Cold start problems

[EGG80X]

I noticed recently the engine hesitates to accelerates below 3500rpm on cold starts once its warms up its fine....... also still having idle dip when the engine is cold too grrrrr

[fig]

Join the club!

Where are all the so-called experts when you need 'em

Someone must know of a solution?????

[Garry]

I fixed my idle dip by cleaning the air bypass passage. Both my MX5's ran like crap when they were cold on light throttle low RPM. Quite normal according to several Mazda Dealers. Though replacing the oxygen sensor helped my SP considerably.

[DanielB]

My NA 1.6 experiences this too. On a cold start, if i bring the revs to say, 3,000 and hold the throttle there, it will slowly dip down to say, 1,500 then climb back up, and does this over and over until the car is warm

No idea what the cause of this is. New plugs/leads does nothing.. It feels as though the car is only running on 3 cylinders when it's doing the above.

[Andrew]

You guys tried this -

I'd be guessing contamination of the throttle body - either clean it, or adjust the bypass screw.

[JBT]

Be careful what you use to clean the throttle body because it can be damaged with the wrong solvent. See miata.net garage or search that forum for more info. Also see the post here by Fra66L.

[Craig]

My NA 1.6 experiences this too. On a cold start, if i bring the revs to say, 3,000 and hold the throttle there, it will slowly dip down to say, 1,500 then climb back up, and does this over and over until the car is warm No idea what the cause of this is. New plugs/leads does nothing.. It feels as though the car is only running on 3 cylinders when it's doing the above.

Crappy running whilst cold and OK when hot is usually attributed to the Oxygen Sensor. It can't get a reading so it goes into a limp mode.

[Andrew]

Be careful what you use to clean the throttle body because it can be damaged with the wrong solvent. See miata.net garage or search that forum for more info. Also see the post here by Fra66L.

Here is his post to stop any confusion -

Normal NB8A problem.

Try taking off theintae crossover tube and caefully cleaning the throttle body and butterfly plate with a VERY SOFT, CLEAN rag and some (oxygen sensor safe) carby/throttle body cleaner (pressure pack can). I do this every oil change and it pretty much eliminates the problem.
The throttle clearances at idle are marginal and once you have a nice coating of Ick (technical term) thanks to EGR and PCV, the clearance is worse so a regular clean keeps things happy...

Cheers,
T