Beer Me!

I apologize that this is my first post -- I've been lurking here for approx. 1 year and wish I found the RX-8 Club much earlier. It is a fantastic compilation of information. I am hoping the community can help me understand a few things to help me figure out what I need to do next. I've read the newbie guide and Google searched the forum and gotten a lot of good info, however I have a few questions I couldn't find the answer to. From what I've read, I trust the info you can provide here more than what I hear from the dealer.

My Situation
I recently had my 2004 RX-8 (93k miles, AT) towed to my local Mazda dealership (Bommarito in St. Louis) because I could not get my car to start after replacing my battery (original was dead). It was discovered that the new battery I purchased from a local parts house was defective and the car started once rectified. I had the dealer run a compression test while it was there and it failed. Prior to compression test, the car appeared to run fine. I had trouble starting it on occasion in recent weeks, but I attributed that to the nearly dead battery and extremely cold weather. There is a chance I might be moving to Denver within the next month, I am trying to figure out whether to pay to rebuild / get a reman engine (I love my car!) or just get another more snow-friendly car as a daily driver. I am trying to make it last until I can find out for sure if I am moving.

The Compression Test Results (waiting for a callback to get the rpms):
Rotor #1 = 5.7, 5.6, 5.5
Rotor #2 = 5.4, 5.4, 5.5

Assuming that it was performed even somewhat close to 250 rpm, it would appear the time has come for my engine.

Car Details:
* I am the original owner (purchased in 2004) and have followed the Mazda maintenance schedule like a blind sheep.
* The car is my daily driver and was typically driven on 15-20 mile one-way highway commutes and around town, with periods of sitting 1-2 weeks at a time at airport for business trips during its life.
* No mods, all OEM parts except the exhaust (replaced 2 years ago due to rust).
* Spark plugs/wires were replaced once around 50k miles
* Original starter
* Thermostat failed around 75k and was replaced, but no other major corrective maintenance has been done.
* It has never been de-carbed (unless it was part of the 50k major maintenance).

My questions are:
1) Is the engine truly screwed (as I suspect) or is there something I'm missing? Any additional questions I should ask the dealer that performed the test?
2) Is there something I should do to try to temporarily extend the life of the motor (PreMix?, Worth paying to decarb and replace the plugs/wires (that other members have had some success with)?)
3) If it is failing, what should I expect as I continue to drive it? Will it be a slow, noticeable decline in starting ability/power/idling capability or will it run fine one day then suddenly die for good? Chance at either scenario?
4) Am I an idiot for considering to continue driving it in the short term or should I just park it and rent a car until I can decide how to move forward?

My apologies for the verbosity (trying not to get flamed too bad for lack of detail) and if these questions have been answered elsewhere. I've found some great and relevant info in my search, but would really appreciate the community's opinions and experiences as it relates to my situation specifically.

Thanks in advance for your help,
Beer Me!

Karack

test parameters would be nice to know, if the cranking speed is low then the numbers will be skewed.

you could buy more time with a 2Kilowatt starter and be sure your battery is good, a tune up won't hurt either(plugs, wires and coils).

a decarb might be beneficial, it may not. premixing has the same result. but if the numbers are really that low and the crank speed is 250 then the numbers say the engine has little hope. performance won't be hindered much above 3k RPMs, a low compression engine still will perform nearly perfectly in that respect, but idle quality and low speed take off power will suffer.

Beer Me!

Thanks. I hope to have them when the dealer opens tomorrow morning. They omitted them from the report I received this afternoon.

RIWWP

iTrader: (2)

1) Yes, in order for those numbers to be passing at sea level, your starter would have to be cranking at ~170-180rpm. However, this will climb a bit based on a higher than sea level for St Louis. At a guestimate, I'd put it somewhere around 210rpm or higher and the engine fails. That being said, the original 2004 starter was known to be rather weak and it's 10 years old, so it is actually reasonably possible that your starter speed really is that low. There is some bit of hope if those numbers are not yet normalized. If they are normalized, your engine is certainly failing.

2) There are ways you can fool the compression test to get it higher, but nothing that lasts past a few combustions. Compression that low can't be corrected short of a rebuild. Even if it's low from carbon displacing the seals out of place, a decarb wouldn't save anything since it's been wearing wrong.

3) It will be a continuing slow decline of what you are already experiencing. Difficulty starting and it will get worse. Spark plugs will keep fouling faster, mileage and power will keep dropping.

4) No, not really an idiot. It's one of the things about a rotary. It will run well after it's "dead"



Other points:
Your engine failure is likely sourced from one of two sources, or both:
A) The thermostat failure. A coolant seal can fail as low as 220F, before the needle starts to move on the gauge (which is 235F), and a thermostat failure will send it skyrocketing rather fast. The slow coolant leak will take it's toll on the engine.
B) Insufficient ignition maintenance has lead to significant fuel wash inside the housings, removing the needed lubrication from the seals.

You followed Mazda's maintenance intervals, but Mazda doesn't have sufficient maintenance items indicated. Ignition coils can start failing as early as ~20,000 miles, and tend to be in rather terrible condition by 30,000 miles. They CAN last a lot longer, as you have found, but your engine is simply not performing as it should. Dyno testing on 30,000 mile old coils, plugs, and wires showed a 28whp loss over brand new of the same. I'm positive that you have been down on power and gas mileage for a long time, and just haven't really noticed (or noticed, but haven't commented on).

If you keep it, I'd highly recommend replacing the ignition, radiator, coolant bottle and cap, and coolant lines. Not at a dealer, or they will charge you more than the car is worth. You can replace everything from Mazmart for about $900 in parts, and the work is all relatively simple.

Beer Me!

Thank you very much for taking the time to respond, RIWWP. I appreciate all the feedback and advice. FWIW, the service agent said he thought the compression test was performed at 250 rpm, but I don't have a lot of faith in his response and didn't push him any further.

I think you are correct about the thermostat failure being the root cause of the issues I am having now. It was a very acute failure -- I was on the highway driving home in rush hour and couldn't even make it all the way to the side of the highway after I noticed temperature rising before it shut itself down. The car was so hot I could barely get the hood open. I let the car cool completely and then started it back up and tried to get it somewhere more safe. I barely made it a few hundred feet before the temperature pegged out on the gauge again. The sad thing is that the thermostat went a couple of months after the warranty ended.

I wish I would have found this community shortly after I bought the car. You guys have built a wealth of great RX-8 knowledge that would have been very helpful though my years of ownership.

I can't be too upset, though. I managed to get 10 years of fun out of the car before my current engine troubles. I will certainly follow your recommendations to replace the ignition, radiator, and cooling system if I choose to keep it.

Thanks again!

Karack

the test can't set the perameters for cranking speed. ie the battery, starter and wiring will define the cranking speed during the test and then the figures taken are corrected to a meaningful averaged number.

many dealers do not correct the value and give you either just the jibberish(if it's below failing) compression number or the tested compression/cranking speed. it seems to be a very uncommon practice for just about any shop to give you a corrected number.

RotoryVirgin

You paid for a compression test but were given incomplete results. Without cranking speed, the test is inconclusive. This is a very expensive situation to settle for an "I think" from the tech.