Engine abruptly loses all power for a second or two
Discussion
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I'm sounding like a broken record as I often suggest checking the AFM for all poor running issues. Disconnect the AFM and drive for a while - its an easy way to tell if the AFM is duff.
I'm on my 3rd AFM in 4 years - almost like a service item !
2nd suggestion is to check all of the HT leads. I had some magnecor leads started to break apart.
I'm on my 3rd AFM in 4 years - almost like a service item !
2nd suggestion is to check all of the HT leads. I had some magnecor leads started to break apart.
As it happens I do have a set of bog-standard Lucas HT leads waiting to go on, to replace the Magnecores that are currently fitted. Will add the AFM to the list of potential culprits; I suppose if it were to suddenly say "there's no air coming through" then the ECU would respond by cutting the fuel right back, which might give these symptoms. I'll try things in increasing order of price, so I suspect the AFM might be some way down the list!
If it's a very sudden loss of power I'd def say that's electrical,,,,
Could even be one of the two connections on the coil briefly loosing contact,
I had that once,, driving along then massive engine breaking then even bigger acceleration then it stopped,, luckily I found it straight away, made a better connection. And no issues since..
Just a thought. Goodluck
Could even be one of the two connections on the coil briefly loosing contact,
I had that once,, driving along then massive engine breaking then even bigger acceleration then it stopped,, luckily I found it straight away, made a better connection. And no issues since..
Just a thought. Goodluck
Id say the AFM is not number one suspect, normally the outputs go out of range (high) so make the cars run very rich, and its unlikely be sudden on / off like you have. The TP is a major suspect because the ECU uses the output voltage to tell if the throttle is shut. The carbon track inside wears out, so you get dead spots and the ECU then greatly reduces the fuel for idle at this point- hence the instant power loss. In terms of ignition failure, the rev counter will drop suddenly if the amp or dizzy are failing (as already stated). If you are lucky the ECU may have thrown a fault code if you have access to a fault code reader / Ecumate / RoverGauge.
The ECU does a whole load of calculations on the Throttle Pot value, rate of increase, decrease, direction of travel, etc., where ultimately the TPS rate of adjustment is used to set the fuel value in conjunction with the AFM value. I think it's possible an electrical glitch on the TPS input may cause the ECU to hiccough at some random point during measurement or value processing.
Bassfiend229hp said:
If it's the throttle pot then shouldn't it be repeatable every time at the same point in throttle travel?
No not if its dependant on a condition i.e temperature change etc or in my case being bolted to the plenum at running temp if I allowed the engine to cool it would give a nice linear resitance scale/sweep with no drop-outs at running temp it was a different matter 
davep said:
The ECU does a whole load of calculations on the Throttle Pot value, rate of increase, decrease, direction of travel, etc., where ultimately the TPS rate of adjustment is used to set the fuel value in conjunction with the AFM value. I think it's possible an electrical glitch on the TPS input may cause the ECU to hiccough at some random point during measurement or value processing.
The ECU should be smart enough to throw and error code as the two conditions of throttle pot low voltage should with a high airflow reading never occur so someone's lying, but how long this condition has to occur to trip a code I dont know.blitzracing said:
The ECU should be smart enough to throw and error code as the two conditions of throttle pot low voltage should with a high airflow reading never occur so someone's lying, but how long this condition has to occur to trip a code I dont know.
The fault code reader not readily available in my case Mark 2005 things are so much easier for the Lucas/CUX fan users now an essential bit of kit IMO 
I had similar issues with my first chim
1.When the engine became hot it would cut out,ended up changing the coil and switch next to it,doesn't matter how new either is,the heat effects these two..problem went away.
2..no heat issue this time,but kept cutting out..changed dizzy cap and roter arm..problem went away
3..had a service,car lost power under acceleration..garage changed a switch related to the acceleraer pedal,which turned out to be faulty,swooped for a replacement.problem went away.
Try 1 and 2 first,as you are improving what eventually needs replacing anyway,if that turns out not to be the issue.
I will be surprised if one of the above doesn't sort your problem
1.When the engine became hot it would cut out,ended up changing the coil and switch next to it,doesn't matter how new either is,the heat effects these two..problem went away.
2..no heat issue this time,but kept cutting out..changed dizzy cap and roter arm..problem went away
3..had a service,car lost power under acceleration..garage changed a switch related to the acceleraer pedal,which turned out to be faulty,swooped for a replacement.problem went away.
Try 1 and 2 first,as you are improving what eventually needs replacing anyway,if that turns out not to be the issue.
I will be surprised if one of the above doesn't sort your problem
blitzracing said:
davep said:
The ECU does a whole load of calculations on the Throttle Pot value, rate of increase, decrease, direction of travel, etc., where ultimately the TPS rate of adjustment is used to set the fuel value in conjunction with the AFM value. I think it's possible an electrical glitch on the TPS input may cause the ECU to hiccough at some random point during measurement or value processing.
The ECU should be smart enough to throw and error code as the two conditions of throttle pot low voltage should with a high airflow reading never occur so someone's lying, but how long this condition has to occur to trip a code I dont know.davep said:
The ECU only throws an error code (17) if the TPS value is less than 75mV for longer than 160mSec (lowered on later LR tunes to 39mV). So with an 'electrical glitch to zero/open circuit' scenario that is less than 160mSec in duration, maybe the ECU sees this as a deceleration fuel shut-off and temporarily sets fuel injector pulse width to zero.
That is a very strong possibility Dave 
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