i apologize in advance for this long post, but i wanna be as detailed as possible so that you guys might better be able to get a grasp of the whole picture.

i have the following mods.... Z-tube, Popcharger, Motordyne 3/8" plenum spacer, TopSpeed headers, Crawford high flow cats, Fujitsubo Y-pipe, and Fujitsubo Legalis-R exhaust

the Z-tube and Popcharger were installed with roughly 1200 miles on the car.... odometer now reads at 20k and change. on very rare occasions over the past 6 months or so (once every 4-6 weeks if i had to put a number on it) when idling at a light, the motor would feel "jerky" is the best way i can describe it.... the idle was lumpy, like it was about to stall. you could feel the entire car shuddering alittle. since this was always at idle or just when easing onto the gas, i attributed it to a crappy 5AT.

like i said, this problem was random and VERY rare, so i never really took note of it as a serious problem. also for the past month or so, the car was throwing a CEL, which read a lean condition on bank 1. i finally tracked that culprit down... my plenum bolts needed to be retorqued. did that, reset the ECU, no more CEL. that was about a week ago.

this past weekend, we put the car on the Dyno Dynamics at MRC Motorsports. the car turned a 247.3 (another 5AT pulled same number with just intake and a borla exhaust... which is weird). while she was on the dyno, after Julian let off the gas, you could hear tons of backfiring and gurgling coming from the pipes. ever since the dyno run, the shuddering, "like i'm gonna stall feeling" happens every time the car is idling.

so i thought to myself, maybe the motor's not getting enough air at idle? checked my popcharger.... thing is filthy. so, i went thru the whole cleaning process today. cleaned, rinsed, re-oiled, let dry a long time. i briefly started the car (like 30 seconds) without the Popcharger filter attached, and it seemed to idle fine. after re-installing the filter, the problem returns.

once you get going, she runs fine and feels just as strong as usual. however, the lumpy idle is there, it hesitates slightly when you ease onto the gas, and the idle is lower than i feel it should be (it hovers right around 600rpm right now)

so.... any thoughts?

my car is in the midst of a full ECU reset right now, so maybe tomorrow morning when i reconnect it will be better. if not, my next step is gonna be to 86 the whole popcharger filter element and overnight a new one from JWT, but i'd rather not spend the $65 on a new one if it's a simple problem that i'm just missing. thanks in advance for any insights you guys might have

 

You will notice a big difference once you take care of the ECU issues...
One of the major problems on this car was a feedback system that compensates for modifications. The oxygen sensors detects fuel mixture and will tell the ECU to richen up or lean out the mixture. This correction factor was way too wide, so some performance components upgrades (intake, exhaust) would actually result in a loss of HP below stock!
We adjusted the correction factor to reduce that compensation reaction. Our tests showed consistent power and torque improvement following installation of an intake system.
We will be conducting additional testing on various intake and exhaust systems for the compatibility of our ECU. Although we anticipate a dramatic improvement per component upgrades, some may require custom tuning to take full advantage of their performance. That info was taken off of Technosquareinc.com Good stuff, and good luck!!!

 

A leak in any one of the components except the Fuji exhaust could cause the symptoms you describe.

A spacer leak can usually be heard if you move hand along the sealing surfaces. Moving your hand over the spot will cause a change of sound if its there.

A header leak can very easily cause it too but of course its a little harder to trouble shoot and fix.

The cats can too but its easier to deal with than the headers.

To trouble shoot possible exhaust leaks get yourself a 2 foot length of 1/4" OD copper tubing and a 3 foot length of 1/4" ID vinyl tubing. Plug the copper tubing into the vinyl about an inch and now you have a improvised stethoscope.

While holding the end of the vinyl tubing near your ear, point the end of the copper tubing against the headers and cat exhaust flanges. Move it around their respective circumferences. If there is a exhaust leak, you will hear its exact location loud and clear.

Once you find the leak you will know what to do.

Hope this helps.

 

If you had a dyno run at MRC Motorsports, why not ask the technician for assistance. I mean the technician was there and saw the situation first hand.

 

i just did an overnight full ECU reset. problem seems to have disappeared.

what happened was this. G-Squad had the dyno meet on Sunday. on saturday i finally fixed the CEL by tightening the plenum bolts. i wasn't gonna dyno, but the car seemed to be running fine... so i figured what the heck.

the problem cropped up on the drive home from MRC, so Julian and the MRC guys didn't know about it or experience it.

the popcharger filter is back on now, clean and reoiled. seems to be working right again.

 

I wonder if this problem could be abated by using that MAF sensor cleaner spray. It's a cheap thing to try in any case...

 

i doubt it... the MAF is fine, b/c the motor ran perfectly without the popcharger filter attached.

 

What kind of spray works good for this? I know some are pretty harsh like the throttle body cleaner STP makes and could damage it. Maybe some type of Electrical cleaner?

 

70% Iso Propyl Alcohol

 

any thoughts on what the idle is supposed to be? my car seems to idle kinda low, like 600rpm. at that rpm, it still feels alittle rough.... if i ease the gas up to like 800rpm it idles smooth as silk

 

650rpm with AC OFF and 800 with AC ON. Too bad current Cipher version cant rise idle on our cars.

 

+1

650 +/- 50 is the spec.

 

anybody else have any ideas?

i've been thru 2 ECU resets in the past week, the rough idle persists. and although the reset killed the check engine light, the car wouldn't pass inspection this morning b/c the "emissions control system" is not ready to be tested thru ODB-II so soon after an ECU reset. the guy told me to drive 100-150 miles, although i guarantee the CEL will come back at that time

Tony, where can i get my hands on 70% Iso Propyl Alcohol? is it really possible that a leak at the headers could be causing this much trouble? maybe they're leaking at the point where they connect to the block? every other part of the exhaust from my crawford cats thru the fujitsubo muffler have been checked. i've also checked all the intake connections, the Z-tube, popcharger, and the plenum bolts have been retorqued.

oh, and the idle problem seems to be intermittent. sometimes it is absolutely fine or very minimally rough. other times it's quite violent and annoying. for example, i drove a maybe 40 mile per way round trip on saturday night without so much as a hiccup, but this morning on my 5 mile commute it was unbearable.

 

subscribing

 

I can't say what the source is, but a leak at the headers can very easily cause exactly what you are describing.

I had TS headers that leaked and it caused exactly your description of idle. I replaced them and the problem went away.

Did you do all the various leak checks? You need to find the source to have any chance of fixing it.

You can find 70% IPA at any local supermarket.

 

havent done a listening check b/c i don't have ready access to a lift. i have been avoiding the headers as an explanation b/c i SURE don't want to re-do that whole thing

one thing to note, the problem is less severe at night (when it's cooler). also, turning the A/C on and off has no effect on the idle RPM. it stays between 600 and 650.

i knew the topspeed headers weren't going to last forever for their price, but i was hoping they'd survive long enough till i go FI. i guess we'll find out

 

Did you check your fuses?