Is my JB map sensor a crap sensor?

[enthuzed]

So I've been having issues for about three weeks with my stock JB.

Initially I thought it was an ignition problem so I've played with plugs & leads, dizzy cap, then replaced the fuel filter to be sure. I've cleaned all engine bay connectors with alcohol spray & swapped the coolant temp sensor...no appreciable difference.

The car runs rough at idle and when I gas it, it gets even worse. The gauge at idle shows negative 0.2, and anything over minor throttle means it'll run like a tractor. It then might show just over zero on the gauge before putting like craps. Interestingly, every so often it'll run well & will go full throttle without a hiccup & will boost to about 0.6 with its standard turbo. What should the gauge read at idle usually, and at full boost?

Seems to me like it runs really rich. It chuffs black smoke when it putts poorly at idle, I cannot see behind me for black smoke when I give it heaps of throttle & even without doing that my economy is about half of what is normal for this car.

I did swap the map sensor with a spare, but the car wouldn't even idle. Swapped the knock sensor also, same deal. Checked the hose to the MAP sensor & couldn't see anything wrong with it.

Help!! Can I trial someone's good map sensor & I'll buy if it fixes the problem.
Or is there something I've overlooked?

Thanks in advance, its very frustrating!

[limau]

how bout ignition coil?already check it?

[Alspos]

Could it be an injector is open or closed circuit? Have you checked the TPS resistance is consistent through it's range?

I'll look and see if I have a spare map in my box of derelict bits....

[redzone]

Coolant temp sensor or wiring thereof

[enthuzed]

Replaced the coolant temp sensor early on Dave (just after our convo) & replaced the plug with a Narva two way connector housing set with terminals, (part #56272BL) not long afterwards. Checked continuity from the wires to the plug terminals, all good but no difference. BTW it fits perfectly, I'll add this to the aftermarket parts guide.

[enthuzed]

Anyone pulled a JB map sensor apart & knows a bit about it? Could it be caused by the vacuum/check valve thingy right next to it?

[ProZac]

The solenoid valve next the map sensor is used to switch the vacuum line the map sensor is connected to, to atmosphere when the key is first turned on, allows the ECU to get a barometric reading and adjust for altitude.

A leak in the intake system, before the throttlebody, could cause the problems you describe.

I'd tend to think that since your boost gauge works, your map sensor is probably fine.

[Komeuppance]

The solenoid next to the MAP sensor checks barometric pressure every 2 minutes or so by switching from the manifold pressure to ambient. If the signal or vac line gets messed up the car will run terribly.

Your gauge should be somewhere around -0.6 at idle. Sounds like the solenoid is bad, or the vacuum line is bad.

Try turning the car off and then back on, to "reset" the ECU. See what it does then.

-Robert

[thrash]

Try turning the car off and then back on, to "reset" the ECU. See what it does then.
-Robert

You work in IT Rob? :P

[ProZac]

Do JB's have the black plastic MAP sensor, or the older metal case one?

Have you tried reading the error codes out of the ecu? Are the JB's late enough to give error codes?

[Komeuppance]

Try turning the car off and then back on, to "reset" the ECU. See what it does then.
-Robert

You work in IT Rob? :P

Lol, when I did, my suggestion for the gullible was to give it a hard punch first, and then press the reset button.

-Robert

[enthuzed]

Thanks guys for the info, some further things to check now.

Zac, as far as I know there are no codes that the computer spits out, and yes it's the black plastic one with the solenoid next to it.

I forgot, I replaced the airbox to turbo pipe too, no change either.

[ProZac]

Hmmmm, you might actually be able to get error codes out of a JB if they've got the later model electrics?

Do JB's have the T-Bar style fuel rail, and a motor to control the idle speed?

If so, pretty sure the ECU will have a diagnosis output pin.

[enthuzed]

The little solenoid has a split in it, so I've fixed it with some Q-bond & plastic filings. Great product that!!

It's still not 100% but will idle at -0.6, is much more driveable but still coughs and splutters at full boost.

It's actually always done it, but only when boosting it flatout and when the revs are right up there. But it's not as good as it used to be.

Will have to replace the solenoid I'd say. Who has one for sale??

JBs do not have fault codes or diagnosis output pin AFAIK, unless you can lead me to it Zac. Does have the T-bar fuel rail you describe & there's an idle control on there too.

[Komeuppance]

That little solenoid was also used in other Mitsu's around 89-94 here in the States, might have a look at them if you can't source a staz one. It's a simple three port solenoid that switches between the two output ports.

As for full boost sputtering, what's your plug gap at?? Make sure your intake piping is tight with no leaks, and also ensure no vacuum line leaks. Also, how's your vacuum advance and mechanical advance??

If you do have a ECU code output, and is similar to the later models, it could be a round three pin connector with only two wires, and be located next to the air filter. Look for one that is terminated with a plug, or it might simply look "disconnected".

-Robert