Crazy 3.5 efi misfire

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ozzytupo

New Member
Posts
9
Hey I just got a Rangey with 108000 miles. I've been having a puzzling misfire which causing lumpy idle and lack of power thorugh the rev range, sounds more like a 5 cylinder car. I changed rotor arm, distributor cap and leads. Ran tonight and it ran incredible, all the power was back and smooth, even up to normal operating temp. Parked up at shops, came back 3 mins later started her up and started running **** again. It does have high lift cams and had a recent new ecu + I got the old one too. What could it be? Should I change the spark plugs?The misfire is consistant not intermittent, checked oil and water and no sign of head gasket. I thought it may be fueling but when it starts doing the misfire you can smell the exhaust is richer with fuel. I popped the plugs out today and they looked fine. Its just annoying it was running perfect for 30 mins, park up and it runs ****e. Any ideas I would be grateful!!!
 
If it's alright sometimes then I reckon it could be an electrical problem - when it is misfiring pull the plugs one by one to see which ones if any are wet - at least this would show what cylinders aren't getting a spark
 
Hey dude, it was only today it ran good for a bit when i changed what i did, as i said didnt change the plugs. But then it started running **** again after shutting it off for a few mins. Ive had it for a week and its been doing it since I got it so just wondered if it could be spark plugs?
 
You can check the plugs one by to see if they are getting a spark before you go changing the whole lot
Have you checked the spade terminals on the coil - could be a loose wire ?
Are all the plug leads on properly since you have changed them ?







Oh, and by the way............................................................my names not ****ing "Dude" ! ;)
 
Haha not to worry you dudeness jk, yeh well plugs are coming out tomorow gonna try them, leads are all on fine, its just weird that short time of it working properlly, then running as was before(****e). I took some of the plugs out and put them back in that was the only other thing i did when i changed leads etc, could it be a fuelling fault maybe? If it was though would I still get the rich smell from exhaust whilst it misfires?
 
if it was fueling it wud probably still fire, but puff black smoke....u smellin unburnt fuel so i would go with the spark problem.
 
Just thought I'd run it to see if there was any difference before putting new sparks in and there wasn't but now today i heard popping and the power dissapears and the brakes have gone really heavy + the rich fuel exhaust smell any ideas?
 
New plugs still the missfire, brakes still heavier than before, how do i test though to see if the servo has gone?Could the missfiring cause the vacuum from engine to drop hence the heavier brakes? Also pumping the brakes makes the braking heavier when i pump them!
 
well its not the brake servo, i tested it, im at a loss now could it be the coil or alternator? I heard the alternator can cause miss firing if its had it? What is the normal voltage it should be putting out? Also how do i check the coil?
 
Hey is that the sensor on the intake manifold, there are 2 next to each other?by the thermostat and radiator hose?
 
yes its the rear one of the 2 mine was misfiring and stinking of fuel, changed that and its cured. Some days it would be ok. They are under a tenner and its worth changing it. It feeds the ecu not the temp gauge.
 
Hello Ozzy,

Could be the non-return valve in the Plenum to Brake Servo pipe has jammed or the servo is breached and wont hold a vacuum.

With this wide open then it is a serious plenum air leak and will create fuelling/mixture problems.

Otherwise there is another serious air leak into the plenum chamber which is preventing sufficent vacuum being generated to run the brake servo.

To check for air leaks read the PDF available from here:
Rover SD1 Efi Plenum Chamber
 
Hey I will check that tomorow, i took the pipe off the brake servo and there was good vacuum when i put my thump on the end of the pipe, but didnt seem to make a difference in the running of it which must meen its something else maybe?
 
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