RajDatta

Hi guys, I finally put the car back together after the turbo upgrade. The car started on the 1st attempt but the idle is hunting between 1k-1.8k. To troubleshoot, I did the following:

1) Disconnected TPS - Idle stabilized but was high at 1.4k

2) Disconnected ISV - No difference what so ever

Also, I noticed a honking sound coming from the engine. I was unable to locate the location.

Does everything here point to ISV? Don't want to remove intake manifold unless I do my due dilligence. Checking all the vacuum lines to eliminate that as a possibility.

Thanks.

black944 turbo

Have you pressurized the intake to check for leaks? If not this is where I would start. It seems awfully odd that the isv would go bad when nothing was done to it, but pull the line to remove the manifold.

Ski

I'd start with double checking all the manifold connections, then vac lines, all lines to the MAF tight? Do you have an MAF that needs to be clocked right, an older one, just curious. Any issues with the manifold setting down right on top of the turbo, the bottom screw on the TB return spring bracket?

Tom M'Guinn

Congrats on getting it back together -- I fear I let you down on that part, but it's on its way...

As for Idle, start by setting the base idle -- i.e., jumper the diagnostic port in the engine bay (assuming you have a 951 harness? ). Clarks has the procedure. If the idle is still high, confirm the throttle plate us physically closing all the way with nothing (inlcuing the throttle stop screw) holding it open even a hair. If the plate is closed all the way, then try setting the idle with the screw on top of the throttle body. Screw it clockwise to reduce the idle. If you have to screw it all the way in to get the idle down to 840, or can't get to 840 by turning the screw, then you need to find where other air is getting in -- i.e., you have a vacuum leak somewhere).

RajDatta

Thanks Gents.

The intake manifold is sitting flat on the intake ports and does bottom out on the front, by the mounting plate.

Ski, the maf was never removed from the J-Boot, so orientation did not change. It is a Max PH Maf kit, which connects to the factory harness port.

I tried starting the car again today when cold. I closed the idle adjustment screw completely and for a sec the idle stabilized, only to start hunting again. I will set the idle as per clarks manual and go from there (it is a 951 harness Tom).

I find it odd that all of a sudden, an almost new ISV gave up and is now acting up. I have a feeling, there is a big vacuum leak somewhere.

Thanks everyone.

Tom M'Guinn

If you turned the adjustment screw all the way in and are still getting a high idle, then air must be getting in somewhere else. ISV's can stick after sitting a long time -- you can pull the hose off the intake and plug both ends to check. Agree it sounds like a leak somewhere.

RajDatta

Well, checked all the vacuum lines and dont see any issues. I can definitely try plugging the ports for ISV to see what happens.

A thought crossed my mind. I did have to realign the rear mounting plate(black piec) for the intake manifold. I wonder if that is set too high and is stopping from the manifold from sitting flat. Anyone ever have that as a possible cause.

At current state, idle is still hunting and goes high if I disconnect the TPS. Maybe a smoke test might be inline. I didn't want to drive the car just yet, until I am 100% certain everything is sorted out.

RajDatta

Thought I was on to something yesterday. I tightened the intake a bit to make sure I had no leaks, only to make matters worse. All of a sudden, the car started running real rich and I saw minor wetness on some of the intake gaskets.

I removed the intake and found #1,3 and 4 intake gaskets all leaking. Also, saw that the intake was rocking a bit because of the rear mounting bracket being too high. Adjusted the 2 bolts by the downpipe and brought the bracket down. Double checked the manifold and now it was no longer rocking and sitting flat without even the gaskets on. Put everything back together and the rich situation was gone but the idle hunting is still there.

At this point, I am leaning towards getting a new TPS and both temp sensors to start. I still think the ISV is not the issue as it looks pretty new. Might also change to a new O2 sensor while at it. Spent plenty in the past, what is a few more $$. Time is $$. I rather save time than get frustrated.

More to follow.

Jfrahm

I would at least check the ISV, since it controls the idle and you have an idle problem.

racerxrick

When my car had those symptoms it was the TPS...but I didn't have any honking sounds

Tedro951

Have you reset the idle AFTER sealing intake (per Toms advice above)?

adrial

Raj,

If you are confident that the intake is sealed up, I'd start with the TPS since that stops the hunting idle.

I'd also suggest you double-check the adjustment of the idle-stop screw -- it should be tightened 1/2 turn after initial contact and then locked in place with the jam nut.

Also check that the TPS clicks when you move the throttle off idle.

If the idle-stop screw is set correctly and the TPS clicks ... replacement is probably your next option.

Crazy Eddie

Hey Raj
Ya know I was down a similar road in the not too distant past....
Don't know with those manifold gaskets maybe leaking etc but you may want to see if its the KLR ?? Could be a long shot but ya never know .. If you have access to the boxes I would just move them around a bit, and see if the idle changes
https://rennlist.com/forums/944-turb...dle-issue.html

Good luck
Regards
Ed

RajDatta

Adrial, I did all those checks besides not setting idle screw at 1.5 turns. Will do that today. But the idle-step screw is set per specs and the TPS clicks right before full throttle close.

I will try a couple of other things today. If I don't get this thing sorted in the next couple of days, I am ordering a TPS.

RajDatta

Ed, I will defnitely try that. Tom McGuiness has been a godsend to me, directing me at some of the possible causes. He did mention the KLR being the case in your car.

I am willing to try anything at this point.

Raj