Mystery D-Jet lean condition., mystery no longer... Options

[Olympic 914]

Car started going to an intermittent lean condition.

'73 2.0 d-jet system 037 ECU.

Starts up fine, idles Ok.

But when I start to drive it, it starts running bad and the AFR goes to 17-18, Sometimes if I feather the throttle I can keep it running and it settles back to 12.5 – 13.0, normal running.

Other times it dies. It will start right up again though.

I have a fuel pressure gauge but it is mounted in the engine compartment and I can’t see it when driving. Pressure is set at 29 now. and holds at that during idle

In January I had an issue with the fuel pump wiring, So I redid the wiring with 12ga from the rear to the front. I didn’t like the sound of the Bosch 044 pump, it was way too loud.

So I installed a Bosch 69133 pump. Much quieter, drove it around for a while and everything was working perfectly.

Spent all of February doing a cut and buff on the car, then drove it for a bit again everything still working fine.

The most recent thing I did was remove the rear brakes to fix my parking brake. Didn’t touch anything in the engine compartment. But when I took it for a drive after working on the brakes the lean condition arose.

I had already purchased a FI harness from Bowlsby So I took the opportunity to install it. Hoping that would solve the problem.

Well it didn’t.

Have a ¼ tank of gas, and I checked it with a dowel rod to make sure the gauge wasn’t reading off. Then added 2 gallons anyways.

Still no change. Changed out the fuel pump relay, No improvement.

I have no idea what brought this problem on. I can’t rule out the new fuel pump. But it ran good with it for at least 200 miles. Changed the fuel filter and cleaned the screen when I had the tank out. the screen wasn't dirty though. The tank was cleaned before I put it back in 4 years ago. No rust inside.

At this point I won’t go further than around the block, and it will happen a couple times on each trip around. But hasn’t stuck me totally yet.



Guess I could set up the endoscope to watch what the fuel pressure reads when it goes lean and take it from there.

I have to just walk away from it for a while, but my mind is reeling.

[Flyingmonkey]

I think Jeff is on the right track. TPS, MPS are easy enough to check. Pull the dizzy & clean up the contacts. Just do them all one at a time so if the car runs better you know which item was the culprit. Also verify your ECU & MPS are both for MY 1973- I know, if mismatched it wouldn't have run well before but it's an easy thing to check. Hope you get it sorted out.