MX5 no power

dr.fuzzenstein · 03-10-2014 11:42am #1

Have a 00 MX5 1.6 and it is very slow. 140k miles. Always babied and serviced.
It starts fine and runs good, but let's just say you stick it in 3rd and floor it, it revs quite slowly and painfully. There is no power or pickup. I have driven faster Micras.
Work carried out so far:
Usual service items, e.g. oil and all filters, new sparks and leads, new coil pack, new cat (rest of exhaust OK), new oxygen sensor, timing belt, water pump, rad (not related, but to give a picture), there is no smoke, engine sounds fine, burns very little oil, uses no water, sparks have nice, even, light, grey-brown coating (clean/replace makes no difference), no warning lights and when I hook up diagnostic, no error codes. There is some hesitation, but only when the engine is cold and just been started, once on the go,it is fine.
Hooking up diagnostic in them involves shorting out two terminals and stick a multi-meter in two others and codes are displayed in electric signals.
I did short out those terminals once but after replacing fuse, it started again, thought I fried my car's brains there for a second.

What could be the issue here? One thing I haven't changed is the MAF (Airflow meter) and I'm contemplating doing this next.
Problem is, they're expensive new and I wouldn't trust them second hand.
Any suggestions where to go from here? I do suspect MAF, because it has eaten two catalytic converters over the years, i.e. burned a hole in them.

hi_im_fil · 03-10-2014 1:13pm

I'd check the timing. If its not timed right it won't make the power its supposed to.

dr.fuzzenstein · 03-10-2014 1:51pm

Alright, will try, this video seems to be good.

https://www.youtube.com/watch?v=3CL563X1Oqs

dr.fuzzenstein · 08-10-2014 9:32am

I checked the timing.
The MKII MX5 does not have a distributor cap, but a solid state coil pack.
Timing is picked up via a fixed sensor from the cam. Very little can go out of whack.
The crankshaft pulley has two marks (Damn you Mazda!) that line up with a scale.
One mark lined up with 0 and the other with -10 under the gun, so ignition is either absolutely spot on or 10 degrees out. And if it was 10 degrees out, the car would run like a bag of nails, which it doesn't.

Will try new airflow meter and see where that leads me.

Waterson · 08-10-2014 9:43am

If you have access to a scope, this will be your best friend in diagnosing this problem. I think youre probably onto something with the airflow meter. The reason you have no fault codes pertaining to it could be that the failed unit is still operating within whatever parameters are pre mapped into the PCM. If you can get hold of a workshop manual and get the specs for voltage output at a) idle, b) mid range load i.e. 3rd gear 3000 RPM and c) wide open throttle and compare these with what your MAF is putting out, it will give you a direction to move in. Similarly fuel trim values are very inciteful for these types of low power issues.

dr.fuzzenstein · 08-10-2014 12:51pm

Oscilloscope? Bit tricky that, only have a few multimeters lying about the place, but will dig up a manual and check voltages.
The airflow meter is a three pin type, how hard can it be?;)

Waterson · 08-10-2014 1:15pm

dr.fuzzenstein wrote: »

Oscilloscope? Bit tricky that, only have a few multimeters lying about the place, but will dig up a manual and check voltages.
The airflow meter is a three pin type, how hard can it be?;)

Ha ,I get you there, the only issue I find with testing mafs with multimeters is that they're too slow to register the quick changes in voltage when say you blip the throttle (and if your problem is a hesitation in acceleration, this can be revealed with a scope). However they're grand at WOT and idling conditions, checking supply and reference voltages etc. I wonder how she drives with the MAF unplugged...

dr.fuzzenstein · 08-10-2014 1:54pm

Wonder if there's an Android app for that?

edit:
turns out, I wasn't far off the mark:
http://www.instructables.com/id/Use-Your-Laptop-as-Oscilloscope/

Waterson · 10-10-2014 4:17pm

dr.fuzzenstein wrote: »

Wonder if there's an Android app for that?

edit:
turns out, I wasn't far off the mark:
http://www.instructables.com/id/Use-Your-Laptop-as-Oscilloscope/

Good find sir, that looks like a sunday afternoon project...

vinnie13 · 13-10-2014 5:53pm

My guesss is it's just a slow one.
We had two identical Fronteras here a few years ago both running great one would fly past the other and pull better.
Fuel consumption was pretty much the same

MX5 no power

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