Help me pin point this rought idle...!

[Ed_Strong]

All I can think of at this time is maybe shrinkage for lack of use!

Little history:
The van came into my hands at 33K from my parents (my dad was a Mechanic). They bought it used in Puerto Rico (no winter driving whatsoever) at around 11K and after about 4 years of ownership they had it shipped to me here in sunny Florida.
It gave me the 171 & 174 codes at just 43.5K, (that's what had me thinking of DPFE sensor as a culprit) and I took care of it myself with the help from the leckemby.com writeup.
The van runs and looks great (no leaks of any kind, engine looks new) which leaves me scratching my head as to why so many problem with such a relatively low miles vehicle.

There's also a little issue with a loud growl that feels like it's coming from the tranny. I've replaced the right front hub and axle to no avail. But other than that there are no other problems with this van, I just wish Ford would've make a better design.

The other thing that could have caused it to fail in my thinking would be something like gunning the engine (like to pass a slow vehicle on the road) which make the tranny kick down and put a stress on moving parts.

Or if any of you are familiar with the weather here in Florida, when it decides to rain it really pours down and all that water coming down so hard so fast has nowhere to go. When you're driving the tires not only kick up all that water out the sides, but also into the engine bay. Maybe the sudden cool down from the water causes the parts to shrink and expand and become loose.

All I know is that is started really low and in about a 3 to 4 weeks periond it felt like the engine was missing. I really though a plug had gone bad or that a fuel injector had plugged up on me. I hope this all helps

[aussie_bob]

I have a 1996 3.8L windstar and it has developed an engine vibration ... 700 revs idle is noticible, 1000 revs it seems to resonate and the whole van shakes and the passenger's voice changes due to the vibration ( funny actually to hear ) and when I accelerate, the vibration tends to go under load but I can still hear something ar 2000 revs ... Plenty of power, no CEL and I have checked some for vacuum leaks and the 2 front engine mounts ..
Need to check the back one ... but I think it is the engine vibration ... too rich fuel ?

[olopezm]

Originally Posted by aussie_bob

I have a 1996 3.8L windstar and it has developed an engine vibration ... 700 revs idle is noticible, 1000 revs it seems to resonate and the whole van shakes and the passenger's voice changes due to the vibration ( funny actually to hear ) and when I accelerate, the vibration tends to go under load but I can still hear something ar 2000 revs ... Plenty of power, no CEL and I have checked some for vacuum leaks and the 2 front engine mounts ..
Need to check the back one ... but I think it is the engine vibration ... too rich fuel ?

Welcome to the forum!

I think you might have a problem with the harmonic balancer, it is the crankshaft's pulley you might want to take a look at it.

What do you guys think?

Best regards,

Oscar.

[tempfixit]

Originally Posted by olopezm

Welcome to the forum!

I think you might have a problem with the harmonic balancer, it is the crankshaft's pulley you might want to take a look at it.

What do you guys think?

Best regards,

Oscar.

My thoughts also,

[aussie_bob]

Hi Guys I'm back.

My engine vibration has gone away 9 times and come back 10 times. I can't explain what causes it to come and go but once I parked in the street and it had the vibration and the next morning starting cold it was gone.

I spent some time replacing plugs and spark plug leads ... no change.

I have also had a problem with coolant loss and the cylinder 4 missfire very randomly maybe once a month. Various people have looked at my 96 3.8L Windstar and said vacuum leak was causing the vibration / rough idle ... normally I can track down a leak but was not able to . Radiator stop leak helped stop the coolant loss ... but I finally pulled the plenum and lower intake manifold to see if there was a problem there with coolant or vacuum. Both gaskets showed evidence that coolant was leaking across to cylinders 1 and 4 ..

I replaces those gaskets, cleaned out the clogged EGR ports and replaced the 12 isolator bolts with green ones. Plus I soaked the inbectors and replaced O-rings + plastic washer + plastic cap.

No change regarding the vibration ... but I expect the coolant loss issue to be resolved.

Here is why I don't think I have a vacuum leak .... because with open throttle at 2000 or 3000 rpm, I still feel some vibration and some loss of power. With a vacuum leak, I would expect at open throttle it would be a non issue since the vacuum is much less and a leak would be swamped by the open throttle ( correct ? )

Also I isolated the EGR exhaust source incase that was the issue with a stuck EGR valve / clogged EGR ports but that had no effect.

1) So I will inestigate the "harmnic balancer".
2) I swapped the 3 injectors for cylinders 1-2-3 with cylinders 4-5-6 to have access to them as I thought removing the wires from #1 injector hade no change in idle rpm.
3) My only other thought was that the coil pack has 3 coils ... if one coil is going bad could it cause a vibration due to poor spark on 2 cylinders ?

4) a clogged catalitic converter ?

If I could describe the vibration better, someone may nail this ... it is a mechanical vibration... the whole car shakes and at 1000 rpm, it resonates ... and at 2000 or 3000 rpm I can feel a background vibration via the steering wheel. BUT, when it decides to go away, the Windstar runs so smooth and I believe has about 20% more power.

I am determined to fix this and want to use the "scientific method".

Thanks in advance ... Bob.

[olopezm]

Hi Bob,

Good to know you spotted and fixed that coolant leak!

If you noticed no change in RPM's with injector #1 it could be also because of bad spark or low compression .

You might want to measure resistance across each pair of the coil towers (secondary coils) and compare them; if 2 are nearly the same and one is different that could indicate a bad coil. Same thing applies for the primary side; you'll see 4 terminals at the electrical connector 3 of them correspond to one coil and the remaining is the common for the 3 terminals. You'll be measuring resistance across the common and one coil terminals and compare the 3 readings.

A bad coil could surely cause the shaking but I don't think it would be like yours. I still think you might have a problem with the harmonic balancer, make sure the rubber around it is in good shape.

