hot and cold start issue, 180-ish rpm crank speed
 

Hi all,

First off I've resigned myself to the fact that my 8 has a motor that is in the process of dying. So if it indeed is dying then you don't need to press home that fact. But, in light of some new things I've read, I'm looking to see what ye hallowed experts might have to say.

The car: 05 Manual with currently 100,400 miles, the warranty expired in november.

The problem: I first started having hot start problems where it got progressively harder and harder to start when warm, but the car does eventually start. Even now after a few months of this crap I've never had it not start after more than 2 tries when it's hot, but it's never easy.

The hot start has now progressed to a cold start issue. When cold, The car cranks a little more than normal and stumbles a few times, but once she starts up then she runs just fine.

I have the original starter that came with the car, it was never upgraded.

More info:
-The idle at 750 rpm when warm is a bit rough, but it has always been.
-I'm noticing a slight lack of power below 4k rpms, or more like a bit more of a kick once it hits 5k, but this might just be the butt dyno since I started looking for power variations
-Gas mileage is completely normal
-I've never replaced the ignition coils, so they have 100k on them. the current plugs have about 20k on them

When I finally got around to calling the local circus (dealership) and took it into the clowns at South Tacoma Mazda, they told me that my problem is just carbon and they would do a zoom zoom clean. I really just wanted them to do a compression test and tell me what it was. After having my car for like 5 hours to do what amounted to 1 hour worth of work and never calling me back, I had to call them and they told me my compression is shot and I need a new engine.

Now, I unfortunately don't have the numbers they pulled off the car, but it was something like 5.2 to 5.7, pretty uniform across both front and rear rotors AT 180-ish RPMS, 185 tops. There were multiple misfires during the test (like 20 per side average)

Now, I know that the numbers are low (which is why I'm resigned to the engine going out) but the mechanic there said my starter motor is going out because it revs so low. Again, I have the original starter.

My points of contention with their test: That their mechanic didn't know that the original starter revs lower gives me no confidence in their diagnostic ability, and they never gave me adjusted compression numbers. Even if they're being honest to the extent of their knowledge, I know that they just charged someone $8000 for a reman engine install which is entirely too much, per the cashier who probably slipped up telling me that.

If I were to replace the engine (which I won't), I wouldn't do it with them.

Questions:

What do you guys think of the compression numbers (from 5.2 to 5.7 @ 180) if they were adjusted to 250 as they should have been?

Is my motor actually dying? The stuff I read that led me to post this were a few posts where people stated that they were surprised a car would start at all when cranking at 180 rpm

I know a new starter motor will fix (yes, I know, mask) the problem, the question for those of you with experience in dying engines is: is how long will the motor actually go before it dies with the symptoms I'm describing?

I owe about 3 grand on this car still. If it were to finally crap out on me the day I paid it off, which is about 6 months away, I would consider myself satisfied with the ownership. Do you think it would be worth it to throw about $500 worth of parts at this problem?

I don't intend on keeping the car after it finally dies, for the money I can spend on an engine rebuild I will likely buy a subaru that will last 100k.

Crossing my fingers for good news, but give it to me straight doctors :)

Nobody can tell you that, but there likely won't be any shortage of guesstimating experts. Its not really that bad, the starter speed is just too low.

https://www.rx8club.com/attachments/...n_chart_00-jpg

The 2009+ S2 starter is your best bet (assuming you have a 6 spd manual) since it cranks the fastest, but it also costs the most. With a good battery it can get 280-300 rpm cranking which is a big help

Also, misfires aren't possible during a compression test; the engine is only cranked over by the starter and not running. Not sure if there was some confusion or mixup about that.


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If you want to keep the car i would upgrade the starter, change the coils and wires, plugs and seafoam it yourself. And then see what happens.

They should be in the low 7s, maybe high 6s. It's not a 'great' engine for sure, but you may not actually be failing. Your starter is clearly shot though.


Correct, see above about the engine. 180rpm is REALLY low. I'm not at all surprised that you are having trouble starting, and more surprised that you can start at all with that speed. Even more so knowing that you are on original coils.


If you retest at ~270rpm, and the numbers are where I expect they would land, you could easily have 20,000 miles left in the engine, if not more.


Yes, I would say that it's worth it.

I smile at this a bit, considering that your 8 lasted 100k..... :)



Another thing to think about is that the fuel wash from failing ignitions will clear some of the compression-assisting oil film from the internals of the engine, accelerating wear and hurting compression results.


I think that if you replace the coils, plugs, wires, and starter, you will inject quite a bit more life into the engine, probably to a degree that will surprise you.

I agree along with starting to premix as well.....it should last awhile longer....

I've premixed for a while, I'll definitely keep that going

So I did this in stages for lack of time to do it all at once and I'm glad I did.

I replaced the starter and the car started better, both hot and cold. It turned less times than before but it still seemed to struggle a bit so I wasn't sure that the car didn't still have a problem.

Then I replaced the coils... and WOW. The car starts almost instantly from either hot or cold. There were the telltale white spots on the bottom of the coils. They were the original ones from the factory.

Thanks for the help guys, I'm glad to keep the car and feeling renewed faith in the wankel.

avoiding the FAQ thread and expecting the worst always gets people. it's good to see some people finally doing the obvious and getting more life from their car.

The white spots don't mean anything, so don't diagnose by them. Failing coils can be without spots, and spots will exist on good coils.

But yes, your ignition was shot, your starter was shot. Your engine probably isn't.

Gratz. Always nice to see when someone actually believes that we might know what we are talking about :lol:

After driving it, I also now have my low end power back (what little it is that we have of low end...)

Now I can go and look at a motorcycle that will help keep miles off the car :D

Doing red line runs through 1st and 2nd gears will help with keeping carbon down too.

not driving the car won't necessarily make it last longer, rotaries need to be driven periodically otherwise they tend to get angry.

Angry!

I finally found the piece of paper from the compression test. It showed my cranking rpms were 167, not 185.

makes sense that the car runs perfectly now.