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> Tach/engine jumping up and down... help please
tod914
post Jul 8 2007, 11:20 AM
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Just started happening. The car is a 75 2.0 with fuel injection. It has a pertronix ignition. The problem is, it seems to be jumping up and down in the rmp's and idles very low. Idle adjustment didnt seem to help. I checked all the grounds and contacts including the tranny strap. I swapped out the voltage reg and throttle switch and the problem still persisted.

Computer problem?

Timeing problem? timeing was done last year, fi trigger points a few years old.

Pertronix problem? its about 4 years old

Bad coil? 4 years old

Grounding issue? has new fi harness from bowsby - 2 years old

Head temp sensor? its about 2 years old.

What would you all suggest.


Thanks for the help,

Tod
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IronHillRestorations
post Jul 8 2007, 11:37 AM
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I'd guess something in the ignition. If it had points, I'd say swap the points and condenser. Given the info provided, I'd say put a set of points in and see if that resolves the problem.
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tod914
post Jul 8 2007, 11:55 AM
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ok thanks, i'll try that. it's ok at start up. then when it starts to get warm, the problem starts.
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Michael N
post Jul 8 2007, 12:10 PM
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Have you checked all your fuses?
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So.Cal.914
post Jul 8 2007, 12:20 PM
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Check for a slightly tight valve, as it warms up the valve can raise up off the seat

lowering your compression in that cylinder. (IMG:style_emoticons/default/smile.gif)
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shaggy
post Jul 8 2007, 01:00 PM
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when i still had points mine did that same thing.

as i investigated i found that the plastic part on the points had broken.

i changed to pertronix.

is it possible you fried the pertronix?
this can be done by turning the ignition to the on position and leaving it there.
if the unit is on a closed position you can toast the unit.
i did trying to prime the fuel system...

if you have a dead pertronix it will do all sorts of funny stuff.
ex. not light. not idle. stumble. ect.

hope that has in some way helped.
-jim
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shaggy
post Jul 8 2007, 01:02 PM
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you also might wanna check that the bearings/bushings in your dizzy shaft are good.

-jim
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tod914
post Jul 8 2007, 07:10 PM
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Ok guys thanks for the tips.. I'll order some points and a condensor, and check all the fuzes. I try the original distrib to rule out bad bushings on the current one. I'll see when I can get the valves done as well, I think they only have about 1000 miles or so since the last adjustment. Btw is it easy to replace the Distributor Contact Breaker Plate? The original is alittle corroded.
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McMark
post Jul 8 2007, 09:58 PM
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Also, make sure your coil isn't loose and grounding to the engine tin. (IMG:style_emoticons/default/wink.gif) I've had that happen to me and it's the first thing that popped in my mind when I opened this thread.
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ConeDodger
post Jul 8 2007, 10:58 PM
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QUOTE(McMark @ Jul 8 2007, 08:58 PM) *

Also, make sure your coil isn't loose and grounding to the engine tin. (IMG:style_emoticons/default/wink.gif) I've had that happen to me and it's the first thing that popped in my mind when I opened this thread.


I agree! Especially the 75 -76 cars. If your tin on the passenger side is ripped and you cannot really torque down the coil, it can turn and ground on the tin. The tach will jump around and the car will run like (IMG:style_emoticons/default/stromberg.gif) . Then it will kill when completely grounded...
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tod914
post Jul 8 2007, 11:38 PM
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the coil has the rubber insulator pad around it and its tight. it hasnt been moved in some time. how could i tell if it was grounding to the tin? would there be a visual sign? very much a novice when it comes to electric issues (IMG:style_emoticons/default/huh.gif)
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ConeDodger
post Jul 9 2007, 12:43 AM
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QUOTE(tod914 @ Jul 8 2007, 10:38 PM) *

the coil has the rubber insulator pad around it and its tight. it hasnt been moved in some time. how could i tell if it was grounding to the tin? would there be a visual sign? very much a novice when it comes to electric issues (IMG:style_emoticons/default/huh.gif)


All that needs to happen is for one of the electrical connections to contact the tin. If it is tight and none of the connections is touching tin that is not your problem... But it still could be a grounding issue... Just not a simple one.
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tod914
post Jul 16 2007, 12:45 AM
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swapped out the distributor with one the orginal one that i put a new contact plate in; as well as points and a condensor. new cap and rotor, and replaced the bosch wires with the set of firebraids i had. set the dwell and purchased a new timing light from sears (dead out of the box). so the dwell is set and the issues seemed to of disapeared. timed it sort by ear if there is such a thing so its running. tomorrow ill replace the timing light and time the motor (not by ear). seems the pertronix was the culprit. was about 4-5 years old. I'll stick with points from this point foward (IMG:style_emoticons/default/smile.gif). anyway, wanted to thankyou all for your expertise and timely responces. i'll let you all know how it runs once i take it for a spin tomorrow.
the voltage at the coil is 11.6 while at the battery terminals it's 12.8 with the ignition key turned on. so i assume thats good numbers?
Rob btw, how do you like the 240Z?
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