I know slower hot starts are a symptom of low compression. Is this the only possible cause?

I had a new S2 starter installed on an 05. It starts immediately when cold. It varies when hot. Sometimes it is immediate, and sometimes it takes 2 - 3+ seconds.

 

do you have the stock catalytic converter installed?

 

How often does it take longer?

Taking a few seconds every once in a while is normal.

 

CAT is the original. Starter was recently installed so not too many hot starts so far. I would say it is about 50/50 at this point. The longer starts may be a bit more frequent.

 

Oh, so I am not alone.

I find my car to have occasional longer hot starts when it's raining outside in winter, and it's usually cooled down a little bit when I try to crank.

But have you taken off the catalytic converter and looked at the honeycomb inside to make sure it hasn't collapsed, melted, etc.?

 

No, i havent done that yet. Are there any other indicators that would be indicative of a bad CAT. The car has 29k miles with new plugs, wires and c coils. There was no indications of misfires prior to the new ignition. Is there something else beside misfires to screw up the CAT? The previous owners babied the car which is why i have been running it hard. The only thing i think they may have done was overfill the oil from time to time based on oil residue in the air intake. The MAF was just cleaned as well.

 

Even with 29k, misc. engine damage or wear could have occured.

You can go 100k on a motor till it wears out and needs to be replaced yeah..

But by that same idea, anyone couldve gone 10 miles on a entirely brand new Rx8 out of the showroom anytime during its production, overheat it a bit and ruin the compression before you even got it home.

Mileage isnt a direct reflection of engine health. Compression numbers are a reflection of engine health.

Get a compression test.

 

Wow! If the engines are that fragile, why would so many still want to deal with them?

 

He didn't say they're fragile, he said they don't do well with abuse . Same goes for most engines...

We're all guessing as to what may or may not cause your hot start issues, the real way forward is diagnosis, so compression test would rule out compression - related causes. After that it's a short list that has been discussed countless times: ignition, fuel pump, battery.
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Abuse by way of neglect is probably more precise.

If the PO neglected the ignition, the cat could be damaged. It doesn't take long to clog a cat - maybe 5K miles. You should definitely remove the 3 nuts on the front flange, pull it down, and look for signs of clogging just to be sure it's OK. The better way to inspect it is to take it off, drop a small LED flashlight down the back end, then hold it up and look at the light from all angles from the front end.

The mantra is:

BAD COILS KILL CATS. BAD CATS KILL ENGINES.

It is a mantra for a reason, and the cascade can happen quickly. Good job on taking care of the ignition components, but the cat is the other half of the equation.

Also, do get that compression test, so you have a baseline for engine health.

 

when my cat collapsed i could hear a rattleing when parked and id rev the car, but rattles can be caused by a few things. a good test is to drive to operating temp at night then when its still warm look under the car and if ur cats red hot its clogged. dont drive it until thats fixed. but best solution is to take it off and look at it.

 

I have followed all the advice in the forum. I bought it at 26k miles. No issues, ran smooth, no misfires, no CEL etc. The car was not abused, just the opposite, it was babied, which could be considered abuse. I had a compression test which may have been faulty. With weak starter it showed suspect results. Rotor 2 which is the one that fails first from what i have read, passed at 198 rpms which is the average speed of my wimpy starter. Rotor 1 which failed showed 292 rpms which is why the test is suspect. The original starter doesnt turn that fast.

Later i replaced the starter which now turns at 320 rpms and we tested the old starter still turning at 190. I seriously doubt the CAT is bad as the ignition was replaced before 30k miles in a car lightly driven. No issues with a fuel pump. The only issue on the short list is i had a very weak battery due to a power drain. It flooded as a result. I followed the deflood procedure from a Mazda bulletin which didnt work. I went to the next step disconnecting an air pump to the CAT as prescribed. It then took a bit to get it started using another battery, but after multiple trys, it started. Ive since kept a battery tender on it.

One thing for sure, ive done everything right as far as preventative maintenance. I will look at the CAT, but based on everything else, it is my guess there is nothing wrong with it. Unless trying to start it after it flooded, screwed it up. However the slower hot starts existed before the flooding.

How many of you experience a slower hot start occasionally even with a healthy engine and CAT as was indicated in previous posts?

 

an occasional slower hot start is normal. but like stated before, if your doubtful of the compression test results go get one done from a real rotary compression tester. if it was driven lightly thats just as likely to kill the cat/engine due to carbon buildup. our engines need a little time to play. as they say a redline a day keeps the carbon away. starting after flooding wont screw it up so long as you did the procedure correctly. also if ur having to keep your battery alive via a battery tender when not storing the car for winter or something...its time for a new battery, that just might be your issue. any engines gonna have a rough time starting when the batterys toast.

 

Oh OK great. So if you had a weak starter and they misread 192 rpm as 292, and failed rotor 2 based on that, then it sounds like compression is OK. Could do with a retest, I suppose.
Could also do with examining the spark plugs just to make sure they're in good shape.

