The best way to explain it is when you apply say 50% throttle, it seems to go between 45% and 55% on it’s own.
You can feel it speeding up in stages.
If you go flat out it seems to go away but it’s a bit annoying!
Any help would be great!
Check the throttle linkage. At the throttle body end, does the throttle open and close smoothly. Is there excessive play on the cable. At the accelerator pedal, when you depress it; is there movement in the bracket; are there any cracks in the bracket (1.6 gas pedal boxes can break, I think because of a sticking throttle cable)…
Basic throttle cable checks and adjustment:
Just given a go and the throttle is definitely better. Will give it a run tomorrow to test. Thanks!
Ok so this didn’t seem to work I’m afraid. Car runs almost perfect but it just has this weird slightly surging throttle. Hardly noticeable but it’s there. I have recently changed the tps to an aftermarket one from mx5 parts, could this be the issue? Worth trying to fit the old one?
Do all the basic checks; reset base idle (see Miata.net for instructions), Check all intake trunking connections are tight, and there is no damage tothe plastic, give the butterfly on the throttle body a clean (use xylene based intake cleaner NOT benzene based carb cleaner); clean but don’t scrub (clean before setting idle speed). What made you change the TPS? Fault code?
Ahhh ok great thank you, will have a look at all that. I changed the tps as the car was struggling to rev, bit that wasn’t the issue, it was the rear coolant temp sensor…
How old is the car? You have set the replacement throttle switch up correctly haven’t you?
The car is a 1990 1.6. I haven’t set up the TPS as such but I arranged it as close to where the old one sat as possible (can see the marks where the screws sat). I’m not sure how to do it properly, I’ve seen it needs feeler gages??
Cheers
Yes, it should be set up using feeler gauges and an ohmmeter. Do you want the process?
That would be really good if that’s ok?
Cheers
To check its adjustment, with a 0.4mm feeler blade between the throttle stop screw and the throttle mechanism, ie the throttle is open by 0.4mm, you should read continuity between the middle (TL) and bottom (IDL) terminals of the throttle sensor but no continuity between the middle and upper (POW) terminals. With a 0.7mm feeler blade between the throttle stop screw and the throttle mechanism you should not read continuity between any terminals and with the throttle wide open you should have no continuity between IDL and TL but you should have continuity between POW and TL.
Adjustment is a bit of trial and error, you basically set it by rotating the throttle sensor with the 0.4mm feeler blade in there until you are just on the point of continuity between IDL & TL, then change to a 0.7mm feeler blade and check that continuity doesn’t exist.
Brilliant, thank you very much for that!
I tried this, seemed to improve throttle response!
But the throttle issue is still there! Could it be the MAF? Or timing?
Have you tried new HT leads?
Not yet, I’ll try that next 
cheers
Ok so I tried new HT leads and no change. Have advanced timing to 14 deg and also no change. I’ve also noticed a lag sometimes if you step on the throttle quickly (rolling up to a roundabout about and then pulling out for instance)
Somebody mentioned the timing could be out by a tooth or so? How would I check this?
Thanks
Get in the drivers footwell with a torch and inspect your actual throttle peddle mount ( and the others whilst you are there ). Our’s had a crack which affected the way the throttle responded.
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