which way to go?

frankb_cJune 16, 2005

Have a 2000 Mercury Grand Marquis 80,000 km. 50,000 Mi.

The following is happening.

When I am accelerating at the 47 km (30 Mi)approx and again at the 67 km (40 Mi) the car "jerks" as if the transmission was slipping.(My guess)

But if I accelerate like as if I was using a manual, listening to the engine, I don't get the slipping.

Transmission specialist suggested to see dealer first as could be wiring problem. His "tester" (ABD) does not give a faulty transmission reading.

So off I went to dealer that sold me the car. Warranty no longer applies. Mechanic tested, confirmed the slippage and said" Ya, this happens to some models" "changed the fluid, ran a road test, and all OK". Well, when I took a trip to NJ 756 km (470 Mi) Car ran fine. but for this slippage if not applying proper gas. This is a vexing situation.

I have purchased ABD (On Board Diagnostic) unit, and get no readings. You would think that "slippage" would leave a code. But NADA.

Mechanic's on board?

Could the wiring be faulty?

That this occurs. How do you test?

I have read, and I did change wire harness on my 88' Buick, which now has 300,000+Km (186M Mi) Son in Law using to go to work and back.City transport only.

Could it be an electrical computer problem?

Having to do with the gas feed to carb?

This would explain the reason having to be "Hard footed" to run smooth.

Ideas! Before I go to my Garage.

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Have the sparkplugs and wires been changed?

You might have pending code which your OBD reader cannot retrieve. Eventually a pending code will turn on the check engine light, BUT if the problem goes away before that happens, that pending code is erased from the computer's memory.

Essentially, a problem has to repeat a minimum of two times in two different "drive cycles" to change from a pending code to a code that turns on the check engine light.

If the problem does not happen again, the pending code is erased.

Better ODB scan tools can retrieve pending codes, so you might want to see if you can borrow one.

    Bookmark   June 16, 2005 at 11:13AM
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The codes and OBD (on board diagnosis) are for emissions controls, not for how well the car runs.
And I do not like this, but that is the way it is - for now..
A possibility exists that the 4th gear lock-up solenoid is not functioning well..Automobiles are becoming extremely complex.
The transmission repairman must have the intelligence of a brain surgeon (and be paid accordingly)

There is a mailing list for transmission specialists - needs a moderator, does not work that well but has great possibilities...

    Bookmark   June 16, 2005 at 11:19AM
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If there's a transmission problem there will usually be a code stored for it. I'm not sure, but I think some scantools may not be able to retrieve transmission codes.

    Bookmark   June 16, 2005 at 12:07PM
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The Scantool that I have is INNOVA OBDII model 3100.

    Bookmark   June 16, 2005 at 1:05PM
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I've seen consumer handheld scantools retrieve transmission codes, so I know there are transmission-related codes. If there is no check engine light and your tool also comes up with nothing, then I think the most likely conclusion is that you don't have any codes stored. That doesn't mean you don't have a problem, but just that whatever is going on isn't something that OBD II is "seeing."

You said this doesn't occur when you accelerate as if you were driving a manual, listening to the engine, but what's actually different about your acceleration when you are listening to the engine? Do you accelerate more rapidly, or less so? Do you ease off the gas pedal when you think that the transmission is about to shift?

    Bookmark   June 17, 2005 at 8:50AM
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Your right on.
I ease up on the gas as I hear the engine rev up and than press again on the gas pedal, and I get a smooth shift.

If I press the gas pedal steady from the start, I hear the engine "race" and than get the shifting, and in most instances the "jerking".
This procedure, sometime can be tricky in city traffic, as lights, stop signs, vehicles in front of you.

In the city that I live in, I don't know of a street corner that does not have a light and or stop sign. In fact I have been caught at a stop sign, waiting for the light to change.
Now, is that a sign of geting "Older".

It has become more of a habit now, listening to the engine, press more or release gas pedal, and once the engine settles, just hold steady for cruising speed required.
On the highway in the 100-120 Km (60-70 Mi) range no problem, I can even set the auto cruise and runs smooth.

I have perused various forums, including "Ford" but have not come accross anything, that would relate.

    Bookmark   June 17, 2005 at 10:20AM
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For those that don't know what kind of a tool he has, here is a link to a product evaluation. I'll have time to look into his transmission issue in more detail tomorrow.