Mine takes a second or so longer to start once in a blue moon. Definitely not 50% of the time.
I don't think we were accusing you of neglect, it's more the guy before you and/or the general public who doesn't perform preventative maintenance as a rule

 

I didnt think you were accusing me of neglect. I just wanted you guys to know that im doing everything right including trying to make up for the babied use it has experiened. I redline several times per trip. Get it as fast as possible whenever possible. 115 mph so far where i can. Havent had a ticket in 15 years.....we will see how much longer that lasts.

I plan on another compression test. I just wanted to give the car an opportunity to blow out as much carbon as possible. It was actually rotor 2 that initially passed. It was rotor one that failed at the suspect higher rpms. It is rotor 2 that usually fails first, correct?

Just curious, what is the top speed you guys have reached?

 

its not the speed persay but the rpms that can help the "self cleaning" process. as far as top speeds the alledged top speed is in the 180s on very healthy rx8s. but if i remember correctly its limited in 6th gear to lower than that

 

The battery is good. Ive got a drain somewhere. The car sometimes sits for a couple of weeks. Originally it was draining faster before i disconnected the aftermarket alarm. As far as the plugs, they are new along with wires and c coils.

 

Yes, i do realize it is the rpms. That is why i redline several times a trip. Even hit 9k in 4 th gear once or twice. The speed was meant to show i am running the car hard as i can in the hopes of reversing some of the issues from it being driven normally in the past.

 

Now you have a Schrodinger's cat: it can be simultaneously clogged and unclogged until you look at it.

There is no straight stretch for me to safely go faster than 3rd gear top speed. And I don't think this is the best way to spend CAN$1k(towing and speeding ticket).

From what I have read, the top speed is limited to 5th gear redline which is around 146 MPH. 6th gear won't have any acceleration when you upshift from 5th redline. The aerodynamic drag is simply too much.

 

Rpm is irrelevant. Full throttle temperature and pressure is. If you have a hill, accelerate into the hill in a moderate gear to get the longest period of self-cleaning conditions.

 

Jinx, you been watching Big Bang Theory.😃😃😃

Loki, isnt rpms correlated and not correlated (Schroedingers cat). Its correlated when you are flooring it and pushing the car as hot and hard as possible. And not correlated if you are hitting 9k rpms while going downhill. 😃😃😃. Seriously i get what your saying. Ive also pushed the car hard under heavy loads at lower rpms. Higher gears like 4th or 5th, flooring it on straight aways and inclines.

 

I still think you need to inspect the cat just to be sure. If one or more training coils fails, the driver will not notice it, and no misfire will be registered, yet unburned fuel and oil are passed into the cat. And coils are finicky. I had a Rev B trailing coil fail in under 10K miles and only noticed, because I had bought a BHR kit and pulled the plugs when I installed it. Around 5K miles of a bad coil or two can clog the cat. A clogged cat WILL kill your engine.

BTW, top speed is drag limited to 169 MPH in 5th gear, however some people (myself included) have managed 172 MPH with a little help from the wind.

 

Yes, i will get it checked. I noticed for the first time a smell coming from the exhaust. The best way i can describe it was something like alcohol. It was there for a couple of minutes upon initial start up. Any thoughts?

 

I mean, you can buy a Corolla and forget about any maintenance other than oil change. It's also a very good car for you learn how to text and drive because it's about as exciting as a toaster. The only reason I stayed awake in my Corolla beater was that it was a stick shift.

I only watched a few episodes quite a few years ago, LOL.

Cold start for any car will stink because your cat hasn't heated up yet and your car also runs rich on cold starts.

 

Back again to deliver some harsh reality to this scrub.

For better or worse, your updates since my last post have meant nothing. A bunch of exposition about different subjects but no concrete information to work with. But i will comment on one piece of said information.

You, Petscar, purchased a Rx8 without having gotten a PROPER and credible compression check. You did follow every point on the buyers guide except that one. Whatever test you did do, it means NOTHING.

My Rx8, my very own beloved Rx8 in my driveway right now, cold starts perfect and hot starts usually okay. My ignition system is running perfect and all new, my starter cranks the engine around 320rpm, fuel system and everything is perfect.

Guess what, my motor's compression numbers corrected and adjusted to 250 rpm are 60-61-59 psi on the front rotor and 53-54-52 psi on the rear rotor. All it takes is one hiccup and my motor is going to have a disasterous failure, hence why it is in my driveway with a car cover on it and wont be leaving that spot until the motor has been replaced.

All of that said, ill spell everything out for you again and you wont have any answers to your problems until you follow my instructions.

1) Take your car to Mazda and get the fuel pump recall done for free. You will get a new fuel pump housing, which is for your safety ultimately, and usually they just replace the entire assembly because its much faster and as a result cheaper, so you will get a brand new fuel pump. That resolves that issue

2) Dont overfill your oil ever again, thats what a dipstick is for ya dipstick. Helps keep you from cleaning the MAF a bunch too.

3) Get off your **** and check your damn cat converter already. Your meaningless jibberish means nothing with it being all speculation. CHECK IT.

4) Do a proper compression test like the last time I chimed in. A proper test with a rotary engine compression tester. RECORD the tester so you can keep the results properly documented.

We can go from there after you have responded to all 4 points appropriately. Until then posting in this thread is meaningless.

Sincerely,
The next 9krpm, Xero