles test your battery.

 

dude....this is the 2nd thread you've put up......WHY WHY WHY WHY are you putting up another thread when you have the other one right there. SECONDLY, you haven't even answered my question. i have told you NUMEROUS TIMES NOW that i know what your'e problem is and you still feel the need to ignore that.

I KNOW WHAT YOUR PROBLEM MAY BE.

you have grime build up in your butterfly valve of your throttle body. the grime builds up and the airspace between the valve and the TB is less. when you snap to idle, the car drops to lower RPM because you dont' have enough air. immediately, the ECU compensates for the low RPM and raises it up. THAT is why you go down, then go up. it happened to me. i fixed it by cleaning the butterfly valve.

for the record this is the 5th fuking time i'm saying that it's the butterfly valve, but either he can't read or he's just a dolt.

 

WRONG......

first off there are two threads because they were started about two weeks apart and i just wanted to update both to get peoples responces.

second, U R wrong! there is no grime build up, tb was cleaned 6 months ago and when i took it apart today, it was spotless!

 

aaaaaaaaaaaaaaaaaaaaaaaah

he responds. what a great idea. actually responding!! next time, tell me i'm wrong or that's not the case and we won't be going through this. it only took you what....4 times to say something?

edit: before i really shut up, when you say TB, you also mean the Butterfly valve as well i hope.

 

lol newbs aer so awesome rofl this is great like 40 thousand pages of sht and somehow people cant figure how the ***** to go to page 2 then 3 then 4 or search the website from either google or yahoo or donate but oh well their choice

 

yes, i do mean the butterfly valve.
and what are you talking about???

 

Sorry....im new to cars and ish...where are these numbers coming from? RPM at 650? How do you test that?

 

hey man, i got similar probs, but mine shuts off instead of reviving itself. I looked at it w/ my mech. and on his OBD, the TPS wsasn't working. It said 4% @ 1100rpms, then 4% @5400RPMS. I havent had time at all to work on it, but he told me to clean TB(seems you already have) and change the TPS(might be your problem). Let me know if it helps, im curious as to whether or not it will help me.

 

urs sounds like a dirty iacv, but could very well be the tps. i checked my tps and it does work.

 

hey, i figured it was worth a shot... i saw my TPS in action on the OBD reader, and its shot, but will take a look at the iacv as well, thx... hope you find your prob.

 

before taking off the tps check the resistance with an ohm meter when the car is completely cold. when ur gonna install the new one try to get it as close as possible to that reading.

but i realize if ur tps is bad the original reading will be wrong anyway......

basically u may notice hesitation due to tps being off. it should read about 800-950 ohms in closed position. (or set to .5 volts) tps is a biatch to adjust, id suggest replacing the two screws with hex screws form home depot, that way adjusting will be a thousand times easier.

 

Just from what i've seen working at a dealership, I would replace your upper intake plenum gasket. It's a 4.00 gasket, thats not too hard to replace. We keep about six of them in stock if that is any indication. This could easily be the cause of your problem. The ECM is trying to correct your idle, but its very difficult due to the uncounted incoming air.