On my 2wd cosworth im getting a problem with missfires and erractic rev counter. My rev counter doesnt work at all for about the first five mins and the car runs fine. Then once the rev counter starts working its jumping all over the place and then the missfires start when driving around normally. Then suddenly the rev counter works fine and there are no missfires for a few mins and then goes erratic again and missfires start etc etc.

Does this sound like the phase sensor or phase sensor wiring being intermitant?
It has got a coilpack conversion aswell, could it be the coilpack going down?

 

I've had the exact same symptoms as you are having when my ignition amplifier started failing, the only difference being that I was still running a standard coil.

Might be worth looking into still though!!

 

It could be the rev counter causing the problem, ie causing both the dodgy readings and the misfire, as it is connected to the coil.
Maybe disconnect the tacho and do some driving, if the misfires gone the tacho is the faulty item, I have had this on cars inc sierra before with the tacho going down.
tabetha

 

ok cheers, Ill try both as I have a spare ig amp in the shed and disconnect the tacho.

 

As above, had a similar issue, traced it to the wiring in the engine bay on the bulkhead where the loom connects (there are 3 multiplugs i think). Anyway my SECS monitor showed that the ECU was reading double the actual RPM, and hence the ECU "thought" it was hitting the limiter all the time when it was only hitting about 3500 rpm. Give the wires a wiggle and see if it cures the rpm counter fault, maybe a biut crude but atleast it'll give you an indea where to start, and it's a really common problem.

 

Crank Position Sensor Mike

 

An obvious one we've missed, good suggestion!

 

I had similar problems with my car, engine loom was shagged


Luciano

 

my rev counter recently started reading half of what it should and was backfiring on boost as if it was hitting the limiter, i wiggled my standard coil wires and both faults were cured

 

Well i've done a wiggle test on all the wires a re-positioned them slightly but no differnt. Ill start looking at sensors next week as its going back in the garage now.
Thanks for all your suggestions, I was thinking also it could be any of the above. Ill let you know how I get on!

 

Mine still done this before I took it to bit's to restore it,

I tried 2 different sets of clocks in it,

GrpA coil then a New Genuine Ford one,

New HT leads and coil lead,

New Ignition amplifier,

Checked all 3 of the mutliplugs,

New Phase sensor

New dizzy cap and arm,

and it's still the same.

I had a missfire around 4500-5000rpm and the needle would bounce right off the clock.

On idle it used to jump a little, no more than 500rpm either side....



I'm putting all new everything on the car whilst I'm rebuilding it and I'm gonna replace the wiring from the coil to the rev counter and the crank sensor, the only things I hav'nt done yet....

 

I hope its not that bad

 

That's be a shagged engine loom or the CPS then

 

I had this problem when I bought my cossie and replaced the phase sensor but eventually traced it to the multiplugs at the back of the engine bay. The connectors get filled with dirt. I totally removed the connectors and soldered the loom together and it's completely cured it. Only took about half an hour. That was about 4 years ago and never had a problem with it since. Hope you get it sorted.

 

It's not the wiring plugs on his car - 2wds don't have them!

Inspect the crank sensor wiring on the loom side. Could be a bent/corroded pin in the connector.

 

I had the same fault years ago, turned out the engine loom was knackered.

 

If the rev counter plays up when the miseries starts this normally indicates crack sensor or phase iirc

 

I put a new CPS on this morning and it didnt make a difference. Will prob try a phase sensor next and check all the wiring loom and the earths. Will give it another go on my next days off.

 

dodgy phase sensor or wiring going to it,

 

I'm having a similar problem.

Rev counter goes mad, but only under boost. If I accelerate through the revs with only a little throttle it's fine. Didn't notice any misfire yet but I'm only running std power.

My mate had the same problem and it was the coil. Any other ideas? 4x4 Saff (YBJ) btw.

 

I had same problem with my 2WD Sapph. Tried 4 different rev counters,all doing the same thing. Took it to a local auto elictrician(cornwall).It turned out to be a faulty suppressor near the coil.He cut it out,reconnected the wires and solved the problem.The suppressor is black. Best of luck D.B.

 

Time for an update. Put a scope on the ecu and check all the sensors were working correctly which they were and all continuity is good. Now the rev counter has stopped working all together and it hasnt miss fired once. I have taken the rev counter out and tested it using a signal generator and it worked fine. Also tried different ign amps aswell and no change.
Because its got the MSD wasted spark fitted, the green wire that would trigger the rev counter from the coil is no longer connected and hasnt been for some time. Where does the rev counter now get its signal/pulse from? I just cant get my head around it, its probably so simple Im overlooking it.

Dangerous Brian - Im not sure if the suppressor is still part of my circuit as the wasted spark is fitted.

 

Up for the morning!

Where does the rev counter pick up its signal from with wasted spark fitted? I just cant think!!

 

P21 on ECU I believe?

 

My wasted spark wires go to pin 21 and pin 26, not sure if that helps.

Steve

 

send me your email address.I will send you my phone number.and talk to you if ok, Better than printing on a bloody screen? D B

 

Yeah the msd wasted spark loom connects to 21 and 26 and from what I have worked out, these are the trigger to the ignition amps 1 and 2 driven from the wasted spark driver. I have checked then for continuity and they are ok and I also connected pin 21 directly to the back of the rev counter expecting it to half read but it was dead.

Ill send you an email Brian.

 

Right, I know what Im going to do now, Im just going to make my own loom for the rev counter as I mocked one up last night and it worked first time. Nice simple easy fix and just disconnect all the old wires that are not needed. Thanks for all your suggestions and dangerous brian, I probably wont be giving you a call at the weekend! cheers.

 

as above !! ive just ordered a engine loom from carlooms uk mines doing all sorts of things the wiring is corroded nearly all the way to ecu!!!!

 

Wish i had of read this earleir i am having the exact same problems apart from i am not running coil packs.

So far i have changed.

Cap and rotor arm.
Tryed different spark plugs.
Thanks to loader a different coil.
Brand new phase sensor.

Also my rev counter only works some times but i have a missfire even when its not working. But when it does work it jumps all over the place.

Oh and Adam send me ya number bud could do with a ctach up at some point.

 

[quote=sierrsteve1980;5372619]Wish i had of read this earleir i am having the exact same problems apart from i am not running coil packs.

So far i have changed.

Cap and rotor arm.
Tryed different spark plugs.
Thanks to loader a different coil.
Brand new phase sensor.

Also my rev counter only works some times but i have a missfire even when its not working. But when it does work it jumps all over the place.

Oh and Adam send me ya number bud could do with a ctach up at some point.[/quote
sent you a pm !!!

 

Did you get it sorted Mike?

 

Yes and no. I made up my own loom taken from each side of the coilpack using a couple of diodes and wired it directly to the rev counter. Started the engine and it worked spot on, then after about 30secs it started fluctuating and then stopped. Took the clocks out and plugged it into my other sierra and the rev counter works fine. I compared all the connections from car to car and the only difference is that at idle the voltage on the rev counter trigger is 10V in my sierra running standard coil, but at idle in the cosworth its 16V. Not too sure if this is making something on the gauge cut out after a few seconds due to to much voltage? Because the rev counter works when I start the engine everytime then stops. Its a nightmare!!

 

Will be interesting this one once you've got it sussed mate!

 

Tell me about it. Ill try again next week.

 

Had this on my 4wd.. Changed the fuel filter and all of a sudden all was good again

 

Did this ever get fixed, be interesting