bigport 4age super rich

[smackdownz]

hey guys could really use some help here.

Problem, bigport 4age running super rich. i clean plugs car will idle well for 5 mins and then idle will start get choppy and idle will slowly decrease, lose throttle response and engine will die (will restart but then die again. pull plugs and all 4 are absolutely black as black can be (not wet just black) and this is just at idle with some slight revving. im at a loss where to check next.

things ive tried.

145-150 across all 4 cylinders
timing set at 10deg bridged (16ish unbridged) timing is spot on
new ae82 fuel pump (45psi just before rail - checked with gauge)
fuel filter.
new coil
new leads (spark is healthy -when plugs are clean lol)
injectors are clicking fine
no error codes yes diagnose is connected correctly
ox sensor isnt hooked up as there is no place on the new extractors at the moment (before anyone says this is the problem, theres no way it should be running this rich just with no ox sensor?)
tps adjusted to spec
new coolant temp sensor and bled cooling system.
have checked alot of continuityfrom sensors to ecu and all seem ok - but ill gladly check again if anyone has any ideas
+ im sure alot more ive forgotten.

so any ideas? a fair bit of black smoke out exhaust and blackens plugs in 5mins of idling. im kinda running out of ideas on where to check or what to do next.

forgot to mention, it has a MAP sensor. one pin out has 5.02v another has 4.3v and the other im guessing is ground. is that right? i thought only one side needed 5v

Thanks!

[jondee86]

Check this thread... viewtopic.php?f=13&t=17799

Last couple of posts deal with MAP sensor readings.

Cheers... jondee86

[smackdownz]

hey mate, that thread with your post is actually where i got the idea to check the MAP sensor. the results

startup - (all results are from PIM on ecu)

1800rpm - 3.00v

(rev while warming up) 3000rpm - 2.7v

(idle dropping down) 1200rpm 3.4v IDLED AT 1200 FOR ANOTHER MINUTE AND VOLTAGE WHEN TO 2.6V AND STAYED STEADY THERE


at 1200rpm when i rev'd the motor the voltage went down.


is that correct? sounds wrong to me?

Cheers.

[jondee86]

It works more or less like this...
- VCC is the nominal 5V sensor supply from the ECU. With the key ON (engine OFF)
there should be 4.5 - 5.5V between VCC and E2.
- E2 is one of the ECU ground terminals. If your ECU ground terminal and battery
ground are good, E2 should have no measurable voltage to ground.
- PIM is the sensor signal voltage. With the key ON (engine OFF) the PIM voltage
should be 3,3 - 3.9V measured between VCC and E2.

When the manifold vacuum is high (engine idling) the PIM voltage should drop to
a value approx 2V lower than the value you measure with the engine OFF. When you
apply load to the engine, the PIM value will rise closer to the value you measured
with the engine OFF. Under WOT (as in accelerating hard in a high gear) the PIM
value would be the same as you read with the engine off.

As there is virtually no load on the engine at idle regardless of engine speed, you
should be getting less than 2V at at idle. And while it is difficult to apply load to
the engine while it is parked, revving the engine sharply will cause a momentary
drop in manifold vacuum, which should cause the voltage to rise briefly.

So check your ECU grounds are at zero and the ECU power supply is at 12V. Check
for any bad connections (high end to end resistance) or damaged wires between
the ECU and the MAP sensor. If nothing obvious, try another MAP sensor.

Cheers... jondee86

[smackdownz]

Your an absolute legend jondee, really appreciate you going into so much detail and effort to help. So have followed your instructions and MAP seems to be in spec, however i have earthed e2 to earth and get almos .007v.. Sigh should have check earths first. Checked all other ecu earth and all seem to show some voltage including the injector ones.

So whats the reason behind this? How do i go about fixing this.

Ive had a look and the injectors have an earthing point on the intake manifold, there is a big earth wire from block to negative battery, and bellhousing also has a strap.

Any where else??

[sirdeuce]

If you are still running rich after testing everything else try introducing a 1.5v DC signal across the O2 lead. It will simulate a rich mix and lean it out. Don't need anything bigger than an AA class battery to do this test. Don't go higher that the 1.5v though. If it turns out to be the problem you'll need to weld on a bung to screw the O2 sensor into.

[smackdownz]

Hey mate thanks for the reply, im very keen to give this a go, is it as simple as an AA battery + side to the 02 wire and - side of battery to ground?

[jondee86]

...however i have earthed e2 to earth and get almost .007v

No problem there That's only 7 millivolts which is fine. To get the symptoms
you are experiencing, you would need to be measuring 1 or 2 volts.

So back to basics... check that the vacuum hose from the manifold to the MAP
sensor is not split/leaking. Then get a hold of a vacuum gauge and see how much
vacuum you are pulling when the engine is idling. If you have normal vacuum (15"Hg
or 50kPa) at idle and the MAP sensor checks out, the problem is elsewhere.

Cheers... jondee86

[sirdeuce]

Yes, + to the O2 sensor lead and - to engine for best results.