By steve brooks on Friday, July 13, 2001 - 10:41 am: Edit

I have a 95 Disco with 78Kmiles. I have changed spark plug wires, plugs, rotor cap, and button. Sometimes runs good especially if I leave in 3 instead of D. Worst miss is when it shifts to overdrive or I am going up a hill. What am I missing? Thought maybe oxygen sensors bad, but Meineke told me that would not make the motor miss just loose power. I thought the sensor would load the motor like a choke if it was bad.

By Ron on Friday, July 13, 2001 - 10:47 am: Edit

Fuel?

Hows the filter? Original pump?

Ron

Is the air cleaner clogged? Not that would do it but it would be a contributing factor

By Kevin D on Friday, July 13, 2001 - 11:13 am: Edit

Does the misfiring occur over a particular RPM range? (i.e. 2300-2700 RPM in D which would be >3000 RPM in 3)

Is the misfiring worse when you switch a lot of accessories on (i.e. headlights, auxiliary lamps, air conditioning, windscreen heater, etc.)?

If so, it could be a bad alternator causing an ignition problem. To check this you could try running the engine with the alternator disconnected. If the misfiring symptoms do not recur under this scenario, then you may need to replace or rebuild your alternator.

Kevin D

It worked for me...

By Kyle Van Tassel (Kyle) on Friday, July 13, 2001 - 11:37 am: Edit

You have to find the cylinder first. Once you have check for gas,compression , fire. You will find a lack of one I am sure. It could very well be missing all the time and is just exagerated under a load.

Kyle

By jcw on Saturday, July 14, 2001 - 05:38 am: Edit

It's also possible that even a new plug or wire or cap could be bad. Did it miss before changing these? If not, change back one at a time.

Also, the fuel filter, as mentioned above, can definitely cause symptoms like there, so it's worth a try.

By Steve Brooks on Monday, July 16, 2001 - 02:20 am: Edit

Thanks for the advice guys. Yesterday it got totally worse. Would go dead when I stopped at a light and would hardly run at all unless I drove it in 3. I will check the fuel filter, alternator, (tack is working intermittantly too), and fuel pump. I have gone through the other two and three times. Thanks again, I will let you know what works.

By tmsltd on Monday, July 16, 2001 - 08:27 am: Edit

You said the tach is also erratic, and that when you drive in third, the engine runs differently? I would almost be willing to suggest an alternator problem due to the fact that the tach signal is generated by the alternator and third gear suggests more rpm for the alternator to produce enough power.
What is the voltage with the engine off?
running at idle?
What did you 'check' on the fuel pump? The harness connector may have melted enough to reduce available fuel pressure/volume. Have you measured fuel pressure?
Need more info!

By steve brooks on Tuesday, July 17, 2001 - 04:22 am: Edit

Shouldn't the motor run fine with only the battery if it is fully charged, as it is, even if the alternator is not putting out? Also, I am not getting any fault codes. Could the cats be the problem after all? How do you check the cats? I guess I could take them off, but seems there should be another way. I am getting exhaust at idle. Haven't had an extra hand to check under rpms. Sputters at first but then catches and revs up. Doesn't sound powerful though. I haven't checked fuel pressure and don't have anything to check it with. Have listened to injectors and motor with broom stick and everything sounds normal. All injectors are opening and sound the same. No real difference in the sound of the banks on either side or the top end. Again, how do you check the cats?

By Ron on Tuesday, July 17, 2001 - 05:09 am: Edit

Go underneeth and wack the cat with a soft mallet. If it rattles really bad it "could" be clogged. You can disconnect your O2 senors from their holes. If the situation improves then it is possible that a cat is clogged. I doubt it though.
If the battery is good enough to turn the starter you "probably" don't have an electrical problem unless it is ground related (clean the grounds). I am betting the tach is not directly related but check the voltage as TMS suggests. 2 seconds to rule out that issue.

Ron

PS Still betting on Fuel. Did you change the filter? If the pump is bad you will get the symptoms you describe. You might want to consider changing it and see if it fixes the problem. If it does not fix it I would suggest checking ignition/timing. How long after you changed the cap/rotor etc did it go bad. If it was immediately after or shortly after you might want to check that.

By Andy Nix (Andy) on Tuesday, July 17, 2001 - 06:29 pm: Edit

Those are the same symptoms mine had. Bad fuel pump. It ran fine until under load. Have the dealership do a line test to see what the PSI is...my money is on fuel pump.

Andy

By Kevin D on Wednesday, July 18, 2001 - 05:24 am: Edit

How much is the wager?
Ron's pink slip for his Series (or POS du jour)?
I'm still backing the alternator.

Kevin D.

Been there, fixed mine.

By Kevin D on Wednesday, July 18, 2001 - 05:28 am: Edit

My mistake, Ron prefers to bet dollars to donuts.

By Ron on Wednesday, July 18, 2001 - 05:29 am: Edit

Yes,

Dollars to donuts (Krispy Kreme).

Ron

By tmsltd on Wednesday, July 18, 2001 - 08:38 am: Edit

Is this Rover anywhere near Baltimore, by chance?
Trevor

By steve on Wednesday, July 18, 2001 - 11:16 am: Edit

You guys are having way too much fun at this. The alternator is putting out like a high school cheerleader, not the problem. Tried to get the filter off last night. Loosened the nuts but couldn't pull hose off. Got too many sqeeter bites to stay with it. Will try again after work. Is the fuel pump in the tank? Haven't spotted it yet.

By Ron on Wednesday, July 18, 2001 - 11:23 am: Edit

Kevin D, I want those donuts!! LOL

Fuel pump is in the tank. Lift the rear carpet and pad and you will see a black disc with a bunch of screws. Carpet and pad come up easy after you remove the trim piece on the rear door sill. Take off the black disc and you have access to the pump. Not being able to get the filter off is a bad sign. A clogged filter could have overworked the pump. If you are in Baltimore or nearby go see TMS. He knows better than anyone how to fix it. If not change the filer and if that does not help swap out the pump which is a hour job tops.

Ron

By Andy Nix (Andy) on Wednesday, July 18, 2001 - 11:23 am: Edit

LOL-I liked the cheerleaders analogy. Kind of like what a blonde says after sex "Way to go Team!"

Fuel pump is in tank, yes. Take the carpet out of the rear of the vehicle, and you'll see the access door. Easy job if you've got half a noodle. (npi)

Krispy Kreme's are worth more than the paper money is printed on, so I'll take those as payment.


Andy

By Kevin D on Wednesday, July 18, 2001 - 01:25 pm: Edit

No donuts yet, Ron...

"The alternator is putting out like a high school cheerleader, not the problem."

Please note that I did not suggest that you test your alternator's libido; instead I suggested -

"To check this you could try running the engine with the alternator disconnected. If the misfiring symptoms do not recur under this scenario, then you may need to replace or rebuild your alternator."

Alternatively you could switch alternators from another Disco with no misfiring problems, and see if the misfiring recurs. If so, then go for the fuel pump and I will send a dozen glazed to Ron.

Kevin D

P.S. My alternator was putting out like a Gold Club entertainer during Super Bowl week, but replacing it eliminated my mysterious misfiring symptoms (that seemed very similar to yours).