Need help w/ 99 Miata

I just found a deal on a 99 Miata that I couldn't pass up. It appears to have the #4 cylinder problem, but I haven't been able to check it out yet. I have been told that one of the cylinders has no compression, but they weren't sure if it was #4. The car has 90K miles, and I thought that the #4 problem usually happens earlier than that. The car was purchased by a kid 4K miles ago and he defaulted on the loan. I bought it from the bank. Supposedly the car was completely checked by a mechanic at the time the kid bought it and it was fine. Seems like it ought to be hard to break a Miata engine in those 4000 miles!

That's the background, my question is .... What is the best/most cost effective way to fix the problem if it is the #4 issue. Looking quickly for engines online, shows that the 99-01 engines are more expensive than the earlier 1.8 engines. I suspect that all I would need would be the short block. Is there a reason why I couldn't use the earlier 1.8? Also, what about the 2002 and later engines. I know that they went to variable valve timing, so I am sure that that adds a level of difficulty. And I have also heard that a Ford 1.8 from an escort can be used, but I would prefer the solution to be as much "plug and play" as possible.

I already have a 5.0 Miata, and the LS1 option hasn't escaped me, but I need to pass emissions in Ohio, and the OBDII body with and engine swap, might not be licenseable. If anyone has any Ideas on passing emissions I would love to hear those also. Is there a way to make a by pass that tells the OBDII reader that "Hey I'm a mild mannered Miata minding my own business, and every thing is cool!"?

A compression check first and then a leak down test will help locate the problem. Could be something with the valves .

The "#4 issue" usually refers to a thrust bearing problem, not a problem with the #4 cylinder. Check the crank end play. If it's out of spec (don't know what it is offhand, but it's a few thousands IIRC) then you typically want a new bottom end as most people don't do anything until the crankshaft is busy machining itself against the block. But the thrust bearing problems did manifest themselves pretty early, so it's highly unlikely that's your problem.

So, what is the car actually doing? If it doesn't have compression in a cylinder, then the head's coming off to fix the car regardless. You can drop compression either by detonating hard and hurting a piston or by overheating and popping a head gasket, both of which can be performed over a very short distance.

To answer the engine swap question: all the 1.8 bottom ends are slightly different (mostly in compression ratio), ranging from 8.8:1 to 10:1 and rising through the years) but interchangeable. The reason the 1999-00 engines are more expensive than the 1994-97 is they have a better head - and that head was only available on the 1999-00 Miata, not any of the other BP implementations. But you can put the head on any 1.8 bottom end, and as long as it hasn't been starved of oil pressure (again, typical of a thrust bearing problem with the sort of owner that comes in when the engine stalls when the clutch is depressed) it'll be okay. If it has been starved, the cam journals are the first to go.

A VVT 2001-05 engine definitely and dramatically adds to the difficulty of the swap if you want to keep the full VVT function. If you don't want to keep full function - some people claim it works okay if you run it as a two-postion setup - then it's easier. But I wouldn't bother.

There are no OBD-II bypasses. A magic OBD-II spoof box would be a wonderful thing to have, but so illegal. Get the Megasquirt crowd on that.

Thanks Keith. I just got the car home, and I can start doing some Diagnostics. I'll post what I find. I didn't think that it was likely that it was the thrust bearing, but I will check the end play. The battery is too dead to do much, so I am charging it and I'll play with it tomorrow.

Additional info:

Radiator has only water in it. Leads me to believe that it was run dry and could have overheated. (There was some pretty minor damage to the bumper cover and the very front of the hood. I doesn't look like it damaged the radiator, but it could have a leak under pressure.)

The computer shows "no codes"

No sign of coolant in the oil, but I haven't pulled the valve cover yet.

It will crank but not start. Sounds like it isn't getting fuel, or possibly out of timing. I need to check the timing belt to see if it could have lost teeth.

I'll do a compression check next.

I did a compression test, and compression in #1 is about 90, the others are 30 or less. Leak down showed that blowing into #3 comes out #4. I am hoping that a new head gaske is all it needs, but either way the head must come off.

You have to love the wonder that is Craigslist!

While looking for a solution to my cylinder head problem, I found a guy selling a complete '99 engine for $100. By complete, I mean from throttle body to exhaust manifold! All of the sensors, the clutch, coil packs and wires. Its only problem is that the thrust bearing failed.

This should provide all of the parts that I need to repair my car, but since it was so cheap and will give me a surplus of parts to sell off, it brings back the possibility of getting this car running for under $2009.

My question is .... Would it be better (Cheaper) to repair the bottom end of the $100 engine and put it into the car complete, and sell off the original engine, or pull the head off the new engine and put it on the original engine? What would it take to fix the thrust bearing issue in a Grassroots fashion? What would be the cheapest most readily available parts that I could use? (assuming that the block is usable,)

For Challenge purposes, if I understand correctly, If I fix the original engine, I could only sell parts off the new engine for a total of the $100 that I spent for the motor. If I put the $100 motor into the car, I could sell the parts that I take out of the car for a total of $1004.50. ( I bought the car for $1800.) Or I could leave the original short Block in the car and swap to it as many of the parts from the new engine and sell the otherwise perfectly fine parts that came with the car. While I hate to do unnecessary work just to artificially buy down the challenge budget, this seems like the most expedient way to maximize my Challenge budget.

Any suggestions?

IT .... IS.... ALIVE!!!!

Fired on the first try with the "new" head! Runs great, but haven't driven it yet.

'Grats. Sounds like you got a sweet deal.

Thanks.

I got lucky....twice. Driving it may cause other problems to show up. But I am not expecting too much else to need to be done.

Pull a cam cap and check the condition of the journals. When the thrust bearing fails, oil pressure drops. One of the first places to take damage is the head.

Thanks Keith. I will.

Keith wrote: There are no OBD-II bypasses. A magic OBD-II spoof box would be a wonderful thing to have, but so illegal. Get the Megasquirt crowd on that.

couldn't you just get a 99-up LS1 with ecu and harness, then when the inspection folks hook up to it, they get the "no codes" from the ls1 ecu. not like you're wanting for power with a stock ls1 in a miata anyways. if so, theres all sorts of stuff that is emissions legal for them as well.

dunno if ohio is similar to texas or not, but in texas as long as the engine that goes in is from the same year or newer, it'll pass inspection.

The legalities change from state to state. Every LS engine came with OBD-II and it's not that hard to make it function - although it may have some complaints about obscure things like fuel tank pressurization due to the different size of the tank. I don't think ours has complained about that one yet though.

A stock LS1 would be plenty. I live in one of the counties in Ohio that requires emissions testing. On the OBD1 and older cars they use a sniffer test and as long as the new engine is cleaner than the numbers assigned to the body you are good to go. My 88 RX-7 passes with a 350 Chevy and a pretty agressive cam, carb, and hollowed out cats. My 92 Miata passes with a fuel injected 5.0 with 2 cats. It is less than 10% of any of the emissions requirements.

On OBD2 cars they plug into the test port and if there are no codes, the car passes. Does the computer tell the code reader, what engine is in the car? If I put a LS1 into a Miata and installed the OBD port in the same place as the stock connector, would the LS1 computer just tell the reader that there were no codes, or would it tell it that "I'm the wrong motor for this car, but otherwise I'm runnig fine" ?

Mallet is putting LS1 motors into Solstices, here in Cleveland, they must have a way to make them legal, but I don't know how they do it.

You don't have to move the OBD-II port, just hook up a couple of wires. It does not identify itself as the "wrong engine", but a savvy tech might notice a couple of extra O2 readouts :) If all you need is a clean bill of health from the OBD-II system, that's certainly doable.