NA 1.6 throttle response roulette

Technical Area Engine, Transmission, Exhaust etc
1
  1. My model of MX-5 is: 1990 mk1
  2. I’m based near: Black country, west Midlands
  3. I’m looking for technical help or recommendations on: dodgy throttle response

Before Christmas I noticed the throttle wasn’t responding properly, I would put my foot to the floor and it was 50/50 whether it would respond or just not rev at all. I got told it would be the throttle position sensor so got a new one, set it up properly with the feelers gauges but didn’t improve it any. I’ve also checked the throttle cable isn’t stretched and haven’t had any other suggestions.

Does anyone know of anything else that would affect the throttle response? I’ve had suggested possibly a vacuum leak in one of the old rubber hoses but want another opinion before I buy the silicone hose set if I don’t need to do that job yet.

Thanks

2

Is this when driving or when trying to increase the engine revs from idle when stationary and out of gear?

3

Doesn’t seem to do it when parked up and in neutral, only happens when it’s driving

4

How are your spark plug leads? It not an HT misfire when loaded up is it?

5

Haven’t considered them, I do have brand new leads and plugs though that I bought as part of its service so will try them after my holiday and get back to you, thanks :+1:

6

A quick check:
when it’s dark, proper dark, open the bonnet and prepare to watch the leads and coil-pack carefully. Ask someone to start the car and then gently rev it for you.

If the blue sparklies appear around leads and/or coil-pack; the leads are rotting, or a plug has gone high resistance, or both.

I found this out one winter evening in the mid 1970s with my old Bitsa after adding a home-brew CD ignition unit (loosely based on Ray Marston’s Wireless World circuit) for a bigger, fatter spark, and brand new plugs and leads.

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The new bright red Halfords Sparkrite leads turned out to be absolute dross, even the Manager could not deny the evidence of his eyes.
With refund in my pocket I refitted the five-year-old purple leads (which were still perfect) in front of the manager, and eliminated all blue pyrotechnics.

7

“Wireless world” that takes me back, I used to be an avid subscriber to “practical wireless”, also known as Camms Comic..