Hi, I'm Steve, based in the UK and in the last few months I've been enjoying wafty X300 transport in the form of a 1997 3.2 Straight 6 sport auto.


How it has a few electrical issues which I'm hoping someone on here might be able to provide an answer for.


When I bought the car a few months ago, the fuel computer worked fine, displaying miles till empty, average mpg etc.


Driving home it misfired (three quick pops in succession) although it has only done this once (and hasn't done it since) but enough to blow a hole in one of the back boxes (mufflers). I will mention that the car was sat for about 3-4months before I bought it and drove 60 miles home.


Now the average mpg reads zero all of the time, and the range display shows a reading of 44758 miles till empty all of the time, and average mpg reads 99.


Fuel economy has dropped through the floor (around 12-13mpg round town)


I've got no record of when the oxygen sensors were last changed (only two of these on UK cars) but plugs and filters were changed less than 1000 miles ago. The car (apart from the horrific fuel economy) drives absolutely fine and revs ok, although it 'rocks' very slightly in park like the engine is hunting but the rev counter is steady at 850-900rpm. (no MIL lights lit up)


How does the display for mpg get its readings?


What could be causing these problems?


Any thoughts?


Thanks
Steve

 

The 'could be' list is rather long and we have darn little to go on.

There is plenty of history of ignition coil malfunctions causing both intermittant misfires and crazy instrument cluster behavior....but your trip computer failure falls outside what we've typically been hearing.

I did have a coil failure that 'took out' my airbag control module. I mention this only to illustrate the weirdness of it all.

But, it's too early to actually condemn any of the coils. Keep it in the back of your mind, though.

I'd have the OBD system scanned and have someone look at the data stream...and hope some sort of clue pops out.

Investigating the trip computer failure and how it relates to the backfire and poor fuel economy will take a bit of research...or someone with more expertise than I have.

Others will chime in with more info and/or thought starters.

Cheers
DD

 

Hi, I did take the car to my local garage who plugged it in and the only code that it threw up was a P1621 - Engine control module engine immobilization input circuit malfunction


I think this may be related to an issue that the previous owner may have had as there is a remote start switch wired up underneath the dash as I think he must have had issues regarding the j-gate starter inhibitor switch (j-gate switch has been replaced)


Just as an aside. Is the fuel pump supposed to run constantly as soon as the ignition switch is turned on? Mine does this even if the key is in accessory position II

 

Has all that stuff been removed?




I'm 99% sure that the pump should run for 2-3 seconds only with key 'on'. If the key is turned to 'start' it should be switched 'on' again.

Cheers
DD