I'm driving last night and my wideband started showing some reaaaaally lean spikes. It got to the point that I couldn't get it past 20% throttle without leaning up to 18's in the AFR's When it gets to that point it lags up, kinda hesitates a bit.

I'm about to get this thing rebuilt in two weeks, but until then it's kinda my DD.

Background information:
I'm 99% sure an apex seal is blown on the rear rotor... I know, I know, I shouldn't be driving it, but at the moment it's a necessity situation.

Mods:
Emissions removed
Rats nest removed
720cc sec.
Walbro 225
E-fan
Greddy FMIC
Greddy BOV
RB DP
S-AFC
Greddy EBC
PYX Wideband

Is this lean situation caused by the blown apex seal, or is there something else?
No CEL's, everything else is running properly....

 

I dunno for sure, but if your rear chamber is not combusting, then wouldn't the O2 sensor just be reading the increased unburnt air coming out of the port?

 

i would think it would tend to be richer rather than leaner with a missing apex seal. so i wouldnt think that your 2 problems are related. have you checked to see that you dont have a vaccum leak somewhere like near the afm, TID, intercooler, etc. (sorry, dont remember now if you said it was NA or TII)
i know that my car had that problem more than once, due to a crappy TID not holding its boost, and leaking.

 

It's a FMIC, so there is all metal piping.... I popped off an intercooler coupling before this happened, wasn't even really boosting hard at all. I obviously had to pull over and fix it, otherwise it wouldn't drive, lol. But that was way earlier in the night. I'll check again for vac leaks though.

 

Also, you might drive around w/ a voltmeter backprobing your fuel pump. Observe the pump voltage during these spikes. I had a similar problem on one of my old fc's where voltage would drop and a lean spike would happen (bad enough the car bucked). A fuel pump rewire fixed it.

 

hmmmmm..... that sounds interesting...... just got a new multimeter too. I will investigate tomorrow and report!

 

so any news?

 

If the rear rotor is not firing then all bets are off. A wideband will read misfires as lean spikes. There's no point trying to troubleshoot with a wideband on a blown engine.

 

Yea, it was blown. It finally completely died about a month back, and when we took it apart it had chipped seals on both rotors. BUT it's almost back together now.

Curiously though, just before it finally keeled over it would be rich as hell (10's in the AFR) until it was completely warmed up, and when it did occasionaly lean out it wouldn't really spike per say, but it would hang out in the 18's until I did something to change it. But I think that is most likely due to the bad seals, like aaron and other suggested.

Moral of the Story: Get dem apex seals fixed.

 

JB weld?

 

Magic Putty preferably....

 

sorry, dont mean to hijack the thread, but what all does it take to hook up a wideband and get that goin?

 

Oh, also you've probably killed your wideband O2 sensor so make sure to replace it when you rebuild/replace the engine.