77 2.7L with very difficult problem to fix

[PK 77 911]

Very difficult problem to diagnose.

Bad stumble between 1000 rpm and 2000 rpm. Very noticable at stop lights/signs. More noticable when warm.

Cleaned injectors, changed fuel Distributor. Adjusted and readjusted timming and fuel mixture. Even my very experienced porsche mechanic is having trouble with this one.

Any sugestions. I feel like i should be offering a reward to the person that solves it.

Thanks for any help

[laughac]

Warm Up Regulator caused this problem on my '77 last year.

[PK 77 911]

Would you give me more details on exactly what your problem was.

Thanks

[RoninLB]

I'd start with confirming the distributor vacuum hose is blocked off or removed. Run full mechanical and set full advance at 35deg. Initial should fall into 0-5deg advance. There is a 35deg timing mark on pulley.

The vac retard really screws up timing and low rpm engine operation for smog reasons.

[PK 77 911]

Vacume advance is not hooked up. . By setting to 35deg advance will that tell me something else. Tried further advance but makes adjusting idle impossible. At the moment the timming is set where the engine runs best for performance and idle.

Pk

[RoninLB]

Originally posted by PK 77 911
. By setting to 35deg advance will that tell me something else.


At the moment the timming is set where the engine runs best for performance and idle.

you'll be able to map timing curve correctly at 35 total with a timing light. You may be covering up a different problem with tweaking the curve. Distributor weights may be jammed, etc?

[Early_S_Man]

I suggest checking your centrifugal advance mechanism to see if it is sticking or is frozen. Your distributor specs are the same as 1972 - 73 2.4 engines in this thread:

distributor lube...

[stlrj]

Start with the basics. Replace your ignition cables and go from there.

[PK 77 911]

Originally posted by stlrj
Start with the basics. Replace your ignition cables and go from there.

Wires are brand new.

I will go through the distributor to see if all is OK there to.

[unclebilly]

Is this a California car? My 77 is and I had a similar problem a few years ago. I advanced my timing until the car started to ping under load and then backed it off slightly - it runs awesome now.

[kach22i]

I had to go with slightly larger spark plug gap to get around some issues, don't know if this will help or not.

Make sure everything is "fresh" is all I can say. Wires, plugs, cap..............etc.