Strange engine behaviour?

[Mazzyrx7]

Got a bit of a problem.

Engine runs fine and then around 5 minutes of driving it\'ll stop want to rev. and feels like its misfiring on anything but light throttle. It starts doing this when your on the throttle. Stop turn off the car and restart it i\'ll work fine for about 5 minutes and then start doing the same.

It seems like an electrical problem to me with it being temporally solved with a restart.

Now am I being blind and thick here... But I can\'t see the check engine light. I\'ve seen a video that shows the cel next to the clock, but on mine it\'s a fog lamp indicator.

[BinoX]

This seems like pretty much the same problem that I have been having recently... It feels like fuel starvation to me though... so when the weather brightens up again I\'m going to investigate the wiring and pump...
 
I\'m assuming that the pump isn\'t keeping the fuel pressure high enough and it eventually gets to the point where nowhere near enough fuel is being injected.... But at the moment this is pure speculation

[Mazzyrx7]

The car revs smoothly to 7000rpm under load before misbehaving. It doesn\'t really feel like fuel starvation to me.

Been having a bit of a think. Car sometimes struggles to turn over the starter. This morning it was really playing up and had to flick the ignition on a off to get it to turn over. I\'ve not started for a couple of weeks due to waiting for parts. It\'s seems like the starter isn\'t getting enough power to turn over the engine. I\'m starting to think it could be bad earths around the car that\'s not helping. It did go funny after hard braking this morning come to think of it. I\'ve cleaned up all the factory earthing points that I can find but they don\'t seem at there best even after cleaning.

Also when accelerating hard it felt like I hit fuel cut once. The car has a decat pipe and the last owner had a recon turbo fitted. Maybe I\'m getting boost creep as the wastegate can\'t cope as it wasn\'t ported?

I\'ve checked the resistance of the TPS. It\'s a little high on closed throttle but at full it\'s within limits. There is a smooth increase in resistance and no dead spots from what I can tell.

I\'ve tried shorting out the wire to get the cel light to give me the fault codes. But there is definitely no flashing cel in the car... well that i can see.

I think I\'m going to try running new earthing cables to the engine and also one to the ECU mount. See if that solve the issue as I think it\'ll be the cheapest solution.

[m1tch]

When did you change the plugs and HT leads - they are both perishable items.

[Brett]

It\'s quite possible it\'s going into limp mode... You can hook a lamp up to a spare pin on the ECU and it will flash the codes.

[Mazzyrx7]

Brett that\'s great. Can it go to any spare pin or a specific one?

Why didn\'t Mazda put the CEL light in the dash like they do on the US cars.

[Mazzyrx7]

I think this might work to get the cel off the car, as I have the green connector in the engine bay?

http://fc3spro.com/TECH/HOWTO/ERRORCODES/ZENKI/zerror.html

[Mazzyrx7]

Just been out to check the connector which is the same as the one in the above link. But it only has three wires going into it. So guess thats not the way to get the CEL codes off a turbo 2.

Is there a correct guide on how to do this anywhere?

[m1tch]

Im pretty sure there is a port in the engine bay labeled \'diagnostics\'

[Mazzyrx7]

I just had another look around for a diagnostics port, but there is nothing in my engine bay.

[Brett]

There\'s a pin out diagram in the FSM, I don\'t have the info to hand though....

[Mazzyrx7]

Figured out how to get the codes out of the car using the connector in the engine bay. No codes.

But I\'m pretty sure the TPS needs adjusting and should solve the problem.

[m1tch]

You have new plugs and HT leads already though yeah?

[Mazzyrx7]

Nope not changed plugs or leads yet. But if it was these I don\'t think the problem would go away as soon as you turn the car off and back on?

I\'ve been having a go at setting up the TPS today. I\'ve set it up so you only get one 12v out of the test connector. It\'s a very narrow band from having one 12v to two 12v from the test connector. Sometimes you go for quick drive and when you come back they will both be giving out 12V again.
If found when driving along put the car in 3rd and accelerate with constant throttle it\'ll hick up at around 3000rpm and then the throttle doesn\'t work properly and anything over very light throttle the car will splutter and not want to rev. But it will go funny at any RPM and speed. It doesn\'t seem to go wrong whist sitting on the drive and will rev to the red line on full throttle and not go wrong.
I\'ve checked for fault codes out of MIL (CEL) connector. But if it\'s logging a fault it\'s cleared as soon as you turn the car off. If it was a faulty TPS wouldn\'t log and save this as a fault?  
I\'ve tested the resistance on the TPS and it\'s a smooth increase on both censors. No steps or dead points.
Could it be a coil pack going down? But the car idles fine and drives on very light throttle just fine.
Could it be a bad speed signal to the ECU? Would this course a problem? As the problem doesn\'t show it\'s self when the car hasn\'t gone any where.
I did notice the idle isn\'t rock solid and will slightly hick up every so often and when I lights are on they\'ll dim for a split second then the car hick ups.

[Mazzyrx7]

This is a very useful thread for anyone experiencing the same problems as me. The car is going to limp mode as duff oil metering pump has more than likely fried the ECU.

http://www.rx7club.com/2nd-generation-specific-1986-1992-17/s5-mop-ecu-failure-diagnosis-710938/