schubaru

hopefully someone can shed some light on this problem.

it started when i put the cat/downpipe back on my car for the mot, by the time id got it to the test centre it was hunting, revs would drop to 300 dropping the clutch and come back. it was also running rich, only just made it through (feel the guy was being kind that day too). natural response was lambda shot, computer hook up showed it to be switching slowly. i replaced it with a uni one and the situation is the same. i have checked the TPS voltages, transition is smooth and as it should be 0.4v idle - 4.4v WOT. i have cleaned the idle control valve and MAF to no effect (have new MAF on order). currently the problem is more sever after a good run, hunting more noticable..sometimes it will not hunt for a min or so and sometimes the revs drop on clutch dipping and sometimes not. The ECU memory was cleared so this could present a problem in failing sensors right? also cat was bought off ebay, bought the car decatted so not sure how exhaust should be!

the questions i have are as follows..

i have only one lambda in my downpipe right after turbo - nothing in exhaust manifolds either side, nothing in up pipe, no wires or connectors free around there. is this right?

if it is the MAF sensor, why does my car stink of petrol and get bad fuel economy? thought they failed lean?

my ICV (that i can see) seems different to other peoples. mine is electrical stepper motor with plunger looking thing on the end, other people seem to have a bigger unit with coolant routes and vacuum pipes on theirs from photos on forums..am i missing something?

Apologies for the essay - wanted to give all the facts, any thoughts greatly appreciated!

TonyBurns

iTrader: (3)

Could be more than one problem? maf and o2 sensor?
o2 sensor could make it run rich if it fails?
You probably need a proper diagnostic to show any major problems.

Tony

schubaru

thanks tony, gonna try and book her in somewhere for this weekend. see what happens with the new MAF tomorrow.

P1 FEK

iTrader: (1)

Had a similar problem with mine, turned out to be a split in the turbo inlet pipe where the pipe clamps onto the turbo, letting in unmetered air.

Sonic'

Sounds like the MAF to me

The O2 sensor IIRC should only read up to 1v from 0-1v

Edited to add, if you have the engine running, and then disconnect the MAF if the engine carries on running then the MAF has failed

If the engine cuts out as soon as you disconnect the MAF then the MAF is pretty much ok

scoobycraig

i've got the exact same problem as you mate! I've gone over every sensor! So im guna whip the plugs off in a min and the coil packs and have a look for any cracks!

Have you checked yours?

craig

Sonic'

Have you tried unplugging the MAF whilst the engine is idling scoobycraig?

schubaru

i checked tps sensor, volts all ok... unpluging the MAF or ICVS makes the car stall. both have been cleaned. havnt checked plugs or coil packs but will do.. split on the inlet pipe to turbo sounds interesting.. do i just check visually or is there any special way to test for splits there?

scoobycraig

nope, i never knew about that trick! i'll try it now!

scoobycraig

on the coil packs just peel the ends back very carfully and inspect for any cracking

hope that helps

P1 FEK

iTrader: (1)

They tend to split or perrish next to the jubilee clip at the turbo end, a bit tricky to see, might be worth loosening off the clip and using a small dentist type mirror.

schubaru

thank you all for your input. fitted the new MAF sensor yesterday morning, drove it around most of the day and problem has dissapeared. revs drop smoothly and slowly and catch at 900. idle is spot on. power is good too. This is real interesting as many people on the forums seem to have a similar problem but may be put off the MAF sensor as a cause because like me, they unplug the sensor when running and it stalls. Most people advised me if this were the case, the sensor is ok. Maybe others should try this if they havnt already.

thanks again everyone!!