So here's the deal -

2000 Discovery 2, 4.0 V8. On my way back from a weekend off-roading at Rausch Creek in PA, I found myself struggling with some codes and symptoms. I've done a pretty thorough search for similar situations but none that match what I am experiencing - hence my plead for wisdom of others...



SYMPTOMS:
- Codes: P0301 (cylinder 1 misfire), P0303 (cylinder 3 misfire), P1300 (cooking the cats)

- Rough idle at cold, evens out once running temps are up and system is running Closed Loop.

- Losing relatively small amount of coolant. No white smoke under load or cruising, but slight at start up. Temps between 188F - 194F cruising speed.

- Sluggish when under heavy load, does not like to accelerate. Misfire is very obvious.

- Anything more than a 5% grade truck cannot keep constant speed. Going up hills I've seen RPM's go up to ~3K with ~90% on the throttle, but speed does not increase.

PARTS REPLACED TO DATE:
- ERR6045 Coil Packs (2)
- Magnecor 80242 8mm Ignition Cables
- (8) Bosch FR8DPP30X Platinum Spark Plugs
- (2) Bosch 15175 O2 Sensors
- Hayden Automotive 2991 Fan Clutch
- URO Parts STC4378 Water Pump
- Catalytic Converters (Exhaust manifold to mid-pipe, not through cat-back)
- Expansion tank and cap

CURRENT NEXT STEPS AND THOUGHTS:
- Combustion and pressure test

- Inspect injectors and clean/replace with new seals (UREMCO Fuel Injector Seal Kit - purchased)

- I want to say it's not a coil or wire issue. P0301 and P0303 are on different coils and the other cylinders seem to fire just fine.

- Possible issue with the gasket at the water pump? I watched the BA water pump install video and they mention that if the gasket for the cover is not seated correctly, coolant tends to leak into Cylinder 1.

- Possible issue with the valve cover gasket allowing coolant to enter Cylinder 3 from Cylinder 1?

If anyone can chime in and help point me in a direction that makes sense before I jump to HG issues I'd appreciate the insight. And, if you're local to the Philadelphia area, there's a case of beer/bottle of booze/extra pair of hands to wrench if you're interested!

 

I would rent a CO2 combustion tester for the coolant. That way you can rule out a head gasket. Maybe also pull the plugs and do a compression test on all the cylinders and see if 1 and 3 are low. If you have a scope you could take a look in them to see if anything seems amiss. I don't know how long ago you did the plugs, but you could see if some are cleaner than others.

 

Since you just replaced coils, wires and plugs. Just re check connections from spark plug to coils. Pull, plugs 1 and 5 and check condition. You can also replace the 2 plugs if possible. Reset code and observe.

 

Coils, wires and plugs were done about 2 months ago (~500 miles?). Where would you suggest renting the CO2 combustion tester?

 

Plug 5 or 3? No issues on 5 but just making sure I'm not missing something from your suggestion.

 

I rented one from AutoZone for free, it was part of their loan-a-tool program. If not, then Harbor Freight should have them. I'd also take a look like at the wires / coils on 1/3 like LR03NJ said. Could be simple bad connection.

 

Perfect I have both close by. And I agree with you and LR03NJ - I'll take a look at those connections.

Would you suggest a multimeter to test the connection or just swap it to a different cylinder and see if that cylinder code is thrown?

 

I'd call AutoZone and see if they have it first, would save you a trip in case they don't. At mine, I had to wait until they ended up getting it back from someone else.

As for the spark plug wires, I would just check them and put them back, maybe add a little dielectric grease in the boots. Then clear the codes and see if they come back like LR03NJ said.

 

+1 AutoZone for the Block Tester. Just a headsup, AZ will charge you about $25 for the tool (you get that back) and about $9.00 for the chemical. You won't get the $9.00 back, but you will ONLY NEED 1 Bottle.

 

OverRover - Perfect timing chiming in with this. I went to AZ not knowing exactly what it looked like so I did not leave with the tester. I'll be heading back to pick it up!