8 replies to this topic

[kangaroomadman]

My MPI recently had a quite bit of work done to it to get it through the MOT: New rear subframe, rear wheel arch, exhaust, ball joints as well as fixing some oil leaks from the timing cover and head gasket.
 

It had also failed the emissions test which was thought to be caused by a hole in the exhaust and dodgy HT leads - the HT leads and plugs were replaced to be sure they're all good. Whilst it passed second time, it only just scraped through as the lambda was right on the high limit.

 

Anyway....since getting the car back it started to stall at junctions and generally sounds rough on idle, possibly misfiring. I guess this could be caused by many things as during the work the whole inlet manifold was removed and disturbed to replace the exhaust so could be faulty connections, pipes etc. The engine would also stall on idle if you just blipped the throttle very slightly.
 

I took it back to the garage to try and diagnose the issue but, whilst being a Mini specialist, they are much less familiar with injection engines. We managed to improve the issue where it stalled when blipping the throttle and it was better at junctions and rarely stalled - still not right but better at least. The following was done:
 

1. There was quite a bit of slack on the throttle cable, so this was adjusted to remove the slack (probably shouldn't really effect anything other than initial response when pressing the throttle)

2. We used some carb cleaner (it stated it was also OK for injection) sprayed in to the manifold

    This stated that we needed to disconnect the purge valve which seemed to improve the running

    Because of this, the purge valve was replaced with a spare to see if this made a difference - it did seem to but I'm not sure how. As I understand it, the valve only opens when up to temperature and when the throttle is open quite wide so it shouldn't affect the behaviour on idle!

3. We looked at the charcoal cannister which smells heavily of fuel - Is this normal? There did not seem to be any way of cleaning this out and I can't find a new replacement.

 

After doing the above it is much better on idle if you just blip the throttle but it still seems to struggle a little but at least it is not stalling.
 

My current issue is that the brake pedal feels strange and also when releasing the brake (when idling, e.g. after stopping at a junction) causes a similar issue to blipping the throttle - the revs drop significantly and the car feels like it is going to stall. Whilst driving the pedal seems to initially stick and you need to push past this, at which point the pedal will drop and then start braking normally.
 

I'm assuming the problem with the braking is to do with the servo but not confirmed this yet. My question is does it sound like the brake servo is the cause of issues, a symptom of other issues or unrelated to the car stalling?
 

i.e.
 

1. Could the brake servo be leaking, therefore causing higher pressure (lower vacuum) in the manifold and thus resulting in the idling/stalling issues?

    I have checked the one-way valve for the servo and it appeared to be OK with a suck/blow test.

2. Could low manifold vacuum be causing the strange behaviour with the brake servo?

3. Could the brake servo and the idling/stalling issues be completely unrelated?
 

I've checked the pipes around the manifold for cracks/splits and taken them off, sealing at one end and blowing through the other - they all seem sound.

I've disconnected both the IACV and MAP sensor, cleaned and re-fitted. No effect.

 

I'm hoping to get someone round with a diagnostics reader later this week to see what the vacuum level is etc. to see if this gives any indication.
 

Sorry for the long post, any advice would be very helpful!

 

[orcadian]

Starting right at the beginning, did the car show any of these symptoms before you had the work done?
If not, the parts disturbed were the the timing cover and cylinder head, correct? Depending on where the timing cover leak was, did they have to remove the inner cover too? If so, they could have been a tooth out when refitting the chain, very doubtful. Removing the head would necessitate disconnecting the servo take off at some point. This pipe into the manifold on the MPI is simply a push fit, so the seal could be poor. Also there are two locating rings between the manifold and head, missing those out and not replacing the gasket could cause lots of mixture related problems and the lambda sensor would detect an increase in oxygen from an air leak and the ecu would lengthen the injector pulse accordingly, putting more fuel in. One way to check if the servo is suspect is to remove the pipe and block the hole with the shank of a twist drill or equally sized rod. Be very careful where you go for a test drive, private land would be best as the pedal will be very hard but not impossible without the servo. Carbon canister will smell of fuel because that's where it goes, but purge valve as you say is not open constantly.
Lots to think about, but you have to be methodical and try to eliminate one thing at a time.

