200 miles into a journey tonight I felt a sharp bump from under the car (like when you stall a manual), then it went into failsafe mode (trac not available, engine failsafe, gearbox fault mils).
I was doing around 70mph so luckily had enough momentum to pull over.
Switched engine off, then restarted, all was well for the remaining 50 miles.
I had noticed previously and after a slight hesitation at cruising speed, felt alomost like hitting a strong head on wind or when braking slightly. The car has been doing this for a while.
When I got home checked for codes but none stored.
I will run some injector cleaner through it and maybe clean the MAF and TB, but has anyone else had this happen, or any thoughts on where to start looking?

Thanks
AndyP

 

Just guessing because we don't know what your driving, but my first guess would be your in a XJ8 and the A drum failed.

 

I got a couple of unusual drivetrain pulses at speed. At first I thought the transmission may have momentarily slipped. I happen to get lucky and catch it while looking at the tachometer --- never moved. It only did it a few times.

It was really strange --- next day my fuel pumps failed. Got all the warnings -- including one telling me ... I think it was "engine stalled". First time for that one.

 

many thanks - I can rule out gearbox failure as I was able to drive the car after the incident. As the warnings flashed up the engine was still running but in failsafe mode, Also, when the "hesitation" occurs the tacho does seem to drop slightly.
The fuel pump does make a humming sound, particularly after a long journey or if the tank is low on fuel. Its been doing this since I bought the car (3 years ago).
The car is 2000MY XJ8 N/A btw.... A recon gearbox was fitted by PO about 6 years ago.
No codes were picked up by my basic reader so difficult to know where to start.

AndyP

 

A few years ago I had a period where I had a problem with the car going into failsafe. It would usually happen at moderate speed -- once it occurs it does not fix itself. Turning car off and then on would often do the trick. I would say it did it 10 times over a couple of months. The TPS on the T-Body is a likely cause -- in my case the car was infrequently driven ..... I made a point of fully pushing the gas pedal through it's range in hopes of cleaning the contacts. I did this about 50 times every day for about a week ... never has happened again.

 

AndyP,

The bump you felt that made you think of a transmission issue seems like a clue. In addition to the other good suggestions you've received already, it would be worth checking your transmission fluid level and checking the transmission electrical connector for fluid leakage and contamination.

Cheers,

Don

 

Thanks for the suggestions.
@yeldogt - Sounds interesting, I might give that a try. I believe the TPS Denso part (198500-3250) is not available separately for the X308 ? Seems ridiculous to have to replace the entire TB for the sake of a detachable sensor if that is the culprit.
@Don B - Could well be a gearbox/electrical problem, I'll have my mechanic give it the once over, and also check for any shadow codes that my cheap reader may not have picked up.

Meanwhile have cleaned the MAF and TB (which was quite black around the butterfly section), probably wont fix the issue but worth doing anyway.

 

Kyle04: from all accounts the TPS is not available. I did not know the part number thanks! -- is that number printed on the part?

It is beyond annoying -- it would solve many problems if we could just switch out the TPS. I'm not sure why the T-body rebuilders are using.

When the car goes into "failsafe" -- it's still running .. but ...the engine will just go above idle no matter what you do to the pedal. My assumption is the designers wanted the steering and brakes to fully function.

The TPS has two sets of contacts -- either one giving an odd reading will trip up the system.