Need help. Poor running. OBD-1 w/rk tunes. Not sure what else to look at.

[328iFun]

Do you have any E36 guys close by that can come by and help you out?

Maybe someone on here? If I were near I'd try to help you

It always great to have a second set of eyes

[vr6dubny]

No one very close. That’s ok though. I am gonna get a second set of eyes on it.

gonna chase wiring tomorrow.

[vr6dubny]

car is finally running after a long time with a knowledgeable mechanic

so the main culprits were a bad ground that was allowing the charging system to not run right, the timing/vanos was not timed correctly, random wiring/grounds needed to be refreshed, wideband O2 sensor was not accurate.

crazy this has been over a year of trouble shooting.

[Mklock]

Congrats, let me know about them wheels! Happy for you! Let it rip!!!

[pbonsalb]

Great news! A sorted out turbo E36M3 is a lot of fun but many of these older and modded cars need some sorting and it helps to have someone with both stock and modded experience working on it.

[vr6dubny]

I completely agree. I wish I had brought it to someone last year so I could have enjoyed the car all summer.

from what I have been told it runs fantastic now, can’t wait to get it back.

[ty20404]

Reviving an old thread - hopefully vr6dubny is still on here. After getting married, two kids, COVID, new job, house, etc, etc, I'm finally back to trying to figure out my idle issue with my OBD1 RK Tuned car.

vr6dubny, do you still have the car, does it idle great?

I've done much of the same that you have except replace the stock FPR with an aftermarket. Since this thread, the only change I've made is adding a ground wire to the DME, but that didn't help. I do plan to go to OBD2 eventually but need to get this thing running right so I can enjoy it once again.

The car made 515 rwhp at CES when originally tuned, but never idled right, with one caveat, so I think you're on to something with the charging system... The only time it would idle right is when I would jumper the battery to my (old) E90 M3. I have tried two separate alternators in this car and neither made a difference, so I'm assuming it is something between the Voltage Regulator in the DME and the alternator itself.

Do you have any insight on this?

THANKS!!!

[vr6dubny]

My issue ended up being a wire/relay grounding out causing the low volt signals to be erratic. I would check in your fuse/relay box by the driver front shock tower. Also run a volt meter to the wiring for the MAF and the coil packs.

- - - Updated - - -

The fact that when you had sustained voltage from your other car it ran correctly, makes me think it is prob not a fuel issue. My guess is old garbage wiring.

[ty20404]

My issue ended up being a wire/relay grounding out causing the low volt signals to be erratic. I would check in your fuse/relay box by the driver front shock tower. Also run a volt meter to the wiring for the MAF and the coil packs.

- - - Updated - - -

The fact that when you had sustained voltage from your other car it ran correctly, makes me think it is prob not a fuel issue. My guess is old garbage wiring.

Were you checking these voltages with ignition on, or engine on? I'm guessing engine off, key on. I would think it would blow a fuse if a power wire was grounding out? You mentioned alternator issue earlier, was there a problem there?

I ohmed all of the sensor wires in the engine harness years ago, but maybe it's time to do it again and check all of the wires in the fuse/relay box.

[vr6dubny]

If I remember correctly it was a relay in the fuse box grounding on a ground post. There was never an alternator issue. It was not a 12v issue it was a signal wire issue.

[ty20404]

Hopefully someone else can confirm here - is O2 the only sensor that becomes active in closed loop?

My car idles fine until it hits open loop. If that's the case then I'm going to dig right into the O2 wiring first and see if my issue is there.

[vr6dubny]

I had an 02 sensor that was faulty out of box and a wiring issue. I would make sure your MAF signal is staying good while running as well as O2

[ty20404]

So I checked the O2 Sensor wiring back to the DME and relay.

At first start, relay is off and not sending 12V to the heater circuit. Once it's warm, I'm getting 13.5V at the O2 sensor on the heater circuit (pins 3 and 4). It looks like this is ass backward, no? Shouldn't the heater only run while warming up?

I've got continuity between the O2 sensor plug and the DME/Relay all reading 0.5ohms or less.

As a side note, it looks like someone went through this harness and removed unneeded stuff before I got my hands on it. They did a good job, but that doesn't mean they didn't make any errors.

[ty20404]

I had an 02 sensor that was faulty out of box and a wiring issue. I would make sure your MAF signal is staying good while running as well as O2

How steady should the voltage be coming off the MAF at idle? With O2 unplugged and a steady idle (12.5AFR), It's fluctuating from 0.68 to 0.74 Volts.