(T) Engine's still got bad hesitation problem

I thought it must be the MAP sensor, as if I disconnect the vacuum hose from it, the car runs fine (although the tickover is lumpy). However, I bought a sensor from 'surfin_fella' from these forums (he says it worked perfectly in the car it was in) and that hasn't sorted the problem. If I blow into the vacuum pipe with the engine running and the pipe connected to the MAP sensor the revs pick up, but nothing happens if I suck.
I'm thinking about replacing the coil packs next, but that still doesn't explain why the car runs fine if I disconnect the MAP sensor. Hmmm...

Just get a diagnostic done and it will tell you whas up rather than changing everything and getting annoyed when they don't cure it.

You sure the HG is ok?

Liam

Hi,
Still seems to point to the map sensor, supposed to work with vacum on a Normally Aspirated engines (No Turbo) and pressure on Forced Induction engines (Turbo)..

Thanks
Paul T

Hi
See my reply to your last post on this subject
Cheers
Adrian

Could you explain why it's called Mass Air Pressure, it still works on pressure not vacuum.
Is the hose clogged by any chance?

there not all the same you know.. in the old days they were blue then they changed to black with differences between the numbers printed on the little sticker, it must match 'exactly'.

The MAP Sensor worked fine in the car it was in

nah, your wrong there.. i think. Confusing acroynms for two sensor types there.

MAP = Manifold Absolute Pressure
MAF = Mass Air Flow

annyyyway..

hesitation is normally map, or lambda. You have a known working map.. so lambda?

If disconnecting the map makes it idle oddly, then it shows its working - if you were to then drive (a fully working engine) with the map connected, and then disconnected - you'd spot the difference.

One more thing to try, if ur old map was indeed faulty - the ECU may have written off as faulty and so is ignoring it. Try unplugging the battery for 10mins, and then letting the ECU relearn whats going on.

Thanks for all the replies everybody.
I did a couple of things on it yesterday. I unplugged the MAP sensor from the engine and drove without it attached. The idle was lumpy (as it is anyway) but there was no hesitation - smooth acceleration at any revs in any gear. So it all points to something being up with the MAP sensor (no worries surfin_fella, I totally appreciate that it worked in your car, I figure there's something weird going on in mine!).
Also, I tried resetting the ECU buy going through the whole unhooking the battery thing (followed the Haynes manual procedure) but now the idle is actually a bit worse than it was before! Is there any way to test the MAP sensor is definitely working?

if you suck on the pipe going to the map sensor(honest)you should see a rise in revs(IIRC)

Definitely without a doubt there is no change in revs if I suck on the pipe, but the revs rise if I blow on it. By the way, what does IIRC stand for? (sorry, just me being thick! )

thats what i mean there not all the same.

Hmm, that only clears the RAM. If an ECU Error goes permanent at any time,its written to EEPROM (permanent memory) and stays there until cleared by a code scanner.

The ECU puts the light on when an error is logged in EEPROM and RAM memory, so a sensor dies, the error goes to EEPROM, if the power is cut off for a while, say 10mins, the RAM is cleared, but the ECU will still find the diodgy sensor when it next powers up

yeah i know, but if its had a new one fitted since - it won't find a faulty one.. it'll find the working one.

Ok, one more thing to do before I take it to Fiat rip-off garage for the diagnostic.
The rocker cover gasket is leaking oil around the rocker cover, so I'm gonna order one today and put it in at the weekend. I wonder if that could contribute to the hesitation problems?
Although I still think it must be something to do with the MAP sensor as the car runs fine with it unplugged.