sproggy57

My 1994 1.3 fiesta with the hcs cfi engine is being naughty. it only runs for a minute or so on idle before cutting out and if you gun it, it stutters and stops straight away! the plugs are sooting up and the pulse air system has stopped working(hot exhaust is blowing back through it!). i've checked the valves and they're ok, i've changed the ox sensor and the pulse air solenoid, i've tested the iat, tp sensors and the charcoal can solenoid and all appear to be working and i,ve put on a new ecu! i had a diagnostic test done by a mechanic which came up with the pulse air solenoid prob, but after i changed the solenoid the diagnostic test came up clear no faults! i could just change sensors but it's getting expensive then! the plug/pulse air prob must be connected? now the question, could the map sensor be causing both faults?

alexno1dj

sounds like valve seats or piston rings

AndyST

Check the map sensor pipe to make sure it's not kinked, especially where the plastic clip goes round it.

martysmartie

iTrader: (1)

Do not go randomly changing sensors without good reason to do so, as you have found out your just wasting money.

The car sounds to be running rich so as said I would be checking the condition of MAP sensor hose make sure it is not perised or split, other thing that can make it run rich is the CTS.

Martin.

sproggy57

thanks for your input! have checked all the breather hoses and any others that only carry air and they all appear fine. tested the coolant temp sensor with a multi tester while it was in situ and then again after i had the sensor in the fridge for a few mins and it seems to be working ok. i'm thinking now,thst rather it being a sensor prob its the pulse air system breaking down that is also causing the mixture prob? might be wrong as i'm reakky clutching at straws, as they say!

AndyST

The pipe here @ 2 is for the MAP, take it off, remove and drain the flame trap if fitted (little plastic drum) blow through the pipe, make sure it's not kinked or crushed, then make sure the steel pipe in the manifold isn't clogged.

tabetha

Take the pulse air off, gives you extra room, it's only there to admit extra air into exhaust when cold to help with burning of fuel(in the exhaust) that has not fully burnt in the engine due to a rich mixture.
I took mine off me mondy, but make sure you keep the differential pressure esensor, other wise some when this part is is removed can spas the ecu out, had to plug the lecky bit back in but otherwise perfect.
tabetha

sproggy57

so,i managed to locate a map sensor in the local breakers yard and that hasn't made any difference. not that it's foolproof but lets assume it was ok. the fiesta it came off was a cfi hcs but without the pulse air,so i'm thinking of taking the head manifold and inj unit off all in one and simply swopping them for mine,thus eliminating the pulse air prob. the thing is would the ecu complain and are the cylinder heads for the 1.1 and 1.3 the same?

AndyST

A replacement MAP won't make any difference if its feed pipe is still blocked. Both the pulse-air solenoid and the MAP rely on a good vacuum supply to operate correctly. Did you check the pipe as in the pic?
The pulse-air is there purely to bring the cat up to operating temp as quickly as possible from cold by injecting air. I notice you said the problem occurs after a minute or so, this just happens to be the cut-off point for the pulse-air system (you hear the exhaust note change).
Can you confirm said vac pipes are fed ok?

sproggy57

yes. i have had all the pipes off and they are all clear with no kinks and no breaks or cracks. the whole starting for a few moments and then stopping appears to be a bit hit and miss cause when i tried it again this afternoon it wouldn't fire up at all! going back to the start of all my proplems... the car had an intermittent miss at first and then on the way back from Oxford it would only go up to 3500 revs and not much power output and it has slowly got worse. i started from the beginning by changing plugs and leads petrol filter etc and then the pulse air system stopped working and the hot exhaust comes back up it and melts the filter housing! so even if the engine was to carry on running it would damage anything plastic. the ceiling of 3500 revs at the start might be a clue if someone had had that problem before?

AndyST

Armed with this further info it's sounding more and more like a blocked cat or exhaust, the gases may be trying to find an alternative route out; try seperating the cat from the front pipe at the flexi-joint to test.

sproggy57

i had a feeling it might be something to do with the exhaust. what i did was disconnect the exhaust manifold from the head and then tried to start her up. no joy with that and managed to start a fire as well! rather than changing the head i've seen a couple of pictures of fiestas on ebay and they seem to have sealed off the pulse air pipes at the head with bolts. that would take out the pulse air problem if as said i still leave the solie plugged in the ecu would think all is ok? i would then just have the air fuel mixture prob and i can get the iat sensor from the breakers and try that tomorrow and see if that helps!

sproggy57

tried the ehaust again as suggested and disconnected it the engine side of the cat, but it hasn't improved matters. still think it's a sensor problem that isn't showing on the diagnostic scanner(perhaps one is partially working) as far as i can tell the only ones that would influence the air/fuel mixture are the ct and iat sensors?