Its doing it again :( - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

03-07-2002, 09:03

Hey dudes... I got a problem but now it seems much worse.
Before when i had my CFI - I had a problem with it stalling at
a certain engine temp. Now ive got my MPFI, its going cRaZy!
The car will start ok, but after driving a few klms the tacho begins to go crazy and the car starts jerking. Im talking revving up and down between 500-2500 rpm, basically going spastic@! After about a min or two - it will stop and begin driving normally again! - This one has really stumped me.
Anyone have any ideas?

Brent

galapogos01 · 03-07-2002, 09:26

possibly your EGO sensor?

the EGO doesnt get used until the exhaust is hot enough to get a valid reading. thing is, the ECU is supposed to ignore it if the readings are too far out.

other thing could be a MAP sensor? but i think you got a new one for the convert? is your battery voltage consistant?

good luck!

03-07-2002, 13:47

Hmmm...yeah, i was thinking the MAP sensor - maybe this is
also what is causing the hesitation at low RPM? I tried running the selft test thingo but i didnt get any pulses??? Something isnt right with my conversion i think...hmmm

Brent

03-07-2002, 14:38

hmm I think This problem is slightly the same as what Im having. I start the car drive for a bit it misses and trys to die for about 2 seconds but the rest of the drive is fine. It only does it once everytime I start it up.

galapogos01 · 03-07-2002, 18:04

a dodgy map sensor can cause hunting on cold starts, black smoke, rich running. as far as i know anyway.

the stuttering could be anything - its hard to explain i guess. a pinched fuel hose starving the engine?

map sensors can also go ****ed only at certain vacuum ranges - which corresponds to an engine load+rpm combo. so it could be that still.

i need a new map sensor for mine, i think, as i get extremely rich startups - to the point where it stinks of fuel out the exhaust. it might even be my injectors - DOH!

good luck mate.

03-07-2002, 20:04

Rich on Start up black smoke. Pain in the backside.

03-08-2002, 00:14

Yeah I got a new Map Sensor and it works well only when NOT mounted on the firewall This confuses the hell out off me

ben · 03-08-2002, 01:43

i dont mean to cause any "ben shut the **** up, or ben were only trying to help u ass", but i think you should disregard the sensors as the problem, the sensors are acting this way because of a hard fault. I think you will find disconnecting either the oxygen or MAP sensor will still give a default mixture and will still cause this problem, by removing the map vacumn if the problem goes away, this does NOT indicate a faulty MAP sensor necessarily.

I think theres a fuel problem, in the lines somewhere, either your pump is faulty, low pressure, or there is a leak of some type, or your fuel rail is dodgy. Did you replace the fuel pump during conversion, if so, was it a new pump or a secondhand wrecker pump ?.

check the fuel pressure regulator, if this is heat sensitive and faulty it will most certainly act quicker than the ECU can compensate for, causing all sorts of psychotic reactions.

I had a fuel leak once, burst a hose, and what happened is that it thought it was getting fuel but it wasnt, and because the amount of fuel varied so much, the revs went up and down like crazy exactly as u described, and would then settle down (even though it dripped abit of fuel). as soon as the pressure (due to hose burst) was fixed, the problem immediately went away.

I say get a pressure gauge, and check the input and output, also check your fuel filter if you havent done so, and check the fuel pressure regulator, remove the vaccum from it to get max pressure and see if the problem goes away. After this check the operation of your injectors.

remember, if you poored fuel into your intake or drained fuel from the lines manually, this is what would happen, so whats causing it to do this ?....injectors or fuel pump. (or regulator).

Its possible the problem is electrical, but it would be continuity if this was the case, as if a sensor was faulty it would cause this problems at all times not intermittantly.

Hope this helps a little.

ben

galapogos01 · 03-08-2002, 07:10

removing the vacuum from the map sensor makes the ECU default to running full richness - ie: black smoke.

try it.

most cars die from the extra fuel (when idling).

03-08-2002, 08:23

Ben, It aint no fuel or ignition problem. I had a new pump, filter and regulator has been checked and fuel delivery is no problem. All ignition parts have been changed aswell. Dizzy,
coil, leads and plugs were renewed.
Ive also dissmissed the MAP sensor as we tried one out of another falcon and it still did exactly the same thing.
Im puttin a new coolant temp sensor in on monday too.
I think its strange why im not getting any self test codes from the ECU!! Maybe they stuffed up the wiring somewhere and have grounded some EFI sensors? Anyhow im ****ed with it
and its getting worse so im taking it to a specialist. This conversion is getting costly. I should have got the EB2 :(

Brent