Random burst of Performance?

[4babycar]

Ok, I am not sure if this is my imagination or just a strange dream but in the off chance it is real..... it is worth asking, for me anyway.

For the past few weeks I have been driving my '80 converted to Dual 40 Idf's and have enjoyed her immensely. She runs well but hasn't seemed to have the same level of .... Umph that I remember my 81 FI having. Granted, I last drove that one 10 years ago. Anyway, on a short trip to the store (~1.5 mi) everything went fine and I didn't notice anything out of the ordinary occur but on the return trip she acted like someone gave her a good swift kick in the a**. I mean that she accelerated noticeably faster and harder than ever before, squealing tires and snapping my neck back! I'm thinking WOW, I guess she just needed to be driven a bit after her long sitting (8yrs) so I enjoyed the new found power all the way home (with an extra trip or two around the neighborhood). The next morning though, it was gone and I have not had it happen again. So my question is, was I dreaming or is there possibly and explanation for this type of behavior and what can I do to fix it? As always, thanks for your help.

[mbouse]

(cue the Twilight Zone theme music).....

so, it briefly ran BETTER according to the self-installed Butt Dinomonitor? Of course, we've eliminated restricted fuel line, sticking brake caliper, collapsing brake hoses, timing, loose plug/coil wires, worn cap and rotor, and fouled plugs.

then, i am going with a sticking throttle cable, which momentarily freed itself. of course, a sticking cable sticks going up AND down the rev range.... so you would have already eliminated that when you solved the intermittant too high idle RPM issues.

[4babycar]

Yes, assuming the self installed Butt Dyno was installed correctly and was operating correctly.
I have checked all brakes and they are free and do not appear to be sticking at any given time. All plug and coil wires are also firmly seated. Timing was checked when the carbs were tuned and the clutch changed and was set at 10 deg. Plugs are new and I have not checked them since they were put in approx a month ago. I have not checked the cap and rotor (what should I look for?). Regarding the sticking throttle cable, I did have another issue with it sticking in the nearly wide open position about 2 weeks ago but a little white lithium grease on the throttle linkages and the exit of the cable seems to have addressed that but I was planning a replacement of that cable in the near future.
The car currently runs and idles well and concistantly (~1100 rpm). I do not have any noticeable misses or changes in performance in any given range of rpms that is why I am confused because it was just this once. Thanks for your help.

[engineerted]

Two things that come to mind, Floor mat, limiting the accelerator travel, 2. lean condition due to fule pickup in tank or filter, or even sticking floats in carbs. Ok thats four things.


Ted

[racydave]

Makes me wonder if the distributor centrifugal advance is sometimes bound, or the vac advance bound. Also poss an intermittant ground issue somewhere??? Corroded terminals to the coil or ign module? Faulty coil or ign module?

[4babycar]

Well, I can rule out the floor mat and I believe that I have sufficient fuel to the carbs as I had a clogged filter previously and after changing the element I verified the flow. The fuel filter is a placed just prior to the carbs in the engine bay and has a clear viewing window so i can see the condition of the filter as well. I had personally ruled out the ground issue since I don't have condition that fluctuates often and I don't seem to have any other ground type issues at this time. Also during the changing of the clutch, timing, and diagnosing a bad plug, my mechanic indicated the coil was strong and I was getting sufficient juice to all of the plugs (for what that is worth). Regarding the lean fuel mixture idea, I just checked the MPG over the weekend and it was ~15 which I though was low, based on my previous experience, but I was attributing this to the carbs since my previous was a FI. I hope this helps.

[mdrburchette]

15 mpg seems awfully low, even for dual carbs. I just checked the fuel mileage on my higher performance 1608 w/idfs and got 28 mpg. My 71 can get 33 on the highway.

[racydave]

Grounds and connections arent always good or bad, sometimes margional is enough to affect a coil or module. Its a weird problem anyway... Always a good idea to have a second groundstrap engine to chassis ...

[baltobernie]

I'd rule out all electrical maladies with a trip to a mechanic with a Sun machine. OK, maybe I would try an aerosol can of carb cleaner first, but I'd spend the $100 to verify all the electrics before going back inside carburetion.

[4babycar]

I think I am going to take the route of checking all of the electrical and adding another ground strap, examining the distributor and parts, fuel filter, plugs, etc. before I go the route of the carb cleaner. I have read far too many posts on this forum that started with a little carb cleaner and I am not quite ready for that level of stress at the moment. Thanks for all of your suggestions and I will keep you posted.

[manoa matt]

Don't know if this is it, but maybe one thing to check. For the electornic distributor, there are certain rotors that will stop the advance weights from moving like race dave stated. The rotor is usually black and contains a single continious piece of brass, with no resistor. Looks like this: http://www.partsamerica.com/ProductDeta ... 93&PTSet=A

[4babycar]

Well tonight I only got a chance to look at a few things since the wife took the spider for her first solo outing. Anyway, I looked at the distributor cap and rotor and they were both in good shape but I had new of each so I replaced them both. The original rotor was a burnt orange color and the new one was black and similar to the once Matt mentioned but the construction seemed to be nearly identical. How to I check the centrifugal advance? I also replaced the fuel filter element. After each of these I took her for a test drive and there was no noticeable change in performance. Hopefully tomorrow I will be able to do some ground cleaning and maybe add and additional ground from to the block.

[manoa matt]

You can get that black one to work if you file or dremel out some of the material under the cap. That cap presses down on the centrifugal advance weights and won't let them move. With the rotor installed try to reach in and pull out the advance weights, or just try to spin the gear at the bottom and they should move or fly outward.

That cap "will work", however the one intended for the electronic system is the brown bakelite version with the resistor between the carbon button contact and the rotor tip. Should look like a puddle of epoxy. The resistor may be one of the keys to getting proper performance.

[manoa matt]

Almost Forgot... Those rotors are so cheap you might as well get the right one designed for the system. Keep the black one in the trunk just in case you need to limp home some time.

[4babycar]

Well the rotor is the correct one, it is black but does have the resistor. I did find another issue, or shall I say my wife found a broken wire on the magnetic pickup. She took the spider out for her second solo outing with my oldest daughter (6) and it broke down in the middle of the road. The wire was completely corroded on the inside and had simple snapped in half. I had looked at the wires last night but didn't pull on them because I knew that they were notorious for getting chewed up. I guess in my changing of stuff last night I moved it around enough that it broke due to vibration. luckily, I had a spare and got it back on the road and home again but it still didn't fix the performance problem.