Severe hesitation/cutting out

AbusedJalopy · Post by **AbusedJalopy** » Mon Feb 14, 2005 12:18 pm

Now that we have all the vacuum lines hooked up correctly without leaks or problems, the car runs great! However, one problem is left that we experienced before. The car seems to experience extreme hesitation at partial throttle in second gear all the time, and first gear some of the time. It always happens at 3000 rpms, sometimes going a little over or under, but for the most part exactly at 3000. The car doesn't just hesitate, like feel sluggish, but completely cuts out. It's like the car completely misses and jerks just once, and then goes again just fine. Under wide open throttle, it still does the same but it's hardly noticeable.

My question is, what happens at around 3000 rpms that would activate that is causing this? I would lean towards something electrical, like one of the solenoids or those vacuum cut offs (labeled S/W in the book) not functioning. Only other thing I can think of is timing advancer, but what is most likely the culprit? I couldn't find anything in the manual about something activating at 3000rpms, so hopefuly someone has an idea. Thanks in advance.

Adelard of Bath · Post by **Adelard of Bath** » Mon Feb 14, 2005 1:10 pm

AH HAH! Mine did the same exact thing! And it drove me crazy and nobody knew, I rebuilt the carb but that didn't really help, so it probably is one of those 400 or so little solenoids they put in there....

But I DID solve the problem....sold the car for $100!!!

Tee hee, sorry no help, but I couldn't resist

takza · Post by **takza** » Mon Feb 14, 2005 7:01 pm

I think 3ACPower was talking about gaining power at 3K. With my car I see a gain at around 2300 RPM probably due to the second barrel kicking in...not much difference going thru 3K.

Accordng to the Bentley manual for 83-84 3AC......the centrifugal advance peaks at 11.5 degrees around 2600 RPM and drops to 11.1 degrees at 3K. Maybe this is where the problem is?

Could be the EGR opening up for some reason? Have you tried bypassing it?

AbusedJalopy · Post by **AbusedJalopy** » Tue Feb 15, 2005 10:15 am

You know, now that you mention it, we just got the EGR all cleaned and working in our attempt to pass smog. Maybe now that it is working, it's causing this. The weird thing is that it doesn't just run crappy through that power range, it full on stops as if you took your foot suddenly off the gas and then slammed it back down. What is this centrifugal advance, is that the thing on the bottom of the distributor? It seems like with only half a degree change in timing wouldn't cause the cutting out we feel, but maybe it's messed up and retards/advances it way more than it's suppose to? I know the advance works on the bottom testing it with a vacuum tester, but I don't know about those two tubes above it.

takza · Post by **takza** » Tue Feb 15, 2005 7:06 pm

The centrifugal advance is usually just a couple of weights that swing out and advance the ingition as they spin faster...how they get to the place of reducing the advance at 3K...I don't know...maybe some over the center kind of setup that might be messing up?

Might check to see if the springs are OK?

This advance is independent of vac advance....and generally they work in opposite directions.

You have a lot of vac advance at idle and no centrif. advance then...and sometimes the opposite at 3K.

There is a specific method to test those vac advance diaphrams....need to close some while testing the others.

dug320 · Post by **dug320** » Fri Feb 18, 2005 1:14 am

It still sounds like a vacuum issue. I had the same problem. I had to get a toyota manual for the car to find the exact routing. The Chilton mnauals are terrible for vacuum routes. The other thing was the vacuum hoses were imperial (previous owner) and not metric in size. The fits are close, but as the hoses wear, through vibrations, the quality of the fits decrease.

Hey just my two cents. :rolleyes:

AbusedJalopy · Post by **AbusedJalopy** » Mon Feb 28, 2005 12:07 pm

Well I disconnected the vacuum advance and it still has the problem, so it's not related to that. All the vacuum lines are routed properly using new tubes, so no leaks are present. So either something that controls the vacuum (like those S/W vacuum switches) or something else electrical must be messing up.

chilibilly · Post by **chilibilly** » Tue Mar 08, 2005 10:26 pm

I have had the same problem and I don't know what to do about it. The bucking bronco syndrome. I have a friend with the same 83 4X4 model as me and his does the same thing. I thinks it is related to something in the emission solonoid system, but I don't know where to start. I am not sure if it is electrical, because it feels like gas distribution is stopping and starting. It only happen during deceleration and acceleration at around 10 to 20 mph. This is a weird one. Wish I could fix it. There's probably a magic bullet to fix it but I certainly don't know what it is. No help here!

takza · Post by **takza** » Wed Mar 09, 2005 6:11 am

chilibilly wrote: I have had the same problem and I don't know what to do about it. The bucking bronco syndrome.

If it's down below 1500 RPM....it's likely the EGR putting too much exhaust into the carb (for whatever reason)...test by removing and plugging the vac line to the EGR.