Engine misfire - Rolls-Royce and Bentley Forums
Reply
 
LinkBack Thread Tools Display Modes
post #1 of 17 (permalink) Old 06-17-2014, 02:44 PM Thread Starter
Member
 
Join Date: Jun 2010
Location: Scotland
Posts: 42
Engine misfire

Hi all, I'm hoping someone can solve a small problem I have on shadow 11 1980 model.If I leave it ticking over for a while then drive off the engine does not run properly and it's like the timings out and it backfires. When I leave it to cool down it runs ok can it be some sort of sensor I really don't have a clue. Help

ally
eminthere is offline  
Sponsored Links
Advertisement
 
post #2 of 17 (permalink) Old 06-17-2014, 03:25 PM
Senior Member
 
guyslp's Avatar
 
Join Date: Aug 2007
Location: Staunton, VA - USA
Posts: 2,910
I presume since your location is Scotland that you have a UK spec car that does not have catalytic converters.

If you've got backfiring going on then you definitely have loads of unburned fuel in your exhaust vapors. Your comment about the change in engine behavior makes me think that something's going on with the ignition system such that you lose a cylinder (or more) after things warm up and you're getting unburned fuel being sent downstream in the exhaust from those cylinders.

The first thing I'd check is whether spark is present at all cylinders when the change in engine behavior presents itself.

Brian

The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth.
~ Niels Bohr


guyslp is offline  
post #3 of 17 (permalink) Old 06-17-2014, 05:13 PM Thread Starter
Member
 
Join Date: Jun 2010
Location: Scotland
Posts: 42
Quote:
Originally Posted by guyslp
I presume since your location is Scotland that you have a UK spec car that does not have catalytic converters.

If you've got backfiring going on then you definitely have loads of unburned fuel in your exhaust vapors. Your comment about the change in engine behavior makes me think that something's going on with the ignition system such that you lose a cylinder (or more) after things warm up and you're getting unburned fuel being sent downstream in the exhaust from those cylinders.

The first thing I'd check is whether spark is present at all cylinders when the change in engine behavior presents itself.
thanks for your reply I was wondering if the excess heat in the engine compartment maybe affecting the distribution cap causing it to expand slightly and causing a misfire?? Any ideas on that.

ally
eminthere is offline  
 
post #4 of 17 (permalink) Old 06-17-2014, 06:21 PM
Senior Member
 
The duchess's Avatar
 
Join Date: Apr 2013
Location: Essex ,united kingdom
Posts: 86
Hi
Many years ago I ran an old Morris which suffered backfire when it got warm and on one occasion it was late and I had to pul over down a dark country lane on lifting the bonnet/hood I could see stray sparks from one of the HT leads arcing from the lead to the base of the spark plug!!! (Near the cap)
I replaced the lead the next day and it improved the problem but I could still get an occasional backfire so I replaced the spark plug and it stopped I checked the plug under a magnifying glass and it had a fine crack through the insulation,,,sometimes it's not a as complicated as you think!!! try looking under the hood in the dark it may show something,,,
Gremlins like this can be tough to answer but keep it simple at 1st isolate the easy solutions 1st before looking deeper how old are your plugs? Is your distributor cap in good order,,check sparks are getting to all cylinders one at a time,,,
Good luck

Silver shadow MKII 1977 SRH31709
old English white
Chris
The duchess is offline  
post #5 of 17 (permalink) Old 06-17-2014, 06:29 PM
Senior Member
 
motorman's Avatar
 
Join Date: Nov 2011
Location: Northern Scotland
Posts: 517
Garage
I agree sounds electrical.
if car has been idling ok then missfiring on move off does sound like more than one dead cylinder, good idea to open up the bonnet in the dark its amazing what you find is arcing on the plug leads distributor etc, have a look inside the distributor cap for tracking, if you see any nick the wifes nail varnish, give the tracking mark a quick rub with sandpaper then paint over with nail varnish, that is a temporary repair and will prove if dist cap is faulty, that gets my vote as you can run on seven cyliders even with a duff plug but straight grounding at the dist cap is taking out most of the HT to more than one cylider me thinks.

Good luck

john
motorman is offline  
post #6 of 17 (permalink) Old 06-17-2014, 07:27 PM Thread Starter
Member
 
Join Date: Jun 2010
Location: Scotland
Posts: 42
Quote:
Originally Posted by motorman
I agree sounds electrical.
if car has been idling ok then missfiring on move off does sound like more than one dead cylinder, good idea to open up the bonnet in the dark its amazing what you find is arcing on the plug leads distributor etc, have a look inside the distributor cap for tracking, if you see any nick the wifes nail varnish, give the tracking mark a quick rub with sandpaper then paint over with nail varnish, that is a temporary repair and will prove if dist cap is faulty, that gets my vote as you can run on seven cyliders even with a duff plug but straight grounding at the dist cap is taking out most of the HT to more than one cylider me thinks.

Good luck

john
thanks lads but the car does not idle ok it just seems to come on when driving and runs tough on idling as well I must admit this a queer one as it is ok if left for 20 mins to cool down it then runs fine however keep the ideas coming all helps.it like some sort of sensor kicks in I will try again tomorrow fingers crossed oh and legs. Lol

ally
eminthere is offline  
post #7 of 17 (permalink) Old 06-18-2014, 09:23 AM
Member
 
howard's Avatar
 
Join Date: Jun 2013
Location: merseyside uk
Posts: 42
Misfire

I had exactly the same problem a few years ago, it turned out to be the ignition module in the distributor braking down when hot, ran fine when cold, i replaced it and it is now perfect, howard.
howard is offline  
post #8 of 17 (permalink) Old 06-19-2014, 04:03 PM
Senior Member
 
Join Date: Oct 2010
Posts: 217
Re: Misfire

Quote:
Originally Posted by howard
I had exactly the same problem a few years ago, it turned out to be the ignition module in the distributor braking down when hot, ran fine when cold, i replaced it and it is now perfect, howard.
Completely agree a sure sign the ignition module is on its way out is backfiring . Much better to change it before it fails completely.
rollmech is offline  
post #9 of 17 (permalink) Old 06-22-2014, 12:51 AM
New Member
 
Join Date: Jun 2010
Posts: 11
Agreed. Sounds like the ignition module. When the engine begins to run rough pull plug wires one at a time at the distributor cap. On cylinders that are getting spark, the spark should jump the gap to the cap. When the module goes bad, one or more cylinders is not getting the spark and on those you would see no spark. Make sure to use insulated pliers to avoid shock.
Paul K is offline  
post #10 of 17 (permalink) Old 06-22-2014, 05:16 AM Thread Starter
Member
 
Join Date: Jun 2010
Location: Scotland
Posts: 42
Quote:
Originally Posted by Paul K
Agreed. Sounds like the ignition module. When the engine begins to run rough pull plug wires one at a time at the distributor cap. On cylinders that are getting spark, the spark should jump the gap to the cap. When the module goes bad, one or more cylinders is not getting the spark and on those you would see no spark. Make sure to use insulated pliers to avoid shock.
thanks for that I will try that.

ally
eminthere is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Rolls-Royce and Bentley Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



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
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome
 

Garage Plus vBulletin Plugins by Drive Thru Online, Inc.

SEO by vBSEO 3.6.1