Limp Mode

[trannyheap]

I've had a problem with my 2.4 RWD going into limp mode. At first it was just a momentary glitch but eventually became a 20mph full limp - on a motorway. On that occasion a mechanic pal suggested I remove the plug from the common rail sensor then re-connect it. That got it going ok and we concluded the sensor was faulty so I replaced it with one from Transit Parts UK ltd, who say it is a Delphi item although it didn't come in a box, just a plastic bag with a part number sticker. The new sensor was ok for a month or so, but the van has started it's limp mode nonsense again. I thought Delphi was a good brand but have been told recently they have parts made for them in the land of carry-outs, so maybe not so good after all. So the thing is, is it a faulty sensor, or a faulty wiring loom, or a faulty ECG. Any ideas?

[knobby1]

Have you had the codes read..? The sensors rarely fail.

Lord Knobrot

[the dutch guy]

Check wires near the connextors for possible breaks.

[ned]

Is this a mk6 135 tdci? Or mk7?.

Going by the Delphi part I would assume mk6, if so get the code read but be prepared for new injectors. N

[trannyheap]

Is this a mk6 135 tdci? Or mk7?.

Going by the Delphi part I would assume mk6, if so get the code read but be prepared for new injectors. N

It's a Mk7 140 TDCI RWD

[trannyheap]

Have you had the codes read..? The sensors rarely fail.

Lord Knobrot

I'll check them today but have to admit I don't have an awful lot of faith in codes/sensors etc. The engine management light has been on for 18months, code says the engine is suffering from excess turbo pressure, yet there is nothing wrong with it. I feel the sensors by large create more problems than they solve and provide dealers with windfall type billing opportunities.

[the dutch guy]

sensor errors have a reason and no car maker puts something on a car they can leave off.
dont trow money at a dealer, get someone that knows what the codes mean and solve the cause, it can be a dickerd sensor or wire or something much more expensive if you dont solve it in time.

[trannyheap]

Have you had the codes read..? The sensors rarely fail.

Lord Knobrot

I'll check them today but have to admit I don't have an awful lot of faith in codes/sensors etc. The engine management light has been on for 18months, code says the engine is suffering from excess turbo pressure, yet there is nothing wrong with it. I feel the sensors by large create more problems than they solve and provide dealers with windfall type billing opportunities.

Only error code is P0234 turbo overboost condition. The van went in and out of partial limp all the way home tonight. It's a bit embarrassing when you're half way past an artic when your vehicle decides it's only going to go at 30mph

[knobby1]

Only error code is P0234 turbo overboost condition. The van went in and out of partial limp all the way home tonight. It's a bit embarrassing when you're half way past an artic when your vehicle decides it's only going to go at 30mph

Turbo overboost/underboost fault codes are usually the EGR valve playing up, sticking either open or closed...sometimes they can even be stuck partially open/closed...fairly common on the Mk7 engines.

I'll try to explain..:
The engine PCM, (Powertrain Control Module), is expecting to see a certain mass airflow through the MAF sensor and air pressure within the inlet manifold via the MAP sensor depending on engine rpm, throttle position and load. When the EGR valve sticks open or closed this airflow and/or pressure is not what the PCM expects to see and it will throw up a fault code and light, if this carries on for a few engine on/off cycles the PCM will often put the engine into "Limp Mode" to help prevent possible engine damage.

I suspect your EGR has possibly stuck closed, hence the "overboost" code.

Lord Knobrot

[trannyheap]

That's very interesting. The EGR valve was blanked off a couple of years ago, and the computer re-mapped so that it doesn't know it should have one. That was done because it was throwing up a fault code and the Ford bandits wanted £400 to replace the EGR valve. At the time I was tearing my hair out at the continuous barrage of component failures, a situation that remains. After that the engine management light came on again and I purchased a reader which is where the excess turbo boost comes in, but for all I know it may have been displaying the same code when it was in the bandit's garage.

However, as i said, the EGR was blanked off a couple of years ago and the limp mode is a relatively new problem. I have noticed if I keep the revs to around 2000 it doesn't go into limp so often, and when it does usually recovers on it's own after around a quarter mile. As there is no error code being thrown up for this I'm wondering if it may be a fuel starvation issue and nothing to do with the rail sensor at all.

[knobby1]

That's very interesting. The EGR valve was blanked off a couple of years ago, and the computer re-mapped so that it doesn't know it should have one. That was done because it was throwing up a fault code and the Ford bandits wanted £400 to replace the EGR valve. At the time I was tearing my hair out at the continuous barrage of component failures, a situation that remains. After that the engine management light came on again and I purchased a reader which is where the excess turbo boost comes in, but for all I know it may have been displaying the same code when it was in the bandit's garage.

However, as i said, the EGR was blanked off a couple of years ago and the limp mode is a relatively new problem. I have noticed if I keep the revs to around 2000 it doesn't go into limp so often, and when it does usually recovers on it's own after around a quarter mile. As there is no error code being thrown up for this I'm wondering if it may be a fuel starvation issue and nothing to do with the rail sensor at all.

Ah...Fair enough....Whilst blanking the EGR and having it mapped is fine...but from May 20 this year, it WILL fail it's next MOT...they'll be checking for it. If the vehicle came from the factory with an EGR and/or DPF fitted, they must be fitted and "work correctly"....big fines may apply.

Lord Knobrot