Oscar.

[aussie_bob]

Thanks Oscar,
I will do as you say ... 1) check out the coil pack. and 2) pull the front wheel off and check the harmonic balancer.

Since my last loooong post, I did remove the auxillary belt to isolate anything like the air conditioner clutch etc. no change except the belw was actually split over about 18 inches ... I replaced with the spare I carry in the back. ( I have a whole kit of spares I carry incase I break down or incase I see another Windstar on the side of the road ! )

Will let you know when I return from Thanks Giving ...

PS... would clogged catalytic converter/s do this ? I doubt they would fix themselves ?

[olopezm]

Originally Posted by aussie_bob

Thanks Oscar,
I will do as you say ... 1) check out the coil pack. and 2) pull the front wheel off and check the harmonic balancer.

Since my last loooong post, I did remove the auxillary belt to isolate anything like the air conditioner clutch etc. no change except the belw was actually split over about 18 inches ... I replaced with the spare I carry in the back. ( I have a whole kit of spares I carry incase I break down or incase I see another Windstar on the side of the road ! )

Will let you know when I return from Thanks Giving ...

PS... would clogged catalytic converter/s do this ? I doubt they would fix themselves ?

Nice, have a great time!

Good thing you found out that old belt, one broke in my Pontiac and caused a BIG mess...

About the cat converter (I forgot the last time, sorry) they wouldn't fix themselves; even when the honeycomb inside could be loose it shouldn't cause your problems.

You should be noticing a rattling sound but no vibrations at all and if it would be clogged the engine would bog down and have a lack of power; I know a clogged cat can even blow your upper intake manifold due to excessive back pressure.

Oscar.

[aussie_bob]

Still have not checked coil pack or the harmonic balance pulley assembly.

Vibration went away again and now is on its way back. ( takes about a week ).

I purchased a cheap timing light with the idea that if the harmonic balance pulley moved, it could be seen via the timing mark but I have not been able to make the measurement. Is it done from under the Windstar , or do I need to remove the belt to see the timing marks. ?

Thanks in Advance, Bob.

[olopezm]

Hi Bob,

If I remember correctly the marks are on the harmonic balancer so you will have to remove the front passenger side wheel in order to be able to see them and would be a good time to check the rubber around the balancer.

I remember my dad used to put a mark with correction pen on the belt and that was what he used to check the timing on older cars. I've never done it myself so I can't comment any further on that.

If the balancer is bad you will see it instantly (the rubber will look like it's chipped) some times they even rattle or you can also see if it wobbles by moving it with your hands.

Oscar.

[aussie_bob]

Many Thanks Oscar,

I have done 2 other tests since my last post.

1) removing the front spark plugs leads one at a time .. actually started with one at a time disconnected ... no apparent change in the rough idle or at 2000 rpm in park ...

2) with a mechanic glove on to provide some insulation, I started with the plug lead off and moved the cup to the plug for all 3 front plugs and noticed a definite increase in rpm but the rough idle was present with and without the plug lead attached. I also saw the spark jump to the plug when the lead got close.

I assume this data tells me the spark is present and fairly healthy on the 3 front leads and since there are only 3 coils , I believe the other side of each coil goes to the back 3 cylinders ( at firewall ). To be complete , I need to run that same test for the 3 back cylinders .

I will take the front wheel off next and auxillary belt to inspect the harmonic balance pulley + timing .

[olopezm]

You're very welcome Bob,

You're right, if the spark was OK (blue colored) then the other 3 plugs should be OK but still doesn't hurts to try (although it will be a PITA LOL).

There's something that hasn't been asked before: What type of plugs did you use? Double platinum plugs are a MUST for '99 and later models. I'm not sure about 98 and previous models.

Did you use propane or carb cleaner when looking for vacuum leaks? I'm still thinking about the possibility you might have an unspotted vacuum leak...

Oscar.

[aussie_bob]

Back again team .... had the on and off vibration for a year now ... but I have new info and thought I had solved it but had not.

New Info 1: I purchased a cheap timing gun from Harbor Freight but was not able to find the TDC timing mark on the crank pulley ... so I put a whiteout mark on the pulley to see something. On the front 3 plug leads, I get a 120 degree pattern of my white timing make that is stable ... but every second or so the mark shifts about an inch or so. This tells me that the timing is atleast nominally stable but the occasional one that is off causes a "miss" . But the miss is not logged as a check engine light / code. ( Also the timing light flashes off ocasionally .. could this be a built in test that an ignition pulse is outside outside of an expected window ? ).



New Info 2: Now , I connected my scope to the primary connections of the coil pack and didn't think I could see any issue there. But the shifted pulse may be difficult to capture. I thought the coil pack may be breaking down at 167k miles I removed it cleaned it inspected for cracks , measured primary and secondary and then re-installed it and the vibration was gone ... But it came back after a day or so. So I went to the parts shop , bought a new coil pack installed it and the vibrations were still there.

Any ideas ... I am thinking that if the primary input is bad ie pulse out of timing occasionally, then that would have to be the ignition computer, crank TDC reluctance sensor or the camshaft position sensor.

I am having trouble probing either of those sensors.

Thanks in advance. Bob.

[94LebConv3La604]

This may sound silly, but have you checked your engine mounts?

[aussie_bob]

Thanks 94Leb ..... I did check the engine mounts way back but kind of discounted them as a problem after that and since the vibration has come and gone about once every 10 days. I am not sure how an engine mount could fix itself but it is possible. When inspected they looked to be fine and I couldn't see any cracks or obvious failures.

I would like to probe the crankshaft position sensor and the cam shaft position sensor outputs but am having trouble getting to them to "back probe" and figure I may need to use insulation piercing probes . Any ideas ?