Someone help? Power loss!

[GuyKitch]

Hey all..

First post on here!

Long story short... I had a heavily modified Cooper S that for one reason or another blew up on me a few weeks back... it's currently in the garage on axel stands... I'll be investigating it soon (prob a bent valve).

Anyhow, picked up a C270 CDI from a mate for a bargain price. It has 170k on the clock (which really does not bother me) and drives lovely... has all the options, full leather heated electric seats and so on.

I only have one complaint with it, and it's a bit of an annoying one. Sometimes it just won't accelerate. I'll floor it (even to the kick-down click) and it will only rev to about 2,100rpm and will change down. If this happens, I can stop, turn it off and back on, and usually it corrects itself and goes back to normal. There is no pattern with this. This morning the car accelerated fine, but after I pulled to a stop, and went to pull off again, it went into this "limp" mode. It usually happens when I stop at a junction. The power is literally non existant, and makes pulling out to overtake/fast lane maneouvres extremely risky.

When it's not playing up, the car is seriously torquey (its been tuned). But this little problem is really getting on my nerves. I've been told maybe a faulty MAF sensor etc.. but wanted to get some opinions first.

I know the car is old, but the engine is bulletproof and runs lovely when it's not doing this!

Cheers,
Guy

 

[Deleted member 37751]

I'd also say MAF.

Great car by the way, the 270 CDi is a brilliant lump and will easily do 500,000+ if serviced well.

 

[nick mercedes]

Get the codes read, could be low rail pressure.

 

[GuyKitch]

Does it require STAR diagnosis? Or can I plug in a generic OBD2 reader?

In all honesty, after a 18mpg Cooper S, I bought this car to lower costs (which in fuel, it really is) but I don't want to be spending loads on it :-(

The engine is awesome I think - so much torque and makes a lovely 5pot warble for a diesel.

 

[grober]

Wonder if you actually have a gearbox [ TUNED ENGINE??] rather than an engine problem which is causing the car to go into limp home mode. Probably need to get the car onto Star to get the codes read.

ps.
doubt if a generic reader would pick this up

 

[GuyKitch]

The tune is a tuning box. I've seen it in the engine bay on the right. It's from 'Dieseltuning.nl' or something.

 

[grober]

These 5 speed gearboxes are known for having 2 problems 1. with the actual electrical connection plug to the box getting saturated with oil and 2 partial failure of some of the components on the gearbox conductor plate which is the unit that contains switching solenoids and speed sensors - in other words the brain of the automatic transmission Fortunately the rest of box is quite robust meaning its unlikely there's a mechanical problem -- but if its been regularly subjected to excessive torque by that tuning box its always a possibility some of the internal clutches may be on the point of surrendering.
Mercedes Transmission Problems, Limp Mode, No Shifting: Troubleshooting Tips - Mercedes Medic

NOT saying your limp home mode is due to this but its one possibility.

 

[GuyKitch]

Thanks for that Graham.

I know that the tranny oil has recently bene changed. The tuning box was fitted in 2013 by a specialist. I believe it cost in the relms of £200+ so it wasn't a cheap eBay box.

 

[GuyKitch]

Just read that article. The car changes gear, definitely. But it just won't rev much past 2,000rpm.

 

[camerafodder]

Diagnostics on a star would always be recommended but I'd bet the problem is either MAF sensor (very easy replacement) or air in fuel lines between filter and pump on front of the engine. Does it ever give problems when starting?

 

[GuyKitch]

Starts perfectly. Idles perfectly. Quiet as hell when warm. Engine is in top notch condition.