acceleration issue under 2000 rpm


Asked by Aug 21, 2013 at 08:48 PM about the 1990 Mazda MX-5 Miata Base

Question type: Maintenance & Repair

My 1990 mazda miata will not accelerate sumtimes under 2000 rpm, it is like it is under a
heavy load. When this happens you can push the clutch in and the throttle seems to
come back to normal, release the clutch and the problem may or may not return. You can
slip the clutch to get going and most of the time the problem goes away. I have
elliminated the cat and there was no change, so it's not a back pressure issue, some
suggested the mass air flow is having problems. Oh new ngk plugs, wires, pcv, air filter,
fuel filter, fluids were all changed and a new clutch kit was installed.

6 Answers

suspect a vacuum leak~ wave an unlit propane torch over the engine to pinpoint the leaker~

Michael Kane

My 1990 miata had the same issues, I too thought mine was the mas air flow flapper. It ended up being I had the dreaded short nose crank failure. I got lucky I was able to get it repaired without tearing apart the motor. The 90 was really the only year this was a problem for the Miata since Mazda installed a long nose crank for 91 and up Miatas. Heres a link on what to looks for:

3 out of 3 people think this is helpful.
Michael Kane

Heres another link with more info:

1 out of 1 people think this is helpful.

wow Mr. Kane, I had no idea...a simple design not considering the harmonics would actually make the bolt come loose and the keyway jostle around until breakage~~whew, am sure glad I didn't have one of those...what I did have was a BENT crank that I'd have never spotted until after installation...had to sell the was an Impala 400 a 1966 Chevy C10 sold it to a plumber in Marin Co.~....for five hundred dollars~

Michael Kane, You have a rather impressive garage of cars that you've owned. I've had like more than 26...not counting the fifty dollar SALT beaters to get through winter~

Michael Kane

Thanks Roy, I have been slowly adding all the cars Ived owned / driven / want. My wife and I have owned 13 Miatas over the years, I kinda have a soft spot for them. I noticed your classic benz you owned, i had a friend with the same car ( probly why I like Mercedes so much, lol ) I have fond memories.

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