Engine shaking at idle.

[NobleRogue]

glad to help where I can.

[— Madaboutmx5s —]

Well I had a play around with Friday:

1. Did the compression test again the proper way: 180, 180, 180, 150 (same cylinder that was down before)
2. Checked timing and even with base idle reset in place difficult to get a reading due to engine shaking and best guess was it was around 16 degrees.
3. Checked for air leaks again but found nothing.
4. Played around further with base idle reset to adjust revs but still its lumpy on idle.

To add to the fun the clutch slave cylinder seems to have packed up as clutch wouldn't engage and foot went straight to the floor with clutch pedal. I've hopefully done a temporary fix as clutch fluid was low so topped up, pumped system and got it going again but imagine slave cylinder has failed. That adds to the slipping clutch I had.

Likewise spoke to a mx5 specialist I know well and given the short crank engine and the other bits I've replaced they also mentioned it could be a bad loctite fix done before I got it. They have a car running lumpy like mine before but like a bandit down the road (like mine) and this was the route cause.

So plan of attack is new clutch, new slave cylinder and I think a decent replacement engine. I've found a 108000km so around 67000 miles long nose crank JDM 1.6 engine with good even compression around 175 across all cylinders. Likewise will come with the inlet manifold, fuel rail, idle control valve, throttle body, CAS installed and I've heard it running so makes the change easier.

So the red car will now owe me more and seems extreme replacing the engine but given the tests all seems to point back to the engine don't see anymore point in wasting time on it. Whilst I bought as a non runner I was told it ran fine before being parked up but think the issues I've found was probably why the car was laid up for the last 2 or so years.

[NobleRogue]

My advice would be to keep the old engine after the swap. Do a leak down test to make sure the block is not cracked. If it is not cracked. Keep it as a back up. Looking at the compression numbers you are looking at a top or bottom end rebuild maybe even a complete rebuild. Or if you are particularly lucky, it may only need a new head gasket. Also your timing should be at 10 degrees before top dead center at 850 rpm. This to is obviously a cause for your rough idol. Before you go replacing your engine. Adjust your Cam Position Censor and fix your timing. Then do another compression test. You might be surprised at the result. Then again like you said you may have gotten a loctite P.O.S.. If this is the case and the block is not cracked you could use it as a project block. Bore it. Stoke it. do whatever you want with it. make yourself a nice little sleeper Miata. You will be taking down Porsche's in no time.

[— Madaboutmx5s —]

Thanks for the advice. Even with the ecu in reset mode on the diagnostics and adjusting the cam angle sensor it was difficult to get a timing reading as engine shaking at idle. Best guess was 16 degrees when adjusting it to improve the lumpy idle a tiny bit. Whilst it going to wipe me out I think replacing the engine, clutch, slave clylinder will hopefully resolve the issues. Positive is the car is a 2009 Japanese import low mileage 1990 roadster and never welded solid shell so out of all of this I'm putting together a nice (abit more expensive then I planned) restored roadster.

[NobleRogue]

I hope you enjoy it.

[— Madaboutmx5s —]

I hope you enjoy it.

Thanks.

[alexlula]

Could be the engine mounts ??

[— Madaboutmx5s —]

Hopefully now resolved the issue as fitted a long nose crank engine which fired up today. This had even compression of around 175 and had done 108,000KM so about 67000 miles. Whilst it went in also replaced all the coolant hoses with silicone versions, replaced the radiator, fitted the missing engine under tray whilst the clutch that was shagged has also been replaced with a new one together with a new clutch slave cylinder. Started fine first time and warmed up to temperature OK and the lumpy idle and vibration has gone away. Still on the ramps at the moment but hopefully will get a drive tomorrow.

[NobleRogue]

Glad to hear it. One thing though. Since you replaced the Clutch slave cylinder you will want to replace the clutch master cylinder as well. If you go to long without replacing it you risk getting stranded. Often times the new slave cylinder will cause an old but good master cylinder to blow out. It's like replacing the wheel cylinders on drum breaks. If you replace one you need to replace the other.