Fixed. Thank you.

 

So what the heck? Because I was pointed in the o2 direction in an accidental thread I posted in the wrong part of this forum and this thread. What could this be then? That's what I figured it was by now.

 

Find out which sensors are involved in both, then test the ones that could cause these issues.

 

I took the o2 loose from the car and cold started the car. It never ran so good since I've had it. The car still ran rich once warmed up but was more predictable and had better Afr over all. So long story short, I will buy an o2 today and keep you guys updated. I really appreciate all the generous help.

 

That makes no sense, but never look a gift horse in the mouth. LOL

 

Well when the o2 was plugged into the plug it went lean when cold started and wouldn't idle. The part throttle when cold would lean all the way out. When warm it went all the way rich. When cold started with o2 unplugged the car hits stoich and sits there. When it warms up it Richens out a bit. When there is no o2 warmed up Afr reads 13-14 part throttle. When the o2 is plugged in it sits at 10-11 part throttle. In my eyes that tells me something. If I'm wrong I have put a new o2 in the car. No harm there.

 

Did anyone rule out exhaust leak ?

 

no O2 at cold start = stoich and then rich once warmed up makes sense, even though i'm a bit surprised. but weird that the sensor was causing cold start issues when it's not used.

maybe the sensor wasn't showing it warming up properly, so the ECU went lean in an attempt to do so. but if that were the case, it would do the same when not plugged in. the O2 must have been sending a REALLY bad signal to the ECU LOL.

you never got a CEL for O2 sensor heater malfunction? either way, good that you found it. i'll make a mental note about it actually affecting open loop. i had no idea.

nice find, dude!

 

but if it was an exhaust leak, it would be rich when it was plugged in....oh wait...




btw.."part throttle" does not necessarily equal open loop. Messing with the 02 sensor will have no affect on open loop fueling.


OP...it sounds like when the sensor is not plugged in, the tune is actually setup quite well to where it does not "need" the sensor. It would make perfect sense that if there was an exhaust leak pre-o2 that it would "fix" the issue by dumping fuel during closed loop condition, meaning that it is working properly. Im also willing to bet that a few gaskets are cheaper than a factory o2 sensor.

 

+1 which would explain why it reads lean during open loop. i'm still thinking it's not the sensor. exhaust leak would make waaaaay more sense. i'm glad someone else chimed in. while at work, it's hard for me to concentrate on the easy answers

 

I think it does have clicking but I assure you an exhaust manifold isn't cheaper than an o2. But you guys may be on to something!

 

I have done some more testing and found out that the bottom of cylinder one on the tubular manifold was cracked at the weld. The whole thing all across the bottom. So I guess let us start there. Thanks for that information.

 

An exhaust leak at idle in closed loop pre wideband, post nb will yield a lean reading on your gauge while fuel trims are still 'good'. An exhaust leak pre nbo2 will yield fuel trims typically positive.

This works because a leak will draw a vacuum with the flow of exhaust essentially scavenging fresh air through the leak.

That close to the head I don't have any experience with. I've always had a leak at my o2-down pipe connection (buschur downpipe). Solved with some proper o2 housing fitment mods.

You can get a lean reading in closed loop and still lean in open loop, but you can add enough fuel to make it read right, just know that it's much richer than it would suggest.

This is reason number 1 why I have my wideband up front. Idk if it kills a sensor in 2 years, the quicker response time on top of less Murphy's law is where I'm at

 

funny, my BR downpipe has always leaked as well. Im pretty sure it only affect the readout at idle as once I started cruising, the WB would read 14.7 indicating that the o2 was doing its job. But this definitely threw me off during my early days of dialing in SD at idle.

what did you do to fix the leak? Mine is currently off the car and Ive got a new o2 housing. If there is something I can do to make sure it doesnt leak, Id like to do it now.

My experience was that during part throttle, cruising and WOT; the leak didnt affect anything and I could trust my WB. Im assuming that is because the exhaust pressure is enough to make it expel exhaust gas out of the hole as opposed to sucking it in. But Im sure that is directly related to the size of the leak.

OP...Id look into getting a used stock manifold. My old tubular cracked 3 different times and after the 3rd, I decided it wasnt worth welding back up and junked it. This is exactly why I just got the FP cast mani. You got to pay alot for a tubular that you can trust.

 

I used a n autozone gasket for a rx8. Worked well. The main problem was te o2 housing didn't fit securely into the downpipe. So check that they lock in when you have it off the car. The gasket was insurance. Search in engine turbo drivetrain and the part number is in there along with others who fixed it the same way.

Yeah really killed my first year of speed density lol.