1997 XJ6 Engine Dies after 30 miles

My 1997 XJ6 with 54,000 miles has a very peculiar problem:

After driving for 30 minutes or 30 miles (either one) the engine starts missing and gets progressively more severe until Check Engine light goes on and Transmission light after that. Eventually, it refuses to keep running. After parking overnight the check engine and transmissions lights are off and the engine will run smoothly and the pattern repeats.

I have replaced:

  1. All 4 O2 Sensors and both Catalytic Converters
  2. All Spark Plugs and Ignition Coils
  3. Air and Gas filters and cleaned the Airmass sensors
  4. EGR valve
  5. Inertia Switch
  6. Battery and Alternator

I get a P1775 code from the last episode. Local shops have tried multiple times and have not been able to fix the problem.

Any suggestions?

Desperate but love the car!

Joe in Virginia

I don’t think p1775 is relevant since this is just confirming the stall.

I guess you need to identify whether you have no spark or no fuel when it stalls.

I would suggest a fuel pressure test to begin with.

Then fuel trim to see general health of the fueling system.

Then buy a cheap spark tester to make sure you have strong coils.

Thanks for the comments. What is it and how do you do a “fuel trim”?

The cars ECU constantly measures the amount of oxygen in the exhaust using the o2 sensor. If there is too much

Sorry pressed send too early!

If there is too much oxygen then the car is running rich. It therefore reduces the amount of time the injectors open which in turn leans out the mixture.

If there is too little oxygen then the car is running lean. Ot therefore increases the amount of time the injectors open.

The fuel trim is the % rich or lean the computer is sensing. Ideally it oscillates between -5% (reducing fuel by 5%) and +5% (increasing fuel by 5%.

If the computer has to increase or decrease fuel by over 25% then it will set a check engine light.

You can check this data using any OBD scan tool.


Try checking out the fuel tank breather is clear and is not restricted right through to the open end.

Depending, if and how, the tank is fitted with a “crash inverted breather” you may have to dismount the valve and clean out any gum deposit.

If the tank breather system is compromised the pump will be gradually throttled from drawing fuel, until the fuel delivery is not enough to support engine operation.

Beware that throughout any fuel throttling phase the ECU will attempt to correct the gradual fuel leaning.

How old is the gas on the car or how often do you drive
After everything you replaced
It sounds like crap in the tank with junk ethanol gas
Of gas is old
Drain the tank or pump out as much as possible
Then put a new fuel pump
The junk is sucking into the screen and pump
If you stop the car and wait a half hour
Does it start up?
If so it’s the above

The first thing to do is to replace the CKPS (crank sensor) if that has not been done for several years (or ever?).

Agree with the CKPS - Part Number DBC11501…different than the CAMshaft position sensor. It’s probable.

What I would highly recommend is to get an OBD2 device that can do more than pull codes. You have that port giving you access to all kinds of useful info!

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Thanks everybody for your responses.
The gas is fresh as I regularly drive the car for local errands under 30 miles. Only use premium from COSTCO. I have recently done a 1-pint Seafoam treatment thru the intake so the engine purrs nicely at idle.

Sometimes, I drive 25 or so miles and park it with no symptoms. After an hour or so, I start it again and within 5 miles, the engine starts acting: miss, cough, dies at a traffic stop until transmission goes on limp mode and eventually forces the complete stop. After an hour or so, still no go. After sitting overnight: runs like a champ again.
I have ordered a Crank Position Sensor and will install it this week. Stay tuned!


Don’t forget about an OBD2 reader!

Don’t forget about an OBD2 reader!

Avoid the cheap ELM readers on eBay and the like - they are rubbish!

I get all the data I need using one from Carista, along with their app.

Hi Russell, at the bottom right of your posting there is a pencil, this allows you to edit your post (rather than admitting that you did a boo boo :grinning:)

I bought a cheap ELM dongle from eBay for about $10…works fine. No issues.

Agreed, I have used them for over 12 years or so with no problems along with various apps! Just make sure it’s OBD2 with Torque.

I installed the new Crankcase Position Sensor yesterday and tested the car today by driving 25 miles and then parked for 1 hour. Car ran smoothly until I parked it.
At the restart after parked for 1 hour, the engine started acting up with the same identical symptoms!!! Argh!
I had a KONNWEI KW818 OBDII/EOBD scanner plugged in the whole time today and when the engine got progressively worse and it finally refused to go, I pulled the codes:
P1790 Automatic Transmission
P0727 Engine Speed Input Circuit No Signal

Any suggestions?

Please don’t turn this thread into a OBD scanner discussion!


There aren’t many faults with the x300 set up but…
The plug harness on the side of the transmission can be pulled and cleaned if it’s corroded , kind of typical after the crank sensor but…
I still think it’s your fuel pump and filters restricting them heating up

Hello Joe - your words of “30 miles or 30 minutes” reminded me of a problem I had on my 1975 Audi 100 LS fuel injected automatic back in 1982 - it would stop running after 30 miles or 30 minutes - no garage could decipher - I researched and found that there was a designed circuit that would shut off the fuel pump if the brakes were worn below a certain level - apparently this was for driver safety to not get too far from service help- not saying this is your problem but you may want to research.

I’m old and was around these when new…
When everyone is done
I’m betting on the pumps as you mentioned
Audi had many other issues such as launch control through store front windows as well😀
They were bullet proof other than that

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Yes it was a very good car, with the 4 cylinder fuel injection, and very advanced at that time.