Interesting problem...

[Moose]

So, having cleaned the oil pan and replaced the spark plugs, which cleared all codes mentioned in another thread...something was bound to happen.

Today I left from a camping/wheeling trip about 200 miles from home, and after ten miles (give or take), I began to have a severe loss of power and the engine started to miss. The miss sounds like a missing spark, and it sounds like it's coming from the back center area of my engine compartment. I know that the coil pack (for lack of a better phrase -- it's a 1996 so it's GEMS) is back there. I have brand-new spark plugs, and the original plug wires (108K)

Has anyone had this problem before? I literally can drive 59 mph without any problems -- shortly after hitting 60+ mph, it has the miss and loss of power. If the engine sits for a while it's fine again...as long as I don't exceed 59 mph.

Any suggestions?

 

[Slam]

I had to replace my wires at around 80K miles. I think it is pretty common. I opened the hood and I could actually see the electricity arching at night. The wires are pretty cheap. I got them from Roverconnection.com.

 

[disco1]

Since you changed your plugs, just check and make sure that one of the leads hasn't touched your exhaust. This will cause it to burn through and short on the metal.

 

[joey]

Wires would be my first course of action.....

Being a magnacore fan, I would call these guys... cheapest place on the net to get them. Not listed on there site, but they have the best prices.

http://www.apexperformance.net/

 

[62Sunbeam]

Let me know when you figure it out as it seems I have the same problem.
My guess is miss due to over lean situation due to inadiquate fuel pressure.

I'm hoping to have the dealer look at it when they replace my gas tank.

Good luck and keep me posted.
Eric
95 Disco

 

[Moose]

I'll post up with an update. My miss is over rich though, which made me think from the beginning it was inadequate spark (no problems with air system).

 

[Moose]

Bump-to-top / Update:

...so I drove to Black River Falls (approx. 3 1/2 hours) last Friday, and was humming along for about 45 minutes at 75mph with no problems, when the miss started up again.

Since last update I:

Replaced the stock wires with 8mm Magnecors (properly seated)
Changed the oil twice
Ran Seafoam through the intake

I drove another 3 hours at 60-65mph with no problems, wheeled all day Saturday and Sunday with no problems, and drove for about 2 hours home at 60-65mph with no problems. I have noticed the oil pressure idiot light at times, but I think that is an unrelated issue (leakage at the oil pan gasket) based on low oil level -- and that's being corrected.

However, I got within 55 minutes of home and the truck developed the stumble again. I got off the highway, parked, waited, and on restart the engine ran fine, so I decided to test the theory on VSS. I drove for about 8 miles at 65 or so in 3rd gear, and it stumbled and missed. I drove backroads at no more than 50-55 the rest of the way home with no problems. I read somewhere (here?) that the VSS won't malfunction in 3rd because it knows it can't go that fast in 3rd gear. I'm puzzled by this because the truck runs so great up to those speeds...and I was under the impression that the VSS caused a fault (and therefore a cylinder run-rich miss) that was corrected when the speed was corrected to an acceptable level.

Any ideas? Joey?

 

[disco1]

I'd check the TPS (Throttle Position Sensor). Under certain conditions, the signal from the TPS to the ECU can be intermittant which causes the engine to drop back to idle suddenly and momentarily.

 

[Moose]

This is sudden in onset, but continues to worsen and does not end until the truck is shut off. It starts with what feels like a one-cylinder misfire, and worsens until it feels like the whole engine is going to vibrate right out of its mounts. I don't think it's the TPS, because it doesn't happen until a certain speed -- it doesn't seem to be throttle dependent.

 

[disco1]

The trouble here is, that you can end up spending a lot of money changing out parts until the problem is found. Unfortunately, fuel and electrical problems are very closely related symptom wise, and have to be usually worked through one at a time.