Nissan Frontier Forum banner

Idle Problem

11K views 28 replies 7 participants last post by  GotToGo 
#1 ·
Hi Guys,

I have an annoying stumble at warm idle. I think the stumble is there when cold too, but it's not noticeable until the idle comes all the way down.

I've read many articles on idle issues and nothing seems to be working.

I have replaced the TPS and the IACV. The MAF tests fine with a meter. Also has new wires, cap, and rotor.

The idle relearn had no affect and there are no codes.

It runs fine, it just has a random stumble at idle like a single misfire.

Any ideas on where to go next?
 
#2 ·
Perhaps some of your small vacuum lines/hoses are needing replaced? They can degrade over time for sure.
 
#4 ·
How do the plugs look comparatively?
Original distributor? If not, hoping it is OEM replacement.
 
#9 ·
Original distributor? If not, hoping it is OEM replacement.
Was referring to the actual distributor core...not the cap. It has been repeated around here that it is best to go OEM when replacing.
 
#8 · (Edited)
Well you can rule out the fuel pump, injectors, FPR, and plugs. Already tried that. No change. Only thing I can't rule out 100% is a micro air leak somewhere. Other possibilities include the fan or Engine mounts. Removing the fan and fan clutch reduces my vibrating to a degree, but then I was missing a blade, so it's to be expected. Still got enough of a shimmy to set off the knock sensor though.
 
#11 ·
I guess I forgot to get back to you guys. :)

I wanted to clean the throttle body before I did anything else so I cleaned the crap out of it. It does seem to run better but no help with the idle problem.

As a work-around I shimmed the throttle off the fast idle cam to give me about 850rpm at hot idle. This seems to be enough to keep the stumble from pulling it down low.

For now, it's just going to have to do.
 
#12 ·
UPDATE:

I had noticed in my Chilton's troubleshooting section that a miss at idle could be bad timing so I decided to check it out.

I followed the ignition timing procedure in the manual (there are some special steps) and found the timing to be at least 5 degrees advanced past the last mark.

After setting the timing to 20 degrees and resetting the idle, its perfectly smooth at idle now. Engine feels and sounds so much better, and quieter too.

I hope to see better mpg at my next fill up.
 
#17 ·
This is what you do:
-Run the engine @ 2000 RPM for two minutes; turn off engine.
-Disconnect the TPS connector (this will pull the ECM in "timing set mode" when you restart.
-Start engine, rev engine several times and then let idle.
-Adjust your ignition timing to spec. using a timing light and by turning the distributor as needed. *Note: most Nissan engines run better with an additional 2-3 degrees of advance to the factory spec.
-Adjust your base idle to factory spec. This is usually done at the IACV-AAC valve adjustment screw (lower-turn clockwise; higher idle-turn counter-clockwise).
-Turn off engine and reconnect TPS.
 
#21 ·
Before messing with timing I should confirm my timing belt is correct. When I put it on I matched the lines accordingly, then varified the 40 teeth between cams and 43 from cam to crank. After rotating it, the L cam mark was about a tooth off so I backed it up one. So now I have 39 teeth from cam to cam, and it runs smoothest this way. Did you guys have to do this as well?

Note: The idle vibration is the same for both configurations
 
#22 ·
I never counted teeth, I just followed the directions supplied with the kit I used. Lined up the cam marks with the marks on the inner cover, I didn't have a crank TDC mark so I dropped a ⅜ extension into the #1 plug hole and found TDC like that. Then I lined up the marks on the belt with the cams and crank.
 
#23 ·
Brown connector is for the throttle position sensor. The gray connector is for the closed throttle position switch.
 
#24 · (Edited)
Took a while, but finally got it figured it out. This whole time (since purchasing it) the AIC Valve was bad. Like so many other things the previous owner covered it up by detuning it and jacking up the idle via the TPS sensor and fast idle cam. Once I set both of these back to factory specs the bad AIC Valve came back into play causing the truck to idle erratically and stutter at low RPMs. The low RPMs caused one or two plugs to foul during stop lights, which in turn caused the lack of power and stuttering during take offs. So... Swapped out the AIC Valve, new plugs, and did the relearn and now everything finally seems to be running good. For now.

Moral of the story here is that a truck is so much harder to repair when you buy it from a lying piece of **** off Craigslist.
 
#25 ·
A while back my idle started messing up again. It was also just running a bit crappy.
After a recent problem with my Dodge turned out to be a bad ignition coil, I decided to check the Nissan.
Yep, it was bad. I replaced it, reset the timing and the idle and now it runs better than it ever did.

The coil is inside the distributor, but it's not difficult to change the coil.

I used this one from Amazon. COIL
 
#26 ·
Did yours ever have a Check Engine Light? I have a 2002 2.4L and it seems to have a very similar hiccup on idle as yours. I don't have a Check Engine Light is the only thing that confuses me. I you didn't have one either I may just try and swap out the coil in the distributor. I actually have a spare distributor I can just swap out to try.
 
#28 ·
Well, it wasn't the coil, but I'm glad I replaced it anyway! The original coil had a pretty big rust spot on it that was definitely going to cause it to fail eventually. Glad I got ahead of that one!

I did find my real problem though! There's a big crack in my exhaust manifold, haha. I found said crack back when it was just a small crack, so I patched it with JB Weld Exhaust Manifold Repair. To be fair, that stuff bought me an extra 3 years, but now it has all burned off and disintegrated, and the crack is even bigger than before. I found that this was the issue by using Nissan Datascan II on my laptop while idling. The live data graph for the Air/Fuel alpha was a perfectly timed pattern. I didn't notice that until I could see the idle stutter graphically. Sure enough, it wasn't random after all, but a perfect pattern of fuel trim going up and down.

I realized "Hey... the ECM is doing this because the O2 sensor isn't detecting enough gas vapor in the exhaust (because so much exhaust was leaking from that open crack). Thus, it's giving feedback to the ECM to ADD MORE FUEL!"

The stutter I was having was the ECM flooding the chambers with too much fuel. The ECM would then detect the rich condition and would back off on the fuel (and the stutter would go away). This pattern happened over and over again, like you could set your watch by it.

Anyway, I got one of those Dorman exhaust manifold kits from RockAuto and I'll be putting that in as soon as I have time. I should note that I did not get a check engine light for anything, UNTIL I did a system value CLEAR on Nissan Datascan II. I got P0171 - System Too Lean. That is what led me to take off the heat shield and inspect the crack in the manifold that I had patched years ago.

I hope this helps someone, haha. Thanks for the interest, GotToGo :)
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top