my 1974 911 is hesitating while accelerating

[80sc4me]

I have a 1974 911 with the 2.7L just fully went over the motor and the car no broken head studs, did a full tuneup plugs,wires, valv adj, fuel, air and oil filters but she still seems to have a hesitating while accelerating starts right up idles good doesn't seem to be running rich or to lean and I don't think I have an air leak but any help would be great I was going to look at getting a new fuel distributor but not really sure????

[docrodg]

Check fuel pressure and flow.

[ossiblue]

Hey James,

Welcome back to the Tech section, I think you will find the answer to your problem here without the expense of new parts.

First, follow docrodg's advice and check your fuel pressures. If you don't have a set of CIS fuel pressure gauges, you should plan on investing on a set if you intend to keep your car. You should test your system pressure, cold control pressure, and warm control pressures as a first step. Like all good investigating, you want to eliminate suspects and this first test is the easiest way to start. Lots of info on the board on how to do the tests, or you can take it to a Porsche mechanic who has experience with CIS and have him perform the test, but it is very easy to do yourself if you have the gauges and are minimally competent with tools.

Let us know your plan and ask for any help in your investigation.

[80sc4me]

I will start with that thanks!! any other suggestions?

[ossiblue]

Originally Posted by 80sc4me

I will start with that thanks!! any other suggestions?

One step at a time so you don't get ahead of yourself, IMO. Report back on your fuel tests--including a fuel flow test if possible.

[80sc4me]

Yeah good point I will do the tests this weekend and I have a feeling that since my rusty gas tank was replaced a few years ago before I got the car some of that my be clogging my lines or fuel distributor...will let you know what I find
thanks
James

[4sd911]

Does this hesitation happen at any RPM. The 2.7 CIS is know for a little stumble at around 2700 RPM's. The above advise of checking your system is always good to do.

[T77911S]

the fuel filter should keep the stuff from getting to the FD.

timing/advance and fuel mixture.

i assume cap and rotor with all the other stuff.

if you still have problems after all this, i would look at the injector spray patersn and flow volume. for that matter, air leaks at the injectors and other places.

i have had problems with mine and i was always thinking FD, glad i never spent the money because it was always something else.

[80sc4me]

yes cap and rotor are new it seems to hesitate around 3k and after till4k then ok...sometimes in the lower gears a few flat spots...

[Steve@Rennsport]

This is not uncommon with CIS engines.

I would:

1) Check & confirm that the distributor advance mechanism is functioning correctly.

2) Put all six injectors into some baby formula bottles, turn on the key, remove the air cleaner and lift the sensor plate to make sure all injectors are spraying a nice umbrella-shaped spray pattern. Any of them that are streaming or even partially streaming should be replaced.

3) I'd run a large bottle of Techron through the fuel tank to clean the valves.

4) Using the CIS fuel pressure guages, make sure the CPR for throttle position is functioning. This drops control pressure when you open the throttle to accelerate the car.

This will help a great deal,......

[80sc4me]

steve- thanks for your time and I will post when I know more but I drove her all weekend good most of the time once fully warm. Drive her easy and she does great..still when you really get on it same stuttering...Hopefully I will have some time in the next week to see what I can find out basied on your suggestions.
thanks
James