1997 XD runs rough when warm, HELP!

[dogpoor]

Hello all, I have a 1997 XD with 170,000 miles. Starts right up, idles great and runs great, UNTIL the engine gets good and warm. This takes approx. 10 minutes, that's when the engines starts to run rough and won't rev past 3,000 rpm and steadily declines UNTIL it won't rev past 1500 rpm. Still idles fine, will start and restart fine, but backfires inside the intake, and at the exhaust. Let the engine cool down, everything is good UNTIL it warms up.
No engine codes being thrown

I've got 30 psi fuel pressure at the rail at idle and the regulator goes to 38-40 psi when revving up, (until it sputters then regulator jumps up and down with the engine).
New auto lite plugs and 8 mm wires within the last 20 miles.
new fuel filter at the same time.
I've taken the fuel pump out twice and examined it and checked for debris, first time seemed to help things a bit, until I let the rover set for 3 months (dead battery).
sea foamed the intake less than 100 miles ago, and stuck some in the tank.
Rover has been fairly well taken care of.
Ideas? Thoughts? Fuel temperature sensor?
thanks a bunch!

[mearstrae]

Hmmm...Backfire through the intake is usually a lean miss, and through the exhaust, an over rich mixture. Perhaps the MAF needs a cleaning, the mass air flow sensor might be giving the system false readings. The auto parts have a spray can of stuff to do this. Worth a try, before getting into more expensive fixes or checks.

'95 R.R.C. Lwb (Gone...)
'76 Series III Hybrid 109
'70 Rover 3500S

[dogpoor]

THanks for the reply back, your right it is worth a try. It bucks and snorts like a mad Buffalo when you give it throttle once it's warm.:confused:

[dogpoor]

Ok, so I cleaned the MAF sensor per the instructions, reinstalled and started the disco. Everything was good until the engine got good and warm approx 10 minutes. Then the old cough and sputter was back.
I hooked my obd live data scan tool to the disco before the sputtering started to try and interpret some of the information.
Here is what was going on.

Engine running smooth
Engine coolant temperature around 175 +/- degrees.
Rpm at 3000
Fuel load at approx 25%

Engine running like crap
Engine coolant temperature at approx 190 +/- degrees
Fuel load at approx 100%
Lots of raw fuel smell (exhaust)
Engine power degrading and rpm dropping even with the same pedal position

Vehicle still idling good and runs ok up to approx 1500 Rpms

Ideas? Thoughts? What should I be looking for?
Thanks in advance

[dogpoor]

Just ordered a coolant temperature sensor from RN. Less than $20, worth a try.
Any input? Hello.... Anybody out there?
Thanks

[Les Parker]

Sounds like the correct way forward.
Let us know how the engine performs when you fit the new coolant sensor.

[dogpoor]

THanks, spoke with the guys at Platinum Motorsports and they stated that cleaning up the TPS might be helpful as well.
I'll update as I go along.

[dogpoor]

I cleaned the tps sensor that didn't help. Cleaned the the throttle body and assembly as well. No change.
With the live data you can see the fuel load creeping up.
From 19-22% to 35% to 60% to 100%. All within a 30 second window.
I kind of think the temperature (185-195) is going up because of the fuel load
Let off the throttle, fuel load goes to 20% +\- and temperature goes down 175 +/-
I unplugged the coolant sensor and didn't to seem have an effect except to show -40 on the scanner
So I'll wait for the coolant sensor and put it on.
Then go for the fuel sensor after that if that doesn't help.
Any input at all would be helpful.
thanks

[dogpoor]

Ok got the coolant sensor from RN. Got it within 3-4 days with 2 of them the weekend. Way to go RN!
Installed everything was working great, went for a drive.
Within 2 miles Disco started acting up again. ARGH!!!!
Took it back to the house and just parked it with the vehicle still running.
I let it idle for about 20-30 minutes, and tried revving it up.
Disco revved up (3,000 rpm) with no problem?
Did this a few times over a period of 45 minutes with none of the "spit and sputter"
Went for a drive 5 miles with no issues at all.
So whats up with that? I like a "self healing" vehicle as much as the next guy untill the next time.
Could it be an aging fuel pump?
Something to do with sitting for long periods??
Thanks for the input

[joshua.mcguoirk]

dogpoor,

Sorry for the late response... I had the same issue over the summer. The following was my solution:

Crankshaft Position Sensor located on the LHS of engine was becoming overheated. I removed the housing and cleaned all of the debris/mud from both the sensor, housing and harness. Additionally, the harness wires were becoming frayed. I electrical taped the individual wires then wrapped the entire harness in tape. I decided to wire loom and reroute the harness closer to the bulkhead and away from the LHS exhaust downpipe.

Easy fix for me and only the cost of electrical tape and wire loom.

Good luck,