wont idle when cold - CEG Archives

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first off i want to say im new here.. now i have a 99 Mystique V6 automatic. my CEL is on and i am gettin a bank 1 and bank 2 lean code... and now since the cold has hit DC so hard when i start my car it wont hold an idle unless i idle it myself until it warms up completely and its has really harsh vibrations... and i dont have any busted mounts, and jus got a tune up using Motorcraft Platinums.... any suggestions??

I.A.C. module may be bad.

Having BOTH banks lean PO171 and PO174 means intake or vacuum leak. Having an intake or vacuum leak and your car wont idle correctly.

Spray around your intake gaskets with the car running at idle does the engine stumbles if yes theres your leak, if no then it is a vacuum leak, very hard to find so my best advice is buy hose for .99 foot at Autozone and replace the lines till the idle stays normal and the code goes away.

Originally posted by HITMANinMI:
Spray around your intake gaskets

You should probably explain what to spray. Starting fluid or carb cleaner are good choices. Just be careful as you're spraying flammable liquids around a running engine.

I just had this problem myself last week. Unfortunately I ended up having to take it in to a shop to have the work done, but they replaced both sets of manifold gaskets which eliminated the problem. Seems like the onset of cold weather causes older gaskets to develop leaks, as this is the third instance of this I've seen (including mine) in the last couple weeks.

ill try that and see what happens.. now i gotta get the car from philly to dc so i can try it...

Originally posted by hetfield:
...they replaced both sets of manifold gaskets which eliminated the problem. Seems like the onset of cold weather causes older gaskets to develop leaks, as this is the third instance of this I've seen (including mine) in the last couple weeks.

Make it four. My wife's 2000 Mystique LS (AT) just rolled over 100k and started this today, to the extent of being nearly undriveable. Keep the revs above 1000 or 1500, and she runs alright. Slow down though, and it sputters and chugs almost like it's missing, and sometimes stalls out entirely. At first I thought "plugs/wires" but after reading the forums here, it sounds like it might be the manifold gaskets.

Is there any DIY information anywhere (preferably including photos) (other than a Haynes/Chilton) on how to replace those? I'm pretty familiar with my car (a '90 Miata) but her car is much newer and very different - FWD and much less room in the engine bay to work. Is this something I can do myself, or is it going to have to be done at a garage? If you don't mind my asking, what did you pay to get that work done?

Oh, also I've seen some info that says it may be the IAC (valve?). What's that? What's it cost to fix/replace?

Thanks very much.

So what was the verdict? It has been at 5 degrees here in CT lately and my wifes car (99 SE V6 with 95,000miles) started doing the same thing.

I got a left bank lean and right bank lean when I first looked at it. Cleared them and took it for a test drive (20 minutes mixed driving) and got another left bank lean no right bank that time.

The idle gets better the longer the car is running. Something in the engine bay is not happy with the cold and as it warms up it starts to function better (not quite properly though). I had the wires and plugs replaced over the summer and I know the shop put a new manifold and gasket on the upper intake.

busychild424 -

Here's info on the IAC:

http://www.contour.org/FAQ/FAQ.php?s=probs&displayid=7

Thanks. I'll give that a try.

No verdict yet. We replaced the IAT sensor and thought that had fixed it for a while, but now we're getting the same trouble again. I'm going to get an OBD-II reader to help diagnose the problem. It's inconsistent enough to make me doubt a gasket leak and makes me suspect something electronic (the PCM...ouch).

hey dont worry i had exacly the same problem and it bugged the hell out of me bc my car would just die on stoplights.anyways its definatly your MAF sensor and nad new they are very expensive. good news you can save money but doing it your self. its easy and does not take long

you will need 2 cue tips

saw(it will come handy)

flat head screwdriver

Begin by taking the filter off, then disconnect your MAF pipe where sensor located. The hardest part is to get the sensor off the pipe because you will need a special scredriver to open it and ive looked everywhere for it untill i came with this idea. I sawed the screws head inhal so i could use flat head instead. When you done carefully lift the black box out and you will see 2 little sensirs there. Use cue tips to clean them careflly making sure you dont bend them blow some canned air if you want. just make sure sensirs have no dirt on them after you dont assemble back and connect the sensor.Restar your cars computer by disconnection car battey. Reconnect and the light will go off.
My light still hasent came on and the show said that they will fix it for me for estemate of 175 bucks.

hope this will help your problem,

Originally posted by drfrankenstein:
first off i want to say im new here.. now i have a 99 Mystique V6 automatic. my CEL is on and i am gettin a bank 1 and bank 2 lean code... and now since the cold has hit DC so hard when i start my car it wont hold an idle unless i idle it myself until it warms up completely and its has really harsh vibrations... and i dont have any busted mounts, and jus got a tune up using Motorcraft Platinums.... any suggestions??

Same exact thing happened to my '99 Mystique recently. In extremely cold weather, it wouldn't idle unless I kept my foot on the gas, and even warm, sometimes the idle was unstable. Took the car to the dealer last Friday, they got the lean codes for both banks. Had to replace the intake manifold gaskets. Sum total of $425. Runs great again.