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Old January 10th, 2018, 19:15
ert01 ert01 is offline
NAXJA Forum User
Join Date: Jun 2006
Location: Edmonton, Alberta
Posts: 623
Re: Idle drops when HVAC controls are adjusted

Originally Posted by HttpWayne
He's right. The chances are your idle is just low and it only seems normal to you when the ECU bumps it up when the AC compressor is turned on (defrost does that).
AC compressor is deleted currently. Idle is usually around 900rpm IIRC...

Originally Posted by HttpWayne
You can take out the IAC and try to clean in. Mine just sat for over a year and that think was almost welded shut. I had to PB blast and heat gun that mofo a lot to get it to move millimeters at a time. Most people just have one that needs sprayed with carb cleaner to free up the carbon deposits.
Cleaned the replacement when I put it in from my other jeep. Wasn't too bad at all... just a fine film of black on it. No thick sludge or crunchy buildup at all.

Originally Posted by HttpWayne
Hard starting could be IAC related, but I would think you would have an easier time after it's been warmed up. I know with the coil packs in the 00 and 01 you had to have heat shields put under the fuel rail to insulate them from those god-forsaken cat-converters right under the manifold. If you tried to start it up after the vehicle warmed up and it sat for a few minutes (they call it heat soak, the fuel inside gets too hot and causes pre-ignition, and I bet running a higher octane would stop that). I myself have a 2000 and I am tossing those things out next week when I get my head reinstalled. I'm just going to extend the O2's for the post-cat back to a normal cat setup in the rear. It sounds like you live in a cold environment so I doubt that is your issue at the moment.

What does your voltage gauge read? It wouldn't hurt to check the fluid levels in your battery and top them up with distilled water if they're low.
Has a brand new battery in it... but I did a check just to confirm and everything looks good. Right around 13.6V

I'm in Canada and our version of the 00/01 doesn't have the 2 mini cats (at least this one doesn't... maybe there's different emission packages up here?) It has just the one further downstream beside the transmission.

Originally Posted by alwayzAMC
do a google search for a fuel pressure regulator, it snaps into the top of your fuel tank, it is a seperate unit, you can test if it is functioning by hooking up a fuel pressure guage, start the jeep you should have 49 psi, after you confirm that shut the jeep off, if the pressure drops after it is shut off your regulator is suspect. irc it should stay at almost 50 psi even after several hours after it is shut off.

your coolant temp sensor will likely not need to be replaced, just clean any sludge off of it with a bit of fine grit emery cloth.
Looked at some on google... looks like it's right on top of the fuel pump on the 00/01's at least. The replacement pump I put in definitely had a new one on it as I didn't swap any parts from the old pump over to the new one.

I will do a bleed-down test and see what turns up. I could imagine I might have a stuck injector though that might be leaking past. Fuel mileage is pretty poor at the moment and injectors are already on the todo list. But they'd probably have nothing to do with the idle drop/HVAC... I'm thinking they might have something to do with the long start, but the idle/HVAC issue is the biggest concern at the moment since we've been dealing with a long streak of cold weather up here.

I'll be sure to pull and clean the coolant sensor though. I bet it got grimed up when the old original head went.

Originally Posted by Ecomike
What other issues does it have?

Have you tested the TPS voltage at idle?

You may still have a vacuum leak, disguising a low idle, in the HVAC system.

How does it run once started?

I would suspect low fuel pressure. Have you inspected the spark plugs for fouling, or for signs it is running it too lean?

Have you run a vacuum gauge test at various operating conditions?
No other issues that I can think of... low idle when HVAC changed, long start, poor mileage (but so far i've been accounting that to the -30C weather we've been having).

No I haven't but I can definitely do that. What should it be reading?

I'm also thinking vacuum leak too somewhere... but I was always under the assumption that a vaccum leak would cause a high idle, not a low idle?

It runs great when started. Feels smooth, powerful, no stutters or hesitation. Shifts are all good. Drives very nice overall.

I'll pull the plugs this weekend and look. I haven't checked them since I finished the head swap so I probably should do that anyways.

I don't have a vacuum gauge but I can easily get one... I'm thinking I could just plumb on into the intake manifold somewhere so I can see what's going on in there. Unless theres a better place to tie it into that you can recommend?
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