Lack of Power - Electronics or Turbo???

[Fandango]

Hi
I wonder if anyone could help.
On the way back from Perth today my 1998 300TD just seemed totally gutless, in town I could not feel much difference but getting onto the motorway there was no acceleration at all, as if she was running without the turbo.
I pulled in at the first services to check under the bonnet, nothing seems untoward, the engine was firing on all 6 cylinders and I could not see any wires etc. disconnected.
I turned the engine off and on again; then as I drove off (uphill) everything seemed ok again.
After a stretch of roadworks at 40mph, the fault was back, and I could not make it reset again switching off and on.
It will eventually reach 80mph but only after prolonged slow acceleration.
What do you think, could it be the turbo - there is no smoke either - or would you agree that electronics are the most likely cause?

Your opinion would be much appreciated.

Regards
Karl

 

[Gordon Pidcock]

Hi Karl,

We had exactly same symptons yesterday, (our 300 TD has nearly got to 200k miles though!) I think it is either the Engine Mangement System receivng a spurious symptoms. Checked everything I can, but will take it in toi an independent to see ife computer can find the problem. Let you know if I get a result!

 

[tzar]

Hi
I wonder if anyone could help.
On the way back from Perth today my 1998 300TD just seemed totally gutless, in town I could not feel much difference but getting onto the motorway there was no acceleration at all, as if she was running without the turbo.
I pulled in at the first services to check under the bonnet, nothing seems untoward, the engine was firing on all 6 cylinders and I could not see any wires etc. disconnected.
I turned the engine off and on again; then as I drove off (uphill) everything seemed ok again.
After a stretch of roadworks at 40mph, the fault was back, and I could not make it reset again switching off and on.
It will eventually reach 80mph but only after prolonged slow acceleration.
What do you think, could it be the turbo - there is no smoke either - or would you agree that electronics are the most likely cause?

Your opinion would be much appreciated.

Regards
Karl

hi,
sounds like maf, air mas sensor in air intake, un plug it see if that makes any difference, if not its proberbly that. diagnostics may not pick it up, good luck,..

 

[KLP 92]

I've had this once on my C250TD. Switched it on/off and it disappeared! Thought it was just one of those things!

 

[DrNick]

Yes, go for the MAF. Mine did the same. Also check for air-leaks - mine had a loose inlet manifold after a glow plug change.

 

[se97mlm]

If it's the turbo, you'll get clouds of black smoke out the back.

 

[Fandango]

Thank you all, will try to get a MAF sensor and check for air leaks.

Regards
Karl

 

[Dieselman]

The ECU is going into limp home mode and dropping the turbo. If you stop the car and open the bonnet you will see the turbo wastegate link is relaxed. When restarting the wastegate actuator passes vacuum and the link is retracted again.

This could be a few things but one that will cause this after a few minutes is the EGR valve. If the MAF can't detect teh EGR valve operating it will throw limp home mode.

Check the MAF outputs and operation of EGR valve.

 

[Gordon Pidcock]

Hi Karl,
We had a MercMan look at the E300 with the same symptons as yours. He agreed with my diagnosis , the AFM, (air flow meter), is faulty.
He has fixed it by changing a component, (not the whole AFM).
If the AFM does not signal the true air volume to the ECM then the power produced will be proportionate to the the air volume, (because the ECM will maintain a correct air to fuel ratio then, if only half the air is indicated then there will of course be a power loss. Hope you get it sorted.

regards

gordon

 

[Fandango]

Thanks Gordon, I shall get the mechanic to check the AFM too, I'll be off work for a few days so I can have a look at it properly this week. The fault has gone for the moment, but it seems to be intermittent. Hopefully I can demonstrate it for the garage when needed

Just out of interest, how much was the component you changed and labour etc.?

 

[HackAJack]

I've had this problem for the last 2 weeks or so and finally sorted it out yesterday afternoon.

I read on a VAG tuning site that the Merc MAF's are prone to getting dirty and affecting performance and should be cleaned at 6000 mile intervals. Mine had 93000 miles on and had never been touched.

Went out and bought a tin of aerosol brake & clutch part cleaner, popped out the MAF and cleaned all the sensor section thouroughly and put it back in. The car is now perfect again and has more power than it has for a good few years.

So, before you replace it, give it a clean. It might just save you a big lump of cash!!!

 

[Parrot of Doom]

HackAJack, could you tell me what brand you used? Sounds like good preventative maintainance, unless anybody has any objections to doing this?

 

[Fandango]

Thanks HackAJack, will try that too.

Booked it into TJ O'Neill in Glasgow for Wednesday.

£180 + VAT for the B Service.
I told him about the intermittent power loss symptoms, he agreed that it may be the MAF, he recons it may show up on the fault codes, either way he'll clean out the old parts, we'll see how that goes.
I asked him not to spend too much time on this as the car drives flawlessly just now, could get a bit expensive chasing an intermittent fault
I shall let everyone know when this is resolved.

 

[HackAJack]

If the MAF is dirty it may not show fault codes, mine was tested twice and didn't come up!! This is because the MAF is electronically perfect and is just sending back inaccurate information to the ECU.

The cleaner I used was Brake & Clutch Part Cleaner from Motor World and cost £5.99, I can't remember the brand name just now but will add it to this post later when I get home and look at the tin.



Add: The brand was CarPlan but read the post a bit further down by Tamrsoft which suggests a better product for this task.

 

[HackAJack]

Thought this may help....

My maf is the Bosch one as pictured below. This shows the MAF with the covers removed, yours will look the same with covers on or may be slightly different on later models where a Pierburg MAF was used instead.

Anyway, The green line shows the air flow through the sensor and this is where you need to clean.

I stuck the cleaner nozzle in the air intake end of this and gave it a good soaking and then did the same in the opposite direction. I also gave the "hot film plate" a squirt and the temperature thermistior (on the back) a squirt as well. The cleaner evaporates fairly quickly so no need to touch any of the parts or prod them with anything!!!

When you re-fit this make sure it is facing in the right direction, the air intake side facing toward the air cleaner.

PS: The sensor is held in with security torx screws.... Asda sell Draper screwdriver bit sets with the correct size bit for £7.00.

 

[tamrsoft]

Be careful using Brake and Clutch Cleaner fluid, it can be too strong for some electronic components, I am told it can cause long term deterioration of the part. It's safer to use an alcohol based electronic component cleaner (£3.99 in Halfords). I blast my MAF with this on every 6000 mile service and so far its still working a treat.

 

[HackAJack]

Cheers Tamrsoft for adding that bit of wise advice. I have been and had a look and you're quite right.

Certain cleaners use chlorine to assist the cleaning process which can leave a residue, harmless on brakes but not very useful on the hot film plate. Luckily the one I used was non-chlorinated so no harm caused!!

But, it's always better to be safe than sorry so take Tamrsoft's advice and use a pure alcohol cleaner instead.

Let us know how you get on with this proposed fix.

Cheers,
HaJ.