325ix hard start - poor MPG

[Garemie]

New discovery. The fuel injector plug, C191 I believe it's called, is corroded. I cleaned it up really good but ultimately it needs to be replaced. Going to replace the plug and both coolant senders and report back.


I think this may be my answer here.

[Garemie]

New temp sensors. No change. Scrubbed the c191 and it looks perfect now. No change.


Tested TPS again, it's good.


So either somewhere my TPS wires are broken or I have a DME that doesn't do stomp codes. Any thoughts ?


Edit: tested battery on cold mornings. When started it shows 11.9v until I blip the throttle then it shows 14.4. What's up with that?

[ForcedFirebird]

The voltage is because the alternator needs excitement. They need to be run over 1000 rpm for the regulator to start sending voltage to the battery.

Not overly difficult to do a continuity test from TPS, or c191, to the ECU connector, just need some longer jumper wires. If you remove the zip tie and Phillips head screw from the ECU connector, the white part can slide out if the black casing and plugged in the ECU for live testing break-out-box style.

Also, if you follow the Bentley, there's voltage and continuity tests that you can do when unplugging sensors to make sure reference voltages are on par. If the reference voltages is off, the signal to the ECU will be (some sensors are resistance to ground, some are looking for 0-5v and others are 12v).

[Garemie]

Isn't the engine supposed to be a little high idle when started anyways? It never goes high idle like most other cars do. Maybe that's why I'm having the voltage issue before blipping the throttle. Any ideas what would cause that?


Sounds good about the TPS. I think next I'll do the FPR just because I don't think it's ever been done and maybe I'll get lucky.

[ForcedFirebird]

The FPR is a mechanical device. It's just a diaphragm and spring that closes off fuel pressure at idle to equalize the pressure differential when there's vacuum in the manifold (eliminating the risk of the vac "sucking" more fuel than the engine needs). Easy way to test them is pull the vac line off and smell for fuel, they tend to rip the diaphragm when they fail and additional fuel will be sucked through the vac line. If you are brave (or dumb enough like me), just unplug the vac hose from manifold and suck on it like a soda straw. If you get fuel, then it bad. I have a little hand pump vac puller, but am often too lazy to go pull it out of the toolbox at work lol.

[ForcedFirebird]

Oh, to add. These cars do not rec over 1000 rpm upon startup. If you reach in the window of an e30 with a voltmeter attached, you will see they never start charging until revving the engine. The blue wire on the alternator gets voltage through the idiot light, but is resisted at 10ohm +12v. So, when the alternator sees less vintage, the light trips to ground (uses the lesser voltage in the alternator to "ground" the light into illuminating). We have volt meters in the race cars, and even the early e36's do this. When ECU's became more advanced due to USA regulations and OBD, they would jump up idle just after initial start to excite the alternator. All new cars do it.

[M_3_X]

Not sure if you posted How many miles in the car and what kind of mpg are you getting?

[Garemie]

238k and I was getting awful mileage until doing injectors. Averaging 21.7mpg right now which seems pretty decent for mountain driving in an ix.

[Garemie]

FPR and temp sender replaced. No change, obviously. Need to address the TPS issue.

[Garemie]

Anyone know if there's a common breaking point in the TPS wiring? I'd prefer to not have to fish new wires all the way from the ECU.

[ForcedFirebird]

Did you do a continuity test and find one lacking?

[Garemie]

Did you do a continuity test and find one lacking?

I haven't. TPS is good and properly adjusted so I think it's safe to assume there's a wiring issues somewhere?

[ForcedFirebird]

Check your signals at the DME, not the sensor plug - that's why I asked how you knew the wire was broken on it's way there.

[Garemie]

I don't have a Bentley manual. Do you have a diagram which ones are which on the DME side ?

[Garemie]

Well the car is running flawlessly now. I understand the TPS is still an issue however but that will be resolved eventually. But as of Monday the car is in the shop getting ready for a full re-color paint job to Diamondschwarz. I am scheduled to get it back sometime around April 5th.