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:
All 4 O2 Sensors and both Catalytic Converters
All Spark Plugs and Ignition Coils
Air and Gas filters and cleaned the Airmass sensors
EGR valve
Inertia Switch
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.
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.
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 âcrash inverted breatherâ 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 itâs the above
Agree with the CKPS - Part Number DBC11501âŚdifferent than the CAMshaft position sensor. Itâs 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!
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!
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 donât turn this thread into a OBD scanner discussion!
Well
There arenât many faults with the x300 set up butâŚ
The plug harness on the side of the transmission can be pulled and cleaned if itâs corroded , kind of typical after the crank sensor butâŚ
I still think itâs your fuel pump and filters restricting them heating up
Hello Joe - your words of â30 miles or 30 minutesâ 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.
Terry
Iâm old and was around these when newâŚ
When everyone is done
Iâm betting on the pumps as you mentioned
Audi had many other issues such as launch control through store front windows as wellđ
They were bullet proof other than that
)
