Hi i recently bought an rx8 as a non runner although it had a rebuilt engine and just never ran after.
I replaced the MOP and it started and ran out of limp mode but i had cylinder 1 misfire and o2 sensor code. I then changed the coil packs and leads and she ran perfect for 5 mins then went back to rough with misfire during idle. I have now changed the cat as well as that was red hot all the time. The car now seems to run lean and has still got the misfire. Any ideas?? Barring in mind the block is basically brand new.

 

What do you mean a non runner?

What are the current CELs (MIL)?

Check that the ESS is clean

How do you know the car is running lean?

Did you replace the O2 sensor?

 

It smells lean

Non runner because when i bought it it was stuck in limp mode which the new MOP fixed.

Codes are cylinder 1 misfire and o2 sensor bank 1 sensor 2

What is an ess?

 

ESS is the Eccentric Shaft Sensor
It's how the ECU determines the crank angle and ignition timing

It's exposed to the elements, and is a magnetic pickup

If it's dirty or has something stuck to it like a piece of metal it will wreak havoc
You will also need to a nvram reset ... 20 brake stomp procedure

Recheck the leads or on in the correct order

 

Where is that sensor located? Could be a good shout. I have done the reset afew times.

 

Front cover beside the lower pulley.....on the right side. Looks like a small cylinder

Check it for crap ( it is magnetic) ....if you have the option...swap it out and try another one..where do you live...likely someone close has a spare

 

Im in hertfordshire in england. Ill check it in a minute. Should i use carb cleaner on it?

 

Just wipe it off with a rag..any metal bits need to be removed. The solvent won't clean it off*

 

Not the ess, any other suggestions?

 

Front o2 sensor
Maf
Vac leak
Bad plug or leads
Leads not connected to correct coil
Compression loss

 

Right it runs fine whilst under load only rough whilst idling.

Plugs leads and coils fine. Compression fine as stated its a newly built engine.

Maf plugged all fine.

Code for rear o2 sensor so need to replace that but doesnt cause the misfire

No other codes so i assume front senor is fine.

 

I have seen alot of talk about the engine mounts being a big problem causing rough idle and misfire? Any idea if that could be it since the engine was recently installed?

 

Also would pinched injector wires cause these symptoms?

 

Bad motor mounts can cause rough idle unless you specifically mean it is misfiring at idle?

How hard did you check for vac leaks (I hate vac leak checking such a PITA)

Do you have any means to read parameters from the ECU, like LTFT or AFR

I want to back up a few steps here and ask a couple questions and confirmations:

1) Did you change the CAT or remove it? The car will stink bad without a CAT. The Rear O2 Sensor shouldn't be an issue if you replaced the CAT. Yes the sensor shouldn't cause a misfire.

2) Just because you have a remain engine doesn't mean the compression is ok. How long did this rebuilt engine run in limp mode due to a failed MOP?

3) You said in your OP that you had a O2 sensor cel ... what was the P# do you recall? I'm still suspecting the front O2, especially if you say it seems lean.
Remember as well that "under load" (depending on Calc Load %) the ECU goes in to Open Loop which doesn't use the Front O2 sensor. Only Closed Loop under low load and rpm uses front O2

4) Would really like to be able to confirm its running lean, and you know ... a vac leak will cause a lean situation

5) Can you buy or do you own a HEI Ignition Coil tester, it's really the best way to check your coils and leads

6) It's possible that you have a bad Primary Injector


I'm just brain storming

 

LOL holy crap
Where able to read what I was typing before I posted
lol

 

OH .. one more thing

Any chance you could post a video or sound clip of the idle issue

 

i replaced the cat with a brand new replacement.

the codes a was getting on last check are p0301 and p0037

the front 02 wouldnt cause a mis either really would it?

there is some vacuum between the plastic inlet ans the throttle body i think.

the engine was in limp mode some time but i believe as the garage who put the engine in knew nothing about the cars.
it sat on my drive a week or so and was started a handfull of time before i replaced the pump after adjusting it etc.

the smell i think is burnt oil now rather than fuel it stinks once at optimum temperature but no over heating at all.

the coils and leads are new but i do not have a coil tester.

I might be able to put a vid up tomorrow.

also the engine fault light flashes or goes on solid randomly.

 

I have found a oil leak at the rear of the engine seems to be between engine and gear box. Need to clean it up and trace it back.

 

Hey man ... had some time this morning so I looked up the DTC P0301 and P0302 procedure in the Mazda workshop manual

I also added Engine Runs Rough/Rolling Idle troubleshooting as a pdf document.
It was too long to make screen shots
DTC_EngineRunsRough_RollingIdle.pdf



Hopefully this will help you isolate your issue.
Good luck and keep us updated.

 

Thanks buddy great info! Looks like a busy week for me ahead. I will update soon! Thanks again

 

I have had a full diagnostic done now rather than my obd2 reader and found codes from hi and low input on the maf sensor so i am going to change that as it is most likely the cause. giving off hi and low at the same time i assume the sensor is fudged!!

 

I have a 2004 mazda rx8 and it's been having idleing issues (idles rough, occasionally dies at idle) and it's been throwing misfire In cylandar 1 code (p0301) and has an oil leak from the rear of the engine somewhere.

 

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Google "Rx8 misfire", it is a well covered issue. Inspect /Replace spark plugs and ignition coils and see if that fixes it.

 

I'm having a similar issue, relplaced my ignition coils after i deflooded my car and it ran fine for couple months but recently died on me coming to a stop, then proceeded to start up and sounded like I was trying to deflood it again at a stop!! It finally cought the spark and started up but sounded super rough, could it be my fuel injectors that went bad??? I would misfire at idle but not when I was driving It back to my house, coming up to a stop sounded like it wanted to die and give out!! Any ideas???

 

Very unlikely the injectors are bad. More likely you have a vacuum leak, loose hose or another opening in the intake. Is the intake original?