Nissan Frontier Forum banner

1 - 20 of 24 Posts

·
Registered
Joined
·
337 Posts
Discussion Starter #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?
 

·
Premium Member
Joined
·
6,088 Posts
Perhaps some of your small vacuum lines/hoses are needing replaced? They can degrade over time for sure.
 

·
Registered
Joined
·
337 Posts
Discussion Starter #3
You know, I did a hose inspection first thing. But I didn't do an actual test. So this morning I ran a couple of tests and found no leaks.
 

·
Premium Member
Joined
·
6,088 Posts
How do the plugs look comparatively?
Original distributor? If not, hoping it is OEM replacement.
 

·
Registered
Joined
·
337 Posts
Discussion Starter #5
Plugs look good. I replaced the cap but I don't remember which one it was. It made no difference.
 

·
Registered
Joined
·
306 Posts
Good luck finding the source. If do, then come back and tell the rest of us million+ frontier owners with the same issue how to solve it.
 

·
Registered
Joined
·
337 Posts
Discussion Starter #7
Good luck finding the source. If do, then come back and tell the rest of us million+ frontier owners with the same issue how to solve it.
Really?!

I didn't see any mention of this issue on this forum when I did my searching. But maybe I just suck at searching.

I have an idea for a work-around that I'm going to try tomorrow. I'll let you know.
 

·
Registered
Joined
·
306 Posts
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.
 

·
Premium Member
Joined
·
6,088 Posts
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.
 

·
Registered
Joined
·
337 Posts
Discussion Starter #10 (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.
Hmmm, I was leaning toward injectors. But I'm not ready to give up yet so I'll keep looking.

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.
Oh, gotch ya.

Yeah, original, as far as I know.
 

·
Registered
Joined
·
337 Posts
Discussion Starter #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.
 

·
Registered
Joined
·
337 Posts
Discussion Starter #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.
 

·
Registered
Joined
·
306 Posts
...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...
That's awesome news! Now you just need to explain exactly how you did all that for those of us who are less mechanically inclined :)
 

·
Registered
Joined
·
337 Posts
Discussion Starter #15
I'm curious to know what the difference is in setting timing at idle with a warm engine vs doing the tps disconnect?
Me too. My guess is there is some kind of timing adjust going on behind the scenes that needs to be disabled to get an accurate setting. But I'm just guessing.

That's awesome news! Now you just need to explain exactly how you did all that for those of us who are less mechanically inclined :)
Page 29.

Section Of Manual
 

·
Super Moderator
Joined
·
3,188 Posts
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.
 

·
Registered
Joined
·
120 Posts
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.
When you say "disconnect the tps connector", would that be the top or bottom connector?

 
1 - 20 of 24 Posts
Top