New coil; still missing/bucking; '99 3.8L

[tomj76]

>Still bucking.

>No codes have ever been set with this problem.

This is probably a long shot, but it is possible that it's not the engine, but the TCC instead. My Windstar has a long standing problem of "chatter" from the torque converter that I used to think was a misfire. It would happened a ~30-50 mph, when under load, but not hard acceleration. This would occur not only under acceleration, but also while cruising.

After the transmission was overhauled I learned the real cause of the "shudder".

[serge_saati]

In OP, he saids that he check the EGR valve operation.
To be 100% sure, the best is to go to highway when engine is below 113F (cold mark). Cause the EGR activates only beyond this temp. If it's not possible, disconnect the ECT and go at 50 mph. Then stop and reconnect it the fast as possible (within 10 minutes).

[danielsatur]

Poor deliverable of a engine, can give a false symptom of a hydraulic transmission.
A bad TCC shutter is while the auto is in motion.

I heard of a good transmission, and engine being replaced at the customers expense.

The root problem was the drive-by-wire system, had a stickey throttle plate.

MAF sensors only throw codes when hard at fault, but a slow one with a dirty throttle body will not.

Try running with your fingers in your nose, and see how fast you can go without a misfire.

[Windywoes]

Yes, thought so, 12Ounce. Not enough drive time to set codes.

For the other ideas, it is interesting to note that this engine ingests LOTS of oil-even after the new valve cover retrofit. In the past 3-4 months I have had the upper plenum off twice to mop up all the oil pools. The throttle body was filthy and loaded with oil film. I cleaned the ICR as it too as loaded with oil scum. EGR ports are clean, but the lower plenum and intake ports are covered with oil scum.

If it does not rain tomorrow I may pull the injectors out and inspect them.

I am determined.

[danielsatur]

Think of bucking as gasping for AIR, that could lead up to a misfire.

If you are pulling the injectors out, consider a diesel shop for cleaning.

http://www.automotiveforums.com/vbul...d.php?t=906693

[Windywoes]

If I had to describe the problem with human references I would say that Windy feels like she is gasping for air when she bucks. Just like you said, running with your fingers up your nose.

I have so many things to try now I may never be able to do them all. Especially the tranny rebuild. I could not rule that out as a problem though. Tranny shudder at low RPM's has always been an issue with this vehicle.

[serge_saati]

check the compression on all cylinders, because it ingests oil.

[Windywoes]

Oh no; yet another item to check. Now I need a fuel pressure tester and a compression tester.

I do appreciate all the inputs. Really.

[wiswind]

Even my '96 pulls in a lot of oil......even with a big Greddy catch can in the PCV line.
I am wondering if this is all caused by the TCC as you mention.
Maybe having a trusted mechanic check it out......as you can end up pulling your hair out and buying a lot of stuff and find out that it was the tranny all along....and that can be expensive.
Some tranny problems are cheap....but there are some Torque Converter Clutch problems that you have to tear down the tranny to repair.
What has me wondering this is......from your description....it should be severe enough to be setting failure codes(s) and lighting the CEL if it is a problem with the engine.

[serge_saati]

Check the fluid. If it's too high on the stick or not clean, it indicates a TC problem.
I don't think any mechanic can diagnose transmission problem properly. Only trans specialists are able to do that.

[12Ounce]

Originally Posted by Windywoes

...... it is interesting to note that this engine ingests LOTS of oil-even after the new valve cover retrofit. .........The throttle body was filthy and loaded with oil film. I cleaned the ICR as it too as loaded with oil scum. EGR ports are clean, but the lower plenum and intake ports are covered with oil scum. .....
.

Hmmm ... now you have me thinking there is something amiss with the PCV system. Not only does the valve have to be in good shape ... but the engine block has to be free of air leaks for the system to work properly. If too much air gets into the lower crankcase ... too much water vapor and oil ends up in the intake area ... scum! Lots of places for leaks ... lower manifold gaskets, oil pan gaskets, front cover, etc, etc .... and, of course, HOSES! So a leak can cause (too much) oil to be sucked out of the crankcase .... of course, so can ring blow-by in a worn engine ... but the 3.8 has a really fine crankcase ... quite rugged.

[tomj76]

One other symptom of my TCC shudder was that when cruising, it occurs very regularly if the A/C is turned on (~ every 20 secs), but much less often and less predictable if the A/C is off. It doesn't matter if the O/D is disabled, since lockup is used in third gear too.

It happens for a few seconds at a time, but it can be interrupted by letting off the accelerator pedal. I don't get any codes from it, even when it's happening frequently (i.e. with the A/C on).

[Windywoes]

12 Ounce! I just took the upper plenum off again (did it 3 weeks ago) and I once again found lots of oil. A large amount of oil has accumulated again and this after installing a "catch can". This much oil and oil vapor being drawn into the engine intake can't be good. I am starting to line up with you on a possible issue with the PCV system.

How long do you think I can drive it with the line from the PCV valve to the throttle bottle disconnected and plugged up? I know the engine needs to breathe, but I wanted to see if the bucking condition cleared up.

The lower sections of the intake manifold are covered with dark brown crud and goo, but the EGR ports are still open.

BTW: DPFE is working. I saw a voltage change with engine speed change. I got vacuum from the heater line.

Hey, would you believe I got the upper plenum off without taking off the cowling?

[pat53]

I just had a similar problem with my 2001 GT 3.8L. My car would buck even at low speeds. The bucking would come and go while driving. I cleaned the MAF sensor and the problem temporarily went away. After a week the problem was back. I read an article that the MAF sensor design was prone to intermittent problems and would cause this type of fault without a service engine light. I replaced the sensor and after several months of driving the vehicle can safely state that the problem is gone.
Hope this will help.

Pat53

[12Ounce]

Originally Posted by Windywoes

....How long do you think I can drive it with the line from the PCV valve to the throttle bottle disconnected and plugged up? I know the engine needs to breathe, but I wanted to see if the bucking condition cleared up.....

Actually the PCV systems originally were mandated by the government to keep crankcase fumes out of the atmosphere ... the car-guys were forced into compliance kicking and screaming all the way ... then, guess what?: the car-guys were surprised to find that the mandated PCV system was beneficial to the engine!! Crankcases suddenly were much cleaner than they had ever been before!

Anyway, as a test, you can certainly plug the intake manifold at both points ... but "vent" the crankcase as best you can. Unplug the PCV valve, and supply lines, from the covers and leave the remaining holes open for free breathing ...

Hopefully it won't cause a mess. Years ago, metal gauze was used to keep stuff out of the engine ... and control the oil splash a bit. Oil caps, back then, were often filled with metal mesh and allowed air into the engine upper.

BTW ... have you inspected the oill filler cap? It might be your leak source.