NA 1.6 judder between no throttle and light throttle

Technical Area Engine, Transmission, Exhaust etc
1

I’ll try to describe this as best as possible.

At very light throttle applications either applying light throttle from no throttle or coming off the throttle all together, my car is very ‘lurchy’. It cannot be driven smoothly in slow traffic at all. When I first got the car a few weeks ago, I just put this down to me being out of kilter with a traditional cable throttle response and being too heavy with inputs but now that I have spent more time in the car I know something is not quite right. There is no way to drive it smoothly anywhere around the 0-light throttle zone. This is NA number 6 for me as well and I don’t remember any others being like this.

So… how to diagnose and fix? My strong suspicion is that I may need to check and/or adjust the TPS but before I dive into something like that I thought I better seek some more knowledgeable opinions.

  1. My model of MX-5 is: __ Eunos 1600 1992
  2. I’m based near: __
  3. I’m looking for technical help or recommendations on: __
2

Sticking cable or stuck dashpot?

3

Thanks ast. Both seem okay but I did some general investigating around there and eventually started testing the TPS continuity and found that I was getting continuity with both 0.4 an 0.7mm feeler gauges so I set about adjusting it and then found to my surprise that the upper fixing bolt was in fact completely missing and the lower one was relatively loose so the TPS could actually already move around. I spent a while setting it up to I get continuity at 0.4mm but not 0.7mm so I’m hoping it’s now fixed but I didn’t have time to road test it tonight. I’ll report back.

4

I had a Mk1 that had an odd hesitancy at 4k rpm. Traced to a bad earth for the TPS. The connector for the TPS loom sat under the CAS O-ring. Years of oil leaks had cooked the wiring. The earth actually runs bak to behind the dash. It was easier to run a new earth to the block. Problem fixed.

5

Cheers. I should get a chance to drive it at the weekend so if the issue is still there I’ll be sure to check the wiring.

6

Well, just in case it helps anyone else, I’m very pleased to report that I now have an engine that responds beautifully to the throttle. No hesitations anywhere. It did turn out to be the TPS being not properly secured so I guess it had gone out of adjustment or was just bouncing around a bit. With it properly set up and secured the car is a totally different animal. I wonder how long the previous owner had suffered that.

1 Like