Misfire Map Sensor

nathann88

need to test peoples knowledge i have a slight misfire 🙁

I’m currently at college so i was able to use the lovely expensive equipment today however no joy in what the problem is yet (had to do the work set as well as this). 😃

[FONT=Times New Roman] [/FONT]Compression test all fine
lambda sensors tested (perfect running order) both pre and post cat
smoke tested the intake manifold and breather pipes for air leaks (all clear)
fuel pressure tested 3.8-.9 bar autodata says 3.8bar

plugged into the fault finder/analyser all clear for faults the thing we need to know is what should the MAP sensor be reading?

[FONT=Times New Roman] [/FONT]The analyser was reading 29 kpa (1.1v) ticking over, coolant temp 77 ˚c, air intake temperature 28 )˚C

[FONT=Times New Roman] [/FONT]I had a quick look on autodata for the map sensor details but we ran out of time so any ideas what sort of readings you should get?

The next thing if the map sensor is good will be the injectors I think, take them out test cleaned and see if that helps (another expensive tool they have now)😃
Unless somebody recommends looking at something else before?

MikeS

thats fine

nathann88

so its not that then any ideas on what else?

vocky

misfire with no eml codes usually means it's the coilpack (y)

nathann88

Thanks Vocky
im not at college untill next week again now so without there expensive tools is there a way of me testing the pack

MikeS

buy a 2nd hand one from scrappies

you say slight misfire ?

is it at idle or low revs, or when changing gear ?, does it happen in neutral ?

nathann88

have to be an ebay or online scrappy, are local scrap yard with is pretty big (bridges crawley) iv never seen a z22se up there 🙁

"is it at idle or low revs, or when changing gear ?, does it happen in neutral"

low revs and idle in neutral

MikeS

take it you have changed the plugs ?

nathann88

plugs were cleaned and then changed which hasnt helped,
i made sure everything was clean today, Map sensor, throttle body air intake pipes, inlet manifold etc
i cleaned the contacts on the coil as well no differnce 🙁

MikeS

usually either timing or coil pack

faulty front lambda causes misfire under 3000 rpm

nathann88

it is low revs only i was watching the rev counter today on tick over and you can see it drop as well as hearing/feel it.

ill have to wait untill next week when im at college now so they can run through it with me if we get a chance.

lambda sensors are both perfect tested them both and have a print out for each 1.

only thing is if it is the coil pack is it worth buying a used 1 on ebay?
i could be buying 1 that would break 3 months later. what sort of price is a new 1?🙁

astra22bertoneauto

I have seen an EGR valve stuck open which had no EML (light was not on) causing slight misfire on idle. Is yours blanked off?

nathann88

astra22bertoneauto said:
I have seen an EGR valve stuck open which had no EML (light was not on) causing slight misfire on idle. Is yours blanked off?

yep it is blanked off 🙂
still works tho as the fault finder tested it and we could watch it as it opened and closed.
so its not that either.

MikeS

is it misfire or does it hunt at idle ?

nathann88

MikeS said:
is it misfire or does it hunt at idle ?

not hunting at all, as mentioned above you can watch the rev counter stay stedy then as it misfires it drops and then raises back to where it was.

nathann88

MikeS said:
usually either timing or coil pack

faulty front lambda causes misfire under 3000 rpm

out of intrest how likly is it to be the timming?

MikeS

lumpy idle is one of the symptoms for the timing chain