c320 missfire under heavy load

[roughshooter]

hi guys

I am new to the forum so first of all hello to everyone:bannana:

right down to business I have a C320 w230 2000 petrol advantguard which i only recently purchased I test drove it under light load and all seemed to be fine so I bought it first mistake on the way home i decided to see how she goes so i burried the throttle all the way down and she excelerated excelently until it was time to change up she then slightly hesitated and changed but there was a distinct loss of power and the engine management light came on so i slowed down and stopped now there was a distinct missfire so I turned the engine off and back on again and the engine light was still on but no missfire so drove here home gently and found that if i didn't bury my foot all the way she would behave very normally in fact I could bury my foot right down but not past the doulble kick down point and she is fine but as soon as i went past the doulbe kick down point missfire loss of power etc then i would have to stop turn the engine off and re start and we were back to squre one all was fine so I phoned a friend who had a diagnostic tool and checked the code it turned out there was a missfire on cylinder 6 so I changed the sprak plugs and swaped round the coil packs and replaced the maf sensor again same problem under hard exceleration so I thought i would hunt around the web and see if there are any solutions now i found a thread which said to get some injector cleaner a full tank of fuel and give the engine a really good thrashing which i did every time i did this the engine would missfire then i would stop it turn the engine off and start again i did this a few times and hey presto it stopped doing it :bannana: but after a couple of weeks it has come back again and no matter what i do it wont go away

still the same thing it only comes back when I bury my foot all the way down and keep excelerating hard through the gear change then it hesitates changes and bang the dam missfire is back and power loss stop the car enegine off and on again and all is fine apart from the engine management light is on


i have cleaned the maf sensor and will be carying out a full service including a full set of plugs fuel filter, air filter, gear box filter and oil and engine oil filter and oil


please has someone out there got a solution to this

 

[roughshooter]

no suggestions ??????

 

[kamalpatel12448]

Could be a number of things, I assume you meant w203, based on engine size I guessing it is a V6. Sounds like limp mode after kick down, Maf, O2 sensors etc, suggest getting the fault codes read on a star for best diagnoses.

 

[DSM10000]

Hi and welcome

I had the very same symptoms on my W203 320 shortly after I got it.

Hard acceleration would trigger a warning light. My code reader came up with P0306 - Cylinder 6 misfire detected.

Like you I had rough running when the engine light first came on but normal running when re-starting although the engine light would still be lit . According to my MB specialist when the car detects a misfire it shuts down the injector on that cylinder to prevent damage to the catalyst. On his suggestion I put a couple of bottles of injector cleaner through and I have had no problems since.

 

[roughshooter]

cheers guys DSM it cured mine for a while then it came back i thought it might be a dirty fuel filter so i'll be changing it next weekend and doing the whole service thing i'll let you know how it goes

 

[DSM10000]

If you have already changed the plugs and swopped the coil packs and the misfire is still on mumber 6 it suggests the injector is at fault.

 

[horgantrevor]

hi have you changed the coil pack for cylinder 6 as this is a common fault on this engine

 

[roughshooter]

is it possible to get the star software for my laptop?

 

[DSM10000]

hi have you changed the coil pack for cylinder 6 as this is a common fault on this engine

Hi, are you saying coil packs are a common failure on these engines or the one on cylinder 6?

Thanks.

 

[roughshooter]

i swapped the coil packs round from left to right bank it still came up with cylinder six misfire

 

[horgantrevor]

the coil packs are known to break down on the v6 and v8 engine s

have you checked the fuel pressure at the rail

is it a star system you are using to test

the feed wires of the harness to the cylinder you say is miss-firing have you checked it for heat damage

 

[roughshooter]

yes bud no damage at all

 

[Alex Crow]

Contrary to popular opinion, the coil packs themselves do not often fail - it is actually the HT leads that are prone to failure.

Assuming the missfire is consistently and only on cylinder no.6, the suggestion above to swap the coil and leads with another cylinder is very good.
If the missfire moves to the other cylinder I recommend replacing the HT leads on that coil pack.
Note that there is a very good facility on STAR to test the HT leads on these M112/113 engines.

If the missfire remains on cylinder no.6 it is likely there is an amount of water in the fuel system, when it gets into the fuel rail it is most likely to affect injector no.6 due to the location of this injector and the fuel feed to the rail - the injector itself is probably fine.

 

[roughshooter]

so how do i resolve this

 

[roughshooter]

i used redex first time is there any better stuff on the market???

 

[Adam230K]

Redex won't solve your problem... get it to a specialist or take it back to the dealer you bought it from so you can diagnose and hopefully solve the problem.

 

[Alex Crow]

so how do i resolve this

See post 13#

If that makes no sense to you, see post #16!

 

[MarkJunedd]

Sounds like the exact same problem i had on mine back a few months ago. I changed plugs, leads coil pack no difference at all. Turned out to be a duff no6 injector. Changed it and its been spot on ever since. Injector was about £90 if i remember.