Silver94

first off this is going to be a little hard to explain. I have a 94 rx-7 with the following performance mods dp, and cat back. I just changed my spark plugs today and found a problem, they are white. Not a little white very white. My car is running very lean. Here is the thing I changed my spark plugs 5k miles ago and they were very black and burnt so I thought my car was running very rich because I have a lot of popping in my exhaust and becuse of the color on my spark plugs. These plugs that were burnt only had 5k miles on them to. I have only done a few things to my car since I changed the plugs today. I put a used main cat on my car that was not cloged also I changed my clutch. Those are the only things I have done. There is one thing about my car that I noticed that is very strange. My friend and I went to the dyno last week, and my first run on the dyno my second turbo did not kick in. I knew this was a problem, I thought becuse of a vaccum leak but my suprise when the second turbo did not kick in the car was running lean accroding to the air fuel graph. Now this is the part that is hard to explain. So my second run on the dyno I told him to run it hard throught 2nd and 3rd then into 4th. This is the only way my second turbo will kick in. To my suprise the second turbo kicked in and the car was running rich. I can not figure this out any of you all got any ideas?

Silver94

anybody have an idea what is wrong?

djantlive

Have you changed the fuel filter lately? Maybe it's dirty?

U are using the same stock plugs right?

Is there any exhaust leak?

The main cat that you put is stock or high flow? With DP and CB, if you have a high flow, you'll run lean.

Silver94

I changed the fuel filter 7k miles ago. I am using NGK BUR9EQ spark plugs. I put a stock main cat on the car and there is a little exhaust leak.

djantlive

Maybe it's bc of the exhaust leak. Also, if the O2 sensor is old, you may want to replace it. Check the ECU for an error codes (search for a write up on how if you haven't done it before). Try running a few bottles of Chevron Techron fuel injector cleaner. Just some ideas...

P'cola FD

Do you have a boost gauge to show that your second turbo is not kicking in? Or does the car simply feel slower, and you assume it to be the turbo because it is around the same rpm? I ask because if you don't have a boost gauge to show lower boost, it could be secondary injector related.

Silver94

I am going to check the ECU tomorrow for error codes also I am going to probabbly replace the 02 senor. Yes I do have a boost gauge and seems like the second turbo kicks in but no power increase

P'cola FD

The O2 sensor won't make a difference, because the ECU switches to fuel maps during WOT. If you have good boost, but low power and lean A/F ratios then I would look into fuel problems. Put in a fuel pressure gauge. Your fuel pump could be failing. Or I could have something to do with the secondaries.

SPOautos

It sounds to me like your just running too much boost for the stock ecu, which would cause you to be getting the same fuel that you would with stock boost even at a higher boost level. In addition to that if I remember, right the ecu would also retard timing quite a bit which would cause you to loose power.

How much boost are you running and is it accurate? I know with a dp, cb, and especially if you have a intake your running more than 10psi unless you are controlling it.

Is it possible that your running more boost than you think......or are you running more on purpose???

STEPHEN

im4u

p'cola is on the right track.how many miles are on the car?ur injectors maybe clogged up/thats why when it is being run not so hard at higher rpms there is not enuff pressure to put fuel through the secondaries.and when u put it through the gears hard it could be pissin fuel makin it run rich.white plugs means detonation.get a boost gauge see what kind of vacuum ur getting.it should read a good negative 16-17psi even 20 based on elevation.if it says anything between neg.10-12 psi ur hurtin.i change my plugs every 5k miles.also try resetting the ecu.disconnect the neg. battery cable and press down the brake for 30 sec.no an exhuast leak or 02 sensor will not cause this.02 only reads at idle and up to like 2k rpms.then it goes strictly fuel map.i have a huge exhuast leak it is not effecting my car but then again i have all the upgrades.a minor one shouldnt hurt but u need to tighten those bolts ,cuz if the leak is b4 the caught it might make it run lean.as for ur turbo not spooling....hmm....maybe not enuff exhuast gases to power it cuz it is runnin lean , and there is not enuff combustion.dont take my word for this one.white speckles usually mean detonation,but when they are plastered white umm start savin some money.

Silver94

my vaccum is 16-18 at 900rpm idel and the exhaust leak is right before the main cat.

Blackbeast

What kind of boost gauge is that, does vacuum reads in cm/hg *if I recall correctly* cuz my dual timer and Power FC shows 40-45 at 900rpm idle.

Timmy

Silver94

I am sorry I should have said this it reads 16-19in of mercury

P'cola FD

That is reading vacuum in inHg. An exhaust leak post-turbo won't have an effect on performance or fuel.

Silver94

Ok this is somthing else I forgot to metion. The thing I don't understand is my boost gauge is saying that the second turbo is working but there is no increase in power unless I do what I did at the dyno, running it hard through the gears.

Roadracing7

iTrader: (2)

James,

After looking at the spark plugs, I have to say I don't think it is running lean all the time. The porcelain is a good color, but the 4 grounds have a lot of buildup that is light and black towards the center. I don't believe in spark plugs being a signal of engine condition (except in extreme situations) because engine condition in a turbo rotary varies way too much, you would have to cut the engine at 12psi, 6500 to see what's going on up there. a minute of idling and your results can be lost. Because the boost is remaining around 10psi, and the power is just dropping, it's obvious fuel is not there. VERY SCARY! I say start in the fuel system. Check the pump for proper pressure, high speed and low speed, check fuel filter, and proceed down the line... Of course you know I'll be around if you need help, but good luck.

Richard

im4u

i knew what u meant by boost silver 94.some of us wanna be ****.that is great vacuum and a good idle.check ur secondaries,if this not ur only car i would recommend getting them rebuilt by rc engineering.and a post turbo exhuast leak can have to deal with the leanness.for example what if u just took ur cat off without getting a new ecu to handle this it will run lean in the upper rpm range as his is.so check to see how big ur exhuast leak is.as i also stated if it is small it isnt probably this then.i was giving him some solutions.but i am not doubting ur skills p'cola,i am just trying to point out what i meant.

Silver94

Thanks for all the help from everybody I will et you all know how it turns out.