fast idle problem

mtthmpsn · 06-30-09, 06:41 PM

After a few weeks, I still haven't figured out the fast idle problem I'm having (around 1300 rpm) with my 77FJ. It all started when I sprayed a little carb cleaner around the butterfly when I was changing my air filter. With some help from Pinhead, I found the third hidden idle screw and turned it out which brought it down from around 1800rpm. All idle screws are now turned out and I adjusted the timing again with no dramatic change.

I then capped all vacuum lines coming from the carb and at the distributor (it's desmogged), but no change. I sprayed carb cleaner around the vacuum lines and the intake manifold to check for leaks, but no change. I checked and lubed the linkages and they seem to be functioning okay. The fuel level in the window looks good.

I pulled the solenoid wire. Okay, that made a difference, but it still took a minute to stall out. Any other suggestions before I dissassemble the linkages and the carb would be appreciated. Thanks - Matt

edhCO · 06-30-09, 09:33 PM

Look down at the connection to the manifold at the base of the carburetor, next to the carburetor opposite the firewall. Screw is horizontal to the ground and oriented like your axles. Screw driver reaches from under the brake booster.

I had a similar experience just last week. This was what was going on with my carb. make sure your fast idle screw is not too tight.

Pin_Head · 06-30-09, 10:31 PM

Try disconnecting the pedal linkage and see what happens. It just snaps off and on.
If this won't get it down, check all the external linkage on the carb and see if it is binding holding the throttle open.
Check if the primary and secondary plates are completely closed. If not, find out what is holding them open.

The only way it will run this high is if the throttle plates are open and the carb is getting gas from the nozzles.

INHALER · 06-30-09, 10:41 PM

If your engine is the stock 2F engine, follow the cable from the accelerator pedal to the linkage under the carb. There should be cam pulley that looks like a quarter disc, that rotates with the depression of the accelerator pedal. A few times, when I have walked on the throttle, this cam has flipped over locking into a high idle. I swapped the 2F in my '76 FJ40 for a 350 V8 10 years ago, so I apologize if my description is a little off.

FJ40Jim · 07-01-09, 07:51 AM

Matt,
On the 77, the idle screw is more accessible, unlike EdhCO, who has the hidden 1975 idle speed screw.

Try what Pin said first thing and report back.

Do not go disassembling the carb yet, please.

mtthmpsn · 07-01-09, 09:41 AM

Alright! I got it working, but I honestly don't know the exact fix, though it must of been the linkage. I took off the air filter, got a flash light and made sure the primary and secondary plates were opening and closing fully. They looked as if they were fully closing but it's hard to see down there. I then disconnected the little accelerator ball and socket to see if that was binding anything up, but it didn't seem to change much from it's location, so I popped it back together.

Dissappointed, I started it up to get it warm and check the timing and vacuum again, and yep, it wouldn't stay running (I haven't had to use the choke since this problem began). Excited that it wasn't running (that's a first), I got out, adjusted all the idle screws, then readjusted the timing, and it's back to its normal self. In the process, I realized how sensitive the idle speed is to small screw changes, so it makes sense that a small bind in the linkage could really mess things up.

Anyhow, I appreciate all the help. I can't get it to stay idling consistently below 900rpm yet, but that's a discussion for another day! Thanks guys!