Help me pin point this rought idle...!

[Ed_Strong]

Hey again 12Ounce:
To clear some confusion I'll add that the rough idle started about 1½ months ago, started as a slight engine tremmble and in about a period of 3 weeks progressed to what I could describe best as a bad engine shake/woble. It's also been affected by a shudder or surge (not sure if engine or tranny) at a slight gas pedal depression while cruising.

I immediately thought of a injector plugged or spark plug missing.
Reading so many other posters issues with idle being caused by a bad coil I figured I must had the same problem, so I went ahead and replaced the coil, I figured I should throw the wire set sincew I'll be working around them anyway and it's gatting close to the 60k mark. But the wires and coil didn't fix the problem instead I ended up with a backfire and poor engine performance caused by my own mistake, after taking so many precautions I still ended up crossing 2 wires causing the missfire/backfire which was eventually corrected and bringging me back to square one with the initiall rough idle problem. So again to clear things, the spark cables replacement didn't changed a thing.

Thanks for your suggestions, as I almost did take the whole upper intake out to make sure nothing got screwed, but after putting the old spark plug back on the engine I did inspected all vacuum hoses wire connections and components to be sure I could rule out a leak or a wire fault.

The fact that I never got a CEL, found the engine at a loss of performance and fuel consumption still normal has me confused and at a loss, making me think the engine might not be the culprit here. But then again, I can't be 100% sure!

[CnlK]

In another thread, the crank key sheared allowing the crank pulley/balancer to rotate out of proper position. If you ever had the alternator, idler pulley,
or other accessory seize up on you this may have happened. Scan tool will probably not detect, as it senses that timing is correct. While looking at some photo's of 3.8's, it appears that there is a counter balance driven by the camshaft. If the timing chain jumped as was previously suggested, that would also throw the whole works off, including the synchronizer. Maybe 12 ounce could confirm the presence of a counter balance. You would think any out of balance issue would effect the engine at high speeds also.

[Ed_Strong]

I do feel it at engine high speed, but not as strong as in the idle to 1500 RPM level, at high speed the engine vibrates as similar as when a tire is off the floor in a jack or something... hard to explain! Something like when you drive over a draw bridge (the kind that you can see thru when looking down), or like a rear wheel drive car with a bad driveshaft joint.

My Tech guy checked the crank pulley balancer last nite and he did mention the possibility of the camshaft counter balance along with a bad torque converter theory.
But as I mentioned before the engine performs as normal, there's no loss of power, no bogging down, tranny shifts as it should and fuel comsumption is average. I would assume a bad timming would throw all kinds of weird behavior, maybe a DTC code as one sensors won't be able to keep up with the other. Well I really don't know what to think anymore, I'll have to wait for his diagnose, I just want to get to the bottom of this!

[CnlK]

While I'm throwing some wild guesses out here consider this. On a early 90's Ford Escort a relative owned, the outer pulley of the crank pulley assembly migrated off of its inner hub that was connected to the crankshaft. When looking at a photo of 12ounce's dampner assy, the trigger wheel appears to be attached to the inner hub, the dampner rides on a rubber bushing. If the dampner had some how rotated, this cound throw the engine out of balance. You mentioned pulling the serp belt to rule out any accessories and I assume to check the crank pulley for a wobble. While I don't want to create any unneccesary work on a wild guess, it might be worth pulling the dampner assy and inspecting. Hope you get this one solved soon.

[12Ounce]

As Cnlk points out, the timing ring is rigidly mounted to the hub so it's not apt to get out of place. But if the belt pulley portion of the balancer slips on its rubber bushing ... will that cause an out-of-balance situation? I don't think so ... the belt pulley portion looks pretty symmetric and balanced to me.

Noticing the rubber was a bit cracked on my unit, I did the following check: After the balancer/pulley was mounted on the crank, but before the heads were mounted; piston #1 was brought to exact top dead center ... and then the marking on the pulley was checked and found to be exactly aligned with the front cover indicator. So that pretty well proves my balancer/pulley has not slipped. Now looking at the photo, one can count 8 teeth from the centermark to the tooth gap. This can be a reference for anyone to use to see if their pulley has slipped or not.

[Ed_Strong]

Sounds interesting... but from looking at the picture, isn't the center mark section and the tooth ring screwed together? That would tell me that for the two parts to shift, the screws would either have to break off or come loose.

What I need to figure out is if the center mark and the crank pulley actually shifted from each other, but I don't see anything I could use as a reference point to verify correct allignment.

12Ounce, is there a counter balance of some sort mounted on the damper pulley? If there isn't any, then I would agree with you in not thinking that it will that cause an out-of-balance situation. Also I would assume that for the crank pulley to cause such a wobble/shake/vibration it would be visible if the damper is out of balance, which the Ford tech already checked for.
I'll still run it over my tech guy when he stops again, I havent heard from him

[12Ounce]

No, the toothed ring is bolted to the hub ... but the massive belt pulley is rubber mounted to the hub .. the two (toothed ring and pulley) are not hard attached to each other. I don't know of any "counter balance" section of the belt pulley ... wish I had another chance to look at one. I may pick up one at a parts counter and take some more photos. I think the idea is to use the rubber mount to isolate the serpertine belt and its loads from the small irregularities of crankshaft rotation ... and vice versa ...helping to smooth out both in the process

There is a counterbalance shaft that is above and driven by the camshaft.

