LilJapnBoy

iTrader: (6)

As the title says, lately my idle has been really erratic. When I'm stopped at a light or parked, my idle will jump up and down anywhere from 1000 rpm down to 700 or so. My idle increase/decrease is inversely proportional to my vacuum at idle. So when the idle drops the vacuum moves up closer to 0 and vice-versa.

It never stalls out but once or twice it's sputtered down to 500 rpm or so.

This is a list of my performance mods:
1) TBE (w/ test pipe)
2) MBC
3) Custom dynoflash
4) Grounding Kit
5) Buschur Air intake filter

As you can see I have no cams/cam gears, etc. Basically bolt-ons and tuned.

Here is a list of things I've tried to alleviate this issue:
1) Changed spark plugs (now running NGK BPR8eix)
2) Cleaned intake filter
3) Reset ecu
4) Checked for visual boost leaks (I'm boosting fine, 21psi at peak with no leak)

I've had recommendations to clean the throttle body or check spark plugs wiring.
Before I take it in to get professionally looked at, are there any other thoughts or recommendations that haven't been mentioned?

Thanks in advance!

LilJapnBoy

iTrader: (6)

Bump.

GIsnickers

iTrader: (3)

Stock plug wires?
What is the gap on the plugs?

I just changed out my plugs because my car was doing the same thing, they were fouled to hell. It seemed to drive fine, but ran rich as all hell.

I talked to a few people and wound up going with the NGK BR7ES @ .028. Car idle's great now.. 272 cams as well installed. (stays around 900rpm)

I don't now how to explain the sound it was giving off. But it was more of a steady rumble, then it would try to stall and then try to catch up to itself -> stall -> catch up -> stall -> catch up (in that sequence). It was weird.

I was running the NGK Iridium Plugs before.. Dunno, I am starting to think all these OMFG Parts are all a matter of opinion sometimes. I also couldn't boost more than 19psi without it popping due to the plugs being fouled. Reply when you get an update, I am interested to see if it was the same problem or close to it.

j8

iTrader: (4)

Were you tuned for all the mods at the same time, or did you add something after the tune? Hows the weather? My car idles kind of crappy with the 90 degree weather and 90% humidity. Idles great when I am out at night. Just a thought.

LilJapnBoy

iTrader: (6)

Thanks for your feedback.
I'm running NGK BPR8EIX @ .028 gap, actually these were recently changed out because I thought it would help my idle. The original plugs were in good shape though.

But I got dyno'ed the other day and I definitely am running super rich.

Doesn't appear to be any boost/vacuum leaks, I am running out of ideas. Cleaning the throttle body doesn't seem that common on the Evo for some reason....but it's one of my last ideas.

LilJapnBoy

iTrader: (6)

The weather definitely doens't help, we've had high humidity and high temps here for the past couple of weeks. But before all that when it was significantly colder and drier, I still saw erratic idle.

I have added nothing performance related since the tune. I actually put in a fuel pump just before the tune so I could see some gains by bumping boost.

LilJapnBoy

iTrader: (6)

UPDATE:

Went and got dyno'd and found I had a bad tune. But apparently my tune had nothing to do with idle or RPMS below 2k.

So, I took my car into the dealership to get looked at and see if they could figure it out. Plugged a bunch of equipment in, took a bunch of readings, and didn't know what was wrong.

So they changed the MAF sensor to see what would happen, to no avail.

The next step they wanted to take was to replug my O2 sensor back into the midpipe of the catback instead of where it is currently in, the test pipe.

To my knowledge the rear o2 sensor shouldn't have any deration on the engine and therefore shouldn't effect idle....so this action would be unproductive, right? To my understanding the rear o2 sensor just measure richness and throw a SES light and code if too rich.

Other ideas thrown around were changing the throttle body and idle controller and cleaning injectors....

I just read BishiBoy's thread on lowering gap of spark plugs to .025, thoughts on this? I am running one step colder plugs than stock....

DaWorstPlaya

iTrader: (31)

When the weather gets hot, it happens on stock cars as well ... its normal and nothing to worry about ... as long as your car doesn't die while idling ...

MalibuJack

iTrader: (5)

I actually had a pretty bad misfire early on with my car.. ultimately I upgraded my ignition, but try reducing your gap to .025 (like you mentioned) It seemed to help on my car for awhile at least to improve my idle for awhile.

I also think there may be some validity to the humidity/temp thing affecting idle, when my car was closer to stock, I used to see that happen quite often, even more when the a/c was on.

When they looked at your car, did they look at the long term and short term fuel trims? I find if the trims are +/- any more than 10% the car will have symptoms that your describing, best I can say is its something like hunting for a mixture.. When I made some changes that put my long term trims back within 10% (7% on my car in the summer) the idle speed was more stable, though misfire was still pretty bad with the iridium plugs (thats another story in itself) Ultimately I upgraded my igniton somewhat and managed to get the car to idle real stable now and alot of the other issues (popping or the misfire you described) is no longer a problem.

