Mystery Bucking and Dying

[misszora]

Hello all!

MissZora is having some troubles and I can't quite figure out what it is. She's doing some sputtering/shuddering. At first it was random.

Intermittent shudder/sputter in power at all speeds and gears, acceleration, deceleration and cruising speed. One thing that seems to be repeatable: letting up on the gas can cause this and continues when I accelerate after the shudder/sputter starts. It goes away if I let up on the gas again.

Possible causes - timing? vacuum leak? loose electrical connections? We (Heather & my friend Zach) checked and adjusted the timing (it wasn't far off at all) during a camping trip in May because the shudder started on the drive out. It ran beautifully for a little while. Not sure what has changed. It starts up and runs great, idols nicely. Then it sounds like it’s missing and then the idol drops and sometimes it stalls after it warms up. It does not happen all the time. The shudder/sputter still happened while driving though.

What I’ve done so far to address the shudder/sputter so far:
Corrected timing
Replaced the fuel filter
Tightened a hose clamp on a loose hose attached to the decal valve
Replaced two loose electrical connectors (one was the green wire to the distributor)
Sprayed Deoxit in all connections I could think of except on the injectors. (I was hot and cranky)
Checked and adjusted the valves. All were tight by 1/4 or 1/2 turn except #3 intake which was fine.
NOTE: These are brand new (to me) rebuilt heads with new valves and springs.

As of Monday morning, June 22nd, no shudder detected on drive to work but idol still drops and I have to push on the gas to keep it running at stop signs/lights. As of today, June 23rd, it is bucking and dying at every stop. It died as I was pulling into the driveway and wouldn't start at first and then I got it going. Once I parked and turned it off I tried to start it again and had no problem.

What would cause this? It's like it's not getting fuel but I can start it up again so it doesn't seem like it's the fuel pump.

I have a whole lot of stuff happening in the next two days that requires hauling big items and I need my girl.

Thank you for any suggestions!

[Randy in Maine]

Tell us about your Temp Sensor II.

[misszora]

The one by #3?
Just checked it. The wire connection looks good. The engine is still warm so I'm waiting for it to cool down so I can check to see if I happened to put anti-seize on the threads.

[Randy in Maine]

Really the way to test it is to put your ohm meter on the correct pin at the big plug that plugs into the ECU. The plugs would also be pretty rich as a poor connection makes the ECU think the engine is cold and will richen up the mixture until it dies.

If you were on the road in the middle of nowhere and it happened you would just ground the wiring harness plug to a known good ground and see if that leans out the mixture.

I personally keep a spare Temp Sensor II taped to my leg at all times and this is when I usually install it to note the change.

[misszora]

I don't have an ohm meter.

The sensor looks good. No anti-seize.
I cleaned the threads and put it back in.

[Randy in Maine]

Did that change anything?

[misszora]

Also sprayed DiOxit on the connector before putting it back in.
It started up, idled nicely. I'm going to have to drive it to really see. That has to wait until tomorrow. Fingers crossed.

[misszora]

Drove her yesterday. I could feel a resistance but no bucking or dying. I've got my Ratwell color print out of the vacuum system for fuel injected buses and will be going through it to see if there's anything else askew.