I've got a problem that seems to have gotten worse over the past year. When the engine is cold and I accelerate hard, the engine/transmission cuts back suddenly, probably around 30 to 40 mph. If I keep the pedal down, the engine cuts back, then revs up and the car jerks horribly. I have to let up on the pedal at that point to avoid looking totally stupid. Weird thing is, it accelerates perfectly after the first 3 or 4 minutes when the engine temperature is in its normal range.

Any ideas?

 

Any Codes?

 

No. I did have the dealer check it out last fall. They downloaded and reprogrammed the ECM and TCM?? (I don't know exactly what that means). I didn't have a chance to really push it before I put it away for the winter. In the last couple days though I've confirmed that whatever they did, didn't fix the problem. Before I take it back to them, I wanted to see if anyone else had a similar issue and resolved it.

 

Acronyms - love them or hate them!

ECM = Engine Control Module (collects data from sensors around the engine and sets appropriate fuel trims and much more)
TCM = Transmission Control Module

The dealer could have reprogrammed the ECM but it's more likely they download (and perhaps cleared) the 'codes'.

Another acronym for you:

DTC = Diagnostic Trouble Codes

If the engine runs outside the set limits, codes are recorded which help to determine the cause. With your loss of power problem, there may be codes stored which would help.

You responded to Gus' question by saying 'no' to codes. It's important to know whether there were no codes stored when you first took it to the dealer or there's no codes stored now because the dealer cleared them. Also what they did in an attempt to fix it.

Troubleshooting has to be a logical approach or it's just guesswork and luck. If there's a code or codes it tells you exactly what the problem is. If there's no codes, either the problem hasn't been present long enough to set a code or it's something very simple which doesn't set a code. Where you look next depends on the answer to this first question.

Graham

 

When cold the ECU works in open loop (so it will not adjust the fuel mixture based on the O2 sensor input). I would measure the STFT/LTFT values once the car is warm and is in closed loop, as that will probably indicate in which direction you need to search. Best is to have some check this that has understanding of this, try to make at least 2 measurements, so once during a long idle, and once during a higher rpm and preferable at about 50 mph or so (drive steady for a while and then write down the values).

 

Do you get a Restrict Performance or a Check Engine light when you experience this problem? Take your car to AutoZone, PepBoys, Advanced Auto or wherever and get them to read the OBDII codes. When they read the codes write the codes down not what they tell you they mean post it on this forum or you can look it up on my page at http://www.jagrepair.com/images/Auto..._2001_OBD2.pdf Keep in mind not all situations will generate a code but most do. Let us know what you find.

 

Although these cars certainly have ABS (anti-lock braking systems) and traction control modules, I'm 99% sure that when the acronym TCM is used, it's referring to the TRANSMISSION Control Module.

Otherwise, all good thoughts!

 

Absolutely correct.

Acronym TCM is TRANSMISSION Control Module on the Jaguar. TCCM is the Traction Control Control Module

My mistake. I'm still in trauma from a costly experience with a replacement Traction Control Module on another vehicle.

Graham

 

I have noticed the same issue with my XKR. Usually it's just for the first dozen feet or so if you suddenly give too much gas, after that no issues. Feels almost like fuel cutting out, but there are no codes. Changed fuel filter few months ago, no problem still persists. I just live with it for now.

 

Add BG44K to the fuel and see what takes place.

 

I have the actual work order in front of me now. They claim to have "cleaned MAF, Programmed ECM and TCM... TSB for ECM configuration"

They printed a TSM for me. Here are the notable points on it:
--------------------------------------------
TSM 307-14
MODEL 2000-02 MY XK Range
2000-03 MY V8 XJ Series
Shift Quality Issues / Harsh Engagement With Engine cold - ZF 5HP26
Install New Transmission Control Module

Issue: summarized ... transmission shift quality issues, most notable when the engine air intake temperature is between 20C and 30C and when coolant temp is below 40C. Under these conditions the engine speed will increase to 1300 rpm for an initial 30 seconds and then reduce to 1000 rpm. During the initial period when the engine is at 1300 rpm, customer may complain of the following:
- With no throttle application, the transmission hesitates and then thumps into gear when shifting from neutral to drive
- With no throttle application, the transmission hesitates and then thumps into gear when shifting from neutral to reverse.

Action: In case of a confirmed complaint, install a new Transmission Control Module (TCM) as described below.

Note: If any DTCs are stored in the TCM or ECM, carry out any repairs before installing the new TCM.
---------------------------------------

This TSM doesn't really sound like the problem I'm experiencing. I don't have a problem when I shift from Neutral to Drive, nor Neutral to Reverse. My problem happens for about the first 5 minutes of driving, then behaves normally.

To answer Gus, there is no "Restricted Performance" or check engine light when this happens. I'll get the codes read next time I take the car out.

 

Check your PM

 

I drove the car to AutoZone tonight so they could check the DTC codes. One code displayed, P1111. Based on the document Gus posted earlier, it looks like this is just some type of "System Readiness Test", but not really an error code.

Is it likely that the code only comes up while the problem is happening?

I tried to make the stuttering acceleration happen tonight also, but the engine warmed up before I could get to a spot where I could gun it. I was going to check for any "Restricted Performance" message on the dash.

The next chance I'll have to test it when cold is Friday. I'll do a good test then. I really don't believe I've seen these messages on the dash when it happens.

 

Nope, if a diagnostic code was generated, it would be stored and then visible when the codes were checked with a proper reader.

 

I can tell you first hand that a code is not always stored when a fault takes place. I had situations where I went into restricted performance or fail safe and codes were not present. 2 knock sensor, 3 times throttle body and 2 times with the throttle body plug.

 

I'd follow a avos's advice above, fuel trims. Learn about the short and long terms, and what affects them.

 

FWIW: Your XKR uses a Mercedes Transmission, not the ZF 5HP26 Transmission specified in the above TSM.

 

+1

Many faults require 2 consecutive 'trips' to set a code.

A 'trip' is defined as an ignition cycle (ignition key OFF; wait 30 seconds; ignition key ON plus a minimum engine coolant temperature of 22 deg C after which the engine coolant has to reach a temperature of 71 deg C.

That's what the number in the 'CK ENG' column of the DTC Manuals means.

Graham

 

Actually you do get a code when an issue has arisen, sometimes called a pending code, but it will only light up the check eng after 2 consecutive occurrences exactly as you describe.

 

I captured the "pending code" when I elected to install my OBDII code reader as I was driving. What I was experiencing was a Restricted Performance, Fail Safe on my panel with no codes. I did not know why until I installed my reader to capture the fault.