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 Post subject: Miss fire
PostPosted: Sun Oct 08, 2017 10:33 am 
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Joined: Tue Feb 25, 2014 10:50 am
Posts: 10
ECU Model: S40 Pro
Hi All,

I'm a bit of a novice when it comes to ECU's.

I'm running a pinto engine with Jenvey throttle bodies and a dta S40.

At low rev's (1500 to 2500 rpm) when I apply load to it, a slight miss fire comes into it. If I go up another gear it will clear. If I try and take off going up a hill in 1st gear it will start missing, back firing out the trumpets and won't take rev's. It seems to happen in 1st, 2nd and 3rd gear. Once I've gone past these gears the car will rev clear all the way up to the gear change light.

We've changed the plugs, TPS, coil, crank shaft sensor. Switched fuel pumps. The fuel is fresh in it. But none of these have made any difference.

Any advise on what I can check?

Thanks in advance.


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 Post subject: Re: Miss fire
PostPosted: Sun Oct 08, 2017 12:06 pm 
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Joined: Thu Jul 28, 2011 4:10 am
Posts: 867
ECU Model: S100 Pro
Has it ever been ok?


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 Post subject: Re: Miss fire
PostPosted: Sun Oct 08, 2017 3:13 pm 
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Joined: Tue Feb 25, 2014 10:50 am
Posts: 10
ECU Model: S40 Pro
Sorry, yes it done about 9 or 10 rallys perfect.


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 Post subject: Re: Miss fire
PostPosted: Sun Oct 08, 2017 3:14 pm 
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Joined: Tue Aug 02, 2011 12:08 pm
Posts: 2907
Location: Norn Iron
ECU Model: No ECU
As above...we need history and information.

And basic things to check would be mixtures, is it or has it ever been tuned correctly ? Is timing correct ?

Randomly changing parts isnt likely to get you anywhere.

Was anything changed at all before this "issue" appeared, or under what circumstances did it appear ?


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 Post subject: Re: Miss fire
PostPosted: Sun Oct 08, 2017 5:33 pm 
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Joined: Tue Feb 25, 2014 10:50 am
Posts: 10
ECU Model: S40 Pro
After the build the car was mapped by a professional. Car has competed in 9 or 10 events with no issues and then this miss fire appeared on the last event. All the mixtures are correct and timing is correct. Nothing changed before this event. Only thing different is, this was the wettest event the car has done. The ecu is placed under the windscreen and a very small amount of water got into the car. (Small amount being a shot glass)

Even checked the balance of the jenveys after the miss fire appeared and there all correct.


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 Post subject: Re: Miss fire
PostPosted: Mon Oct 09, 2017 3:37 am 
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Joined: Tue Aug 02, 2011 12:08 pm
Posts: 2907
Location: Norn Iron
ECU Model: No ECU
So rather than throwing parts at it and hoping for the best...

Check to see how many, if any crank errors have been logged. That will give you an indication of whether that side of things is ok.

If the misfire is repeatable, check all sensor feedback during the misfire events to see if everything is normal.

And mixtures during a misfire cannot be "correct"....because they will cause incorrect AFR readings on a wideband. But how are they prior to this occurring ? and when occurring are injector pulse widths normal with no odd changes ?


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 Post subject: Re: Miss fire
PostPosted: Mon Oct 09, 2017 7:47 am 
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Joined: Tue Jul 03, 2012 2:33 am
Posts: 190
ECU Model: S100 Pro
You said the car got very wet, then assuming no errors come up on the diagnostics page and sensors look normal I'd the check coil wiring, coils, ht leads, plug boots, plugs.... Anything and everything to do with ignition.


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 Post subject: Re: Miss fire
PostPosted: Wed Oct 25, 2017 4:19 am 
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Joined: Tue Feb 25, 2014 10:50 am
Posts: 10
ECU Model: S40 Pro
No errors came up on the diagnostics page and all sensors looked normal.

Turned the flat shift off and the miss fire has disappeared! :)
Waiting on a new gearbox potentiometer to arrive to try that.


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 Post subject: Re: Miss fire
PostPosted: Wed Oct 25, 2017 7:16 am 
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Joined: Fri Feb 28, 2014 1:03 pm
Posts: 1127
ECU Model: S40 Pro
Distributor: DTA
Firmware Version: 79
Make sure you reset your gear voltages.


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