Engine breaking up at higher RPMs... need ignition harness diagram.
 

Okay so my car has had a 'hard start' problem ever since my engine was rebuilt, AND it is breaking up at higher RPMs while in boost. Me and my tuner Kane think there is something going on with the ignition. Did all the usual spark plug change, check wires, check grounds.

Tried searching the entire internet and there is nowhere I can find the diagram for the ignition harness to coil packs. After inspecting my harness I can see one of the plugs has a white tape marking around it so I am assuming that there has to be a correct sequence to plugging them in.

Well just for shits and giggles I swapped the harness plugs for the rear rotor coil packs and it seems to have fixed my hard start issue.... BUT, it is still breaking up at higher RPMs. Now I don't even know how the car could actually run with the sequence out of order but it obviously can, because it was running before and after i swapped the harness plugs.

So can somebody out there provide me with that diagram ? and any troubleshooting thoughts ?

This help you at all, or do you need more?
See the attached pdf file for deciphering the wire colors.

While your ass hole response is clever, no that does not help me. After 2days of searching the internet I have found what I'm looking for below.

http://ww2.justanswer.com/uploads/su...02837_rx81.gif

Plugging the coil harness connectors in is pretty self explanatory based on length. I have never hear of anyone screwing this up. But I'm glad you found a wiring diagram.

Does this hard start problem occur when the engine is cold?

The hard start problem is only when the engine is warmed up---- which would lead most to say compression, but we checked compression and its good. Like i said, I swapped the two rearward most coil plugs and it seems to have fixed my hot start problem. I will be comparing to the wiring harness diagram shortly.

How did you check compression? With a rotary engine compression tester? What was the cranking RPM? Did you adjust the reading for altitude, temp, etc?

It's likely compression unless you are seeing some pitiful cranking RPM's. How many miles are on the engine now?

I really have no details of the compression check, the builder was the one who did it. And I do have the old weak ass starter, which I want to upgrade to the 2kw. Engine has 1,000+ now.

:lol:, the guy who built it did your compression test? Well of course he is going to say it's fine. And I highly doubt he has a rotary engine compression tester, but it's possible. If he used a piston tester then the results are mostly useless.

And if it has 1,000 miles on it then it should be worked in by now. My bet is a botched build.

Take the car to Mazda and get a proper test done.

Yea, after 1000 miles if you are still having hard hot starts its compression... I'm betting those large exhaust ports are your main issue...

You used RA super seals right?

I sure hope not. The rear harness can definitely be swapped and the car will still run I'm finding out. Like I said my hard start issue seems to be sorted out. Still breaking up at higher rpm though, I'mgoing to remove tthis whole BHR ignition setup and inspect the wiring.

Theres a thread on testing the coils, you need a special tool.

Be careful not to ground yourself to the tool when testing... 40,000 volts even at 15 amps still causes stomach aches... Ask me how I know LOL.

What seals did you end up using?

I only ask because I just went through a similar issue using RA super seals and they chewed up my front housing. Another member and friend of mine used Atkins seals and he had an issue with them warping after a few hundred miles.

RA Super Seals

You fixed the hard starts by swapping around the ignition coil connectors? Sounds legit, :lol:

Well all I know is it went from taking 20 seconds to start to taking 3 seconds, seems legit to me.

Yea... I had 1500 miles on mine, swapped in a s2 started it helped a bit, but still had minor issues. Piston compression test showed fairly low compression in both housings.

I then got a proper test done with a rotary compression tester, rear housing showed way above minimum with near perfect compression. Front housing showed very low compression.

I just took the engine apart yesterday with the help of my friends. After 1500 miles the front housing was worn down horribly from the RA seals. The rear housing was in great condition with zero wear.

I would get a proper compression test done before you jump to any conclusions, but most likely the seals ate your housings, there is a warranty for super seals iirc... If you catch it in time you might get a refund and catch it before you permanganate damage your new housings.

Yea just removed the ignition setup and all looks fine. Next stepis borrowing some plug wires from another local RX8 then iI'll get a compression test from Mazda... Hopefully they can do it here in Germany :-/

Most mazda dealers have the compression testers. Some dealers only know them as pressure testers.

Compression Check

Bracing myself for the responses, but how do people feel about the methods on that link? The RX8 is an exotic car in my neck of the woods.... So I'm doubtful the dealer will have a rotary specific tester. However, I do have access to a regular compression tester.

Yeah I tried that method, it gives an overall sense of each housing. But its not 100%...

That said if you see an extreme difference say 120 psi int he front housing and 60 psi in the rear you can bet your ass the rear is shot.

Give it a shot and see what you find, pay attention to your cranking speeds with the cobb and log them.

I would call around and try to find a legit rotary compression tester. If they sell RX-8s they should have a compression tester on hand.

looks like there's a dealer close to you that can do flashes, I imagine they can compression test as well.

https://www.rx8club.com/europe-forum...europe-170906/

Yeah the piston method just leaves too much room for error and the results are not specific. Even with the proper tester the results need to be corrected in order to get an accurate reading.

Our point is stop dicking around with other guesses and get it tested so you know one way or another. having solid compression test results gives you an idea of how your engine stands and if compression is good then you can start actually troubleshooting.

This ^^^

1) Ignition, verify all is well.
2) Compression Test

The compression issue would likely not cause spark breakup at high RPM's. But there is definitely something mechanically wrong with the car.