Another Misfire cured
Discussion
I have just diagnosed a misfire on my chimaera after about five weeks of head scratching and thought I would post it up here as I have found this forum very useful in trying to diagnoses it.
The syptoms were a slight loss of power, misfireing between 4000 and 5000 and sort of clearing after that also it hadn't been idleing quite as well as normal.
The first starting point was the ignition although the cap, arm, leads, shrouds and plugs were all new two months ago. I'm in the fortunate position of having a landrover with the same engine to swop parts between the two. After trying a couple of things I swoped everything off the land rover from the distributer to the plugs and still no improvement. So then I tested all the injection components with a mutimeter and still nothing showed up. The next step was too conect up a fuel pressure gauge and I changed the filter as a matter of course (the old one being very old) and whilst the misfire was happening on a road run I still had 42psi of fuel pressure so that eliminated the pump, filter and fuel lines. Feeling a bit depressed I booked it in our local land rover specialist to have to codes read only to find the computer wouldn't register with the igintion on as someone had cut the third wire to the plug off and I ended up with just about every code in the book with the ignition switched off. Then on the way home the fuel pump stopped and I had to push the car the last half mile home! Although that was soon rectified as I had disturbed the spade conector on the pump changing the filter.
Having left it for a week I decided to have another go this weekend in my mind it had to be a weak fuel mixture and all the plugs were the same brown colour with no variation and no glazing which made me think it was the ecu weakening the mixture at higher revs I had already tested the injectors with a mutimeter and they were fine.
Then with the bonnet up in the workshop I reved the engine up to 4000 and the miss was more like a popping back fire sound so I went along the injectors pulling off one connector at a time and reving it up until you could hear it popping and then to my Joy I pulled off no.7 and the popping cylinder changed to a missing cylinder and the culprit was found! It had obviously been delivering a weak mixture after 4000 due to blockage or somthing a quick spin up the road with the plug off confirmed the problem and I now have them all out for repair and a service.
Looking back at it now its probaly quite a simple cause but apparently quite rare as well, so if your trying to diagnose a misfire and it has a popping sound to it, try pulling the injector plugs off one at a time it doesn't take long and doesn't cost anything so its worth a try.
The syptoms were a slight loss of power, misfireing between 4000 and 5000 and sort of clearing after that also it hadn't been idleing quite as well as normal.
The first starting point was the ignition although the cap, arm, leads, shrouds and plugs were all new two months ago. I'm in the fortunate position of having a landrover with the same engine to swop parts between the two. After trying a couple of things I swoped everything off the land rover from the distributer to the plugs and still no improvement. So then I tested all the injection components with a mutimeter and still nothing showed up. The next step was too conect up a fuel pressure gauge and I changed the filter as a matter of course (the old one being very old) and whilst the misfire was happening on a road run I still had 42psi of fuel pressure so that eliminated the pump, filter and fuel lines. Feeling a bit depressed I booked it in our local land rover specialist to have to codes read only to find the computer wouldn't register with the igintion on as someone had cut the third wire to the plug off and I ended up with just about every code in the book with the ignition switched off. Then on the way home the fuel pump stopped and I had to push the car the last half mile home! Although that was soon rectified as I had disturbed the spade conector on the pump changing the filter.
Having left it for a week I decided to have another go this weekend in my mind it had to be a weak fuel mixture and all the plugs were the same brown colour with no variation and no glazing which made me think it was the ecu weakening the mixture at higher revs I had already tested the injectors with a mutimeter and they were fine.
Then with the bonnet up in the workshop I reved the engine up to 4000 and the miss was more like a popping back fire sound so I went along the injectors pulling off one connector at a time and reving it up until you could hear it popping and then to my Joy I pulled off no.7 and the popping cylinder changed to a missing cylinder and the culprit was found! It had obviously been delivering a weak mixture after 4000 due to blockage or somthing a quick spin up the road with the plug off confirmed the problem and I now have them all out for repair and a service.
Looking back at it now its probaly quite a simple cause but apparently quite rare as well, so if your trying to diagnose a misfire and it has a popping sound to it, try pulling the injector plugs off one at a time it doesn't take long and doesn't cost anything so its worth a try.
