Help please with cossie missfire
13-06-2010, 10:46 AM
#1
Professional Waffler
Thread Starter
Help please with cossie missfire
Right i got this car with a slight missfire, got it for the right price knowing this.
Thought id sorted it the other night as there was hardly any gap in the plug on cylinder 2 but alas not!
It will rev up fine once past about 1500 rev if you rev it properly. It only missfires when you gently open the throttle or try holding the throttle steady at any revs! If you try holding the throttle at X revs it just starts to die. SO like if you are trying to set off from a junction you cant hold the revs at say 1500 and let the clutch out and go as it just drops right down to a few hundred revs!
Any ideas? Im thinking fueling myself but open to idas on what it could be???
thanks
Thought id sorted it the other night as there was hardly any gap in the plug on cylinder 2 but alas not!
It will rev up fine once past about 1500 rev if you rev it properly. It only missfires when you gently open the throttle or try holding the throttle steady at any revs! If you try holding the throttle at X revs it just starts to die. SO like if you are trying to set off from a junction you cant hold the revs at say 1500 and let the clutch out and go as it just drops right down to a few hundred revs!
Any ideas? Im thinking fueling myself but open to idas on what it could be???
thanks
13-06-2010, 11:25 AM
#3
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Hard to diagnose over the net Lee, but these are the sort of things i'd be checking:
Sensors - The crank sensor that reads the bottom pulley, does it still have a white sheathing on the wiring - if so, its the original and now 20years old... Gap between the crank sensor and the bottom pulley teeth should be 0.8mm. The phase sensor is under the distributor cap - not uncommon with age for the insulation to come off the wiring, gap between sensor and trigger should be 0.3mm.
Ignition system - when you check the phase sensor, have a quick check of the rotor arm and distributor cap condition inside and make sure the carbon brush is still in place at the top of the cap. Check the HT leads to make sure there's no corrosion/water ingress where they go into the dizzy cap and check the leads where they go onto the plug boot in the cam cover by gently tugging on the lead, if you can feel it moving, it normally means the carbon rod inside is broken. Spark plugs, if they're Motorcraft 071Cs, check the caps are tight (hold the cap with a pair of pliers and put a 16mm ring spanner on the plug and nip it an eighth of a turn). Plug gap for a pretty much standard car should be around 0.7mm.
Fuel system - do you know when the fuel filter was last changed? If you don't - it wouldn't hurt to change it - they're just over a tenner I think! If it's one cylinder that's missing, swap the injector on that cylinder to another and see if the misfire moves. I've seen a few cars on original injectors that have weird misfires and when the injectors and changed they're perfect!
Not saying any of this will fix the problem mate but checking all of that will probably take you 20mins and might shed some light
Sensors - The crank sensor that reads the bottom pulley, does it still have a white sheathing on the wiring - if so, its the original and now 20years old... Gap between the crank sensor and the bottom pulley teeth should be 0.8mm. The phase sensor is under the distributor cap - not uncommon with age for the insulation to come off the wiring, gap between sensor and trigger should be 0.3mm.
Ignition system - when you check the phase sensor, have a quick check of the rotor arm and distributor cap condition inside and make sure the carbon brush is still in place at the top of the cap. Check the HT leads to make sure there's no corrosion/water ingress where they go into the dizzy cap and check the leads where they go onto the plug boot in the cam cover by gently tugging on the lead, if you can feel it moving, it normally means the carbon rod inside is broken. Spark plugs, if they're Motorcraft 071Cs, check the caps are tight (hold the cap with a pair of pliers and put a 16mm ring spanner on the plug and nip it an eighth of a turn). Plug gap for a pretty much standard car should be around 0.7mm.
Fuel system - do you know when the fuel filter was last changed? If you don't - it wouldn't hurt to change it - they're just over a tenner I think! If it's one cylinder that's missing, swap the injector on that cylinder to another and see if the misfire moves. I've seen a few cars on original injectors that have weird misfires and when the injectors and changed they're perfect!
