65 FI hot idle stalling

[Dan C.]

Hoping some of the fuel injection owners can help diagnose my stalling condition during hot idle on a 65 FI car. I am just getting familiar with the car and have adjusted the cold idle to 2200, but from there it gets harder to stabilize. Not sure the tach is accurate on lower rpm but my ear tells me I can adjust the hot idle to about 900 although the tach reads closer to 1300. If the tach is true, I cannot lower the hot idle under 1000 without stalling it. I even got the idle smoothed out so the needle stayed within 2 hash marks at best. Driving the car at that point was very smooth and responsive, no flat spots on acceleration. But when I come to a stop, and let the car hot idle, it becomes erratic after 1-2 minutes then stalls. I replaced the fuel pump and fuel filter, fresh non ethanol gas and octane boost.

Another unusual sign it it seems to take a little longer than it should to rev down. I have more experience with a 63 FI that will wind up and come back to idle quicker. This one tends to float down. I did a quick check on the throttle valve and it does not appear to be binding. Could these problems be related? Any help is greatly appreciated! Thanks, Dan

[John D.]

Re: 65 FI hot idle stalling

Dan, What's the temperature out when you are having this hot idle problem. How many inches of vacuum is the engine putting out?
THe hot idle compensator could be bad/leaking, It's located on the brass throttle butter fly. Info in the '63 shop manual as no manual was ever printed for '65's. Make sure the rubber hoses aren't cracked or loose. Check the 90 degree rubber elbow under the air meter for cracks.
A warped main diaphragm cover could be an issue. A bad main diaphragm could be also. Could also have issues inside the fuel meter bowl (passenger side). Check for vacuum leaks.
Your accelerator return spring could be too weak. Or it could be a bad repro. Make sure the accelerator rod is not rubbing up against the distributor shielding. When the engine is off. Does the spring have any tension/guts? Is the accelerator spring bracket mounted correctly? May be a dumb statement but I have seen the bracket mounted on an intake/baseplate hex bolt.. Make sure it's on the dimpled Stud-FI to baseplate stud. Held on with the 3/8" nut.
If the car has the wrong came that could be why it won't idle below a 1000 RPM.
If the hi-pressure pump (where the drive cable goes) has issues that could cause the car not to idle down.
Your throttle shaft could be sticking. The throttle butterfly may not be centered in the bore. All of this could cause the idle to float down as you said. And the list goes on. John D

[Tom D.]

Re: 65 FI hot idle stalling

1. Check for vacuum leaks, as stated above by John D. Easy thing to check.

2. Use 110 Octane fuel.

[Dan C.]

Re: 65 FI hot idle stalling

Thank you John and Tom. I will investigate your recommendations and reply- hopefully over the next couple weeks. I will check for vacuum leaks and I know I do not have the correct return spring. I have located the 63 shop manual so I will get educated on the hot idle compensator. I really appreciate your help!!

[Duke W.]

Re: 65 FI hot idle stalling

Verify that the VAC is either a 236 16 or B28 and meets spec - starts to pull at 4" and is at the limit at 8". Normal idle behavior for the 30-30 cam is about 10" @ 900. Use an accurate test tach. Also make sure there's not a BB in the rubber hose... seen that before.