Carb, Vac or something else? Rough Idle

MT-PTK · 11-02-09, 06:25 AM

I’m wondering if any of the more experienced Cruiser heads on the forum can possibly point me in the right direction?

Here’s the story:

1986 FJ-60
De-smogged
Used as a DD.

About a month and a half ago my 60 started running pretty rough. After checking around I discovered the boot on one of the plug wires (#5 I believe) was cracked. I changed out the plugs, plug wires, distributer cap, rotor, fuel filter, air filter, oil and filter….it was due anyway. She ran much better for about 3 -4 weeks. Now all of a sudden it’s acting up. It’s running a little rough when cold, but the warmer it gets the worse it gets. I can cruise around town but I’ll need to keep the choke out to keep it running smoother because the rpm’s will drop real low and clunk along sounding like it will stall but it doesn’t. It used to be once she was warmed up the choke was pushed all the way in and it idled fine. If I jump on the hi-way I don’t seem to have any issues running at speed, but when I get off the hi-way it really idles like crap. I can smell gas at times when I park her and come back in a little bit but I see no leaks anywhere. That’s leading me to believe it’s a carb issue. I suppose a vacuum leak could be a possibility but the gas smell and the fact that the PO de-smogged the rig seems to pointing to the carb. In the morning she starts as she always has…two pumps, pull out choke and fires right up. When it’s warm starting is hard at times. She’s driven as a DD and I’ve had no real issues up until this point. I had a local shop who has done some minor work for look at it and they think it’s the carb…but didn’t want to touch it. They say they checked the vacuum lines but didn’t find a leak.

Thanks,
William

alaska60 · 11-02-09, 08:32 AM

Sound like a JimC carb rebuild is due.........Send it to him and all your problems will be solved!

MT-PTK · 11-04-09, 05:18 AM

That's what I figured. A spare carb came with the rig when I bought her. It looks awfully clean and I'm going to probably swap them out and then send the one off the rig to Mr. C.

William

RedfishBluegrass · 11-04-09, 06:05 AM

If it is already desmoged, you could try one of Trollhole's desmoged carbs. I put one one about two weeks ago and love it. Very responsive, idles great, easy install. Just a thought. You may want to spray some starting fluid at the base of the carb to see if your problem could just be a leak.

MT-PTK · 11-04-09, 06:16 AM

Quote:

Originally Posted by RedfishBluegrass

If it is already desmoged, you could try one of Trollhole's desmoged carbs. I put one one about two weeks ago and love it. Very responsive, idles great, easy install. Just a thought. You may want to spray some starting fluid at the base of the carb to see if your problem could just be a leak.

I saw that thread about the desmogged carbs. Certainly had me wondering about going that route.

I don't want to sound like an idiot

but what am I looking for if I spray starting fluid at the base of the carb? Will I possibly get my eye brows singed off?

Reading another thread about a similar issue had me wondering about the exhuast manifold. I had the hood opened with it running and was hearing a sort of "chug, chug" sound and smelling a little exhaust. I couldn't see anything and with the other symptoms I was assuming a carb issue.

William

RedfishBluegrass · 11-04-09, 06:36 AM

You are looking for a change in rpms. As you spray around the carb and intake, if the idle smooths or rpms change you know where your vac leak is. I just thought the bottom of the carb could be where the gas smell is coming from.

MT-PTK · 11-04-09, 06:41 AM

Quote:

Originally Posted by RedfishBluegrass

You are looking for a change in rpms. As you spray around the carb and intake, if the idle smooths or rpms change you know where your vac leak is. I just thought the bottom of the carb could be where the gas smell is coming from.

Makes sense. I'll give it a shot and see what happens. Thanks!

William

Cruzerman · 11-04-09, 06:56 AM

Quote:

Originally Posted by MT-PTK

That's what I figured. A spare carb came with the rig when I bought her. It looks awfully clean and I'm going to probably swap them out and then send the one off the rig to Mr. C.

William

If you have a spare carb, I would put in on. Might as well try to make use of what you already have.

MT-PTK · 11-04-09, 02:10 PM

Question:

Would a leak at the bottom of the exhaust manifold where it meets the exhaust pipe cause some of these symtoms? I was trying the starter fluid technique from above (no change) and started feeling around because of the "Chug chug" sound. I could feel exhaust escaping. Add gasket to the list.

Thanks,
William

jeverich · 11-06-09, 07:48 PM

William,
I'm going through the exact same thing as you.

Already regasketed the carb etc...still won't idle.

I've narrowed it down to a leak in the intake manifold. Most likely a hairline crack that changes as the engine heats up, etc.

Personally, I don't think that a minor exhast leak would be the root of an excessively rough-running condition. However - it could serve as an indicator of a warped manifold.

You should order a Remflex intake/exhaust gasket. Only heard good things about them.

- jake

rchalmers3 · 11-06-09, 08:52 PM

MT-PTK, have you ever heard of "hand-choking" a carb?

Often, a carb receives a piece of crud that blocks the idle circuit jet, which is very small. Prolly the smallest orifice in the carb. When the idle jet gets plugged, you will have the symptoms you are describing. The sure fix is to remove the carb and perform cleaning and adjustment. Or...........

Try this. You can use the running engine to suck the debris through the idle jet...... sometimes. Sometimes the junk won't pass. Trying this won't cost a thing and it's way easier than swapping parts. Here's how:

Pull the air cleaner to access the top of the carb. You will want to block or reconnect any removed vacuum hoses, as you will want to test your idle quality a few times during the course of this method.

Start the engine, and with one hand, operate the throttle up to 3000 rpm, or there-abouts. while holding the throttle, cover the air horn with your other hand, blocking air entering the carb. There will be a lot of force, but you must do your best to create a dramatic suction on the bottom of your covering hand.

Before the engine stalls, remove your hand and use the throttle to recover the engine operation. Repeat this a dozen times, using the highest RPMs you care to listen to, with your best hand choking technique to create and hold vacuum in the carb.

After a dozen times, let it idle and see if you have sucessfully pulled the trash through the carb. If you did, great! I have to warn you, if there is one piece of junk, there could be more, so sometimes this is a temporary fix.

If it does not affect the problem, you can try to affect the poor idle by adding fuel, using the carb idle screw, but that is only after hunting down and eliminating any other defects that could alter the idle fuel mixture.

Hope this suggestion is of use to you,

Rick

MT-PTK · 11-07-09, 01:18 PM

Jake,

Two different mechanics, one cruiser oriented, the other not both point to the carb after checking it out. Joe and Chris mentioned your rig when we were shooting the chit talking options.

Rick,
Good info! Thanks. Definitely worth a try.

Thanks,
William

jeverich · 11-07-09, 03:13 PM

Just talked to Chris - taking my junk up there tomorrow to hopefully get her runnning again.