vulnax999

iTrader: (7)

Basic symptoms :

Signal from Z32 MAF ( now wired in on spade connectors securely ) drops to 0v whilst driving or idling - is 0.5v when powered but not running, 1.1v when idling normally.

Dash water temp gauge drops from normal to cold ( as if ignition turned off ) and recovers to normal position, over a few seconds, often as MAF signal goes funny

Now refuses to drive on load - ok to 3, 4k rpm, or even 5k rpm if gently driven well off boost, but otherwise gets to start of boost or any load and "soft cuts" at 3500 - 4000 rpm.

Idle very uneven, jumps and down, then stalls - watching MAF signal this is up and down, so seems to cause idle problem ( not ICSV ).


SYstem is WRX MY94, Apexi PFC, AVC-R, TD05-20G, FMIC, lambda ( new ) now in downpipe, header hole blanked, new coil packs and plugs a few months ago, remapped to suit.

Car drove fine last night, idled perfectly, but has had this intermittent fault with signal on temp gauge & MAF for a while, worse last 2 weeks.


Seems a loss of power or earth to the sensors; It has 6 earths to ecu case, alternator, 2 top mounts, 2 sides of manifold, and chassis / block.

Any ideas, seems to me to be a wiring fault in loom?

Thanks

Any good auto electrical places / diagnostics in North West?

Neil

scoob east

Check you water temp sensor, This can cause very bad running too.

vulnax999

iTrader: (7)

Cheers, I changed them both earlier this year as the ecu and dash saw different temps! It did make cold running / idling poor,

This seems different.
Cleaned and ran earths to the loom earthing points I found ( by both strut tops and behind o/s strut tower, and cleaned one on starter ) and improved idle.

Now is a little rough idle when fans come on, but not seen MAF sensor or dash temp gauge dip.


BUT Still can't drive on load ... Wonder if Apexi has lost the map and is limiting? Is that possible , anyone ??

scoob east

yeah prob seems very similar to mine

i also run a z32 MAF, all was fine untill one very wet night. Then dash went mental ( rev gauge spinning round, Fan's coming on etc etc ) Now when cold my car run's like a dog, untill warm. Also boost now stops at 0.9 bar rather than the 1.4 it was running before

vulnax999

iTrader: (7)

Added earths to the loom pick up points now, smoother idle, less drop or uneven ness when fans come on, need to run it now ans see if still holding back and won't go on load / past 3500 rpm.

Is it likely the Z32 MAF or wiring to it?

scoob east

as far as i know the z32 maf is pretty hardcore, but you can't rule it out, keep an eye of air flow readings on your power fc,

vulnax999

iTrader: (7)

Done!

Air flow rises upto 2500 mV,( maybe 2560, 2610 mv no more ) then stops / levels off / dips/bounces ... but it's chicken and egg!

Is the air flow limited due to something preventing on load use so 2500 mV is correct reading, or is Z32 MAF stopping reading suddenly at 2500 mV so the engine holds back at that rev / load?
Been for a run, measured this as above, seems the volts flatten off at 2.5v whether gently getting to 5000 rpm or 3000 un full throttle / some load.

Best try a new Z32 MAF then. This one was "new" 2nd hand, 1995 vintage and sat on my shelf for 9 months pending a remap!

Any ideas for good / new ones, what cost?

scoob east

paid over £90 for mine, best try jap breakers yards

vulnax999

iTrader: (7)

Paid £70 plus shipping for mine, but from USA.

Just picked up a new item from japan, £130 plus £23 shipping!!!

Hope that sorts it!

vulnax999

iTrader: (7)

Wondering now, since the engine may rev upto say 5000 if being gentle, or 3000 if not, the common factors are that it won't run on load, or when boost is called for.

When it refuses to pass a certain air flow / rev a howl / whine develops... could it be a mechanical problem with the turbo being stuck or something?

How could the turbo stop spinning? It's new! Do they break / seize or jam somehow??

vulnax999

iTrader: (7)

May as well close this now ....

Checked for boost hose leaks - none on pressure side, fine on inlet side. Span turbo blades with fingers and run free, so not jammed/seized.
Wiggled ecu into usual place and checked for loose wires / pl;ugs again... and went for a run

Fired up and idled fine, ran fine!
No refusal to run on load or boost now! Ran Fine!

Must be a broken / loose wire, or soimething damp, or if the MAF it recovered overnight!

New Z32 MAF on the way, all should be well!!!

vulnax999

iTrader: (7)

New Z32 fitted, all well now.