Have you run the engine with the belt off?

[Ed_Strong]

I know this thread is getting pretty long quickly, but a few posts back I stated that the Ford Tech friend took the belt off and checked the damper turning and also tried prying the mounts to move the engine from idle to 2000 RPMs to rule out a bad engine mount.
He then took my VIN No to check at the dealer and run an OASIS report to check for other repair with the same problems.

[12Ounce]

Yep, I have now reread that post.

The only counterbalance shaft I know of is the one I've already mentioned. Lengthwise ... just over the camshaft and revolves the opposite direction.

I continue to recommend opening up the intake and closely inspecting all plastic parts ... holding them up to the Sun, checking for hairline cracks, ... fit of internal horn-manifold ... air flow blockages .... etc. No telling what you might find. After that, I would drop the oil pan for a look-see. After that, the big one ... heads, etc.. ... ... but hopefully you wont get that far before discovering something simple and easy.

[CnlK]

I realize that a slipped hub on the crank pulley is unlikely, I thought that the
dampner part of the pulley was constructed in a way as to give some counter balance. I felt the pulley on my 3.8 and it is constructed that way, it is not symetrical. A sheared key is also unlikely but can happen. About the only way to confirm would be to get #1piston at TDC and check alignment of timing mark with pointer that is part of the timing chain cover. Getting the #1 piston at TDC can be a little tricky as the crank will turn of few degrees before and after without the piston moving. I've attempted this by inserting a rod in #1 cyl while turning the crank back and forth and watching the timing marks, not easy to do by yourself. If by chance the key was sheared, then ignition timing would certainly be off. If the dampner portion just rotated, then a possible out of balance condition could be present. In a previous post you mentioned replacing the idler pulley, was the bearing seized? That could possibly have caused something to slip. Seems like you definetly have a unique problem.

[Ed_Strong]

The idler pulley felt too loose and wobbly when I did my own pulley check, it didn't seize up on me. But still I decided to replace it, at $15 it wasn't a costly choice and it made me feel better.
So how about the tranny sugestions by my friend? You guys don't think it could be the tranny causing all this? Again fluid is at level and looks/smells good, tranny shifts normal, there's no slippage or hesitation which makes thing harder to diagnose.
Before all this the van used to surge or shudder with a light gas pedal aplied while cruising as posted here many times in other threads. But since I replaced the battery it has not happened again! Other than that and the groanning sound I never was able to fix/get corrected (see thread here) everything seems and feels normal with the tranny.

[Ed_Strong]

I have a bit more info:

My friend took the van again to look it over and discovered that when he tried to verify if the crankshaft pulley bolt was secured by tightening it, the whole pulley assembly moved so slighly and led him to believe that the pulley has shifted off balance.
He assures to me that the pulley/damper has a counter balance, which could confirm the out of balance vibration if it's shifted out of place.

Problem #1
This darn pulley is $250 at the online Ford Parts (Genuine Ford Parts, Y2K Ford, etc.), Rock Auto doesn't even lists it on their onlie catalog.
He suggest buying one from a junkyard for a fraction of the price, but who knows what I could end up with!

Problem #2
When looking for the price at Team Ford Parts they offer an exploded view of the engine components <<check here>> (hope linky works) and it shows the damper pulley as a two piece -Item #30 Pulley and Item #29 Vibration Damper it would be nice if I could just get the Vibration Damper by itself but the online catalog doesn't list it.
On the other hand the exploded view on my Service Information Manual shows it as one whole piece, so I'm not sure what I'm looking at.

[CnlK]

Mr. Strong, you might be able to get by without installing a new assy. Pull the old one, maybe the bolt loosened and the key sheared allowing the whole assy to shift out of proper position. If so you could reuse if the bore is still in good condition. While the assy is off compare it to another one (if available) to see if just the dampner portion rotated, in which case a replacement would be necessary.

[Ed_Strong]

Last Update:

Just got the van back tonight from the shop. New Crankshaft Pulley/Damper installed, problem solved! No more idle issues... purrrs like a kitten. Wife is happy, and that's all that matters.

Thanks to all that contributed to this thread. I really appreciate all your attention, patience and helpfull suggestions. I hope this can help someone else avoid all the headaches I had to go thru!

[12Ounce]

I am delighted that your engine runs better, but totally surprised that the crank pulley was the problem ... especially at the relatively low mileage of your vehicle. Thanks for the feedback.

Do you have any suspicions as to what may have caused the pulley to fail? A lot of exposure to oil perhaps? ... road salt? ??? Was the pulley loose on the hub, or had it just slipped?

I am going to be more critical of mine (230kmiles) now, and closely compare it to a new one.