Engine misfire

[Pauljay]

Hi Guys,

I have a problem with my car misfiring when in park or neutral only!

I took it to MB and they had it for a day but couldn't find the problem! They said that it misfires on cylinders 7,8 5,6,2 basically all of them except 1, but at different times.

If you turn the car off then on again the problem goes away for a couple of minutes then returns. Driving the car is fine with no loss of power or misfires!

Yesterday I took the car to an Indy that specializes with auto electrics, but he too couldn't work it out.

Plugs, coil packs, lamda sensors, compression check, CPS, injectors, fuel rail, vacuum and wires were all checked or swapped in the hope of a cure.

I'm now out of ideas as it seems no-one can find the problem!

Can anyone point out something which may have been missed out please?

 

[kth286]

how do you know it is mis-firing ? How does it behave when it is mis-firing ?

It can be difficult to spot a mis-fire on 8 cylinder cars.

 

[GP801]

Ecu?

 

[SavMan]

Presumably they have looked at the waveforms on an oscilloscope?

 

[Pauljay]

Hi SavMan,

I don't know what they looked at, at MB.
The indy has STAR and cleared the fault codes, some stored, some current.

GP801,

I forgot I got another ECU and the problem persists.


Kth286,

The car shakes when idling after a while in neutral or park and when you then drive off the exhaust note has changed to a stutter and not much power.

 

[Pendragon]

This is a common fault unfortunately. I had the exact same problem with mine. It went to the local MB dealer who had it 3 days and couldn't find the problem. I have my own diagnostics business and it threw up no faults except for 1 or 2 that were nothing to do with the engine or gearbox.

I spent hundreds replacing parts, all coils packs, MAF, plug leads, new injectors, full service and it made no difference at all.

I then used a product called Power Boost which is a decoke in can and there was some improvement. I then had to do a long trip (my car is used locally around Cardiff and never gets a run out) so I gave it some wellie on the motorway..............it solved the problem. That was a few months ago and it now runs very smooth. Not sure if this would sure your problem but its worth trying without having to throw a stack of cash at new parts that you probably don't needs.
Hope you get it sorted out as I know just how ruddy annoying it is.

Keith

 

[Pauljay]

Thanks Keith,

I will try this as I am at that stage of throwing money and parts at it!

 

[Pendragon]

Paul, I think I paid £22.00 or there about for the Power Boost. If you can't find it I will see if I can dig my invoice out and tell you the name of the company or send you the link if they have one.

I would also check your plugs to see what condition they are in before doing anything.

Its worth a go. I take it you do not do any long trips on it ?

Keith

 

[Pendragon]

Just found a link to it on Ebay. Same people I bought mine from but its gone up to £24.00
ECOTEK POWER BOOST ENGINE ENERGIZER CLEANS INJECTORS | eBay

If it does for your car what it did for mine then happy days, if not you lose £24.00 but better that than hundreds.

Don't forget to take it for a long blast up the motorway. I did a 200+ mile trip and all was well.


Keith

 

[Pauljay]

Thanks Keith,

I did a quick search on Google and there's a garage down the road from me that sells it. Same price!

 

[Pendragon]

Even better then as you won't have to battle the Xmas post lol

Good luck and let us know how you get on.

Keith

 

[Dieselman]

I wouldn't be surprised if it is sticking valves, but it could also be an air leak into the intake manifold due to the O rings round the injectors.

 

[Pauljay]

Guys,

I bought a can of Power boost and followed the instructions yesterday.

I used all the can (500ml) as it said to do so even the the shop assistant said it's enough for 2 cars.

Only a little bit of smoke came out the exhaust when applying (I was expecting lots), then I took it for a 15mile drive as the instructions said to use the full rev range where possible for 10mins.

Initially the car felt stodgy and lacked performance, in the night drive on the M-Way and A roads I couldn't see how much smoke came out, but the car began to perk up. 20mins later I returned and parked.

Early this morning the car felt smoother and a bit torquier (if that's a word) than before, performance felt great, but then at work left to idle, she misfired again.

I am going to try injector cleaner as power boost is meant to clean the valves, atleast this way I know my engine internals are clean.

I guess I'll have to live with this for a while until something else comes up!


Keith

Thanks for the advise. I use my car daily with a 50m round trip to work and back on M-Way and normal roads. Hopefully with a little more miles the effect may change, but atleast the car feels better!

Dieselman

I had the o-rings changed on the injectors by the Indy. He looked a vacuum lines and checked connections too.

 

[Pendragon]

Well at least something positive has come out of it and thats what happened to me but the 200 mile run sorted my problem out. It may be that after a few trips out it may have that effect on yours, it was worth a try. Good luck and if it does persist then have a look at what Dieselman suggested.

Merry Xmas.

Keith

 

[WG M-B]

An egr valve sticking open will cause this problem on 112/113 engines.
I have had it quite a few times. Look at increased air intake temp at idle when lumpy

 

[Pauljay]

Thanks after Christmas I'll look into that!

Merry Christmas everyone!

 

[Pauljay]

Hi Guys,

Back from my hols.

Quick update, now solved!

Just before my break I spoke to Robin (rawc43) a member here that works next door to me at an Indie garage. He said the symptoms sounded like sticking hydrolic actuators and to try some additives in the engine oil.

I bought 2 tins of Wurth as each one covers 4ltrs of oil, a quick research indicatated that it's very good stuff. After 15m of driving problem solved, no more mis-fires on idle!

My car runs smoother and quieter than ever before and I would recommend to others to try this product out.

The downside is the few hundred of pounds spent changing parts unnecessarily but atleast they're new now so I can rule changing them for a while.

Thankyou Robin!!

 

[rorf]

I was going to ask when last you changed the engine oil and filter and what oil you use. Dirty fuel filters can also cause similar problems.

Still at the end of the day an Italian tune up will always do the job - all engines need to be worked over on a regular basis to get the cobwebs out

 

[Pauljay]

Hi Rorf,

I change my oil every 6000m and stick to Mobil 1 10/40.

I was told the actuators (lifters) have something to do with the cams and valves. Apparentley at high revs they don't have a chance to stick, but at idle this can happen. The stuff I put in with the oil generally quietens down the hydrolic tappets but also lubricates the running mechanisms.

My car regularly recieves an Italian tune up!