Surasonac

ISSUE:
Rough idle, Reduced power, Fluctuating RPM when holding accelerator still when cruising.
All sparks other than number 1 leading are misfiring, confirmed with spark tester.

Testing/Problem finding:
Cleaned MAF: Unchanged
Checked electrical grounds: All fine
Reset ECU by stamping on brake 20 times: Unchanged
Checked vacuum lines: All were fine
Replaced stock coils with D858 coils: No change
Replaced ignition leads: No change
Replaced spark plugs: No change

Could it be a dodgy crank position sensor? I've heard they sometimes go bad on the RX8.
It's the last resort really.... I'm selling my car within the next 2 months so i'd like to fix this otherwise i'll have to sell it cheaper.

Also weirdly enough the CEL does not flash showing a misfire, but I think thats because the previous owner fucked with the ECU.
Reason I think this is because when I bought the car it had a gutted CAT... the CEL never came on.
And even now with my Decat pipe... no CEL.

- Thanks

Steve Dallas

Have you found this thread?

https://www.rx8club.com/series-i-tec...t-here-222280/

Not every combination of ECU and O2 sensor will turn on a CEL for a gutted cat. Most do, but not all. Of course, it is possible a previous owner turned that code off in the ECU.

Surasonac

Yeah already been though that. Checked it all. Only thing thats plausible is a fuel pump issue, but i'm certain i'd be having far worse problems if that were the case.

Really wondering if anyone has had a crank position sensor go bad?

Surasonac

bump

Steve Dallas

Once everything else has been ruled out, whatever remains, however improbable, must be the cause.

My money is on early fuel pump failure. Think it through logically. If the fuel pump is not providing enough fuel to match the available air, the engine will run lean, and detonation will be the result. Codes are not always 100% accurate. Can you post your LTFT and STFT values?

NotAPreppie

I'm going to put my nickel on vacuum leak.
What are your fuel trims and warm idle MAF rate?

Surasonac

Thanks for the replies. I also had a feeling it might be the fuel pump. Already looking for a new one, quite an easy job since its right under the rear seat.

Vacuum lines were one of the first things I checked, in don't hear or feel any leaks.

I'll get all those values tomorrow for both of you. I'll take it on a little drive and log some data. Thanks again

NotAPreppie

You won't usually see or hear vacuum leaks until the hose or fitting is literally falling apart. Vacuum leaks start well before then.

MAF rate and fuel trims at idle after the engine has warmed up will help rule this out.

Surasonac

LTFT is always 8.59%. The time shown at the bottom of the graph is mm:ss. This is quite mild, its usually fluctuating even more.

NotAPreppie

Your MAF rate is a little low and LTFT a little high but not enough that I'd expect it would cause a misfire. You might have a vacuum leak but, if so, it's really small so I'd bark up other trees for now.

Next step will be to get a fuel pressure test.

Robbby123

I have a P0302 code and have issues starting my car cold or hot
Ive replaced Coils,Plugs,Starter,Wires,Fuel Pump, Cleaned MAF, Cleaned throttle body.
I have no idea what is wrong with my car it seems fine when i drive it only the starting issue.
Ive noticed that if im at a dead crank were the engine dosnt start if I press on the gas pedal a
little bit the car will turn on.
BUT I HAVE TO PRESS THE GAS PEDAL WHEN YOUR NOT SUPPOSED TO
Anyone know what could cause this and misfiring
---Thank you

Coby Malone

Ok. So I had my automatic transmission replaced in my 2005 rx8 and it ran fine for about one day then as I was driving into town, only been driving it for about 15 minutes and I'm sitting at a stop light and once it turned green, I went to hit the gas and all of the sudden, like a flick of a switch, it started misfiring, had absolutely no response from the gas pedal and it just basically idled extremely rough as I rolled it to the side of the road then it died. It will start still but it struggles immensely to start and can barely keep itself running. In park I can floor it and the rpms will go up but very slowly and misfiring and backfiring the whole time to but will die if I let go of the gas. If I put it in drive or reverse, it will idle roughly but the gas pedal does literally nothing. Not even the slightest change in rpms. And it seems like its flooding itself to with all the backfiring and very strong smell of gasoline when its starting and started. I have brand new spark plugs, coils, and wires. A new crankshaft position sensor and I've had it reset with a computer by my mechanic multiple times. It's also had the catalytic converter deleted. I keep getting misfire codes obviously but no other codes. Somebody please help me. Also when the transmission went out, it sat for around a month while we waited for the new one to be delivered. Before the transmission went out, I had no issues with the car, it ran great. Then when we got the new transmission in, it took about 2 hours to finally get it started and it was running real rough for about 5 minutes then it smoothed out and like I said previously, it ran fine for about one day.