Here is a link that might be useful: Innova

    Bookmark   June 17, 2005 at 11:31AM
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Had appointment with Garage to have a complete tune-up.
This was listed as being done before the car was sold to me.
Ford certified!
Ya, the plugs where still the original, 4 where out of gap.
mechanic said that they where showing as burning oil. Grayish. gummed up. Changed for New plugs.
Fuel filter was clogged. New filter. Mechanic said, that mileage will be noticeable.
Oil was very black, changed oil and filter.
checked tranny oil, OK.
Brake fluid,Anti-Freeze, battery, power steering, all OK.
He gave me a bottle of fluid to put into gas tank when I gas up, to clean up the jets. 1-1/2 hour later, road test and I'm gone.
As this is the mechanic I go to, I was next to the car and could see what was being done. Which is not the case at the dealer. There you leave the car and come back in the afternoon like 4:00/5:00 pm to pick up. The service manager says, this and this was done, and the amount you owe is.The previuos owner paid for a full tune-up at Ford. He was taken as the saying goes.

I had some errands to run. The slippage was beraly noticable
and seemed to dissapear. Will have a chance for highway driving in the next couple of days.

Will report back next week.

    Bookmark   June 22, 2005 at 7:15PM
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Did you just buy the car? Could someone have recently disconnected the battery? My understanding is that the newer trannys do not have fixed shift points but instead "learn" how the driver likes to drive (i.e. slowly accelerate vs. aggressive) and they will adjust the shift points accordingly. If the battery is disconnected then the tranny may lose its memory and have to re-learn. During the re-learning process the car might act odd until it finds the an average point where changes in shift points are less noticeable.


    Bookmark   June 22, 2005 at 11:38PM
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The car went very well for an 800+ mile round trip.
Still did get the "tranny jerk", but not as often.
Guess the foot treatment unconciously, left some of them out.

Will be seeing my mechanic and see what he says about diconnecting battery!

I seem to have read something that this is not recommended, But hey, if you have to change a battery, what do you do?

yep, I'dd like to hear comments, too.

    Bookmark   June 27, 2005 at 7:16PM
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Sometimes disconnecting the battery can fix a drivability problem.

My theory as to why is that either the computer has learned bad data due to a temporary sensor malfunction or something similar, or the computer's memory has been corrupted by external causes such as a voltage spike or EMI or even stray cosmic rays. (IBM did a test in the mid-80s that showed that cosmic rays could cause a bit to change from 0 to 1 or vice-versa in computer memory).

The memory I'm referring to here is what Ford calls the "keep-alive memory" which is battery-backed memory that stores data that the powertrain control module has learned about the vehicle's operating characteristics.

This is why it's suggested to disconnect the battery when changing an engine sensor or even when changing the trasmission fluid (new fluid makes a transmission operate slightly differently than old, worn fluid).

    Bookmark   June 27, 2005 at 10:11PM
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?? Do you disconnect both _ and + battery connections?

    Bookmark   June 28, 2005 at 8:12AM
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Just disconnect the negative (which avoids a short circuit should your wrench contact a metal part and the battery terminal at the same time).

Leave it disconnected for a few minutes, then reconnect.

    Bookmark   June 28, 2005 at 10:35AM
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I did the Neg post disconnect. left off for 5 minutes, and reset.

Went to mall for pick up and noted that the clock had changed time lost about 5 minutes.

As mentioned before, the slippage is still present, but not as apparent.
I think that tonight when I get to it, I will diconnect both + -, leave off overnight, and than reconnect tomorrow morning. That would be a more accurate trial.

    Bookmark   June 29, 2005 at 1:11PM
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Went to my mechanic. had the Transmission fluid drained, along with the converter. After some discussion, we assumed that the dealer never did a proper change of tranny oil. As the dealer called me around 2 PM to tell me about the trouble being a found, and that they changed the Oil. BUT my car was ready for pick-up at 4 pm.
In fact my mechanic had me bring my car around 3.30 pm and removed the pan, and than went though the procedure for the Transmission converter plug. when he left the garage just after 5 PM the oil was still dripping. In the morning I was there and watched him place in 12 litres+ . according to manual it would take 13.9 litres tops. As he said he can't drain every bit out.

At the same time he did the Differential.

So much for that dealers mechanics.

As the Transmission specialist said "take it back to dealer"

Saved a bundle... nothing is wrong with the Transmission.

Now car runs smooth. Amen

    Bookmark   July 9, 2005 at 9:23AM
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