the flyin' scotsman

Car starts fine in all conditions but when cold the idle dies within secs of start to the point of almost stalling but not quite. It then recovers and idles well but high.

On a 'quick' trip to town the car ran very well but is still idling high ~1k rpm.

Cables are set, TPS and ISV were checked but not replaced during the '07/'08 intake project. LH is believed original; due to be replaced this winter with PEMS and sharktuned.

worf928

Condition / History of Mass-Air Sensor?

SeanR

Malcolm, mine has been doing this for months and have not traced it down yet. About the only thing that is not new on my car is the MAF, so that is my next check. I've just not had time to take a look.

I'm going to say it's not the LH because mine is a rebuild from JDS.

Mongo

i would take a multimeter to the pins on the LH and EZK plugs before doing anything else. I found that helped me greatly with an issue similar to yours. You can also use the sharktuner as a diagnostic tool for your car if you can find someone to do it.

PorKen

Temp II? (Cold coolant = higher idle speed.)

the flyin' scotsman

Dave..............MAF was rebuilt JDS; 4 driving seasons ago..........consider remote issue with Johns excellent workmanship.

Ken.........tested Temp II a year or so ago............could have went South since..........I'll retest.

Sean...........I hope my MAF isn't screwed again as the winter budget wont support a new LH/PEMS and my contribution to a 'local' SharkTuner co-op. (BTW dont you return voice mails?)

I should also add that the idle is solid; when it recovers from its cold stutter and when the car is warm.

Mongo

Hey Malcom, just curious to ask this: have you tried disconnecting the O2 sensor? I am just wondering if you may have the same issue as I did before I went open loop.

SeanR

You did call then. I had about a 1/2 dozen people call that weekend and I never found out. Sorry my friend.

The same with my idle, a bit high when warm but solid. I'll be keeping an eye on this thread. Are you also getting a slight stumble on cold acceleration from a stop?

worf928

Ok then. I agree.

When trouble-shooting running issues it is very helpful to know what you are sure about and what you are not sure about.

I agree with the other posters - next check the temp II resistances at the ECU plugs.

Also, did you powder coat your water bridge? If you did, then, run a temporary independent ground wire from the body of each of the two temp senders on the bridge to a cross brace bolt and see what that does. (You can just strip a length and wrap the copper around the base.) Do, this, if you powder coated, regardless of what your resistance check shows.

AO

A faulty throttle position switch can cause a high/eratic idle. Don't just listen for the click, ohm it out.

the flyin' scotsman

No powder coat............the intake and valve covers are in excellent shape considering 21 YO.

I'll retest the Temp II.

Andy..............appreciate the input giving your recent issues...........I may try disconnecting the O2 sensor.

Mongo

I figure it's worth a try. Seems like after all these years our cars may be exhibiting all the same problems related to one thing given the age.

H2

My S4 acted like that....WITH a brand new Temp II gauge. After spending several hundred bucks on other possibles...I ordered a new Temp II because I'd about given up and, instantly, the car has run wonderful ever since.

H2

the flyin' scotsman

I drove the car ~250kms today............great to be out in Nov in this part of the world.

Car ran flawlessly but had the high idle when in the big city and anytime it was idling ~1k rpm.............I haven't checked the T2 sensor yet but I'm inclined toward that being the issue.............TPS clicks when it should but I'll also do the checks at the LH harness.

Thx all

Mrmerlin

while your poking around check the plastic hose junctions, inserted on the MAF boot they are thin and can crack this gives the engine extra air and higher idle also it makes it hard to start