Misfiring

[SirDavidAlhambra]

After 190,000 miles the old Alhamb has started misfiring according to the garage (makes a clunky banging noise from engine area) and the fuel economy and power is down so they said it's basically a gonner and not worth fixing. I just can't believe it. They said the camshaft is probably worn.

Does this sound right and also what is a Mercedes Viano like please.

Thank you

[Mirez]

Highly unlikely.

Read the codes but its far more likely to be the injector wiring loom breaking down, about £30 for the loom and about an hour to fit.

[SirDavidAlhambra]

Thank you so much, this is really helpful.

i have some more detailed notes below, which I made a few weeks ago:
 
Yellow engine light occasionally comes on and gives an "Emissions workshop" message.
 
On two occasions, both when the engine was cold and travelling up a very steep hill, it massively lost power (car ended up at 10mph max speed). Almost as if it was in limp mode. But there was no error message on the dashboard. Turning the engine off then on again made it work OK again.
 
Upon hard acceleration (when the engine would be under boost), black smoke now comes out of the exhaust.
 
There also seems to be a general loss of power and fuel economy (fuel economy is down around 25%).
 
I scanned the codes on the car and they were as follows.
 
VCDS-Lite Version: Release 1.2
Thursday, 11 April 2024, 17:27:01.
Control Module Part Number: 038 906 019 PA
  Component and/or Version: 1,9l R4 EDC G001AG  9325
           Software Coding: 00001
            Work Shop Code: WSC 00020
                      VCID: 65BD3297EC79
           Additional Info: VSSZZZ7MZ7V501893     VWZ1Z0F2864948
2 Faults Found:
16955 -  Brake Switch (F): Implausible Signal
        P0571 - 35-10 -   - - Intermittent
16485 - Shareware Version. To Decode all DTCs
        P0101 - 35-10 - Please Register/Activate - Intermittent
 
 
The garage said there is no air leak after the MAF, eg around the intercooler or hoses?
 
Could the wiring to the MAF be loose/bad connection?
 
Note that the MAF is a new Bosch one, I changed it myself a few months ago when the problem first started happening (at the time, I assumed it was probably just a faulty MAF causing the code, and switched it out). The fuel filter and air filter should both be fine, they are also quite new as I did them myself a few months ago.
 
 

[Mirez]

You don't tend to get error codes with the injector loom, it just stutters. Have you cleared those codes? The brake switch is an interesting one because that will give you the limp-home effect without logging any other code, the cat can't understand why you would want throttle and acceleration so restricts performance.

You can simulate that on a quiet road by very lightly pressing the brake with your left foot whilst trying to accelerate.

Clear both and see what comes back.

[Digitalis]

I have an 04 Galaxy 1.9 diesel and last week the glow plug indicator light came on a couple of seconds after engine started, Multifunctional display says "Engine Workshop" and cruise control would not work. VCDS-Lite showed P0571 brake light switch, the same as you have. The switch actually has two switches within it and four wires going to it. With brake pedal at rest,one switch is open circuit to the brake lights and the other is closed circuit to the ECU. When you press brake pedal, each switch does the opposite so brake lights come on and feed to ECU is broken. Not sure if this is causing all your problems but a cheap and easy DIY fix to eliminate it from your fault finding.
HAAS brake light switch 464440221 for £8.82 ordered from Halfords online and delivered within 48 hours sorted my problem after I removed lower fascia around fusebox to get access to it.

[Solentview]

Sorry if I am a bit late with comment, but I am with Mirez and I think you should be looking closely at your injectors. We had to change an injector in the wife's 1.4HDI a while back. In that case, the electronics in the injector itself had broken down and fuel was no longer being atomised in a controlled manner, and rather than progressive combustion there was (loud) detonation. Just after that injector was fixed, I parked in our local High Street in front of a VW Transporter which was making a seriously loud knocking noise under the bonnet, and I mentioned to the owner that it sounded like fuel detonation caused by a faulty injector. He had been advised by his garage that the cylinder head would have to come off! But I think Mirez is right, you need to check everything associated with injectors to make sure that fuel is being delivered and burnt correctly.