So on Thursday I finally got round to replacing my battery on my '96 Fiesta 1.25 Zetec, and ever since then the car has has some serious power lossage problems, I seem to remember I had the same thing last year after a cambelt change, something which also means disconnection of the battery. I had the old battery off for a while so I could clean all underneath it ETC, I think this could have lead to the ECU being reset?
The car tends to struggle to move in first gear when it's cold, then it will burst into life and jolt forward, it was also struggling to get up an incline on the M5, normally even my 1.25 can do over 80, but it was doing 60 and slowing down, had to change into 4th. Is this something that will just go like it did before, or is there something I can do about it.

 

The ECU is self-learning and the factors learned in the past year have gone because the battery was disconnected. Normally, after restarting the ECU should relearn the factors, but maybe the Oxygen sensor can't cope with the current mixture.
It is a sign that something is wearing out.
Get the car on a diagnostic machine to check if the sensors are still working correctly.

 

By something I take it you mean a sensor not an engine part? Last time I seem to remember I changed the spark plugs, leads and fuel filter, and eventually it got better, I shouldn't need to change the plugs after only 10k miles?

 

A car can often run better after an ECU reset

it is possible to change the battery without resetting the ECU, There are devices that plug into the cigar lighter or just keep a constant power source (for example, a second battery connected via jump leads)

if you simply drive the car harder - like redline it through the gears etc(safely, legally once its warmed up, of course!) it can help the ECU relearn - there is a procedure you are supposed to follow after a reset

 

Could I have spiked it, should I try just unplugging the ECU?

 

Should I try cleaning the throttle body and maybe changing the spark plugs?

 

hi did you get it fixed? did you have problems starting it ?

 

No problems starting it, it just doesn't want to go when cold, I'll put my foot down and nothing happens then it'll shoot forward, also on the Motorway i'll be doing 70 and it'll shudder and start to slow down, to get it moving I push the clutch down and rev it.

 

What could have happened is when the car was running last a sensor was on its way out and the ECU had been compensating, adjusting the running inline with the dodgy sensor. Now the ECU is back to factory standard it can't run with the duff sensor. Can happen. People have been know to go to a garage for a battery change and been told that it needs a new oxygen sensor! If it is driveable i'd personally be tempted to try give it a good drive and idle a few times see if it can re learn.

Good luck

 

Where is the MAF sensor on this car?

I tried cleaning the throttle butterfly today with some carb cleaner and it hasn't really done much, the gas pedal feels better and I think it idles better now. However I think that's something that needed to be done anyway, the problem is still exactly the same but if I put it in third and hit the gas it shudders at about 40 and won't won't go any faster. Also tried disconnecting the TPS and driving it, didn't work.

 

OK disconnecting the plug that goes into the bottom of the air box sorted it out, however it now idles like mad, I assume it's the MAF sensor? should I try cleaning it or will it need replacing?

 

Could be the ISCV? Got a picture of it? If you start unplugging sensors it will go into limp mode which uses factory default settings just to get the ar home. You should find the engine management light also comes on on the dash.

 

Sounds like it, BUT you need to be very gentle, as they are delicate, the best stuff to clean them with is "Isopropyl" but seen as you most likely won't have this to hand you can use petrol etc.

Then it would not idle at all, re the ISCV

Martin

 

I do have a big bottle of IPA to hand but not in a spray, and I doubt I could spray petrol either, I do have Vavoline Carburettor and throttle body cleaner.

 

I bought electrical contact cleaner, but it was so grouted I couldn't get it completely clean with just that, is it OK to use vavoline Carb cleaner on it?

 

Yes, it's just the actual "man handling" you need to be wary of.

Martin