Will not go over 3,000rpm Limp Mode?

Hi All,

I have had my P38 2.5 auto for at least a week and had the common hot start issue, so purchased the "Hot Chip Fix" which seemed to sort it initially, however recently the engine has been hard to start when hot, but perfectly okay when cold. This evening, I drove to the shops about 10 miles to the shops was there about 30 minutes, engine still hot took about 10 seconds to start up, then on the return journey the engine seemed to be running okay until I had to overtake someone and the engine went to 5,000rpm then limped at 3000rpm and would not go any higher even with my foot flat on the accelerator. Managed to get home, placed the gearbox in Neutral and reved up to about 4/5000 rpm at around 4,500rpm the engine spluttered and black smoke came out the exhaust and ran fine in idle after that, took for another driver - ran okay but slow on the uptake but did not like going over 3,000rpm top speed about 50mph and now power to pull away underload on hills - could this be my injector pump saying ive had my day? Or is there anything else I could try??

Cheers

On top of the Fuel filter on the right (as looking at) of the engine bay should be a small electrical sensor - this is the MAP sensor, there should be a little pipe connected to this with the other end connecte under the intake manifold between 5 & 6 cylinder (towards the rear)

The MAP sensor thells the engine ECU the manifold pressure and is used for fueling information. Check this is connected and the pipe isn't split!

Failing that, it may be the in tank lift pump getting weak, this can cause starting issues and reduced engine performance.

Test by removing the fuel pipe to the fuel filter and bridge the fuel pump relay, using a measuring jug to catch the diesel....should deliver 180ml of diesel in 10 seconds...any less and the lift pump is tired or duff....

Many Thanks Saint.V8,

I will have a look and keep you posted.

Cheers

Dan

DANTUR77 said:

Many Thanks Saint.V8,

I will have a look and keep you posted.

Cheers

Dan

Click to expand...

Once you have checked the above, which are the common items, it would be then prudent to check the No.4 Injector...this has a needle lift sensor fitted to it and is used for start of injection and injection quantity information, oftentimes if it has been removed and the installer not so diligent on refitting, the wire to the sensor can get damaged.

Also check the Spill pipes (leak off pipes) that interconnect the injectors...these can split allowing air into the fuel system, this can hamper starting!

Could also be a incorrectly installed or faulty hot start fix.

Thanks for your help on this, but I feel a bit of an arse, when I tell you what the problem was!

I checked as you mentioned the flow of fuel to the filter; MAP Sensor; Pipes/connections and split but still had no luck, was running like a dream when cold but got worse when hot - felt like a fuel starvation problem or air even took the Temp Air Sensor off the inlet to make sure it was not faulty and the hot fix kit was fitted to it too - took the cover off the air filter box and work extremely well in the hot (making sure not to absorb anything into the air filter housing), which lead me to thing their was a sensor issue! That was until I lifted the Air Filter out of its housing, which looked okay on the face up side, but when turned over resembled the overalls of a Welsh Pit Miner after a hard weeks work! Fitted replacement K&N Filter today - Purrrrrr fect Now!

Many Thanks to All!

Forgot to mention that I have only had the vehicle a month and as the oil and fuel filters looked new - I assumed the air filter was fine! Wrong! My father (old school diesel mechanic) said that when the engine was cold the automatic choke was feeding the much needed fuel into the engine until the choke deactivated itself once the engine was at temperature, hence the engine working fine when cold but obviously needed the air once hot!

DANTUR77 said:

Forgot to mention that I have only had the vehicle a month and as the oil and fuel filters looked new - I assumed the air filter was fine! Wrong! My father (old school diesel mechanic) said that when the engine was cold the automatic choke was feeding the much needed fuel into the engine until the choke deactivated itself once the engine was at temperature, hence the engine working fine when cold but obviously needed the air once hot!

Click to expand...

There is no automatic choke on a diesel, the FIP just adds more fuel. Air intake is always fully open.
K&N filters are a waste of money and on engines fitted with a MAF can be destructive, Google it if you don't believe me. The standard filter is more than adequate.
First job on any newly aquired second hand vehicle is change all the oils and filters, hope you have done or are going to do the auto box.
On the P38 it's also advisable to do the airsprings unless you are sure they have been done fairly recently.

DANTUR77 said:

Forgot to mention that I have only had the vehicle a month and as the oil and fuel filters looked new - I assumed the air filter was fine! Wrong! My father (old school diesel mechanic) said that when the engine was cold the automatic choke was feeding the much needed fuel into the engine until the choke deactivated itself once the engine was at temperature, hence the engine working fine when cold but obviously needed the air once hot!

Click to expand...

if you had used the Search facility you would have found my post " Wont rev over 2500", I thought someone had fitted a fitted a speed limiter whilst I was away. Changed air and fuel filter, sorted

Thanks

Thanks for the info. The K&N, its the standard filter replacement and not the induction cone kit, but I will keep an eye on it as some mention that the high performance filters do not stop all the dust partials going through the MAF, may change it back to the standard type filter. Servicing shortly and changing box and engine oils too. The original EAS suspension system has been removed and has been replaced by the coil spring kit in the last couple of years, but check it all out when its being serviced.

Many Thanks