Stumbles under acceleration with AC on (1 Viewer)

[Ned]

Like the title says, when I run my AC my FJ60 aka: Walter seems to stumble.

It almost seems like the distributor isn't advancing. Could the AC be pulling power from the coil, I have tune up recently with new plugs wire and coil. I have searched the forums here and haven't found anything relating to this. Walter is still has all the smog pump an emissions hooked up, to the best of knowledge it is working correctly. My ac idle up is working correctly too. Its weird it runs great without the AC, smooth acceleration all the way up to 3000 RPM

I just cant imagine the AC will zap that much power from this thing.

Any sujestions?

Thanks,
Ned

 

[NeverGiveUpYota]

Maybe something in this thread. AC in 1984 FJ60

 

[Ned]

I don't think the AC idle up VSV is the culprit, the AC idle up is what keeps your truck from dying or idling too low when you are in traffic or at a stop light. I do not think it affects acceleration, when you cut off the AC it drops the idle to what you set it at for your base, I set mine about 900 rpm, then when I turn on my AC it kicks up to about 1100- 1200 rpm. That seems to be where my truck is happiest.

 

[Ned]

Ok searching and reading threads here and came across this:

City Racer Carburetor in a 1984 desmogged 60

EDIT : Proper photos of vacuum routing are on page 2 of this post I've been having stalling, starting, stumbling and backfiring issues on my stock (desmogged) OEM carburator on my FJ60 I've been very happy with my Trollhole and City Racer carbs on my 40 and 55 but these trucks are bare bones...

forum.ih8mud.com

It seams sometimes the secondary's stick and do not open under vacuum signal.? I know this is regarding a city racer carb but I believe the same would apply to a stock carb, anyone done this paperclip test? I am going to try this to see if it works.

 

[NookShneer]

Builds - The 60 known as Mamabear: a tale of rust and good times.

The stumble and misfire is back. After a round of frantic diagnosing and parts replacing, it’s driving terribly. -checked for vaccum leaks. Couldn’t find any. -inspected all vaccum lines. No cracks. -replaced the city racer with a factory aisan. No change -inspected and replaced the...

forum.ih8mud.com

@HemiAlex may have just gone thru this in his thread above.

 

[Ned]

I tried the paper clip test and it moved, so back to square one. I briefly looked at the above thread and realized I read it some time ago when I was trying to determine why the tachometer didn't work when I bought the truck. (which I ended up figuring out how to get it to work again) I think I am going to need to sit down and read this again. Maybe their is a correlation to the rough running and this. Also the AC didn't work when I bought the truck, (disconnected) and several vacuum lines were rerouted and disconnected. I fixed the vacuum routing and got a good old school Jamaican mech to fix the AC. Humm... looks like this mystery just got interesting.

 

[HemiAlex]

Disconnect the wires one by one in the coil before you spend any money.

 

[Ned]

Since I have had this truck my mech fixed the AC, then I have fixed the tach and I have fixed the carb fan. I have one random wire which I have no clue what it goes to and I think I wired the fan carb correctly. Here are some pictures

 

[HemiAlex]

Unplug these green wires one by one. One will make the truck not start, the other will disable the ac and tach.

If you unplug the wire that disables the ac, and your misfire goes away...you know that path to follow.

 

[Ned]

I will try unplugging these one by one and driving it to see what happens. But, if it disconects the AC and runs good, isnt that the same as me turning off the AC at the dash and it running good?

 

[NeverGiveUpYota]

As Yoda might say... “Quick this one.”



.... @OSS any suggestions?

 

[OSS]

AC compressor takes a lot of mechanical power. Turn up the AC idle up set screw on the carb so the engine revs to 1200 when AC engages at idle.

With AC compressor on, it's like dragging brakes slightly. If the engine is at 3000 rpm and the AC kicks on, thats a huge pull on the engine. The compressor magnetic clutch draws 4A (~56watts) when it's engaged, so electrically it's not a big draw

 

[Ned]

I think my AC idle up is set properly, as it idles at 1100 - 1200 when the ac is on. I might have the idle set a little high when its off since it seems to be in the 800- 900 range depending.

So got lucky and disconnected the tach on the first try. As suspected it ran as decent as it would have if I had turned off the AC at the dash.

I stopped and reconnected it reaffirming my belief that it ran the same as if I just turned off the ac on the dash.

Now, it does seem a little better since I tried the paperclip test, passably since I manually opened and closed the vacuum plunger that actuates the secondary's. I don't however think I actually opened the secondary's unless they are connected to the choke, because what I thought would open them actually opened the choke.

Could my problem be leading back to the secondary's and them being gummed up.

Who knows how long it has been since this carb was serviced, or rebuilt. And yes I do firmly believe the AC in my truck does zap a lot of power from the engine when its running unfortunately in South FL AC is not an luxury it is a necessity.

I am going to try to open and close the secondary manually a few times maybe they gummed up.

Also anyone have any Idea what this random wire is for?

 

[Ned]

Just took out Walter, he seems to be driving 100% better with the AC on. I think the secondary's were sticking and moving them open and closed along with moving the vacuum diaphragm helped out not sure if its a permeant fix or not but it is working of now.