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Discussion Starter #1
Okay, things have reached a head, my car has begun to have a problem staying at idle.

Background:
Last year, or earlier, my car began to pull occasional 0420 and 0430 Codes.

I've had occasional problems with RPM climbing that is probably related to a sticky IACV. However, it's been so intermittent, I haven't been to concerned.

In the last couple months, my car has developed a hard to describe 'ugly, deep' noise, kind of like a deeper version of a Tap/knock. Two sources of noise in the engine bay have been fixed- The main belt tensioner as well as the water pump and the water pump belt tensioner but, this noise remains.

While there has been no color associated with it, my exhaust has begun to smell like a chemical. Not like a burning oil kind of smell but, I'd almost say a gasoline smell but, different enough for me to be unsure.

Now onto today- A day or two ago, I had a CEL come on in the middle of my commute and I assumed it was just another 0420/0430. Well, today for the first time, my car began to stall at idle. When I started it, it would do it's initial rev and then the RPMswould just drop to zero. I manged to get moving with it and it held until I made it home.

I got out my codescanner and read the codes. Again, just the 0420 and 0430.

I'm thinking that the first thing I should do is replace that IACV. A question I have is that if my car had thrown a CEL during that stall evolution, it would stay in there 'til it was cleared by me, correct?

Any thoughts?
 

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A question I have is that if my car had thrown a CEL during that stall evolution, it would stay in there 'til it was cleared by me, correct?
Yes, so unless you removed you battery terminal then it would still be there.

I'm thinking that the first thing I should do is replace that IACV.
I would check plugs first, see if they're fouled or the gap has worn open. Also, check for things like wire arcing.

How long since last tune up? Throttle body cleaning? Fuel injector cleaning? When were wires, plugs, and/or fuel filter last changed?

I don't think this would do it but I would check the PCV valve too.

Also, does it stall like it's not catching as soon as the starter lets go or does it stall after a second or 2? Any misfires or rough idle?

If all of these come back good I would say change the IACV and if it still has problems then the plugs, then the fuel filter, then the wires.
 

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I don't mean to hijack the thread or anything, but since were on this topic, how does a person really know when to name the IACV the culprit of an idling problem.
For instance, right now my 99 2.5L revs up to around the 2.5k -3k rpms area at start up than moderately drops down to about 1200 rpms after about 6 seconds and holds steady. It will also do the same thing when the clutch is depressed or popped into neutral. Also there is no moosing sound...
Any help is greatly appreciated!
 

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I don't mean to hijack the thread or anything, but since were on this topic, how does a person really know when to name the IACV the culprit of an idling problem.
For instance, right now my 99 2.5L revs up to around the 2.5k -3k rpms area at start up than moderately drops down to about 1200 rpms after about 6 seconds and holds steady. It will also do the same thing when the clutch is depressed or popped into neutral. Also there is no moosing sound...
Any help is greatly appreciated!
It's a guess, but a decent one given that our IACVs are known for failing, and a high idle can be caused by the IACV letting too much air into the engine.
 

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Discussion Starter #5
Thanks for the reply MightyPirate!

I replaced all the plugs and the wires (the wires were arcing) in 2005 (around 90k), and I used Autolite Double Platinum plugs (dread the thought of doing that again).

About 5k ago, I had the big 120k service set, and during that set I had BG fuel system cleaner added to my fuel. That's when I had the drive/serpentine? belt tensioner replaced, and then I replaced my water pump and water pump belt tensioner.

Unless it's in the scheduled maint. guide, I don't think I've ever had my throttle body cleaned specifically.

My fuel filter was changed during the 90k service interval.

It stalled like after literally, 1-2 seconds. The RPMs would climb a bit higher than just when the engine is turning over like it was going to start, then, it would just die.

Once it was running though (after I kept the gas down for a bit), it ran fine (aside from the noise that has been there for a little while).

I'm also wondering if the noise I'm hearing is a spun bearing. If so, what would other symptoms include?
 

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Okay, I had an almost identical problem on a Pontiac grand am, it would start run for about a sec, and then die. A good tune up fixed it but I believe the culprit was that the gap on the plugs had worn out 0.01 inches too big. Re-gapping the plugs fixed it up good.

Also, when this happened I had some knocking as well. The tune up plus some marvel mystery oil cleared that up right away as well.

So, I would check the front bank of plugs and see if they are gapped to the required 0.052-0.056 gap. Also, check to see if they've corroded any. If they are fine then I would try the IACV. Cleaning the throttle plate might fix it up but I doubt it. However, I would do that anyway, it's a good idea to help keep the engine running good and it's only about a 20 min. job and will only cost you $5 and a toothbrush.
 

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Oh, and the spun bearing, here are the symptoms:

The bearing supports the crank shaft with a bit of oil so if the oil goes away the bearing can spin around the shaft. This can cause:

"Clunk, clunk, clunk" sound when rev'd
Probably bits of metal in the oil pan.
Probably burning through lots of oil.
Possible smoking or burnt smell.
Possible low oil pressure (maybe not enough for the light to come on)

Things it can damage:
Bearing (duh, but not much to replace cost wise)
Piston rod
Crank shaft
Piston
Engine block

Never spun one myself but if you think you have then get it fixed ASAP! You're probably looking at a new engine if you let that go for a while. I'd say drop the oil pan and look for bits of metal. Also, see if you've been going though a lot of oil lately, if you have, check for an oil leak first, don't assume a spun bearing right off the bat.
 

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Discussion Starter #8
Thanks again! I'll try and check the front plugs soon (darned lack of garage, and winter weather). However, Autolite specifically stated not to adjust the gap on these plugs (possible limitation of platinum plugs?).

I'm due for an oil change in any case so, I think it would be a good time to have the pan pulled and checked for debris.

I do not believe I've been going through any more oil than normal, and there've been no parking stains that I've noticed.

And oddly enough, the hard starting seems to be intermittent. On all but, one occasion this weekend, it started fine. Even this morning when it was 44F out. But, I did notice something over the weekend while I was out in the evening. Dash panel brightness seems to be directly related to my RPMs now (I normally drive with my dash brightness turned down anyways). I'm not getting a charging system warning light. I know what happens when it just fails- i he car would run on battery until it dies. But, if my car wasn't getting enough juice from the alternator to spark properly, I would get some warning, no?
 

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And oddly enough, the hard starting seems to be intermittent.
Same with the pontiac, would go days with no problems, also started fine when warm but sometimes it would take 3-4 times to start it and always with a little gas.

As for the plugs, that's stupid in my mind, unless you have one of those multi-prong plugs I've always been told to gap them properly. In either case, 30-40k miles is enough for the gap to have worn a bit bigger and in that case you should definatly re-gap the plugs to the proper gap.

Dash panel brightness seems to be directly related to my RPMs now
This could be something else such as wires getting old or what not. Apparently the cougar electrical system isn't the best so it's normal to have changes in lighting by adjusting the HVAC system or turning lights on and off or stuff so I imagine that this could be just normal wear and tear on your car.

But, if my car wasn't getting enough juice from the alternator to spark properly, I would get some warning, no?
Yes, a sucky alternator is a possibility but less likely than the plugs and wires or the IACV. Also, I'm not sure if it would warn you, still new to the cougar myself (got mine 6 months or so ago) but the tried and true method is with a multimeter or an alternator checking computer. Google how to check an alternator for that (and if I remember right the cougar's diagnostic mode can check voltages too, check the FAQ for that).
 
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