Go Back   The 75 and ZT Owners Club Forums > The 75 and ZT Owners Club Forums > Technical Help Forum
Register FAQ Image Gallery Members List Calendar Mark Forums Read
Notices

Reply
 
Thread Tools Display Modes
Old 4th June 2020, 23:00   #1
mbonwick
Gets stuck in
 
Connoisseur SE 1.8 Auto Saloon

Join Date: Jul 2015
Location: Kendal
Posts: 633
Thanks: 129
Thanked 176 Times in 147 Posts
Default K Series Cold Running issue

Right, at my wits end with this, but can't bring myself to go as far as replacing the engine wiring loom as I've had suggested elsewhere.


Every time when starting from cold, the car will misfire until it fully warms up. Most of the time it will start OK, and then develop sometimes to the point of stalling, however every now and then it will stumble into firing up and have a miss from the instant it starts.
The severity of symptoms isn't consistent - sometimes it will be a little fish-bite misfire, other times it will stall 3 or 4 times before it runs. Does seem to be worse in the cold/wet though. And finally, sometimes when driving it feels a bit down on power for the entirety of the trip - not enough to say there's definitely something wrong, but enough to feel like its struggling a bit. Other times once it's warm it's completely fine.



It's a 1.8 non-turbo, VVC inlet manifold and ported cylinder head but both Kmaps and DVApower have said they've never come across something like this before from the inlet/head work alone.


I've done quite a bit of diagnostics/code reading/parts cannon but I don't want to start off by listing it all in case it leads people down the wrong path/into the same trap I seem to have fallen into.


Thoughts and suggestions of what to do welcome, please!
mbonwick is offline   Reply With Quote
Old 4th June 2020, 23:27   #2
mh007
This is my second home
 
mh007's Avatar
 
MG ZT260 SE, MG ZT190+, MG ZTT 160, R75 Conn SE 2.0, R75 Conn SE 2.5 X 3, R75 Club SE 1.8, P5B Coupe

Join Date: Jul 2009
Location: Keynsham, Bristol
Posts: 4,211
Thanks: 65
Thanked 635 Times in 499 Posts
Default

Considering the work that has been done on the head, this may seem obvious but.....


Is there any signs of coolant on the spark plugs?


regardless, I would imagine that one spark plug will be a different colour to the other three unless you have a random misfire going across all cylinders.
mh007 is offline   Reply With Quote
Old 4th June 2020, 23:38   #3
mbonwick
Gets stuck in
 
Connoisseur SE 1.8 Auto Saloon

Join Date: Jul 2015
Location: Kendal
Posts: 633
Thanks: 129
Thanked 176 Times in 147 Posts
Default

No signs of coolant in the cylinders/on the spark plugs.
Plugs all look the same as well, so I'd reached the conclusion that it's a random misfire across all cylinders, which is supported by no cylinder-specific codes, only P0300 (random misfire) and P0316 (misfire excess emissions).


So from that (plus a compression test that showed all cylinders to have similar, normal pressures) I've ruled out anything mechanical.
EDIT: Should also add that I've done the obvious cam timing check as well.
mbonwick is offline   Reply With Quote
Old 5th June 2020, 05:56   #4
Mark Murphy
Regular poster
 
Rover 75, and Mg zt 1.8T

Join Date: Aug 2019
Location: Huntingdon
Posts: 92
Thanks: 302
Thanked 23 Times in 22 Posts
Default

I would look for an inlet leak.
Mark Murphy is offline   Reply With Quote
Old 5th June 2020, 09:57   #5
mbonwick
Gets stuck in
 
Connoisseur SE 1.8 Auto Saloon

Join Date: Jul 2015
Location: Kendal
Posts: 633
Thanks: 129
Thanked 176 Times in 147 Posts
Default

That was my next thought, I've lost count of the amount of times I've sprayed brake cleaner around it looking for a leak - nothing.

Even the couple of garages it's been in can't find any evidence of a leak. Plus I don't think that would explain it not starting smoothly sometimes.
mbonwick is offline   Reply With Quote
Old 5th June 2020, 11:30   #6
suzublu
This is my second home
 
suzublu's Avatar
 
rover 75 1.8 vvc club se wedgwood blue

Join Date: Aug 2009
Location: Seaton Carew
Posts: 26,880
Thanks: 65
Thanked 7,142 Times in 4,642 Posts
Default

What plug gap have you?

Sent from my moto g(7) power using Tapatalk
suzublu is offline   Reply With Quote
Old 5th June 2020, 13:38   #7
COLVERT
This is my second home
 
R75 Saloon.

Join Date: Feb 2009
Location: France/or Devon.
Posts: 14,003
Thanks: 3,851
Thanked 2,167 Times in 1,816 Posts
Default

Mostly cold start problems which tend to disappear when warm are down to the choke not doing its job correctly.--
COLVERT is offline   Reply With Quote
Old 5th June 2020, 15:35   #8
mbonwick
Gets stuck in
 
Connoisseur SE 1.8 Auto Saloon

Join Date: Jul 2015
Location: Kendal
Posts: 633
Thanks: 129
Thanked 176 Times in 147 Posts
Default

Plugs are at 0.8mm, it's even worse at the book 1.0mm!


And it's not the ECU either as Marinabrian has very kindly swapped that already.
mbonwick is offline   Reply With Quote
Old 7th June 2020, 13:39   #9
mbonwick
Gets stuck in
 
Connoisseur SE 1.8 Auto Saloon

Join Date: Jul 2015
Location: Kendal
Posts: 633
Thanks: 129
Thanked 176 Times in 147 Posts
Default

By way of a bit of a bump.

My next thought was a TMAP or coolant temp sensor issue, so these were both replaced with no effect.


Does anyone have any thoughts on a fuel pressure problem? It's had FFS and the clip fitted, but wondering if the pressure being slightly low, but enough to run on, would do this?
mbonwick is offline   Reply With Quote
Old 7th June 2020, 15:28   #10
T-Cut
This is my second home
 
Rover75 and Mreg Corsa.

Join Date: Nov 2006
Location: Sumweer onat mote o'dust (Sagin)
Posts: 21,751
Thanks: 341
Thanked 3,660 Times in 2,924 Posts
Default

Quote:
Originally Posted by mbonwick View Post
Does anyone have any thoughts on a fuel pressure problem? It's had FFS and the clip fitted, but wondering if the pressure being slightly low, but enough to run on, would do this?
When I had FFS, I just fitted an orange clip and the problem wasn't fixed. It was caused by the old and dodgy o-ring. They tend to leak once disturbed and I had opened up the filter to check it inside. Basically, it's an expensive error. Never open up the filter unless you plan to replace everything inside. Just a thought.
T-Cut is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT. The time now is 14:50.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright © 2006-2023, The Rover 75 & MG ZT Owners Club Ltd