boost problem on a 4x4 sapphire cosworth
22-12-2007, 04:53 PM
#1
boost problem on a 4x4 sapphire cosworth
--------------------------------------------------------------------------------
hi,my friend had a small misfire on his cosworth,he was told it was the idle control valve(which was disconnected when he bought the car)that was causing the problem,so he changed the distributor cap,rotor arm,washed out the icv with brake cleaner.he also fitted a full samco hose set at the same time.now the problem is ten times worse,as soon as the boost gauge reaches 0.5 psi the engine cuts out and coughs violently,off boost it drives perfect,when it ticks over it does skip a beat occasionally.it doesnt crack a flame out of the exhaust when it cuts out like when a car overboosts.any help would be much appreciated,ta
hi,my friend had a small misfire on his cosworth,he was told it was the idle control valve(which was disconnected when he bought the car)that was causing the problem,so he changed the distributor cap,rotor arm,washed out the icv with brake cleaner.he also fitted a full samco hose set at the same time.now the problem is ten times worse,as soon as the boost gauge reaches 0.5 psi the engine cuts out and coughs violently,off boost it drives perfect,when it ticks over it does skip a beat occasionally.it doesnt crack a flame out of the exhaust when it cuts out like when a car overboosts.any help would be much appreciated,ta
22-12-2007, 05:05 PM
#2
IDLE SPEED CONTROL VALVES DON'T CAUSE MISFIRES PERIOD, all they do is allow air to bypass the closed throttle so that the engine has air to run on, as otherwise it can't get any!!
It has a fuelling issue, in that it sounds very much like it is running exceptionally rich.
In the first instance check the CTS sensor output and connector, do you know the actual CO, from mot station ?
Does it belch black smoke, what are the plugs like, what plugs does it have, have you checked the phase alignment ?
If the phase aligment is out by just one tooth it will over fuel, will start perfect and tick over perfect, with the occasional lump, drive fine off boost but as soon as boost fuelling is added it is too much, and will often soot the plugs so bad as to cause it to stop completely.
There are so many other causes, check for massive air leaks, all the basic settings, ie cam timing.
tabetha
It has a fuelling issue, in that it sounds very much like it is running exceptionally rich.
In the first instance check the CTS sensor output and connector, do you know the actual CO, from mot station ?
Does it belch black smoke, what are the plugs like, what plugs does it have, have you checked the phase alignment ?
If the phase aligment is out by just one tooth it will over fuel, will start perfect and tick over perfect, with the occasional lump, drive fine off boost but as soon as boost fuelling is added it is too much, and will often soot the plugs so bad as to cause it to stop completely.
There are so many other causes, check for massive air leaks, all the basic settings, ie cam timing.
tabetha
22-12-2007, 06:03 PM
#3
it ran ok before on boost but with a slight misfire on tickover and under hard acceloration,but now it wont take any boost whatsoever before it jerks and cuts out,it happens so sudden its like the spark has been taken away,does the phase sensor have anything to do with it?is there anyway to get a good seal between the connections and the samcos(vaseline etc)without them slipping off.the cam timings ok,the plugs have not been changed since before he carried out any work,it possibly has an air leak as he fitted the samcos himself and he isnt too clued up on cossies,im no expert by any means but i have a basic idea how they work,cheers,lee
22-12-2007, 06:15 PM
#6
what do you check?the air gap with feeler gauges.thats what i suspect it is as i know the are trouble,when i get money to build a big bhp engine im going for a coilpack conversion to save any fannying about with old ignition systems.
22-12-2007, 06:35 PM
#7
phase sensor is in the dizzy take the cap off pull
rotor arm off and lift off the dust cap you will see the phase sensor money is on the wires are corroded,make sure the wire insulation is all ok etc
i seem to remember phase sensor gap should be 0.2-0.3mm
rotor arm off and lift off the dust cap you will see the phase sensor money is on the wires are corroded,make sure the wire insulation is all ok etc
i seem to remember phase sensor gap should be 0.2-0.3mm
Trending Topics
22-12-2007, 07:36 PM
#8
i had a problem similar and mine turned out to be the wiring blocks that mount up near the bulkhead.they sit above the engine and get heated up and they break down.it was once once i turned the boost up aswell.as it was trying to draw more power down the wires to run things.
very common on 4x4's.you could check that
very common on 4x4's.you could check that
22-12-2007, 09:23 PM
#10
As above could be a problem with the engine loom plugs, I cut mine out and soldered them up but enventually I had to replace the engine loom due to mis-fire,
Look at the rev counter when problem occurs, if it goes skyward under boost and the car does not pull as it should its new loom time
Luciano
Look at the rev counter when problem occurs, if it goes skyward under boost and the car does not pull as it should its new loom time
Luciano
23-12-2007, 12:01 PM
#11
cheers,ill check the wiring,somehow the car had deleloped a fuel leak and it was spraying onto the plugs that run along the bulkhead,i noticed it when he was cranking it over.ill check them first before i check the phase sensor as its a pain to get into,also will a 2wd distributor fit a 4x4?might give him a shot of mine to get him going!
23-12-2007, 05:17 PM
#13
Originally Posted by 155lee
just phoned him,he says its not as bad when it is cold,but when it gets a bit of heat in it it struggles to pull away from junctions?is that a clue?
Mine had similar symptoms, fine when cooler but as soon as it got warm after driving for a while mis-fire time, check the loom out
Luciano
23-12-2007, 09:35 PM
#14
checked multi plugs and they look to be in good condition,the car doesnt look like every man and his dogs been at it with a halfords soldering kit and scotchlocks,ok,tonight i gapped the phase sensor which was touching the cams,that made it better,it can now take 0.9 psi of boost(thats what it peaks at in 4th gear floored from 30 mph)but it still loses power and clunks and bangs.i changed the coil,map sensor and 3 of the leads.all of which made no differance.all boost hoses are nice and tight so i dont think thees a massive air leak.all timing marks are bang on.what is the problem caused by the rev counter?can that make it misfire?
Thread
Thread Starter
Forum
Replies
Last Post
