Cookie Monster

'90 Miata bought it cheap hoping to fix it up. The engine was abused had low compression and no power, had short nose crank issues. Replaced the engine with a good one. The new one has excellent compression but still has no power!!! Starts right up it idles pretty smooth but has a slight rocking motion to it at idle. It hesitates really badly and accelerates very slowly.

Checked the AFM, it moves freely. I swapped the FPR with a good one same results, checked the fuel pressure was at 44.5psi iirc with vac hose off. I even clamped the return line to get 90psi fuel pressure and it still won't accelerate. Checked for vacuum leaks, didn't find any. checked ignition timing it's at 10* and the crank pulley is spot on never slipped. Timing belt is good and it's set perfect. Has new plugs. The new engine has 130k miles and has a long nose crank with about 185 on all four during the compression test. It has the same symptoms as the old engine but this one idles much better so WTF?

Some parts were swapped from the original motor to this replacement engine. Includes: Valve cover with pcv, CAS, Intake manifold.

flounder

Check for spark on all four, sounds like a bad coil.

Joe Perez

iTrader: (8)

Sounds about right for a stock 1.6 engine. I assume you're running the OEM ECU, and that the problem is worse when the engine is cold?

Stealth97

iTrader: (5)

Unbolt the cat and see if it runs better, it will be loud and sound like ****, but if the performance increases drastically the cat could be clogged.

curly

iTrader: (25)

The cat's a flash light away from being eliminated as a problem, I wouldn't rely on your butt dyno to tell the difference.

I vote the coil or spark plug wires. I've got a few extra stock coils I could sell you for cheap.

hornetball

iTrader: (4)

Needs turbo! These cars stock are pretty doggish, especially at higher elevations.

Others have covered the basics. I'd add to check/replace the fuel filter and run some injector cleaner/gas drier through the tank. Might have water/rust if it sat before you bought it.

Cookie Monster

Yes, it's 100% stock including ECU.

Oh yeah, I already ran it with header only. Still no power. I checked the spark and fuel injectors by disconnecting a fuel injector one at a time and each time I disconnect one it runs like junk so I know it's it's getting spark and fuel.

Some of you are saying 1.6's are slow stock but when I say it's slow I'm talking really slow! I seriously doubt this one will do 65mph! I've had many of these cars and I still have my '91 turbo car and I know how they run stock.

I revved it in the driveway before putting it away and noticed it absolutely will not rev over 4900rpm! It was in neutral wide open throttle and will not rev over 4900! I tried several times! The engine sounds like it wants to choke! lol. What would prevent it from going over 4900 rpm?

It runs like this hot or cold.


I will be swapping parts from my turbo Miata to see what's good and what's bad starting with the coil pack, cas, and ecu.

Cookie Monster

Yes, the cat was melted inside when I bought it. But even running on open header it still has no power!

Leafy

iTrader: (1)

Did someone put a tornado in the intake tube and it collapsed?

hornetball

iTrader: (4)

There's a 90-93 Mazda OEM FSM here: https://www.miataturbo.net/useful-sa...-manual-48633/. You should download it.

Referring to F-56 of the FSM, possible causes:

1. Low intake air amount
-Thottle valve not open fully (this step incudes checking the throttle switch and making sure the ECU receives it and responds)
-Clogged intake air system

2. Air/Fuel mixture too lean or too rich
-Fuel line pressure low or high
-Insufficient fuel injection

3. Poor ignition

4. Low engine compression

The FSM then goes on with a great sequence of troubleshooting tests to run. One of the things that it checks in several of the steps is the ECU. Assuming you've got air, fuel and ignition at 4900RPM, it could be a bad ECU.

krissetsfire

iTrader: (1)

Since it's doing the same thing on both engines you probably do want to start with the parts you swapped w/. I've read other threads on m.net and the like where the symptoms you are describing are the CAS, Coils, Ignitor.