Not saying any of this will fix the problem mate but checking all of that will probably take you 20mins and might shed some light
Last edited by Big Will_; 13-06-2010 at 11:26 AM.
13-06-2010, 11:37 AM
#4
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I had similar problem once, but mine wudnt rev at all it just kept running really lumpy then stalling when it was reved , in the end it turned out to be the coolant temperature sensor. so may be worth checking that?
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13-06-2010, 01:36 PM
#8
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My theory is, something has hit that spark plug.....the compression will be low and this will cause a misfire as you describe.
I look very bleakly though LOL. Hope its just a sensor
I look very bleakly though LOL. Hope its just a sensor
13-06-2010, 04:43 PM
#10
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13-06-2010, 04:44 PM
#11
Professional Waffler
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Pretty sure it closed the gap when he dropped the plug in instead of lowering it in with something!
13-06-2010, 04:49 PM
#12
Professional Waffler
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My previous experience with missfires on other cars, IE CVH's etc is that if it was compression it wouldn't rev like it does, it revs up great, it just wont steady throttle, so i was thinking it is not fuellling right and remember this being suggested when i had a misfire on my Escos. Turned out to be a dodgy wire at the map sensor on that. Took ages to find.
Someone emailed me a chart thing with all the voltage readings on when i had that problem with the escos, Does anyone have it for the Saff? It gave the voltage readings for each sensor - a reading when ignition on and a reading when running, that what helped me trace the problem on that car
13-06-2010, 08:35 PM
#13
Professional Waffler
Thread Starter
Well i did some checking tonight at the ECU and found that the water temp one was reading ok but the air temp one(brown) was not! According to the info on that site it should read 3 to 1 volts when 20deg(cold) then the volts should decrease as the temp rises and at full temp should read between 1 and 0.3 volts well mine increased as itgot warmer,it read 1.84 Volts cold and as it got watmer got up to 1.97 volts! Reckon thats my problem?
13-06-2010, 09:17 PM
#15
Professional Waffler
Thread Starter
Just ordered the kit mate but off MSD. Crank pos, Water, Air and phase. Got to be worth changing them anyways but that voltage reading is deffo wrong so hopefully will sort it.
Should say too im wrong with saying missfire, Its just like a blip when you first try to open throttle, then it revs fine with just a little splutter, then when you let of throttle it drops right down to less than 500 revs.
Should say too im wrong with saying missfire, Its just like a blip when you first try to open throttle, then it revs fine with just a little splutter, then when you let of throttle it drops right down to less than 500 revs.
14-06-2010, 07:16 PM
#18
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Thread Starter
Right, changed my mind.
I'm certain its the blue water temp sensor!
When cold, the sensor reads 2.90 volts at the ecu plug. The car runs fine until it starts to warm up, thats when the lumpiness starts. Leaving the voltometer pinned into the pins for the sensor at the ECU the vots start to drop as they should according to the info i have on a site. They drop quite fast though and i think thats the problem as when the car was about half warm it was reading around 1 volt, and running lumpy as described, but when i disconnected the sensor multiplug it ran fine!!! until it got warmer then it got lumpy again as obviously it was giving the wrong reading being unplugged!
I'll find out tomorrow anyway as my sensors from MSD should be here! Would be good if anyone had come across the same thing though just to ease my mind now
I'm certain its the blue water temp sensor!
When cold, the sensor reads 2.90 volts at the ecu plug. The car runs fine until it starts to warm up, thats when the lumpiness starts. Leaving the voltometer pinned into the pins for the sensor at the ECU the vots start to drop as they should according to the info i have on a site. They drop quite fast though and i think thats the problem as when the car was about half warm it was reading around 1 volt, and running lumpy as described, but when i disconnected the sensor multiplug it ran fine!!! until it got warmer then it got lumpy again as obviously it was giving the wrong reading being unplugged!
