Rough Idle on 3.8 Non SC - TCCoA Forums
 
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post #1 of 15 (permalink) Old 11-02-2003, 05:39 PM Thread Starter
 
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Unhappy Rough Idle on 3.8 Non SC

I am at my wits end and need some help. No matter what I do can not seem to get a smooth idle on this 3.8. Ran superbly till about a month ago and then this started. Some Details:

Idle is within Specified Range Approx 800 in Park and 600 in Drive.
Timing is at 10BTC with SPOUT out and at about 20BTC with SPOUT Connected.
No Vaccuum Leaks found or all have been repaired already.
Replaced IAC.
Replaced EGR Sensor.

Scan Codes Showed
KOEO 11 on Active 22, 31, & 63 on persistant scan.
KOER Showed 33.

Replaced EGR Sensor and this cleared all error codes but not my problem.

Checked Engine Coolant and see NO Oil present in the Coolant.
Checked Oil and see no Froth in the engine oil.

I will be doing a compression test on the engine in the morning but I don't think that it will show much.

Any ideas?
Scott
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post #2 of 15 (permalink) Old 11-03-2003, 11:44 AM
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How are the plugs and wires? Those could be possible causes of a rough idle.
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post #3 of 15 (permalink) Old 11-03-2003, 12:40 PM Thread Starter
 
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Compression test completed. 160psi all 6 Cyl
Wires Just changed. Motorcraft OEM
Plugs Just changed. Bosch Platinum +4

Could the TPS Cuase this sort of problem?
Code scanner did not show any abnormalities, but I'm losing faith!
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post #4 of 15 (permalink) Old 11-03-2003, 03:00 PM
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ok guessing its one of 2 things...

Presure Feedback Electronic Transducer (PFE)
EGR Vacuum Regulator (EVR)

If you put a vacuum gauge just before the egr valve you can determine which one it is. If the vacuum never changes then replace EVR and/or hoses to and from it. If it does change then its PFE, and/or the hose going to that.

The book I have is a 1990, so 89 could have a different system, check to see if you have a PFE Transducer before you start to get that feeling of hope.
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post #5 of 15 (permalink) Old 11-03-2003, 07:28 PM Thread Starter
 
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Well, there's no PFE but, there is an EVR. However, while looking I found a BAD motor mount. Motor lifted up about 3" while checking it. It looks like the mount completely seperated. I'm not sure if this is "the" problem, but it is a problem.

Feedback please... Does anyone think that this could be causing the problem?
I'm getting hopeful...
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post #6 of 15 (permalink) Old 11-03-2003, 08:03 PM
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Quote:
Originally posted by great_scott
Well, there's no PFE but, there is an EVR. However, while looking I found a BAD motor mount. Motor lifted up about 3" while checking it. It looks like the mount completely seperated. I'm not sure if this is "the" problem, but it is a problem.

Feedback please... Does anyone think that this could be causing the problem?
I'm getting hopeful...
That is your problem Scott! I have the same model/year as my second set of
winter wheels and I went through the same issue a couple'a years ago.
Definetly change the left & right mounts, you'll notice a big change
Busted mounts will give you a wierd idle.

Chris.............

Last edited by ChrisW01; 11-03-2003 at 09:03 PM.
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post #7 of 15 (permalink) Old 11-03-2003, 08:17 PM
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ok then it was probably the type that had it in the egr valve, sooo you replaced it. Change the EVR, and see if it fixes your prob, its just a solenoid between the egr valve and a vacuum source. Its a fairly common part, you can find it easy in a junk yard. Don't think it would cost you more then 20-30 bucks new.

I don't know how a busted mount would be the problem, but whatever works.
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post #8 of 15 (permalink) Old 11-03-2003, 09:17 PM Thread Starter
 
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Ok, I have the Mounts, and they're going in Wendsday. Can't do it tomorrow because I have to work from 5:30am till about 11:30pm so Tomorrow is shot. I will also price the EVR while i'm at it. I sure can say one thing, I've found every problem that this bird had. So when I get done it'll probably never have had run better since I rebuilt it. (After the Head Gaskets Blew ofcourse...)

Wish me luck...
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post #9 of 15 (permalink) Old 11-04-2003, 01:40 AM
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I hope your repair goes well!

By the way, I think the "EGR sensor" you replaced is really called a PFE. It measures the pressure drop in the EGR vacuum lines.

-------------------

Steve

Owner, 1990 Thunderbird SC, white w/ gray cloth
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post #10 of 15 (permalink) Old 11-04-2003, 02:35 AM
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Wait you replaced egr valve positioning sensor (EVP), the sensor screwed to the top of the egr valve? I thought it said just egr. It could be the egr valve itself then.
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post #11 of 15 (permalink) Old 11-04-2003, 04:03 PM
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No, he didn't replace an EGR position sensor. The 89 doesn't have one. All there is is an EVR solenoid, an EGR valve, and a PFE transducer. His first post said he replaced the PFE transducer, although he called it an EGR sensor. So, all codes are gone now. A good sign.

Plus, he has a completely bad motor mount. That is almost certainly the cause of the problem.

I wouldn't spend any money on an EVR until I replaced the motor mounts and saw if the idle smoothed out. I think it will.

-------------------

Steve

Owner, 1990 Thunderbird SC, white w/ gray cloth
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post #12 of 15 (permalink) Old 11-04-2003, 04:25 PM
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I still don't get how a broken motor mount causes a bad idle, but oh well.
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post #13 of 15 (permalink) Old 11-04-2003, 07:04 PM
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I know what you mean, but think about it: the engine isn't properly restrained. So at idle, it shakes more than it should. It mimics some other problems pretty closely.

You're right about the EGR being a potential cause of idle problems, but I think it's just better here to wait and see if the motor mount fixes it.

-------------------

Steve

Owner, 1990 Thunderbird SC, white w/ gray cloth
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post #14 of 15 (permalink) Old 11-09-2003, 02:44 AM Thread Starter
 
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Well,

I finally did it. I had not one but two completely busted motor mounts. I guess that luck was all that was holding that motor under the hood. Nasty, little problems that they can cause. The idle is back to normal. Never would I have guessed it. Bt I'm glad that it worked out the way that it did though. I got to fix every other problem that the car had while looking. These tings were a Bi#$h to change though. I would not want to do them again.

Thanks for all the help.
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post #15 of 15 (permalink) Old 11-09-2003, 05:06 PM
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Congradulations !!

Glad it worked out for you
Its wierd busted mounts would do that.

Chris............
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