M30B35 Conversion Freaks Out When Diagnostic Connector Cap is On?

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Joey28
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M30B35 Conversion Freaks Out When Diagnostic Connector Cap is On?

Post by Joey28 »

I got my M30B32 converted over to M1.3, and it seems to run fine, drives nice. But it seems to freak out when I put the diagnostic connector cap on. Idle slows a little, and runs, but then it will suddenly cough and almost stall before recovering. Then it will do the same thing again in approx. 60 seconds, but seemingly at random. I've cross-checked every circuit from the connector to see if it's grounding to another wire but can't find anything wrong. I know that the cap has pins in it that complete circuits when it's on the connector, and so want to keep it, but I don't get what's going on here.
Has anyone else experienced this issue?
And can the diagnostic connector really be deleted without affecting the engine? Making it go into open loop or something?
Thanks for any input.
Shawn D.
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Re: M30B35 Conversion Freaks Out When Diagnostic Connector Cap is On?

Post by Shawn D. »

Looks as if you're going to have to diagnose each circuit to see which each does and why installing the cap matters.
Joey28
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Re: M30B35 Conversion Freaks Out When Diagnostic Connector Cap is On?

Post by Joey28 »

Shawn D. wrote: Jun 12, 2022 5:14 AM Looks as if you're going to have to diagnose each circuit to see which each does and why installing the cap matters.
Thanks Shawn.
I found the problem circuit: program voltage, but I still can't find that it's grounded to any other circuits. I've cross-checked it for continuity to every other pin on the DME and get nothing. Literally traced it from end to end too. It's weird. I just wondered if somebody else had found some weird cause for the same issue. I wonder if the DME is somehow funky?
In any case, I deleted the Data TX, Data RX and Line Voltage circuits from the diagnostic, but left the rest so it can be reset with a Peake. Seems fine now. I also discovered that the EVAP purge vacuum line needs to be properly connected. I'm using an E24 harness where the valve is under the throttle body. With the EVAP purge disconnected (but vacuum port plugged) the car had a rolling erratic miss at idle. With EVAP properly connected and running the idle is much smoother. These engines are so sensitive. Runs much nicer with 1.3 though!
Ju@n
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Re: M30B35 Conversion Freaks Out When Diagnostic Connector Cap is On?

Post by Ju@n »

Joey28 wrote: Jun 12, 2022 5:48 AM
Shawn D. wrote: Jun 12, 2022 5:14 AM Looks as if you're going to have to diagnose each circuit to see which each does and why installing the cap matters.
Thanks Shawn.
I found the problem circuit: program voltage, but I still can't find that it's grounded to any other circuits. I've cross-checked it for continuity to every other pin on the DME and get nothing. Literally traced it from end to end too. It's weird. I just wondered if somebody else had found some weird cause for the same issue. I wonder if the DME is somehow funky?
In any case, I deleted the Data TX, Data RX and Line Voltage circuits from the diagnostic, but left the rest so it can be reset with a Peake. Seems fine now. I also discovered that the EVAP purge vacuum line needs to be properly connected. I'm using an E24 harness where the valve is under the throttle body. With the EVAP purge disconnected (but vacuum port plugged) the car had a rolling erratic miss at idle. With EVAP properly connected and running the idle is much smoother. These engines are so sensitive. Runs much nicer with 1.3 though!
Mmm haven't seen that one, I do remember that you can't connect to newer ECUs via obd with the cap on (car had 2 obd ports, a normal one inside the car and the round one you are talking about).
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