Technical Four Garages & The AA Cant Tell Me Whats Wrong With My Car, Can You ?

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Technical Four Garages & The AA Cant Tell Me Whats Wrong With My Car, Can You ?

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Please could I call on the knowledge on this forum.

I have taken my 2000 1.2L Punto to four different garages and also had the AA look at it when it first had a problem.

The car just dies when accelerating under load and you go nowhere and the engine wont rev.

I did have a faulty injector and a MAP sensor but they have both been replaced and the problem still persists. Today I took it to a garage and they told me there was an error code for the Knock Sensor, the code was cleared, they took the car for a spin and it came back, tested the sensor and it was working fine. The ECU is saying there is an open circuit somewhere and this knock sensor error keeps coming back even though there is nothing wrong with it.

The car has stumped all my local garages and I'm now stuck, any help would be most appreciated.

Thanks
 
knock sensors normally throw a code due to corrosion of the pins or the wire (they are literally a small microphone)
so suggest you check ecu connections on engine for starters (or in this case non starters:D)
 
Sort the Open circuit

then i'd suggest Resetting the ECU so it can do the phlonic Wheel learn process again

let it idle till the fan kicks in a Couple of time
then Rev upto i think 5k and let the car figure its way back down to idle speed
Repeat a total of 3 times

AND i think that will allow the car to know its new perameters - and should possibly help with the No Revving thing

Also has the car been serviced? No problems with Ignition and fuel feed?

Ziggy
 
to be honest what did all these garages do
if it dies under acceleration it would be fairly straight forward to ascertain why
what happens when a vacuum gauge is fitted on the inlet side? do you have about 18 steady on the needle
or fitted in the lambda hole? do you have it hovering at 1 on tickover ?
have they checked fuel pressure?
activated the firing of each injector?
confirmed ecu earthed
airfilter not blocked
faulty crank sensor? wire chaffing even
constant spark at tickover and at 2500 revs
maybe a smoke test could show a fault on inlet side or exhaust

personally i would find another garage that knows what they are doing because a punto is so simple its why i like them

finally in relation to this open circuit they would need to check the resistance in each wire rather than look at the connectors,remember if theyve all had a prod in here its quite possible a connector has been pushed out of place

ask someone with knowledge and probably a bit more into fault reading and equipment to have a look after the basics ive outlined otherwise you will end up throwing money at it like you already have (ie why did it have a map? was it contaminated? did they bradle the pipe out to the manifold etc etc

:)
 
Luckily I didn't have to pay for the fault finding as none of them did find the problem or the sensor. I guess ill have to find another garage, I've been to most of the ones on Good Garage Scheme and my local where I get my cars serviced, seen a couple of fiat specialists in Birmingham but the car wont make it that far so im limited who I can use
 
Luckily I didn't have to pay for the fault finding as none of them did find the problem or the sensor. I guess ill have to find another garage, I've been to most of the ones on Good Garage Scheme and my local where I get my cars serviced, seen a couple of fiat specialists in Birmingham but the car wont make it that far so im limited who I can use

the problem is they like to find a quick fix these days rather than spend a little time on proper diagnosis,i know time is money but its all knowledge if you are in the business that they could use again tomorrow
sorry i cant help more,so frustrating to see people struggle
 
timing - it fits all the unable to drive thing
No Power - Struggling to run - Wont accelerate - wont rev etc etc
Sounds like a possibly slipped timing belt?

I have a good feeling the electrical and No Rev'in part have nothing todo with each other

Also what was the actual fault code that was produced - if you can find that out -it'll be a great help as well

Ziggy
 
Incorrect valve timing can throw up knock sensor errors.

Need to check the basics- Fuel, Ignition, Air and Timing.

Had a case before where the fuel pump began to die leaving the fuel pressure at only 1 bar. ECU self-adapted as far as it could, and the engine idled fine, but was flat as a turd.

Any garage should be able to check this- Fiat even fitted a handy industry-standard schrader valve to the fuel rail. ;)
 
I took the car to an old fashioned auto electrician today and he got his fancy gadgets on it, turns out the problem is the Knock Sensor, he traced the wiring from the ECU to the plug and it wasn't plugged in and he cant find it anywhere, thus the open circuit problem. I can get another sensor from the breakers, but where is it located, I know its at the rear under the inlet manifold but any particular hole in the block as obviously I cant see mine as there isn't one there, any pictures would be helpful, its a 1.2 8V engine.
 
they bolt on ,on this car but cant remember which side but it is down the back
remember it doesnt need bolting on because as i say its just a crude microphone so you could put it in a match box with cotton wool and tie it out of the way
do buy s/h last new one i bought for a corsa was £55 which is when i found out it was the wires rather than the sensor
 
Had a look at a database and the KS is on the front side of engine close to the exhaust. Looking from front its to the left of O2 sensor - I think.
Tony.
 
remember it doesnt need bolting on because as i say its just a crude microphone so you could put it in a match box with cotton wool and tie it out of the way

Cue the OP's 1.2 8v engine detting it's nuts off and melting the pistons. :eek:

The ECU is constantly advancing the timing to the point of det and backing off to maintain optimum running. Plugging it in and not bolting it to the block means the ECU will never hear the pinking. Leave it off, and the ECU will keep the ignition timing massively safe with low power and poor economy.

Had a look at a database and the KS is on the front side of engine close to the exhaust. Looking from front its to the left of O2 sensor - I think.
Tony.

Fail. Knock sensor is on the back, directly under the inlet manifold, roughly between cyls 1 and 2. You can normally just about see it if you look under the side where the dipstick is mounted. You can get a rough idea using the 1.4/1.2 16v guide pics (its essentially the same block)- https://www.fiatforum.com/punto-guides/125575-were-everything-1-4-16v-fire-will-similar-1-2-16v.html
 
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if engine in tune and proper fuel used then knock sensor is a fail safe,you would have to gun the thing to oblivion to get constant pre detonation as the norm or labour it up the biggest hills:)
 
if engine in tune and proper fuel used then knock sensor is a fail safe,you would have to gun the thing to oblivion to get constant pre detonation as the norm or labour it up the biggest hills:)

Then you clearly have no idea how modern engine management works. :bang:

If the OP was using Race fuel, then yes, the knock sensor would not be needed as the stock ECU would never advance the timing far enough to encounter det.

But even running Vpower, the ECU will be constantly increasing the timing advance to the fuel's limit and will reach the point of det, then retard slightly, then advance again, det, retard, etc- even on a steady throttle opening on a flat road! This is why an engine is more economical on a long, steady run- the fuelling is gradually reduced as low as possible whilst maintaining decent timing numbers.

If it can't hear where the limit is, it'll assume you're on some fancy fuel and self-adjust the long-term trims as far as they'll go.
 
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