Theory to my Maddness! (Troubleshooting)

[Bruzman]

Original Post (Redundant):
http://forums.austarion.com/viewtopic.php?t=14370
Helped me fix my starting problem
Main Post (Ongoing):
http://forums.austarion.com/viewtopic.php?t=14376
Helped me rule out alot of possibility's, but I still am having issues
Side Post (Redundant):
http://forums.austarion.com/viewtopic.php?t=14379
Helped my learn alot the Air Fuel settings

Update:
I started the car on Tuesday (11/01/12) to try and drive the Starion down to a family friends Auto-Repairs shop. The Starion started, began reversing and stalled. Then, it wouldn't start at all.

I had a very close look at the Vacuum lines between the MAP Sensor and Intake as advised by "Redzone". The Vacuum line at the intake end was loose and slipped on and off with extremely little effort. Loose like a wet whore! I mean even a small child could remove it without much effort. It's very possible that this loose line was letting Air in or out. This explains why my Boost gauge was reading around -0.2 of a bar instead of -0.5 of a bar like "Redzone" said it should.

After I pulled it off and put it back on when searching for the problem, my Boost Gauge reads 0 bars of vacuum. Dead set even! (this was before attempting to drive it to the Mechanics)

Because the MAP sensor thinks it's getting alot of Air, wouldn't the engine attempt to correct the Air-to-Fuel ratio by dumping more petrol into the engine. (This would explain why it is/was running so Rich that you could smell it out the exhaust)

Using this theory, it would explain why the Vehicle wouldn't start and doesn't have power under load!
It wouldn't start after the first stall/attempt of reversing because the Spark Plugs have probably fouled up pretty fucking quickly with all this fuel!
It doesn't have power under load because it's getting flooded with way to much fuel.

I got the Vehicle towed to the Mechanics for a compression test to double check before I spend any more money.

So, if my theory is correct, if I replace the Spark Plugs and worn Vacuum Line (Making sure it's secure with no leaks) it should be up to drivable standard. That's when I get it back and the compression test is good.

Would you guys agree that my Theory has logic and reasoning?
Anything else I should consider?

[WidebodyWoody]

Are you sure your Map sensor is working properly? On my old JA, there was spray paint that got into the little pin hole that the little rubber hose goes over. This was causing the Map sensor to go haywire. I would make sure the hole to and from it is good, no leaks and on securely. But yeah, just keep in mind that the Map Sensor could be playing up. Easiest way to test it would be probably borrow someone elses. I was lucky to pick one up from the wreckers back in the day for something like $100.

[djalpha]

Unplug the map sensor electrical connector and start the engine. The ecu will run substitute valves in the event it fails. Inside the map sensor is a diaphram which flexes under vacuum or load which sends a specific voltage to the ecu to use in its calculation with all the other sensors for injector pulse. The diaphrams tend to split over time. I ran a Ja back in the day for years with it disconnected. Used a little bit more fuel, but thats the substiute valve allowing for top end load so that it didn't lean out. U still need to have the vacuum line connected to avoid a vacuum leak which will cause rough running. If the hose on the inlet manifold end is loose fitting, cut an inch off it and refit it so that it slides on tightly. If the fault is still present after u disconnect the map sensor, then u have a problem somewhere else.

[Sargeant_Khan]

Are you sure its not you're MAF? If its plugged in i'd check the wires to it, then try a second hand one from someone on here.

[enthuzed]

Electrical connector to the MAP sensor can be dodgy or not connected. It will then show Zero pressure on the gauge.

A replacement hose might be a good idea from manifold to sensor. Those old hoses can look okay but have cracks where you can't really see them, particularly at each end and where they are mounted near the firewall.


How about your turbo? A non-boosting turbo will show the same or similar fault...but then it would have been squawking for a while before it gave up the ghost.

[Bruzman]

Are you sure your Map sensor is working properly? I was lucky to pick one up from the wreckers back in the day for something like $100.

Are you sure its not you're MAF? If its plugged in i'd check the wires to it, then try a second hand one from someone on here.

I talked to someone parting out their JA Starion. I asked the if they have a MAP and MAF, which they do..
I'd first replace the vaccum line because I am positive it's leaky. after that, I'll try what "djalpha" recommended! :)

Electrical connector to the MAP sensor can be dodgy or not connected. It will then show Zero pressure on the gauge.

Remember, I only got a reading of "0" after I played with the loose vacuum line! before that it was just low, probably from a sight leak...

How about your turbo? A non-boosting turbo will show the same or similar fault...but then it would have been squawking for a while before it gave up the ghost.

I believe the turbo to be fine. I have Revved it in Neutral and got positive boost when greater than 2-3k rpm..