Surge on throttle depression

[stevestafford]

Only driven 2 MX5's, both Mk1 and 1989's, the one was very smooth but the other, the one I bought, has a little surge just as you press the accelerator, nothing dramatic but the other one didn't behave this way and hence was smoother to drive. Also the one I bought runs a little lumpey in 3rd 4th and 5th gears when engine is at low revs, typically around 2000 rpm. Quite ok at higher revs in all gears.
I've changed plugs and leads but nothings changed.
Any ideas?
Steve.
Car is 1.6 Eunos 1989 imported in 2003 manual

[stevestafford]

Just thought b4 some bright spark says it's supposed to do that, it does this when you just want to drive slow and just press the throttle lightly not with the intension of accelerating hard.

[MX-5 Lazza]

Could be a problem with the TPS sensor. Not sure how you test it to be sure though.

[tuttle]

This might sound a bit like stating the bleedin' obvious but check your throttle cable for slack.

[stevestafford]

It's ok Tuttle sometimes the obvious does get missed, I took the slack out of it first thinking that was the problem but no change.

TPS, is that throttle position sensor?

Steve.

[The Tea Boy]

HT Leads? just a random stab after you saying you had done the plugs.

Matt

[MX-5 Lazza]

He said he changed plugs & leads

TPS is Throttle Position Sensor. On a Mk1 I think it's basically a 3 position sensor - closed (idle), open and WOT (wide open throttle). If this is shot then it could cause some odd problems.

I'm not saying that IS the cause, just that it might be. I'm sure there must be a way to test it, try looking in the garage section of miata.net.

[stevestafford]

How do I access the garage section?
Steve.

[MX-5 Lazza]

It's here

I just had a quick search and didn't find anything relevant. A more in depth search might be more fruitful - these things are often hidden away somewhere. Could try a search on the miata.net forum too.

[ncow82]

Mine does this as well. Cant say I'm bothered much but was thinking about it all the way home today.

[stevestafford]

Yep, it's not a big problem and I'm wondering now if it's connected to the not so smooth running of the engine at aroend 2000 rpm, most noticable in higher gears 4th, 5th.

With this in mind I'm thinking about getting it checked out to see if there's anything that can be adjusted on the engine?

I'm based in Stone ST15 Staffordshire, is there a place around here that knows the ins and out of the MX5?

[bert11]

I have the same problem. I'm due to inspect the air intake butterfly thing to see if its operating smoothly; my idea is that it is allowing a sudden surge of air through.

Some thing might need smoothing in that area?

[MX-5 Lazza]

I'm not sure a Mk1 has an "air intake butterfly thing" if what you mean is VICS.

[stevestafford]

bert11 said:

I have the same problem. I'm due to inspect the air intake butterfly thing to see if its operating smoothly; my idea is that it is allowing a sudden surge of air through.

Some thing might need smoothing in that area?

Hi, did you find anything causing your surge?

Mine seems much worse when the engine is cold, more obvious now weather is cooler.

Steve.

[youngsyr]

My Mk2 10 AE surges too on light application of throttle, but runs fine at all rpm. I'm not sure whether the surge is perhaps due to the slightly more aggressive BP5A inlet cam fitted in my engine as standard or perhaps being mapped to make the engine seem eager, but I'd be interested to hear if others solve the "problem".

Edited by youngsyr on Friday 17th September 11:51

[ncow82]

http://www.miata.net/garage/isc.html

Quick clean most issues disappeared. Got to take my car apart in the kitchen (always a pleasure).