missfire and bad running

[stevek7741]

help needed pls.p38 4.0 1997.head gaskets done 5 months (8000 miles) ago.new cam shaft sensor new plugs new leads and new crankshaft sensor fitted at same time.for the last month has been using an egg cupfull of coolant every couple of days,so never investigated as i could live with that.
problem is she has now started to run really badly as though missfiring or missing and fuel consumption has gone through the roof.have looked around all hoses and see no obvious leaks,but there seems to be corrosion around the water pump.can anyone point me in the right direction?

 

[fanatic]

are the plugs rusty,what were the liners like

plug leads possibly

and waterpump shagged

 

[stevek7741]

hi fanatic,new plugs and new leads fitted when i did head gasket,has been running 100% until now,suspicion is water pump but looling to see if it could be anything else.forgot to mention heads were skimmed when gaskets done.

 

[stevek7741]

sorry,forgot to mention,running on new champion plugs and magnecor blue leads..100% until now

 

[fanatic]

Coolant pressure test, heater matrix o rings, water pump and thermostat prime leak causes.

Before worrying- the MAF will give poor running, when warm-does it run better unplugged?

Also a compression test and a gas analyser probe over top of open header tank will tell if hg gone-but looking at plugs and simple things first

 

[stevek7741]

have not thought about maf ,but do have a very slight pressure at header tank when checking coolant....

 

[fanatic]

if it's got pressure when cold more of an issue, system is designed to run pressurised.
If the top hose is rock hard when hot more of an issue.

Main thing not to panic, check the simple things first

 

[rewmer]

Allway start with the simple things first as mentioned. Any dampness around the drivers footwell ?

 

[stevek7741]

hi rewmer,yes i do have a very very small amount of coolant on the drivers side of the centre tunnell and header tank has slight pressure when cold (usally check coolant each morning)coolant in footwell is not there on a daily basis but every now and then

 

[overlandrover]

Sounds like the coolant in the driver footwell is the 'O' rings leaking at the heater matrix, which would account for the small amount of water loss, i had this with mine, the 'o' ring cost a couple of £ from the main stealers. quite an easy job, not what it states in Rave or main dealer will quote to take dashboard out, it can be done insitu.

I would get rid of the champion plugs, they are forever giving up after a short while, NGK every time.

if you have a look at Rangerover.net, there are very good instrutions on there to change the 'O' rings

 

[rewmer]

Sounds like the coolant in the driver footwell is the 'O' rings leaking at the heater matrix, which would account for the small amount of water loss, i had this with mine, the 'o' ring cost a couple of £ from the main stealers. quite an easy job, not what it states in Rave or main dealer will quote to take dashboard out, it can be done insitu.

I would get rid of the champion plugs, they are forever giving up after a short while, NGK every time.

if you have a look at Rangerover.net, there are very good instrutions on there to change the 'O' rings

Agree with all the above inc plugs - BRP6ES every time. The O rings are nothing special, I had a couple in a kit I bought to do another job. My tip is, buy a plasterboard pad saw for cutting duct, lubricate the new rings with a bit of vaseline, dont over tighten the clamp plate. Refer to these tips after you have read the post on doing this job. I took about 2 1/2 hours start to finish (not counting time to get pipe welded ).

Once you have sorted the water loss, you can move onto the next job.

 

[stevek7741]

Sounds like the coolant in the driver footwell is the 'O' rings leaking at the heater matrix, which would account for the small amount of water loss, i had this with mine, the 'o' ring cost a couple of £ from the main stealers. quite an easy job, not what it states in Rave or main dealer will quote to take dashboard out, it can be done insitu.

I would get rid of the champion plugs, they are forever giving up after a short while, NGK every time.

if you have a look at Rangerover.net, there are very good instrutions on there to change the 'O' rings

many thanks for replies.i know the o rings need to be done,but this is nothing to do with bad running.does anyone think the problem could lie with the waterpump causing coolant loss and very slight pressure build up in header tank.top hose is mildly hard when warm,but can be compressed...

 

[Irishrover]

Spark Plugs..personal choice. I have always used Champions and never had a problem. Some people say Bosch others NGK. Originals are reccomended as Champion RN11YCC. Original fuel is stated as petrol or diesel yet people convert to LPG. Reinvent the wheel if you must but bear in mind the original specification worked...usually.

 

[stevek7741]

hello irishrover,have fitted and run with champion as advised by main stealer,have had her running 100% for a few months but now have problem with miss firing and running very badly.have no lpg just pure petrol as solihull intended.am thinking rough running could be down to waterpump but not certain,so am looking for all avenues before i go steaming in...

 

[Irishrover]

:welcome2:

Smooth firing requires two things..good spark at the right time and correct fuel mix.
I suggest that looking at the water pump performance is totally irrelevant.

Take the spark plugs out and see if there is any difference in the appearance at the electrode end...if it looks clean as new, it's probably not even sparking. Another method is to remove the spark plug leads, one by one with the engine running using WELL INSULATED PLIERS to see if the engine runs rougher....if it makes no difference after the lead is removed, chances are that that lead/plug is faulty. Are you sure the leads are on the right plugs??
No change?..do a compression check on all cylinders, there should be no more than 10% difference in readings across all cylinders.
Check the injector and other plugs are located correctly and securely. Are the connections to the coil packs good?

Good luck.

 

[rewmer]

My thoughts are that if you have known leak, its best to sort that before you diagnose any of the other problems.I would expect pressure in the top hose when warm, but hoses should still be able to compress with a firm grip. If your still losing water after fixing the O rings then you know to look closer at other systems. Its not unknown for water to cause a missfire if its getting into a cylinder. A dodgy water pump will not cause it to run rough, but again, if it is suspect change it out and cross it off the list, you`ll have to do it anyway down the road if its dicky and you dont want to risk a boil up.

Have you had the ECU read for fault codes ? If not you may want to start there along with a "sniff" test. Any backstreet garage should be able to do that.

 

[stevek7741]

:tea::frusty:thanks to all for advice,will change pump today and check plugs and leads.did sniff test first as thoughts of head gasket were going round in my head but do not want to go down that road again.once again many thanks to all...