And yes, with the stock ignition coils and wires, running one step colder than stock with the stock gap (or even at .028 or so) will misfire anywhere from occasionally to frequently.. so gapping down to .025 is definitely a good idea.

LilJapnBoy

iTrader: (6)

Thanks for the response Mailbu, I will try dropping the gap to .025 and see how it effect my idle.

I don't think they looked at long term/short term fuel trims.
a) What are the baseline %s to adjust the +/-10% within?
b) How is fuel trim adjusted?

MalibuJack

iTrader: (5)

Basically on an OBD-II scanner, the long term and short term fuel trims are from 0, which is the optimal base tune of the car, the reason it varies can be weather, or other conditions... once it goes over 10% the air fuel mixture swings back and forth periodically as the fuel trims "Reset" themselves, which can explain why it will run ok for awhile, then suddenly feel like its stalling or idling poorly, it happens on alot of cars actually. When you have a bit of misfire, it compounds the issue because it cant fire as well when its a little too rich or too lean, so it stumbles more and can stall.

As far as I know there is no easy adjustment for this, I recall at one time the earlier DSM MAF's had an adjustment on them to allow it though. But on the EVO I have never seen anything on the MAF that was adjustable.

In reality, this is something that would never normally be an issue unless you were in a dramatically different climate, but It would be something that you would adjust with a piggyback, calibrator, or some MAF intercept device. Otherwise it would be something adjusted in the ECU itself and probably done with a reflash

I your list of mods said a buschur air intake filter, I'm not quite sure if you meant just the cone filter, or the filter and hard pipe that goes to the turbo. However I did notice when I first installed the buschur filter (The first mod I ever installed) my long term fuel trims would hover around -23% (Going from memory so I dont recall if it was positive or negative) and on really hot days, I would get the idle being very poor at times, likely because it was periodically very lean and a very lean mixture is sometimes hard to ignite.

I don't know of a simple tool or fix for this, since the ECU is still in control of these settings, its likely a reflash can help it, since it could set the base trims (the starting point) which would make it less likely to have to hunt in closed loop. Now that I think about it, you could have your dealer raise your base idle slightly so when the idle control solenoid resets when the fuel trims reset, it won't drop down in speed as much, that could help a little bit.

Another possibility is a defective (slow responding) front O2 sensor.. I've seen that happen, but very very rarely.

LilJapnBoy

iTrader: (6)

another good explanation, sounds like not an easy solution to change fuel trim levels. although it sounds very close to what's happening with my car. it seems like my ecu is having trouble adjust mixture and keeps readjusting itself.

i do have a buschur intake filter, just the filter, not the hard pipe. i have thought about putting my stock airbox back but other tuner shops and even the dealership tech told me that the cone filter should be ok.

i recently got a dynoflash and while the idle was a little jumpy it would stall out when he put a 'base map' on it. at the time i thought we pinpointed it to a bad connector on my s-afc2 so we pulled it and reset the ecu. it was solid, the best idle i had in awhile but over time it got bad, worse than before.

so currently i know i have a bad flash however apparently this flash is supposed to have no bearing on idle (aka below 2k).

in retrospect should have i gotten the same level spark plugs as opposed to the one step colder ones.

MalibuJack

iTrader: (5)

Idle issues can come from so many obscure places, a vacuum leak, one of the intercooler lines leaking, your DV leaking, the MAF not being clamped down tight enough to the intake pipe, one of the nipples on the lines in the intake pipe falling off (allowing unmetered air)

poor ignition is just part of it... I would suggest temporarily swapping the stock airbox back on and seeing if your idle improves any.. You don't have to drive it around that way for long.. just a few run cycles in one day..

LilJapnBoy

iTrader: (6)

Just wanted to put a final note on this topic, especially for those with similar problems and try to search for idle issues.

I finally got my idle issue resolved after over two months of trials and tribulations. The solution? BOV. Turns out my stock BOV was leaking from 20-16 very slowly. This in turn affected my idle as well, after this was swapped out, my idle has been solid (knock on wood).

I didn't understand how this had such a traumatic effect on idle, I didn't think I was leaking boost because I would punch it in 3rd gear and would hold at 20....it took a dyno to expose this problem.

Here is a list of things I tried beforehand to resolve this issue before this finally was fixed:

1) Changed spark plugs
2) Cleaned air intake
3) Checked for visual boost/vacuum leaks
4) Changed MAF sensor (dealer)
5) Performed diagnostics, confirmed O2 sensors working properly
6) Cleaned throttle body
7) Checked fuel pump, filter, connections
8) Checked grounding kit
9) Unhooked boost gauge and lines
10) Checked IC piping connections

4ringturncoat

iTrader: (21)

The BOV can have pretty big effect on how the car will idle, just by changing the seat pressure on my Type S I can effect how well she idles. Other thing I noticed is the more humid the air the worse it idles. I will start watching the trims to see what they are doing. Also, what rpm do you have the idle set, I have found 100 rpm rise in idle speed will eliminate the idle swings. After I put the DLI-II on the idle got much better and I have been able to open the plugs back up to .028, I am running bpr8es but I think the Denso IW-24's had a more stable idle.