So we bought a 90 Miata with 108,000 miles that needed the crank pulley fixed. We were successful I think, timing is good about 11 TDC but it still runs poorly. It has new plugs, wires, air and fuel filters. Fuel pressure is 40 pounds. We put a new igniter and engine temperature sensor. We put in a different coil pack, no difference. There are no codes however it is sluggish, 0-60 18 seconds, you can smell gas on startup and under hard exelleration and fuel mileage is poor, around 17mpg. Compression is 145,140,145, and 150.not great, but not awful? If it was the O2 sensor wouldn't it throw a code? We are wondering if it might be the injectors but don't know how to check that without shotgunning parts. At idle it will rev with partial throttle but stumbles with full throttle. We could use some guidance. Thanks
Check that the timing mark is actually at TDC. Use something (dipstick, etc) dropped down the #1 plug hole to ensure you are actually at TDC, then the mark should line up with T on the scale. For more accuracy, pull the damper off the crank pulley and use the mark on the block and the notch on the pulley, then reinstall the damper.
It sure sounds like the ignition timing is way off. It's possible for the damper to fail and allow the outer ring (with the timing mark) to slip, so this could be completely independent of your fix.
Also, make sure you actually have the cam timing set correctly. Again, set to TDC and make sure the two marks are at 12 o'clock. If they're off, it'll be by a full tooth so it'll be obvious.
The cars can have errors without illuminating a light. Use a paperclip to pull any existing codes out of the ECU, but it's unlikely that would affect something like a 0-60 pull.
I'll recheck that, thanks
Also make sure the cam sprockets are installed correctly. Last engine I fixed had the I and E marks at the wrong spot on the sprockets...
Paragraph 3 :) Bit the symptoms aren't quite right.
So it was the timing. When we were moving the crank with a 3/8 drive ratchet the bolt came loose, and the mark is a bit off, maybe a tooth. We loctited it again, tightened it down ,and it runs OK now, I'd say average for a 1.6
I think the threads in the crank might be damaged.. When we were pulling it apart the first time,, the bolt was very difficult to get out. . Took heat and a big impact. We put it back together with a new bolt and loctite 242 and torqued it to 100 ft lbs, it shouldn't have been easy to loosen.
Where we're at today, it's running ok but I think it is time to start looking for another engine, a big snout 1.6 or a 1.8. I don't think the keyway repair is going to last. It was pretty bad to start with but it was worth a shot .
Thanks for the help
Are you thinking of now updating to a 1.8? Where are you approximately located? I have the entire wire harness and drive train out of a 1994 Miata. Still need to lift the body off.
In reply to BlindPirate :
If the timing mark moves with the crank bolt loose, you definitely have a key way problem. How did you try to fix it, the Loctite recipe?
Yes, used the loctite fix. I knew it was kind of a longshot, the keyway was pretty mangled but thought it was worth a try.
MyMiatas I'm in Illinois
In reply to MyMiatas :
I may be interested in the harness, if no one else jumps on it.
To far, a parts car there would be better and cheaper. Or just a "new" crank to install.
BlindPirate said:
Yes, used the loctite fix. I knew it was kind of a longshot, the keyway was pretty mangled but thought it was worth a try.
MyMiatas I'm in Illinois
If it's any consolation, I did the Loctite fix on my short nose crank Miata in 2016 and it has still held up okay.