Ian

Edited by orcadian, 27 October 2015 - 04:38 PM.

[kangaroomadman]

Thanks for the reply Ian!

 

Before it went to the garage it still sounded a bit fluffy at idle, possibly misfiring but there were no brake or stalling issues.

 

One thing to note is that it is worse when there is more load on the engine - headlights on etc.

 

Yep, the disturbed parts were the timing cover and the cylinder head and anything associated around these, so all the inlet and exhaust and all sensors associated with these were disturbed. Possible bad connections in the wiring loom?

 

Not sure on the extent of repair for the timing cover.

 

Yep, the servo vacuum pipe was disconnected as the inlet manifold was fully removed from the car. I've taken a look at push fit connection (when I crudely tested the one-way valve) and this seemed OK, perhaps a little loose though.

 

I'm not sure about the rings - hopefully these were put back correctly. I know the exhaust manifold gasket was replaced - the inlet manifold shares this gasket, right?

 

Thanks for the tip about the drill bit - I was wondering what I would have lying around to block this up. I'll try and go for a short spin at the weekend (when there is some daylight) without the servo assistance.

 

If I get a diagnostics reading from it one evening this week, is there anything specific to look out for? Are expected sensor values at idle / fast idle listed anywhere?

[orcadian]

Hi,
Diagnostics read outs can be misleading sometimes, occasionally pointing to a sensor which might test out ok, so try not to get lulled into replacing components unnecessarily. I don't think many sensor values are listed anywhere but in the proper Rover manual, I'll see if I can find them. On a cold engine as you switch on the ignition you should hear the IACV stepper motor move fully one way then search for the right position dependent on water temp, can you hear that?
Have you sprayed easy start around some of the places where air leaks could occur (inlet manifold, sensors,servo pipe) and listen for increase in revs?

Ian

[kangaroomadman]

Switching on the ignition on a cold engine I can hear the IACV move although it only sounds like it moves in one direction. It moves a lot more when switching off the ignition, sounds like it's hunting or something.

I've sprayed some carb cleaner around the hoses but this didn't change the engine tone.

On Friday the car did something strange- it wouldn't start until I gave it some throttle and even then I had to keep the throttle open to stop it from stalling. After about 30s it would idle with the throttle closed but on my journey home it was suffering from a sticky throttle.

Gave it a run yesterday and the starting problem / sticky throttle had disappeared!!!!

[kangaroomadman]

Short answer.....

 

The brake servo was the cause!

 

Long answer....

 

I replaced my old servo with a second hand one and now the brake pedal has returned to normal feel and no longer drops revs after releasing.

 

When removing the brake servo I noticed the oil separator on the clutch case was only fixed by one bolt and was not aligned with the other bolt hole so was possibly venting in to the engine bay and I guess may have also been reducing the manifold vacuum? I fixed this correctly and took the time to remove all the other breather hoses and check for blockages etc.

 

After this work it runs much better now - still a bit kangaroo-like at constant speed and low revs but that's a problem for another day.

[Steve220]

Good start!

 

With the kangarooing - Does it only happen on part throttle?

[kangaroomadman]

Yeah, once you give it a boot it runs fine.

[BKozan]

Man I love it when I find posts like this. Thanks for taking the time to write this up. My '98 Rover is experiencing identical issues, and It seems my troubleshooting led me to the same place as you.

 

Low idle, sometimes stalling

Seems to run better, but not perfect, after hitting some highway for 15 minutes

Checked all vacuum hoses, tried the carb cleaner trick, but couldn't locate a vacuum leak.

Upon investigation, there is also a small leak from the brake fluid canister.

 

I am planning to buy rebuild kits for the servo and the master cylinder, along with all the required seals, hoses, and valves. I am really hoping I can clean and rebuild the lot in a single weekend in the garage.

 

Any tips or gotchas?

 

(by the way, do I need more parts than these to rebuild the whole system?)

 

http://minispares.co...sic/GSM120.aspx

http://minispares.co...ic/GRK1039.aspx

http://minispares.co...os/NAM8569.aspx

http://minispares.co...rs/GRK6009.aspx

http://minispares.co...os/17H2646.aspx

 

 

Thanks!

Edited by BKozan, 01 May 2016 - 12:22 PM.