Mis-Fire - the Fault Codes

[mercman1969]

Garage had car today to read the fault codes...this is what was recorded prior to clearing the codes and starting engine

P2050
P2051 - mis fire Cyl #1
P2053 - mis fire Cyl #4
P2016
P2052 - mis fire Cyl #5
P2043 - mis firing
P2047 - mis fire Cyl #2
p2054 - mis fire Cyl #2
p2004 - B2/5 (Hot Film MAF sensor)
p2085

Codes were then cleared and engine started and test driven

Codes taken as follows

p2043 - mis firing
p2047 - mis fire Cyl #2
p2050 - mis firing
p2053 - mis fire Cyl #4
p2054 - mis fire Cyl #2

Fault is intermittant and all coil packs, plugs and leads were changed 8000 miles ago
Car has ran very well over the warm/dry months

Anybody add any words of wisdom to this fault please?

 

[lynall]

I suppose checking all the loom couldn hurt but i think i would be tempted to send the ecu away for checking and possibly repair, google bba reman.



Lynall

 

[BlackC55]

What car and engine?

 

[mercman1969]

Apologies folks

Car is an ML320 (W163)
52 Plate with 78k miles

Also has professional LPG kit fitted

 

[lynall]

Does it misfire on both lpg and petrol?

If only gas and only when cold maybe the evaporator jobby?

What temp does the engine run at?

I also assume when its on lpg there is something to fool the std ecu petrol injector set up?



Lynall

 

[mercman1969]

Fault apparant under both fuels
Engine runs at just over 80 degrees C

 

[lynall]

Search on here for cps or crankshaft position sensor.
£75 from merc.


Lynall

 

[mercman1969]

CPS was changed on last service 10 months ago

are they fragile and could go again?

 

[alexander patie]

like olly, i loose interest when lpg is mentioned. could be an air draw from 5hitty lpg kit fitting. could be dodgy ht leads, or possibly plus or coils. could also be a zillion other things!! good luck.

 

[stevesey]

Has the MAF been changed?

Other than that, and given the misfire affects a number of cylinders on both banks - it's unlikely to be a coil/plug issue (especially if they have been changed anyway), more likely that these would show on fixed clyinders and not most of them. So suspicion would turn to fuelling and air leaks.

 

[alexander patie]

i should have read the first post better - we must now assume the problematic ignition system is ok i guess. if it were a maf sensor issue i would expect p015* codes. i suspect the lpg or lpg switchover is causing the p030* codes, or possibly fuel pressure if it only happens with petrol. can we have some more specific detail on the fault please?

 

[pro-star]

hi, how long has the car been perfectly reliable since the kit was fitted? (time / distance travelled)

 

[mercman1969]

Car had more or less same fault in damp/cold conditions this time last year
MB indi diagnosed CPS, this didnt cure the fault and as ignition is paramount for LPG I decided to change the plugs/leads & coils

Car ran ok over the winter months and has done until the last few weeks

LPG is serviced every 12 months to ensure it is 100%

Fault is apparant even when running on petrol only

last year i did a voltage check across the MAF and only got a max of 5.9v

I believe you should get in the region of 12v?

 

[lynall]

Not sure on maf but lots of car and truck sensors run on 5 volts, so it may be okay, again try a search as dieselman had a long thread about mafs a while ago with voltages etc.



Lynall

 

[mercman1969]

Hi Folks,

Thought I should update you on this

New Bosch MAF fitted and car is now running and driving like a dream

Thanks to all you helped out......lesson is if you're car is running like pooh dont spend a fortune on people diagnosing it...simply change the MAF

 

[mercman1969]

Spoke tooo soon

Car ran like a dream for 200 miles on journey back home on Saturday and was fine until saturday night

It has now reverted back to playing up as per original fault

I was convinced the new MAF had cured the problem and am now of the mind that something may have 'blown' the MAF

Is this possible, and how do you diagnose it

 

[lynall]

Genuine part or other! try a search almost all who have fitted a pattern one have had problems.




Lynall

 

[gina2201]

I had a MAF issue, misfiring, holding back. Changed the MAF for a cheapo , car despised it. Bosch one? Perfect

( after I had changed leads, coil packs!) I had a thread a few months ago on voltages and testing the MAF whilst running/driving. Lamda sensor was also a suggestion?

 

[mercman1969]

Part is of course and original Bosch part

 

[lynall]

Mercman it was Ginas thread i was thinking about not Dieselmans one, but pretty sure he posted most of the answers you will need.



Lynall