Mk7 bad idle and running

[alan1272]

I've got a Mk7 2.4 rwd t350 100ps with an intermittent hunting idle, what feels like a misfire (but not sure it is) and no power over 3000rpm. It also seems to be slightly slow to start.

Obviously there is plenty of other threads with similar issues, so ive fitted a new diesel filter and plugged in a basic code reader but found o codes.

Im about to download FORscan and order a cable. I can get access to a better code reader in a few days. I intend to do rocker gasket and injector seals/washers/clamps/bolts and the rocker has a leak.

What is my next step? Find someone with IDS? Change PRV and SCV?

Any advice is appreciated.

[knobby1]

When you get Forscan, you won't need IDS. Forscan will find codes if there are any.

A full set of learns is a good place to start. Injector leak-off test is also worthwhile.

Make sure both batteries are good, load test them to make sure.

Lord Knobrot

[davyjcb]

Do 1 thing at a time,if you get Forscan set up firstly check codes if it's got no codes pull up live data and check that the rail pressure desired and rail pressure actual are fairly close to each other and that the actual follows /adjusts to be close to the desired . If figures look alright I would then do leak off test before trying learns as if there's a bad /leaky injector the learns (depending on how far out the leakage is) will possibly fail. As a guess it's a possibility that your scv is playing up, try carrying out the simple checks first it's your money you'll get the "put an scv ,prv, etc" advice and sure enough if you put a heap of parts on it will sort your van.
Identify
Confirm
Rectify

[STEVE P]

I was surprised when I changed my SCV how much more stable the pressures were, with the original valve the pressure were fluctuating constantly even at idle.

Steve

[knobby1]

I was surprised when I changed my SCV how much more stable the pressures were, with the original valve the pressure were fluctuating constantly even at idle.

Steve

SCV is basically a variable voltage solenoid valve acting against a spring.....any wear or crap causing sticking or hysteresis will give grief.

Lord Knobrot

[alan1272]

Thanks chaps, i will plug forscan in when the cable arrives and report back.

Sent from my SM-A750FN using Tapatalk

[alan1272]

I managed to borrow a better code reader tonight and got the 6 DTCs pictured. I cleared them except P0190 which was current.
I will plug in forscan when the cable arrives but is it fair to assume that:

P0190, P268B, P116E - all point to a faulty PRV; a new valve and pump learn should resolve?

P0704- replacement clutch pedal switch required?

P0623 - alternator light related?

P068A - i have no idea!

I appreciate any advice you can offer!


Sent from my SM-A750FN using Tapatalk

[knobby1]

You've got P268B as well, "High pressure fuel pump not calibrated".....You'll need to get the learns done and go from there. Check to see if the PRV is blown.......If the PRV is blown, it will probably be the SCV which has caused it. However, a blown PRV usually causes hard to start due to low fuel pressure etc...

Seems you've also got some electrical gremlins in the van.

Lord Knobrot

[alan1272]

I thought I'd update this seeing as i have some time on my hands now!
A couple of weekends ago i received the cable in the post so i could plug FORscan in; what a brilliant piece of free software! So much easier than the INPA i use on my BMW.

The codes about the fuel pump not being calibrated and the open circuit on the pressure sensor were still there so i began by looking at some live data which showed the demanded FP and the actual FP (pic 1). It was clear there was no signal from the sensor so i started investigating the pressure sensor on the fuel rail.
Looking at it you could see the coloured wires between the convolute and the rubber plug; i gave it a little tug assuming it would a broken wire and all 3 spade connectors came out of the plug! I pushed then back home into the plug and reconnected it then started the van. It suddenly ran better, on 4 cylinders, less knocking, but the idle was hunting up and down and it stalled a few times.
With the sensor code cleared, the data showed the sensor was sending a signal to the ecu, so i tried a pump learn.
It took 3 attempts to get a successful pump learn as the van kept stalling during the process. I then did an injector pilot learn for good measure.
The van then seemed to run, idle and rev up fine. That data showed all the values tracking eaxh other nicely (pic 2). Unfortunately i haven't been able to road test it thoroughly due to the current situation, but i am hopeful the issue has been resolved.

Sent from my SM-A750FN using Tapatalk