I feel I need to come clean and admit I jumped to conclusions too early on this one! I fitted the new injector and the problem was still the same! its just after several weeks of testing everything I was really pleased to of found somthing, but all I had diagnosed was the misfiring cyclinder. I have since taken the engine apart and one of the cam lobes for no.7 was nearly round and there was about a 6mm difference between the rest of them so I finaly think I have got there at last. I have spoken to Rob at V8 Developments and he agreed that was probaly the cause so I have decided to make the most of the situation and I have bought an MC1 cam and some bigger valves to fit in at the same time. Whilst the car is in bits I have bought some other upgrades including silcone pipes and a rare as hens teeth power steering kit, I have also sent the alarm off to have some new remotes programed to it, as I only had one, which was a bit of a worry as I tend to lose keys! so hopfully in a couple of weeks I should be enjoying my car again! (athough I'm enjoying it just as much playing with it in the workshop!)
vrover8 said:
I feel I need to come clean and admit I jumped to conclusions too early on this one! I fitted the new injector and the problem was still the same! its just after several weeks of testing everything I was really pleased to of found somthing, but all I had diagnosed was the misfiring cyclinder. I have since taken the engine apart and one of the cam lobes for no.7 was nearly round and there was about a 6mm difference between the rest of them so I finaly think I have got there at last. I have spoken to Rob at V8 Developments and he agreed that was probaly the cause so I have decided to make the most of the situation and I have bought an MC1 cam and some bigger valves to fit in at the same time. Whilst the car is in bits I have bought some other upgrades including silcone pipes and a rare as hens teeth power steering kit, I have also sent the alarm off to have some new remotes programed to it, as I only had one, which was a bit of a worry as I tend to lose keys! so hopfully in a couple of weeks I should be enjoying my car again! (athough I'm enjoying it just as much playing with it in the workshop!)
With that much cam wear you are in for a pleasent suprise 
i have slight pitting on 3 lobes that i checked when i renewed my sump gasket(earlier stages to what you have)over the winter i am fitting well its a toss up for a MC2 or Kent 234 i will report how i get on,i have the smooth bore kit already fitted but am doing trumpet mods,insulator,port matching etc etc 
Edited by That Daddy on Sunday 3rd August 10:26
Del 203 said:
That Daddy said:
over the winter i am fitting well its a toss up for a MC2 or Kent 234 i will report how i get on,i have the smooth bore kit already fitted but am doing trumpet mods,insulator,port matching etc etc
MC2 With trumpet mods,port matching etc.... 
still to fully decide between the two cams, but i dont do much suburb driving so stuff like low speed running quality is not such an issue anymore,i also like explosive power delivery 
to many years of tuned 4 cylinder motors 
Edited by That Daddy on Sunday 3rd August 12:21
That Daddy said:
Del 203 said:
That Daddy said:
over the winter i am fitting well its a toss up for a MC2 or Kent 234 i will report how i get on,i have the smooth bore kit already fitted but am doing trumpet mods,insulator,port matching etc etc
MC2 With trumpet mods,port matching etc.... still to fully decide between the two cams, but i dont do much suburb driving so stuff like low speed running quality is not such an issue anymore,i also like explosive power delivery to many years of tuned 4 cylinder motors Still say MC2
That Daddy said:
i have slight pitting on 3 lobes that i checked when i renewed my sump gasket(earlier stages to what you have)over the winter i am fitting well its a toss up for a MC2 or Kent 234 i will report how i get on,i have the smooth bore kit already fitted but am doing trumpet mods,insulator,port matching etc etc Edited by That Daddy on Sunday 3rd August 10:26
so that should help as well, it made a huge difference on my landrover!
vrover8 said:
That Daddy said:
i have slight pitting on 3 lobes that i checked when i renewed my sump gasket(earlier stages to what you have)over the winter i am fitting well its a toss up for a MC2 or Kent 234 i will report how i get on,i have the smooth bore kit already fitted but am doing trumpet mods,insulator,port matching etc etc Edited by That Daddy on Sunday 3rd August 10:26
so that should help as well, it made a huge difference on my landrover!
i was thinking more along the lines of a mild clean up(port and throat wise)and possibly larger inlets(not certain bout the later) 
Edited by That Daddy on Sunday 3rd August 18:14
I know what you mean its far more fun making the extra power than using it when you've got it! I'll try and put some pictures up when it is done (if I can work out how!) I'm not sure how much differnce the individual bits make, but my gut feeling is the valves play a big part in it. I would definatly do them, they are not a lot of money you have just got to get your local machine shop to cut them in for you (3 angle seat job). The only part I'm not doing is changing the guides for shorter bulleted ones we shortned the orginal ones last time and it burnt a bit more oil after that so I'm leaving them standard this time although I'm sure the proper hiflo guides would be o.k.
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