mis fire
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Discussion

kerberus

Original Poster:

14 posts

261 months

Wednesday 27th April 2005
quotequote all
Hi all can anybody help, have a mis fireing problem with 94 chim.have changed plugs,coil.leads, heatshelds,discap,rotorarm. the engine is mising on No 4 on tick over.have checked plug is fireing when turning over.ok

Mr Jenks

1,207 posts

294 months

Wednesday 27th April 2005
quotequote all
Have you done a compression test ? If there is a spark then it has to be either low compression or fuel problem, injector not doing its thing etc

kerberus

Original Poster:

14 posts

261 months

Wednesday 27th April 2005
quotequote all
Hi have not done compression test yet.foregot to say car as been of road for about 14 months.engine seems ok above 4000rpm. will do compression test tomorrow
& check voltage at No4 injector,will put injector cleaner in fuel tank & take for a run.

GreenV8S

31,017 posts

313 months

Wednesday 27th April 2005
quotequote all
14 months off the road is long enough for the injectors to dry out and get gummed up, I suggest you get them cleaned.

kerberus

Original Poster:

14 posts

261 months

Wednesday 27th April 2005
quotequote all
Thanks for replying,what sort of price are we looking at,& are there any company's in kent that will clean injectors.Car is booked in for MOT this friday, Dont think that it will make it unless I can sort out the problem.?

GreenV8S

31,017 posts

313 months

Wednesday 27th April 2005
quotequote all
There are probably plenty of places within your area, for example Power Engineering (Uxbridge) or Austec (Gatwick) should be within reach.

kerberus

Original Poster:

14 posts

261 months

Wednesday 27th April 2005
quotequote all
Thanks, will ring austec tomorrow & get quote.

tahiti450

712 posts

266 months

Wednesday 27th April 2005
quotequote all
kerberus said:
Thanks, will ring austec tomorrow & get quote.


Could well be the injector but it's still worth doing the compression test, 14 months is also long enough for a valve to be sticking or the seat / stem of a valve to have corroded and prevent it seating properly. Comp test is quick, doesnt cost anything other than the time and will give fairly good idea of what's going on. Also, if the plug is wet after idling and you can smell fuel through the plug hole then the injector probably isn't the problem.
If you do the comp test do the whole lot and record the values can be really useful info, esp if done perodically. Dont forget to isolate the fuel pump so its not dumping petrol in whilst you're cranking and wedge the throttle at least 1/2 way open.

chimtvr

1,315 posts

263 months

Wednesday 27th April 2005
quotequote all
injectors very unlikely.
as the cylinder fires at high revs a compression problem is most likely .If the engine used to run ok and its been stood for 2 years its probably a valve not seating properly get the hot oh and replace the petrol its going to be stale by now give it a couple of mile drive and it may well sort itself out once the engine is at high enough revs to fire it should burn out any gunk thats causing seating probs
good luck

kerberus

Original Poster:

14 posts

261 months

Thursday 28th April 2005
quotequote all
Thanks guys,Will do compression test today.Will keep all your comments in mind, Thanks again,

kerberus

Original Poster:

14 posts

261 months

Friday 29th April 2005
quotequote all
Hi guys done compression test today, starting with No4
cylinder,all cylinders reading between 12.5 & 13.5 bar.so no valves and or piston ring problems.have spoken to shaun at V8developments and he was very helpfull.After checking fuel pressure in injector delivery pipe work,(very low) a new fuel pressure regulator was fitted along with a full tank of optmax & injector cleaner.Car run ok except for stalling when coming to a very quick stop.Also after setting the timeing up useing the marks on crank pully,I found that the engine ran like a bag of nails.After removing the rocker box on left hand bank & checking valve's & rotor arm postion I found that timing marks are out.I think Steve mention,s this in the bible.

>> Edited by kerberus on Sunday 1st May 12:00

chimtvr

1,315 posts

263 months

Saturday 30th April 2005
quotequote all
this is a common problem with range rovers and discoverys the inside and outside of the pulley are seperated by a fibre vibration damper i would recomend replacing it with a new one from a 1994 3.9 discovery (someone will chip in and say dont its balanced . but as its now turned its out of balance anyway) at least then yuou can set your timing right other wise with the rocker box off you should be able to get a pretty good idea of where tdc is

kerberus

Original Poster:

14 posts

261 months

Saturday 30th April 2005
quotequote all
Hi thanks for info, (re crank pully) Can the pully be removed with the engine in the car,Has it looks very short on space between pully & cross members on front of chassis.

thornogson

833 posts

291 months

Sunday 1st May 2005
quotequote all
Do the later serpentine engines have the same damper fitted and is it possible to get the same timing problem?
G.

chimtvr

1,315 posts

263 months

Tuesday 3rd May 2005
quotequote all
thornogson said:
Do the later serpentine engines have the same damper fitted and is it possible to get the same timing problem?
G.


Im really not sure steve heaths your man to answer this