I, have a 2003 Disco with 98k. The Service Enging Soon light came on I checked it and got the code P0305 ( Cylinder 5 misfire ).

I went and checked the plug wires which are magnecors that the previous owner put on the Disco. The plug wire is fine. I replaced the #5 spark plug. The old plug was fouled but not terribly so. After replacing the #5 plug the shenanigans began. The engine would roughly idle and stutter under acceleration. I starting getting code P0300. Each time I would disconnect and reconnect the OBDII I get P0300 and a different cylinder ( P0308, P0302, etc).

I took off the air intake and sprayed some carb cleaner into the plenum. The engine will not start now and acts as if the battery is dead.

I wonder if the problem could be caused by a short in the engine wiring harness? It just seems odd that as soon as I replace the #5 plug I start getting random misfires and the engine now wont start.

Any help would be appreciated.

 

Ouch.
Don't ever spray carb cleaner into the plenum.
I am guessing you put it into the MAF sensor and toasted the hot wire.

With the engine off - you can only spray CRC sensor cleaner into the MAF sensor.

The MAF has a hot wire to monitor the density and flow of the air entering the engine.
The CARB cleaner may have damaged the hotwire in the MAF.

If the MAF is dead, I am not sure the Discovery II can start.
I bet Mike or Savannah will know the answer to that one.

 

Luckily, I had removed the MAF from the intake and sprayed the carb cleaner directly into the throttle.

I replaced the battery and the disco started. Yeah.

Still showing the flashing Service Engine Soon light. The disco sputters and wants to die. As soon as I can limp up to an auto parts store, I'll run a diagnostic and can give a better description of what's wrong

 

Hi,
Usually flashing Check Engine Light means that damage to the catalytic convertor is occurring and stop driving.

Are you running too rich? Black smoke out the back?
You may have an injector which is stuck partly open.

I would put a code scanner onto the OBD2 plug and look at the fuel trim readings.

Also look if your #1 O2 sensors are oscillating between .1 and .9 volts.
Sounds like you are running OPEN LOOP all the time.

That will kill the catalytic converters.

Or, they may superheat and start to melt wires and plastic nearby.

Would not drive until you get it figured out.

 

Reread your original post.
I bet you have a bad coil pack.
You are running on 4 cylinders or less.
do not drive.

I would replace a coil pack with new.

 

Alright here are some pics from the OBDII that I used at O'reillys auto parts







I'll have to search through the RAVE to make heads or tails of this but it looks like something to do with the fuel system???

I also agree that it may be a faulty coil pack or maybe even the altinator. A random misfire usually has to do with the ignition system. This is frustrating as I could have replaced them about two months ago when I replaced the rocker cover gaskets.

BTW: I have noticed that I used to get the Three Amigos lights all the time. Curiously, once this kicked off, I quit getting those warning lights. HHHMMM.....

 

Before you guess your self into the poor house, you might want to send me your number and let me what you thru what to test.
By the pictures you posted didn't come thru, what were they supposed to show us?

 

The pictures were of the OBD2 readings that i used at O'reillys it did not give the most complete data but it was all I could get to on a Sunday evening. The pics stated the following:

Error. Code p03050
Freeze frame data

"fuel sys 1 OL-fault
Fuel sys 2 OL-fault
Calc load (%) 48.2
ECT (F) 201
stft B1(%) 0
Ltft B1(%) -1.5
Stft B2 (%) 0
Ltft B2 (%) -0.7
Eng RPM 2481

 

Ok, after some testing and trouble shooting.... I'm still dazed and confused.

A great amount of Thanks goes to DiscoMike for suggesting some tests to run and helpful advise.

• The alternator works fine pumping out 14.2 volts +/-
• The plug wires are good. I sprayed them with water and no sparking
• I borrowed a buddies thermal tempature reader and took temp reading of the exhaust for each cylinder both at start up and when running at normal temps:

Cylinder# --Cold --Hot
1 170 260
3 150 360
5 130 300
7 130 200

2 230 160
4 160 240
6 180 260
8 200 390

The cold temps on even # cylinders was higher because they were done last. I am still getting error codes P0305 & P0300. When I ran the test, I was not getting a flashing Service Engine Soon light. The engine sounded like it was missing but not as badly as when the SES light starts flashing and the engine sounds like it will die.

I am starting to think that I have an issue with the fuel system ( injectors fuel rail, etc ) or sensor.

 

Hey, anyone still following this?
I have a VERY similar situation. I put a plug wire test light on the wires and found the signal would vacillate from strong to weak, with occasional misses altogether. While, I did not test every wire, the ones "easily" accessible, all did the same thing. Leading me to think the coils are fried.

So, I'm wondering who's got the best price on BOSCH coils? I've been searching the posts but haven't found any suppliers. All suggestions appreciated.
Thanks