jmkogut

Does it happen? Does it go away?

I experienced a loss of power in an S4 NA that felt a lot like limp mode, but after reading http://fc3spro.com/TECH/FAQ/deton.html I wonder if this was pre-ignition. I get pretty poor compression on both rotors (<70) but the problem stopped after about a week.

The only thing that changed before it stopped was me replacing the leading and trailing coils.

HAILERS

No limp mode for series four. Plug wires on wrong?

jmkogut

I'm not sure they were on right then, I'm 100% sure that they're on right now. I'm just trying to diagnose what the problem was.

It was also intermittent.

Sometimes, with the heater on full blast, the problem would go away.

Sometimes it would come back.

I think I've eliminated it, but I haven't driven the car for a few weeks so I'm not sure.

arghx

iTrader: (3)

change the plugs (brand new ones). after you flood the car it will stumble sometimes.

about 4 years ago I had an 88 n/a which ran about 13:1 AFR and had the CAS advanced about 5 degrees. It never detonated on 87 octane and I utterly flogged it. The motor is still running today with about 40k on a rebuild with used housings.

jmkogut

Yeah I noticed that too, but I haven't gotten to the engine yet on this car.

I replaced the plugs less than 150 miles ago, and they already look blackish and have the same finish as the plugs that I pulled.

helghast7

iTrader: (6)

have you tested all of your sensors.....the car doesnt have a real limp mode...however its default is to dump a **** load of fuel

it happened to me when my tps died.....constant flooding, running so rich i would make the area look like a london fog just rolled in

that could be your issue

jmkogut

I have *not* tested my TPS. I'll check the resistance as soon as I find myself a decent multimeter.

no piston drifter

hahaha ive been there before as well as my 1963 chevy impala. that bitch smokes =D

jmkogut

So.. for what reason would the ECU intentionally run the engine super rich? Is it an overzealous attempt to prevent leaning out?

helghast7

iTrader: (6)

well actually its an ancient safety precaution...you see mazda already knew that any detonation was VERY bad...so they set it as a default....

if the PCM ever lost contact with one or more core sensors it would go to the default mapping and run rich that way you wouldnt ping you would just flood like a **** to protect the engine

if you tend to suddenly flood alot or foul your plugs or anything of the sort you want to check the core sensors....

they would be: TPS, MAP, AFM, CTS and im not sure if i forgot one...i think BAC aswel

if it loses signal with one or more it will run the default preloaded maps....which is RFR or really ******* rich

if they are within spec then you should suspect compression...which means if you want a proper reading you should suck it up and go to your local rotor shop, as decent as conventional testers are they arent very accurate with rotors....

for example i once did a compression test(which scared the crap out of me) it read an average of 30psi

all i could think of was "how the f*ck could this be when the car still runs?!" so i sucked it up and when to my local shop and it turns out my engine is pushing a close average of 116 on all faces (brand new for an s4 is 120psi by the way)

jmkogut

Dude, you just gave me hope. I use a piston tester and it gave me 60 on all faces, even. The engine feels strong though. I'm about to buy myself a nice, quality DMM for TPS checking, and adjustment, I guess I'll use it for tolerance checking the sensors as well. I'll update you all on Saturday. THANK YOU MUCH.

You get 1,000 free internets.

EDIT: There aren't any motherfucking rotor shops around here

Sideways7

iTrader: (7)

Also, check your timing. That can definately cause detonation.

On a side note, it takes a shitload to get a NA rotary to ping. Under acceleration my car runs so lean it is off the scale on my narrowband A/F meter (it runs rich under cruise) and I still have never even pinged. And yes, I am working on fixing it.....

jmkogut

I'm trying to locate the timing procedure in the FSM, and I can't seem to find it..

EDIT: NVM, Engine section 1-8

helghast7

iTrader: (6)

just to let you know how it works....(if you know just ignore)

the tps consists of 3 wires, a ground wire, a constant 5 volt reference, and a receiving wire that goes back to the pcm...thats the wire that will change voltage

a good tps will on idle hover around 1volt....when you rev the engine up to about 3k-4k it should make a clean sweep up to 4 volts and back down to 1 volt....if it doesnt do this then the tps is bad

the afm works similarly...and the CTS is sort of like that except its a thermister, which is what changes the resistance

jmkogut

That clean sweep.. does it go down with the revs, or while you hold the revs up?

helghast7

iTrader: (6)

it moves with the revs....so if you held it at like 3k it should stay at 4 volts(avg off by milivolts)

but say for example if you held it at 3k and you saw it bounce from (while holding) 4v to 3.5 to 4 to 2.5 or whatever then its bad....same with idle

another example....what happened to me with my tps....when i tested it...no matter what i did with revs it would always stay at 1 volt...so my pcm realized something was f*cked up and just ignored the tps....and ran really rich

jmkogut

lol. I love that acronym for the fallback mode.

RFR ftw

Kindof.

It's better than leaning out ^-^

helghast7

iTrader: (6)

no doubt about that