Lack of power at revs

[TheTree]

I have a slightly frustrating issue

The beast started to miss and lose power under heavier loads, eg ascending a steep long hill on the M1.

I suspected fuel starvation so I changed the fuel filter, which was indeed full of crap. This improved things but did not fix the issue completely.

I have checked the fuel pressure and it looks within spec.

It has also started to die completely and then come back on, mainly after a longer run.

I suspect I may have more than one issue here, one post I found said that these were classic symptoms of a dying CPS.

Unfortunately I can't get my nanocom to talk to the ECU for any length of time and what I do get seems scrambled :angry:

I am going to go and hook my nano up to another P38 and see if it is OK or if it is my wiring. It will talk to the BECM perfectly so I think the OBD connector is fine.

My current suspicions are the CPS, good to have a spare of these anyway, and possibly the fuel pump which is about 4 years old.

Any other ideas welcome!

Steve

[davidsonsm]

I'd check the throttle cable adjustment as a simple starter. They have a habit of backing off.

Have you had a look at the condition of the fuel injectors? Have you clearned the MAF. Is the coil pack sound. Just my two pennies worth.

[TheTree]

I'd check the throttle cable adjustment as a simple starter. They have a habit of backing off.

Have you had a look at the condition of the fuel injectors? Have you clearned the MAF. Is the coil pack sound. Just my two pennies worth.

Thanks mate,

I have run some injector cleaner through the system

the MAF clean is on my list though I can't test it until I get the nano talking to the ECU properly

As far as I know the coil packs are not very old either

Steve

[mtb_gary]

Steve

Could be something as simple as plugs and leads

Gary

[TheTree]

Steve

Could be something as simple as plugs and leads

Gary

Thanks mate, I am slowly going through the obvious stuff

They are on the list as well

Steve

[TheTree]

I cleaned the MAF and it seems to be much happier.

Real test will be on the freeway

Thanks for the suggestions everyone

Steve

[mabutho]

I also experienced that problem in a month or so, it was very very frustrating. I wud take off from a robot and the Landy

[mabutho]

Sorry about....I was saying the Landy would take its time to build up speed then all of a sudden it would jump cz my foot is flat on the pedal as m trying to push it..I was relieved to be told by LR workshop that after checking it they found an air pipe loose from the TURBO...so try and check it too...

[Hoges]

Does that model have O2 sensors? Anything available from the Torque app which might give some hint re. fuel trim?

[TheTree]

Does that model have O2 sensors? Anything available from the Torque app which might give some hint re. fuel trim?

Hoges

Still trying to get the nanocom to talk sensibly to the ECU:(

I had fitted O2 sensors but I am pretty sure it will not be seeing them.

Steve

[TheTree]

Symptoms now are that it will rev cleanly to about 3,500 then it dies and falls back to about 3,000 then will rev to 3,500 again etc

It almost feels like some kind of rev limiter is kicking in:(

Steve

[daf11e]

Steve, I read somewhere where a loose wire on the crank sensor gives those rev symptoms......just a thought.

[TheTree]

I have replaced the cps and still have the problem :(

Cold water still does the job so the only other thing it could be is the coil pack

Off to Shirl tomorrow morning to swap BECM and ECU, so I may "borrow" the coil pack from that car as well:p

Steve

[PeterH]

A while back I had a similar problem, it would run fine at lower speeds, but going up the westgate bridge it would develop a miss, you could feel the power cutting in and out, it got quite bad in the end, also did it a bit at 100 kmh.
Turned out to be the plugs on the way out, they were only about a year old, so I was looking elsewhere for the culprit.
As soon as the new plugs were in, is has been perfect ever since.
You might be on the money with the coil pack giving those symptoms.
Have you replaced the leads and plugs?
I got a custom set of good quality leads made up for mine.
Cheers, Pete.

[mtb_gary]

Steve
Just a thought, but have you checked the air filter?
Gary

[TheTree]

Steve
Just a thought, but have you checked the air filter?
Gary

Yes mate the air filter looks almost new
Steve

[TheTree]

So new CPS no change, swapped Throttle PS and no change.

I now have a cunning plan which is to drive it around locally until it starts to play up, then take it home and out the fuel pressure gauge on it and see if it is getting pressure and therefore flow

That should narrow it to either fuel or coil packs:eek:

Steve

[TheTree]

The car runs fine for about 20 mins and then starts to play up and does not want to rev, eventually it gets to the point where the throttle can only be feathered

Stopping and pouring cold water down the back of the passenger side coil packs gets it going again for about 10 mins

When it was playing up the I tested the fuel pressure and it looked fine even when the motor would not rev there was about 35PSI in the fuel rail

I think I will get the coil packs tested as per Shirls suggestion

Very frustrating behaviour especially since it is not throwing any error codes at all :angry:

Steve

[TheTree]

Finally fixed :D

We drove it a small distance with the fuel pressure gauge attached and visible thorough the windscreen :angel: and sure enough the pressure dropped to nothing when the load came on .

So we dropped the fuel tank and it turned out that the base of the fuel pump and it's mesh filter was full of crap. A little dis-assembly and a good cleanup then put it all back together and vrooom :cool:

Two separate things in the end!

Steve

[mtb_gary]

Steve

I'm pleased the problem finished up fairly inexpensive and simple to fix. Hopefully from here on it will be trouble free motoring and a smile on the face :D

Gary

[Striker]

Glad to hear you got the issue fixed mate.

You mentioned to me that you were going to chase an earthing issue.. Was that for this, or was that unrelated?

Vroom vroom!

--Striker.

[TheTree]

I am not sure the earthing issue is related to this but I am slowly going through and cleaning all the earth points and connectors as I encounter them.

I am now firmly of the belief that dirty and/or corroded earth points and connectors are the source of many of the gremlins we see on these beasts !

Steve

[poleonpom]

Steve

One last additional thing to have a look at are the two breather pipes from the rocker covers to the Plenum.

[TheTree]

Steve

One last additional thing to have a look at are the two breather pipes from the rocker covers to the Plenum.

Thanks mate I have cleaned the oil separator and replaced the drivers side hose.

I do have a slightly low vacuum at idle so I need to check further

Steve

[poleonpom]

Thanks mate I have cleaned the oil separator and replaced the drivers side hose.

I do have a slightly low vacuum at idle so I need to check further

Steve
Steve
Let me know how you go as I'm in the same boat (or P38 barge).

Jonathan