misfire issues

[inhUMaine]

So i just bought a 98 Discovery(119k miles) and it has some issues. When i take it out for a drive it run fines for a couple miles or so, then it starts misfireing badly. The power comes in waves. The CEL was on so i took it to get the codes read.

General P-codes were
P0300 - which is just a general multiple misfire code
P0305 - cyl 5 misfire
P0304 - cyl 4 misfire
P0308 - cyl 8 misfire

Manufacture P-codes
P1313
P1314
P1316
P1316 (came up twice)

It also has a high idle issue. The plugs and wires are all new. what do you think is causing all this misfireing?


thanks for your help.

 

[joey]

When it starts having issues, shift down to 3rd gear from drive and see if the issue follows. If it doesn't it could be the Vehicle Speed Sensor. If it does follow, it could be the MAF Sensor. You could try disconnecting it and seeing if the issue goes away... fuel economy will drop hard, but it may be the issue, then you can replace it.

What type of air filter do you use?

 

[joey]

Got this from your thread on the other forum:

119k miles

Previous owner installed most likely generic Advance Auto brand wires and NGK plugs

When did the issue start happening? Just got the vehicle, started happening on my first drive that was longer than a couple miles.

Was there any work down just prior to the issue?
I replaced the steering box yesterday(PITA), fuel pump, wires, plugs, shocks replaced about 2 weeks ago.

What type fuel are you running? Previous owner said all he ran was 91 octane (highest around here), so on my first fill up i put 91 octane in it

Last fuel filter change?
No idea

Last air filter change?
Yesterday, put in a paper fram air filter

Thanks

 

[joey]

If you didn't replace the plugs and he did... I would suggest cheap champions and get rid of the other stuff... maybe even look at some good wires. Rover like good wires and cheap champion plugs.

What type filter was in it and how bad was it?

 

[inhUMaine]

i'll try the shift to 3rd tomorrow. i sprayed down the MAF today with some MAF cleaner didnt make any difference.

filter didnt look bad at all, but i changed it anyway. it also had a paper fram in it. I think its only has the standard grade NGKs in it.


thanks

 

[Disco Mike]

Those are all misfire related codes, get rid of the wires, use 8mm Magnacor wires and either Champion dual platinum or Bosch Platinum Plus 4 plugs, this should fix the problem.
I am concerned that you tried cleaning your Bosch MAF, they don't take to it well and will probably die. Just so you know, a MAF won't cause a misfire, usually only lean or rich banks fault codes and or a tranny code, specificly a 734 or 734.

 

[joey]

Not to argue with Disco MIke, but never ever put platinum or bosch anything in a D1....

 

[inhUMaine]

i put some new champion plugs in it that i gapped, today. took it to town was still misfiring. checked all the stores around and none of them carry any wires for the rover. At the moment, it has Autolite Professional Series 7mm wires in it that were replaced about 2 weeks ago. I looked closely at the wires last night in the pitch black and saw no arching. So while i was driving around town the speedo quit and stopped working. i pulled onto the interstate because it "seemed" to misfire more at high speeds yesterday. i drove 20 miles on the interstate and it hasnt misfired since the speedo stopped working in town. cleaned the maf because of the high idle, didnt seem to make a difference.

tried the shift to 3rd while i was doiing about 55 and it was misfiring and it continued to misfire.

 

[joey]

BAD VSS (Vehicle Speed Sensor)

Go here for how to change: http://www.discoweb.org/vss/index.htm

 

[inhUMaine]

after i parked and started the truck up, the speedo worked again and it continued to randomly misfire. just put in a new VSS and a set of mags. no change, still misfires. although i havent seen the speedo act funny since the new vss.