Technical MAP sensors - Full run down needed

[ronnieronson]

Ok so MAP sensors - I know what it does, which is a start...

1> If it starts to fail will EM light come on?
2> Would incorrect fuelling / Irratic engine behaviour be a symptom?
3> What other symptoms?
4> Where is it located?
5> Rough cost on buying a new one?

This is all regarding a 2003 Sei Active Sport (a friends), although I would imagine it's the same info as for an 01 Sei Abarth? (like mine)- can anyone confirm this?

Cheers, Matt

Edit: Sorry folks - should have posted this in technical (damn those handy bookmarks I keep....) - if any of the mods would care to move it for me I would be most greatful

 

[ronnieronson]

noone?

 

[fingers99]

ePer will confirm if it's the same, but I'd be shocked if it isn't.

Problem with the MPI cars is that there's so little published. You might have better luck in the Punto section.

The symptoms you suggest might be MAP failure. Another is high fuel consumption.

On the MPIs I think it's the one that bolts to the intake manifold (rather than the TB).

 

[ronnieronson]

ePer will confirm if it's the same, but I'd be shocked if it isn't.

Problem with the MPI cars is that there's so little published. You might have better luck in the Punto section.

The symptoms you suggest might be MAP failure. Another is high fuel consumption.

On the MPIs I think it's the one that bolts to the intake manifold (rather than the TB).

Will surf on over to the punto section pronto
Cheers Fingers

 

[randomizered]

yeah, map is on the intake. The connector has 4 or 5 wires, and is both a map sensor and air intake sensor combined. Look in the punto guides section, at teh 1.2 engine layout pictures

If the map dies, i'd def expect a warning light. With my map tube removed, the car hardly runs.

Kristian

 

[ronnieronson]

basically it's running rough on idle, using a bit too much fuel (I get 40-45mpg outta my sei, compared to 30-35mpg outta my friends 03 plate), not losing liquids or feeling underpowered - no EM light (or any warning lights for that matter) not using oil. Have replaced plugs, leads, air filter, oil filter & Flush & change, coolant, and coil packs.

*And breathe...*

...only things I can think of that may be suspect are thermostat, map, and / or lambdas, or possibly Cat on its way out - although it's a quiet runner so I sorta ruled exhaust issues out...

...tis very odd

 

[randomizered]

Those obd boxes you were looking out, can sometimes give lambda read outs, to see if they faulty.... but as it is an obd2 car, if the lambda fails pre cat, the cat doesn't work proprly and triggers a warning light due to the post cat lambda. Thats the whole point of the newer system, to check emmissions, cat and lambda are ok. Can't remember if the lambda readings did work on the sei or not now.

You done a compression test?


How rough is rough? and are the mpg, mesured by brimming the tank, reseting trip, and filling up again? Are they both the same drivers mpg results?

Kristian

 

[fingers99]

Cheapest path to discovery (assuming you have both cars together) might be to subsitute senders.

 

[ronnieronson]

Those obd boxes you were looking out, can sometimes give lambda read outs, to see if they faulty.... but as it is an obd2 car, if the lambda fails pre cat, the cat doesn't work proprly and triggers a warning light due to the post cat lambda. Thats the whole point of the newer system, to check emmissions, cat and lambda are ok. Can't remember if the lambda readings did work on the sei or not now.

You done a compression test?


How rough is rough? and are the mpg, mesured by brimming the tank, reseting trip, and filling up again? Are they both the same drivers mpg results?

Kristian

Compression test no.... not yet anyway - and as for rough, rougher than the usual mpi "V8 Judder" - low revs while idling too... approx 500-800 rpm.
Measured the mpg from brimming to empty then worked out using calculator - but given that she's a conservative sensible driver, and that I plant my foot between every speedhump, I would have said that if either car should have worse mpg it would be mine - especially concidering hers is stock, and mine is less so

Cheapest path to discovery (assuming you have both cars together) might be to subsitute senders.

Unfortunately hers is usually 150 miles away.... getting alot of the feeback via emails!, think I've been kinda turned to as I "know my way round little Fiats".... allegedly... :yum:

 

[FIREsporting]

A vacuum leak can cause a MAP sensor to indicate low manifold vacuum, causing the computer to think the engine is under more load than it really is. Consequently, timing is retarded and the fuel mixture is enriched.

You can use a bicycle pump to pressure the sensor to see if the voltage are within specs. I know at atmospheric pressure (gauge pressure at 0psi) it should read around 1.74v.

 

[ronnieronson]

A vacuum leak can cause a MAP sensor to indicate low manifold vacuum, causing the computer to think the engine is under more load than it really is. Consequently, timing is retarded and the fuel mixture is enriched.

You can use a bicycle pump to pressure the sensor to see if the voltage are within specs. I know at atmospheric pressure (gauge pressure at 0psi) it should read around 1.74v.

presumably a quick test with a fine mist of water while the engine is running will tell us where (if any) there are broken seals etc?

 

[randomizered]

It's very unlikely the manifold has developed a leak so bad it affects the map, you'd have far higher revs then as well, as it would be drawing in a lot more air. Also, as its directly bolted to the inlet, theres no pipe to split or leak.


I can create a leak so high i idle at 1500, but the MAP still stays low as the engine is still drawing a vacuum due to the extra air moved with said leak.

Kristian

 

[ronnieronson]

...well that answers a few questions.... what else could be the cause? Just can't figure it out! :bang: