Dealer compression test questions
 

Long story short. Bought a 2005 RX8, automatic 15 months ago. Ran beautifully. Son takes it to college, uses premix, I have him get the oil changed roughly every other month. He doesnt put a lot of miles on it. He redlines it every chance he can. It has 43,000 miles on it. We just drove it from Texas to FL and Back in June, had the oil changed on both ends and she ran perfect.

Last week he says it put him into limp mode. Because I am out of State and he is in EL Paso, I could not find a good Rotary shop, so I sent him to the dealer. It starts right up, idles fine, runs good cold for 5 miles or so, then limps.

Dealer ran a compression test and said it failed because too much oil is getting pumped into the motor and the apex seals went. Suggest replace motor. I have attached their test. My questions, what else should I do before going with a motor replacement? I know I am 10 years into it, so Mazda prob wont warranty it, it does have low miles. Thoughts? What would you do?

Any advice would be appreciated.

"too much oil is getting pumped into the motor and the apex seals went"
This is not a thing.

Before we get into engine replacements on your own dime, is there a check engine light and a code?

Sorry about that. The only 2 codes they found were:

P1687 Metering Oil Pump Stepping Motor Cont. Circuit #3

P1688 Metering Oil Pump Stepping Motor Cont. Circuit #4

That's good. Not saying your motor isn't in trouble, but this points to an isolated problem with the OMP, rather than general engine failure. Especially if you premix, it's not lethal. And yes, OMP codes will put you into limp mode.

I have no experience with those specific codes, but I'm sure you're not the first, take a look around for threads about that code. It could be as simple as a cut wire/loose plug, suggest further investigation of the OMP.

As for the comp test, sure, fine, but if it has been driving fine, I don't think the apex seals "went".

Thats good to hear. Im thinking at least a new OMP. Its better than a replacement. Thanks for your help.

They're actually really expensive, but I'd be surprised if the actual pump failed, more like the electronic sensor/controller or its wiring. You'll probably want a used one if you do go with a replacement.

Perhaps someone else is more familiar with that particular code.

Back to the comp test, let's say it's true and compression has worn down. You would expect the car to be difficult to start when the engine is hot. Any symptoms like that?

Its funny, sometimes when hot she starts right up but other times it takes a little longer. I dont think it ever feels like its having "trouble" starting.

He did comment last week that coming off the highway as he came to a stop it stalled. But then started right up.

I have a local rotary tech here with a used OMP for $250. My concern is the ability for a non rotary person to troubleshoot wiring to it or harness issues. Would you replace the entire OMP wiring harness too? I did read on the forums another guy had everything replaced and it turned out to be the harness in the end, but he was under warranty.

My issue is lack of a trusted tech out there.

https://www.rx8club.com/series-i-tro...issues-245126/

https://www.rx8club.com/series-i-tec...-179988/page2/


https://www.rx8club.com/series-i-tro...t-here-222584/


Starting the Engine
• Starter
• Battery
• Engine Compression
• Grounding Wires
• Ignition Coils
• Spark Plugs
• Spark Plug Wires
• Fuel Pump
• Fuel Injectors

She is up and running!
 

So basically, when the new(used) Oil Metering Pump was being installed, the wires and connectors appeared to be good on the OEM. However, just as the mech disconnected the connector, he said the red wire fell out into his hand. It seems it was detached but still looked intact.

New pump installed she fired right up. Now the compression could still be low however this RX8 is never going back to that dealer.

Thank you all for your help, it eased my troubled mind.

Good fix. Keep us informed, Cheers !