Help! Low rpm hesitation and bucking

[dbeardsl]

I have had my 74' 2.0 for several years now and love the car, But I have been struggling with one main problem for quite a while. When my engine is below about 2800 rpm and I only give it a little bit of throttle (i.e. not flooring it, just around town usage) the car hesitates, then bucks until it gets above around 2800 where it smooths out. When I punch it at any speed it seems to work fine. I have checked all the usual problems, I cleaned my throttle pos sensor, got new plugs and wires, got new points then electronic ignition, and cleaned and checked my injector trigger points (in the bottom of the distributor). Yet, the problem persists, I would love to have this fixed, so any information you have would be MUCH appreciated.

P.S. Also, one day I noticed that my gauge illuminator lights no longer work (they used to) what is the most common cause of this, any body know?

Thanks,
Danny Beardsley
914@dsb.8m.com

[This message has been edited by dbeardsl (edited 09-19-1999).]

[dbeardsl]

Ok, I unplugged the TPS again, to see if that helped. Now the acceleration sucks(expected) but the surging and bucking is still evident,(about 30% fixed, surging softer but faster). But the hesitation is horrible without the Tps, If I give it a lot of throttle the rpm drops. I'm not sure if this is expected or not. OH, and the plug going into the tps has a wire missing, it looks like there never was one, only 4 out of the five connections on the plug are being used, the one on the far right side(looking at it from the back of the car) is the one that is missing.

Any body have any ideas, pointers?

[djs]

I, too, had the mysterious bucking only at part throttle in my '75 2.0 for the longest time. It was more of a nuisance thing, as othewise the car ran fine. To address the problem, I replaced the TPS and adjusted it per spec first. This did not help.

Then, I attempted to "clean" the trigger points, if such a thing is possible, also to no avail. Finally, I replaced them (they had over 100K miles on them). At the same time, I installed new spark plugs, gapped to spec. The bucking has totally disappeared, but I'm not sure whether the trigger points or plugs get the credit. I get smooth application of power from idle all the way up, and I've been driving it for over a year with no further problem.

I suspect the trigger points, only because a new TPS did NOT seem to fix the problem. New trigger points are around $80, but on a car with over 100K, you could justify it as preventative maintenance even if it doesn't cure the bucking.

I still feel a noticeable transition when lifting OFF of the throttle at low rpms and speed, but this is only on deceleration and close to idle. On acceleration, there is no such lag. I think this comes from my '75's EFI being programmed to cut off the fuel when the throttle closes on deceleration, an emmission-related step. It causes no problems, but is definitely noticeable when the car is slowing down to near stop. Your '74 doesn't have this feature, I think.

So, to sum up, if you can rule out some obvious causes like a loose connection or ignition related problem, I'd replace the TPS AND trigger points if they are the originals.