1976 2.0L D-jet, distributor vacuum Options

[914_teener]

I have lost track of some of this thread, and I know you've still got to rectify the MPS issue, but if you're idling at 1000 rpm with the retard from the TB plugged/disconnected, your idle will likely be too low when you reconnect it. This assumes you're running the stock distributor and not the 123 unit.
No point in messing with it now though until you the get MPS sorted though.

Stop. Follow the above advice.

It is more than likely that your MPS diaphragm is partially cracked. The symptoms of this are exactly what you are experiencing. A slowly leaking MPS and sometimes is runs fine and sometimes not.

The only likely things you will need to replace or rebuild are the distributor, the TB and the MPS. Start with the MPS first.

Test your dizzy advance diaphragm. You don't say if it is the stock dizzy or not...however the stock 76 was a detuned unit and at this stage of the game, I'd toss it and get a 123.

Otherwise you'll be chasing your tail. I'd get it rebuilt, put the car on a trailer and take it to the WCR with the idea of the collective getting it tuned.

I'd love to help but I'm in AZ now and can't attend.

[Ron914]

I have lost track of some of this thread, and I know you've still got to rectify the MPS issue, but if you're idling at 1000 rpm with the retard from the TB plugged/disconnected, your idle will likely be too low when you reconnect it. This assumes you're running the stock distributor and not the 123 unit.
No point in messing with it now though until you the get MPS sorted though.

Stop. Follow the above advice.

It is more than likely that your MPS diaphragm is partially cracked. The symptoms of this are exactly what you are experiencing. A slowly leaking MPS and sometimes is runs fine and sometimes not.

The only likely things you will need to replace or rebuild are the distributor, the TB and the MPS. Start with the MPS first.

Test your dizzy advance diaphragm. You don't say if it is the stock dizzy or not...however the stock 76 was a detuned unit and at this stage of the game, I'd toss it and get a 123.

Otherwise you'll be chasing your tail. I'd get it rebuilt, put the car on a trailer and take it to the WCR with the idea of the collective getting it tuned.

I'd love to help but I'm in AZ now and can't attend.

Hi ,
My Dizzy is stock ,the prospect of installing a 123 on my car is not possible since I live in California and to pass smog I have to keep original equipment on the car . I just had my Throttle body rebuilt by Mark Kinnaman , I finished rebuilding my MPS tonight . I will post more updates here once I reinstall the MPS and test drive my car . Thanks for the input . I am still hoping to drive it to WCR in June .

[emerygt350]

Can't wait to hear how it goes! Fingers crossed.

[HLANG]

Sounds quite familiar to me.Had similar experience with my 2L engine which was always running high idle after warming up. Finally I checked the deceleration valve after many other things and it turned out to be leaking when vacuum is applied. And it makes sense that it gets worse when the engine is hot because the compression is higher so is the vacuum. After changing the decel valve the idle issue disappeared.