FI Idle speed Issues

[Rob Howell]

Hey everyone,

I am still trying to dial in my 62 fuelie and something I have noticed is that very often, the idle speed varies by a few hundred RPM. I assume this might be related to my earlier post about the choke spring being weak and the choke coming on and off.

However, something else I have noticed is that when I engage the clutch, the car reduces in RPMs very slowly. At first I thought maybe the tach or tach cable was still spinning even though the actual engine speed had returned to idle, but if I cut the ignition the RPMs go straight to zero so I do not think this is actually the case.

Sometimes the engine speed hangs around 2000 rpms unless I blip the throttle. Does this sound like an issue with the throttle shaft binding up? If so, can this be fixed by me by drilling it out and adding in some bushings?

Any suggestions? I am getting tired of FI and that is a bad thing . . .

[John D.]

Re: FI Idle speed Issues

Rob, Sounds like a sticking spill valve to me. Over the years guys like Bill Thomas and maybe Smokey Yunick gave nicknames to various FI parts. One of them that stuck is the spill valve for the late 59 to most of the 62 units. They called it the "good guy" spill valve. Well I call it the bad guy. It's a POC. Maybe in the good old days when the things were brand new and the spring engineers didn't mess with them that valve was pretty good. I have even heard old timers say that the "good guy" spill valve gave a little nicer idle.
I'll let you and the other DB members in on a little secret. If you want your 58 to 65 FI to scream and be a lot more reliable put in the later style spill valve. We call it the "thumb tack" style spill valve. That's another nickname.
Go to your shop manual. Corvette Servicing Guide-ST12 manual. In there you will see an illustration with two spill valves. If you have the one with the piston, spring and retainer-can it and put in a nice new thumbtack style. But before you do consult me or others as there is one installation tip you want to be aware of. By the way I should have said long ago that the spill valve is in theory the accelerator pump of the FI's.
Not trying to sell parts on here. I read the note on top of the web page. I adhere to those rules. Just trying to help you out. Could care less about selling parts.
Maybe this is not your problem.Could be something else. But from the zillion phone calls I have gotten your complaint is quite familiar.
JUST SO YOU KNOW-The 62 FI is on of the best solid axle FI's ever made. First year for the carburetor choke which was a vast improvement over the earlier models. A good 62 absolutely screams. JD

[John D.]

Re: FI Idle speed Issues

Rob, Don't even think of drilling out the throttle shaft bushings, etc. That job is a nightmare even for the best. Those bushings are typically offset. That is not a back yard job. It's not that anyhow.
Accelerator spring. Oops. Some guys out there insist on using two springs. AIMS calls for one spring. But the problem is typically the one spring doesn't cut it. I see a lot of 62's with two crappy springs on them. All you need is one good spring. Very few repro springs though are any good for more than a few weeks. Sorry I didn't think of the spring before.