Fumanchu

I searched but didn't find anything to my situation...


Just a few days ago I discovered my boost leak was because my crossover had a crack in the flange and it wasn't getting a good seal.


I replaced the crossover with my buddies good one and discovered in the process, one of the wires on my air pump was melted off. So I replaced the harness where the air pump plugs in with one I found at a hobby shop. Shrink wrapped all the wiring to give it more protection and put it back together.


So I put it all together this morning and drive away. After about 20 min of driving, I go to slow down and my idle is little over 1500rpms and is fluctuating up and down about 2000-3000rpms.


My car has never had any idle problems up until now I was just wondering maybe I switched the ground and positive somehow on the air pump. If I did, would that be my troubles.



Any suggestions???

Mahjik

iTrader: (1)

Is the airpump working? It should be injecting air at idle and low rpms (you can check it while the car is idling).

Fumanchu

How do you check if its working? I have no idea about this crap


*edit* ok, I went outside and fired her up.


The airpump was spinning and the idle was still f'd up. I then switched postivie and negative and it continued to work. How does that happen?


Both ways though, the idle was still messed up.

Mahjik

iTrader: (1)

There is a pipe on the back of the airpump. Pull the hose and see if you have any air blowing.

SWAT81

iTrader: (14)

or u can check the fuse box

skunks

are you pulling any engine check codes?

user 9348703

Junk the airpump, or just disconect it and see if the problem persists.

Could be a reaction from fixing the crossover.

Fumanchu

Can't check tonight...will check the engine codes tomorrow and see..


I am stumped.

skunks

could be that your throttle cable or your cruise control on the fritz. oh yeah, check your isc, that was my problem which i fixed to day.

the things that effect idle=
I was kinda thinking it’s the...
dashpot
ISC
AWS
Wax rod assembly
fast idle screw
the airpump
avc

good luck

p.s. try seeing if there is someone close to you with a fd, that way you can just replace the entire uim to see if there is anythign wrong there, it will solve a whole lot of the problems which are possible

fdbabb

I have the same problem. The club calls it idle hunting.
BTW, polarity of the wires to the air pump doesn't matter.

Few facts:
I had this problem with the stock ECU, as well as with the PFC in there now.

I modded/disconnected the coolant from the throttle body, so I don't think the wax rod's lack of action has anything to do with it.

I had an Autometer a/f meter hooked up to the O2 sensor. I removed it. Ive also, replaced the O2 sensor. Nothing changed, problem still there.

I reset the PFC ECU by disconnecting the battery and hitting the brake. Now instead of idling from 1000 to 1500, it idles 800 to 1200.

A/F meter goes from lean to rich in step with the idle rising and rich then lean when idle is falling.

When in gear & coasting... if your feeling for it, you can feel the car surge ahead a tiny bit and then back off, in step with the A/F meter going rich then lean, rich then lean, rich then lean, ad nauseum....

A friend sed another guy reduced the amount of weight (influence) assigned to the O2 sensor and his problem with idle hunting went away.

I can get it to stop once the car is warmed up, by slowing the rpms down to 5-600 with the brakes on and engaging the clutch. Don't do this to often dont wanna buy a new clutch.

The cops that happpen to pull up next to me at the light give me a dirty look. I think the idle hunting sounds like me revving my engine in an effort to RACE them! :-)


My theory:
I think there's some lag in the loop somewhere. I think maybe a sensor is is responding to slowly, and the ECU (PFC or stock) compensates , gets no response, keeps on compensating until idle is up, sensor (which one??)finally signals that "yeah thats good, in fact too good, you can stop now". ECU stops idle goes down, sensor fraks out starts all over again.


"Ever shave and squeese a cat/dog till it peed??? I have"
OK... why?

skunks

its just something i though would be funny, but something i do many times a day, 2 days a week hehe

in anycase, you did not really touch many of the things which would effect idle.

the things that effect idle=
dashpot
ISC
AWS
Wax rod assembly
fast idle screw
the airpump
ACV

if you wanna go gun-ho like teamstealth did, try to plug all these or take them off or replace them with block off plates and it should stop the idle hunt seeing as nothing could possibly effect idle now except for your injectors/butterflies plates=throttle plates or your ignition system

goodluck

fdbabb

"you did not really touch many of the things ...."

Thats because I don't think those things affect/cause idkle hunting. I know its not wax rod fer instance... Its not air pump either.

J

Fumanchu

So my hunt for my idle problem was put on hold for Xmas shopping and work.


I called Tri-Point today and they told me to bring it down to look at it. So I start her up and head down there. My idle was just as messed up as ever. So 30 min later when I get to LA, I get off the freeway and....


my idle is perfect. No fluctutation, idling at 700rpms. WTF was that?? I was so pissed I made the drive, I turned around at got back on the freeway right away.


Anybody know what was wrong?? Did the ECU just need to re-adjust?

books

iTrader: (8)

fdbabb,

I have the same problem as you. I also swapped the stock ecu with a PFC and had similar results. I went one step further and swapped out the UIM and all of its attached components/sensors including the throttle body from a car with no idle problem. I checked for vacuum leaks via the carb cleaner method. I beginning to suspect the LIM gasket that others have discovered as their culprit.

fdbabb

SOLVED! at least for me.
The AAS (Air Adjust Screw, below where elbow mates to throttle body)...
was backed out 3 turns. I turned it completely in (right 3 turns then back out 1/2 turn. Idles perfect at 800.

books

iTrader: (8)

fdbabb,

Thanks for your update. I have adjusted the AAS to no avail. I blocked off the end of the intake elbow and the car still ran. I sprayed some carb cleaner around and it appears the LIM gasket is bad.