'04 RX-8 115,000mi
BHR ignition system
BHR Fuel Pump
New Plugs

This has been happening for about 6 months now. On Cold/Warm starts engine misfires for about 30-50 seconds. CEL blinks then goes steady.

After 60 seconds the car runs great. Smooth as silk all the way to red-line.

Since this started happening I've upgraded to a BHR Ignition System, BHR fuel pump and swapped the plugs out.

I've treated the engine with Seafoam.

Been premixing for around 6 months.... tried discontinuing the premix for a tank or two.. problem still exists.

The only theory i have left is a leaky injector... possibly an injector stuck open slightly, dripping into one rotor housing flooding it. When started the non-flooded rotor drags the flooded rotor around until the chamber dries out a bit.... i know its a long shot but I'm running out of ideas.

 

bump

 

Hmmm i've had some misfires issues too but only after leaving it for a couple of days and goes away in 5 secs. Do you drive it everyday? Did you seafoam it according to the TSM or just in the gas tank? I might suggest doing it again. Unfortunately the real test would be to have compression checked. Might be a worn seal that only starts to seal somewhat when the engine warms up a bit. That would seem most likely to me but what do I know?

 

^Just reread the OP. It happens on warm starts too eh? Thats really puzzling. Hope someone can help bro.

 

Have either of you tried resetting your e-shaft sensor profiles?

 

I seafoamed to the TSB. I've since tossed the last quarter of the can in the gas tank to possibly clean up the injectors.

I reset the ESPS using the brake petal trick

All of this started when I blew a radiator line last year and had to swap out the radiator.

I actually didn't do the R&R on the radiator myself... could the tech have screwed something up while swapping it???

The point that baffles me is that after its startup problem it runs better then the day i bought it.

 

could have a bad esp sensor or sensor harness. check 'em . clean 'em.

 

hmm that could be it.... I know its filthy around that area. I'll give it a good cleaning tonight.

 

Checked and cleaned your MAF?

Can you provide more details around your blown radiator?

 

It's been a little a while. I'll add it to the need to be cleaned list.

 

As for the radiator... I was driving on the freeway, noticed the temp going up quickly... pulled over tons and tons of steam. Found that my return line had blown. My plan was to swap the hose with a hose from checker. In the process of taking the hose off I snapped the plastic nipple off the top of the radiator. Thus the radiator was toast. Swapped out all 5 radiator hoses along with a new radiator.

 

yea...wonder what damage might have been done by boiling like that. You probably gummed up a bunch of things in there from the esp to intake to even ssv as the car sucked in that steam.

 

I found the source of the problem.

It looks like the problem only happens when the Cold start air pump is running.

The motor was misfiring this morning... I unplugged the vacuum line to the "Air control Valve" connected to the air pump... presto ran smooth, plugged it back in misfiring.. unplugged smooth... pump shuts off plugged vac line back in smooth.

so the question is why is it doing this??? I have vacuum on the line, the air pump is working, the valve apparently reacts to the vacuum so i assume it is working.

Any ideas??

 

Leaking diaphragm, perhaps?

 

What are the side effects of disconnecting the vac line from the smog pump valve???

 

Vacuum leak if you do not plug the vacuum hose and a longer "light-off" time for the catalyst.

 

this is exactly what my car is doing and i dont know what it is. if you find the fix let me know

 

Having the same problem for a while. Dealership said plugs & coils, but couldn't explain why it happened only when the car sat for a while, and got worse the longer it sat. (I assume this is the case with you) Well, I came back from vacation, it did what you're describing, now i have a CEL and I cant get RPMs above 5k. Was thinking of making the appointment for the dealership. My motor warranty just ran up last month (mfr date 2/03) ugh.........

 

That sounds like a bad catalyst.

 

So an update after a couple days of running without the smog pump. Still a bit rough on the idle at startup... depending on how long it sat. Also some wicked white smoke on cold starts. I'm assuming this is a result of the delay of "light-off" in the cat.

In no way is this fix permanent... its a band-aid at best. There seems to be another underlying problem...

I plan on taking out the smog pump valve this weekend to see if its gunked up.

Past that i'm stumped.

 

Doing a little research, seems like CRH might be right -- clogged cat, caused, of course, by failing coils and plugs. I have an appointment at the dealership for Monday. I'll let you all know how it goes.

PS - Incidentally it seems the warranty expiration goes by your vehicle's original delivery date (something the dealership can tell you), not manufacture date, so I've got an additional 14 mos of warranty!

 

Weak coils leading to cat failure is a VERY common problem with the RX-8 and the Federal mandated warranty on emissions-related equipment may be different than the Mazda warranty coverage.

 

So the situation has gone from bad to worse.

Leaving for lunch today the car would barely start.... 3-4 turns on the key leading up to a very very weak start. Lots of white smoke.

After warming up, the car runs great, no hesitation or misfireing.

After lunch same thing.. very very hard start, no smoke.

turned the car off, tapped the break petal to reset ESPS ,went to start, dead dashboard.

This has been happening now and again.. I give a quick twist to the battery terminal and i have power again. Start it back up rough idle then smooth as can be on the freeway.

Could the shitty battery connection have anything to do with this problem???

I'm thinking clogged fuel filter however it should run crappy all the time.

Clogged Cat.. it should run shitty all the time also.

 

OP: just saw you have the BHR ignition kit... how long have you had that? did this problem start before the upgrade?

 

yes it was doing it before the BHR Ignition and Fuel Pump