I'll find out tomorrow anyway as my sensors from MSD should be here! Would be good if anyone had come across the same thing though just to ease my mind now
Last edited by Lee Reynolds; 14-06-2010 at 07:18 PM.
14-06-2010, 08:20 PM
#22
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Ah the ones i been checking thought you meant those but double checked. Bridge out i gather you mean connect together while still plugged in at ecu? Or bridge them together at the sensor plug? Sorry not thick lol just dont wanna blow something up 
Last edited by Lee Reynolds; 14-06-2010 at 08:21 PM.
14-06-2010, 08:55 PM
#30
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Thread Starter
Lol Ive considered that
Hope it is just this. I reckon whats happened is it has had this bit of lumpiness, so the previous owner changed the Dizzy cap, rotor arm and plugs. He somehow got zero gap in plug number 2, which made the missfire worse! Not realising he didnt have no gap he rang me and said it had developed a missfire over the last couple of days do i still want to view. I find the non gapped plug, that makes it loads better but i'm still left with this!
Really hope its the blue sensor, Ive not driven the bugger yet!
Hope it is just this. I reckon whats happened is it has had this bit of lumpiness, so the previous owner changed the Dizzy cap, rotor arm and plugs. He somehow got zero gap in plug number 2, which made the missfire worse! Not realising he didnt have no gap he rang me and said it had developed a missfire over the last couple of days do i still want to view. I find the non gapped plug, that makes it loads better but i'm still left with this!
Really hope its the blue sensor, Ive not driven the bugger yet!
Last edited by Lee Reynolds; 14-06-2010 at 08:58 PM.
15-06-2010, 06:30 PM
#31
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Thread Starter
I fitted a new blue and brown sensor today and it still isnt right.
I say missfire on my thread, but its more like a little 'pop' now n then on tickover and when you rev it up and let off the throttle it pops a bit and then drops to about 600 revs before finding a steady idle! I dont know what its like on road as i dont wanna risk it!
What i have noticed to day though, when running if i unplug the wiring plug from the MAP sensor, it ticks over beautifully, revs up brilliant and off throttle finds a perfect tickover straight away! Obviously i havent gone out on road with that unplugged lol but could this be my problem?
I say missfire on my thread, but its more like a little 'pop' now n then on tickover and when you rev it up and let off the throttle it pops a bit and then drops to about 600 revs before finding a steady idle! I dont know what its like on road as i dont wanna risk it!
What i have noticed to day though, when running if i unplug the wiring plug from the MAP sensor, it ticks over beautifully, revs up brilliant and off throttle finds a perfect tickover straight away! Obviously i havent gone out on road with that unplugged lol but could this be my problem?
15-06-2010, 09:33 PM
#36
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Dont know 100% mate. I changed the blue and brown sensor as said but it still was popping and not liking steady revs but, ive had the loom connections apart on the bulkhead and cleaned em up, all other sensor multiplugs off and back on, MAP sensor off and refitted, re gapped plugs to .7mm again and then reset CO with the 4 forward 2 back method then road tested it and its perfect so with all that done who knows what it was
Got phase sensor and crank pos to fit next as i though id buy them as it cant do any harm the others are 20 years old afterall
Got phase sensor and crank pos to fit next as i though id buy them as it cant do any harm the others are 20 years old afterall
15-06-2010, 09:36 PM
#38
Dont know 100% mate. I changed the blue and brown sensor as said but it still was popping and not liking steady revs but, ive had the loom connections apart on the bulkhead and cleaned em up, all other sensor multiplugs off and back on, MAP sensor off and refitted, re gapped plugs to .7mm again and then reset CO with the 4 forward 2 back method then road tested it and its perfect so with all that done who knows what it was
Got phase sensor and crank pos to fit next as i though id buy them as it cant do any harm the others are 20 years old afterall
Got phase sensor and crank pos to fit next as i though id buy them as it cant do any harm the others are 20 years old afterall
Steve
