I did some more trouble shooting over the last few days since I am now on a fresh tank of fuel. Still have the intermitten stumbling/missfire at idle and from around 1500-2100ish rpm. Comes and goes and I can push past it and accelerate smoothly. While spending 30min sitting in line at the bank tonight, I got tired of the rough idle, shut it off for like 4min, then the line moved so I fired it back up and it ran fine, nice and smooth, and ran that way for the rest of the 25min or so. Got home, idling rough again. Shut it down, counted to ten, then fired it right back up, ran smooth as glass. I can sit there in the driveway, and run all kinds of rpms, from idle to darn near wide open, nice and smooth and this is with a hot motor. Doesnt over heat, doesnt use coolant, new plugs and wires, checked the CPS wireing, retaped the bare parts from heat flaking off the insulation. I dont have any speedo issues, but could the VSS be starting to go south??? Whatever is causing the issue is tied to driving it and not running it in the driveway. I played with the rpms for almost an hour just sitting in the driveway with absolutly no problems. Held it at 2k for 10min, varied it around 2k for a few more, nothing, ran fine. WTF!!! What other sensors would be tied to a missfire/stumble, and needing to be driven to show the problem???? The codes are the same as in my last post, random missfire, cyl 4 and 8 missfire. If the TPS was going south, I would think it would act up just sitting in the driveway when I played with it tonight. Ideas??? Need to talk directly with me? call 814-474-1496. I will be home all night tonight. Road trip tomorrow.

 

Did you ever figure this out?

I have the same issue, and have also replaced the plugs and wires and it is not fixed.

The CEL comes on sometimes and will then go out after a day or two of driving.

The fuel pump is also really loud at idle. I replaced the pump with a new one from atlantic british and it is still pretty loud.

Any ideas?
Mike

 

bump

 

Mike, same problem here with my wife's '03 Discovery. In idle and when pulling a hill. Feels like it skips but I can always accelerate through it. Any ideas after all your tests. I'm a new poster but realize if LR Birmingham is going to charge $350 for a set of plugs when they don't know that's even what it is I probably need to check with you first!
Thanks in advance.

 

Have you cleaned the intake tract? Sounds like it could be dirt on a butterfly valve or even in the egr. Try seafoam in the tank and intake.

 

I talked on the tele with Trailhead 4x4, rover only repair shop in Cleveland, OH. He said, based on what its doing, and what I have replaced so far, that I should change the MAF with a known good used one, and replace the TPS sensor as it does check out bad on a scanner. She is running rich, sooting up the tail pipe, good wiff of black smoke from the exhaust when I push thru a stumbling episode going down the road and going thru tons of gas. She is basicly flooding herself to death right now. He feels that replacement of those sensors should correct the Discos issues. If not I will have to take her to Cleveland to go on thier computer that can talk to the Disco's computer. I drove her to work today, goes down the interstate pretty good, its around town, ie lower rpms that it really stumbles from time to time. Several folks I have talked to, said they have seen a rash of MAF sensors bitting the dust lately. Gotta get a couple more years out of this V8. If she will stablize for awhile, I can save up for the eventual replacement. Mike

 

Rover Mike,

My problem really sounds like the same description as yours.
I just replaced the MAF with a known good used one, with no change in performance.

I will try the seafoam stuffthis weekend, and may try a TPS sensor soon.

I will keep you updated if I can fix it.

Does yours also drop to a really low rpm when you put in the clutch rolling to a stop and almost stall, and then pull itself out sometimes?

Any check engine lights?

I get an intermitent chack engine light once a week or so if it idles a long time, and the code I will get is missfire on cyl 7 and missfires cause excessive emissions. I will drive the car for another day and then the light goes out on its own.

Mike

 

FYI,

Just replaced the TPS sensor, and there was no major change......

Do the coil packs ever go bad?

AZ truck with 146k

Any ideas would be appreciated.

Thanks,

Mike

 

Run Seafoam through your tank. Clogged\leaking injectors can cause a mis-fire.

What plugs and wires are you running, when were they last changed? Look into Magnacor wires and Bosch plugs.

FYI- when your CEL comes on, the truck defaults to a rich mixture. It will soot up the pipe like crazy.

 

when you guy's figure it out let me know. My 97sd7 does it to but not very often.I run an ocrain booster thru it and it seems to help. I run premium and it doesn't matter from what station I get it.