Hi Guys
I have a 1994 XJ40 4.0 litre.
The car has been perfect until the weekend. I had almost completed a 60 kilometre journey then she began to miss, splutter and then would not rev higher than 3000 rpm in any gear.
Yesterday when cold it started and revved out as normal, but as it got warmer the fault came back.
Starting is no problem, just revving.
I dont see any faults on dash, not sure if any displayed anyway.
Fuel appears good flow and pressure. No loose/broken vac hoses. Have tried removing battery lead as well.
All thoughts gratefully received.
Regards
Roger

 

The things to check are..
Rotor arm in the distributor.
Ignition Coil (maybe 'breaking-down' internal/external).
Ignition Coil module (maybe overheating, poor heat sink contact).
CKPS is a known fault for these engines.

I have had a problem with a rebuilt crank damper that changed the air gap at the CKPS. The reluctor wheel varied in distance from the Crank Sensor so I had to remove some material from the mount bracket to get the gap corrected.

Lots of thing to consider.

bob

 

Hi Bob
Thanks for the info.
It definitely seems like hot engine issue now.
I've just started the car cold and runs fine but as soon as it reaches temp. the fault starts.
I thought the temp switch at first as i pulled the plug off and it seemed to run fine, for a while.
I will try the Crank angle sensor on Wednesday when i get a new one.
I read that there should be error codes on the dash but i see nothing ! only engine fault light.
Thanka for your help.
Roger

 

Welcome to the forum Roger,

I've moved your question from General Tech Help to XJ40 forum. This is the place to post questions about your model.

I see you didn't post an Intro when you signed up. Please follow this link New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum to the New Member Area - Intro a MUST forum and post some information about yourself and your vehicle for all members to see. In return you'll get a proper welcome and some useful advice about posting to the forum.

Graham

 

If you've got the engine fault light (check engine) illuminated then you probably DO have a fault code stored, you just haven't displayed it - it doesn't show up with the car running.

In order to see the code, turn the ignition on but don't start the car.

Look at the mileage display and press the VCM button. The display should change to read something like FF plus a fault number.

HTH

Larry

 

Hi Roger,

Sorry to hear you're Jag is misbehaving.

In addition to Bob's excellent suggestions here are a few more thoughts and questions:

Do you notice any white steam/smoke coming from the exhaust?

How did you check the fuel flow and pressure? A failing fuel pump could explain your symptoms if it can provide enough fuel flow to run the engine at lower revs but not enough for higher revs.

Did you happen to stop for petrol on this trip? If so, is it possible you got some fuel that was contaminated with water?

Regarding the temperature switch you disconnected, was that the coolant temperature sensor mounted on top of the thermostat housing (the one with two wires, not just one)?

Please let us know the trouble code displayed in the small window below the speedometer when you follow Larry's instructions. You may have multiple codes stored, but only one is displayed at a time. Write down the code exactly as it appears. Then, with the key still in position II (ON) but the engine not running, remove Fuse 9 from the fuse box under the armrest in the center console. On our LHD '93, this fuse is the second one from the driver's seat, but on your RHD car it may be the second-from-farthest-away from your driver's seat. With the fuse pulled, watch for the speedometer and tachometer needles to drop a little below 0. Wait 10 seconds, then reinsert the fuse. Turn the key to OFF, wait 10 seconds, then turn the key back to position II and press and release the VCM button and watch for a new code to appear below the speedometer. Write down that code, then repeat the process until no codes are displayed.

Report the code(s) here and we'll try to help.

Cheers,

Don

 

HI Don
Did put fuel in but had probably done 40 or so k`s before the problem - no steam or smoke from exhuast.
Just replaced ECU thermo sensor (2 wire ) still has fault.
No faults are up on dash, can bring various faults up when disconnecting MAF and TPS then rests ok.
Also tried resetting calling for any stored codes, nothing displayed.
Also swapped out the coil with no change.
But now i get the auto trans fault light in top left of cluster.
I`m going to try the Crank angle sensor next, then i assume, TPS and MAF metre.

Thanks for your input

Roger

 

So you're check engine light disappeared?

Larry

 

Yes, check engine light cleared. Only auto trans light top left cluster on. No faults on VCM.

Roger

 

Please check the 'crappy' Blue HELLA relays. I replaced dozens and dozens 'back-in-the-day.

TSB for you.

bob

 

It's likely that your Limp Home Mode (transmission locked in 3rd gear) is the result of whatever is causing the rough running, but just in case, on our '93 the most common cause of LHM has been oil contamination of the electrical connector for the TPS. The connector clips to a bracket on the intake manifold elbow just to the left of the throttle body. There's a great LHM diagnostic routine by John Ping in the XJ40 eBook at the Jag-Lovers forum.

How did you check your fuel pressure and what was the reading?

Cheers,

Don

 

Hi Don
Thanks again for the input.
I do not have a fuel prssure gauge for testing. I am ( wrongly ) that the pressure is good. I have broken it at the maniflod and have a good strong flow, also the PSV on the end of the rail does not leak which to me says the system stays charged as the car always starts immediately.
I have removed the TPS for cleaning, the plug is clean and the wires in good condition, i will try a new one today. Ive reada few posts that the TPS can also give auto trans faults when failing.
Thanks again,
Roger

 

YAY

TPS solved problem, cleared Auto trans fault as well.

I`ve lost a few days so don`t have much time today to write a story on how it came about and was solved, but will definitely put some words down soon for others.

Thanks everyone for taking the time to offer your knowledge and help.

Regards
Roger