1.8 Miata sluggish at low rpm

I just picked up a 97 Miata for a winter beater. I was told it recently started burning oil (a lot of oil).

I took it for a quick drive around the block today. Under 2000 or so rpm it feels a bit sluggish and the exhaust note sounds funny, a little buzzy. When it is sluggish there isn't much smoke out the exhaust.

After that it picks up and accelerates much better. When it picks up the exhaust note changes and it blows a lot of blue smoke. In neutral it seems to rev freely.

Any thoughts? I am going to check to see if the catalyst is bad. The check engine light is also on but I will have to wait until I get plates on it to check that out.

Dunno but an oil change followed by an Italian tune-up cures a lot of ills in neglected cars. Good luck with it, NA's are fun.

In my world, every engine diagnosis starts with a leak-down test and a vacuum gauge. From that data you can make informed decisions.

Stuck PCV valve?

Could be mis-timed, could just be that it's a high-strung little engine, I don't recall my Miata having any power down low even when it was running like a top.

Check the crank keyway.

Italian tuneup. Go from there.

I'm inclined to suspect severly leaking valve stem seals, based on your descriptions. Low velocity flow through the combustion chambers lets the spark plugs get a film of oil on them which is sucked right down the valve on the intake stroke, then when the revs climb the increased crossflow combined with the bigger shot of fuel cleans the oil off (allowing the plugs to fire normally) and blows it out the exhaust. When you get then chance, drive it low RPM for a few minutes and let it run like crap, BUT don't let it rev enough to blow the spark plugs clean. Then pull into your driveway, shut it off, pull the plugs and tell us what you see.

In reply to WildScotsRacing:

Bad valve seals will give a big puff on startup from oil creeping down onto the exhaust valves when the engine sits. Usually a gradual thing to happen too.

I have never ever had any meaningful luck with the 'Italian tune up' I do like the Italian guy tearing off the rear-view mirror in whatever that movie was.. A complete and real honest to goodness tune up with real parts and timing and go from there has yielded better results for me.

the beauty of driving a stock-engined NA1.8 is you can give it the Italian tuneup on your daily commute without attracting too much unwanted attention

Slyp_Dawg wrote: the beauty of driving a stock-engined NA1.8 is you can give it the Italian tuneup on your daily commute without attracting too much unwanted attention

Unless, of course, you happen to have a FM exhaust on it

The crank is not wobbling. I am going to try a new pcv valve. The weird part is the very distinct change from sluggish to more powerful that occurs at the same time it goes from little smoke to billowing blue clouds.

I am getting plates for it today so I can drive it more and try some different things.

Timing belt off by a tooth?

WildScotsRacing wrote:

Slyp_Dawg wrote: the beauty of driving a stock-engined NA1.8 is you can give it the Italian tuneup on your daily commute without attracting too much unwanted attention

Unless, of course, you happen to a straight pipe on it

FTFY

About the same symptoms as a bad crank on the NA except the smoke does not make any sense. Timing belt off by a tooth might have same symptom. Sure there is an easy way to check?

If it is a bad pcv you might have the equivalent of a vacuum leak at low rpm, and when you open it up the significance of the leak diminishes since it is relatively small compared to the total air-flow.

Do post results when you get them.

If the cat wasn't bad before it started burning oil, it surely is now.

Knurled wrote: If the cat wasn't bad before it started burning oil, it surely is now.

That was my thought as well.

I'll do some more testing now that I have plates and report back.

I'm going to +1 the timing belt. My Subaru's timing belt was off a tooth, and it had a very nonlinear power band. Lightswitch at 3500rpm.

This wouldn't have anything to do with the smoking, but there's no rule that says an engine can't have more than one problem.

Disconnect and plug the PCV hose and try again. Just let the cam cover vent to atmosphere

Might be worth checking the other hose on the DS that goes from the cam cover to the front of the throttle body. See if it is full of oil and/or cracked?

codrus wrote: Timing belt off by a tooth?

I would go with this. My mother's Escort did the same thing. About a month after the belt was changed I drove it and it wouldn't accelerate. Either it jumped or was installed off a tooth but changing it straightened it right out.

Can confirm mine was off by a tooth and exhibited similar symptoms, minus the blue smoke, and plus hesitation off idle.

If the timing jumped one retarded, it will be gutless like that.

Do you have any codes?

Is it just that it doesn't have a turbo hanging off of it?

wae wrote: Is it just that it doesn't have a turbo hanging off of it?

You know, that could be it.

I'm going to pull the codes tomorrow.