Running rich, with open headers...

[bwh13]

Would running the open headers cause the ECU to richen up the mixture enough to make it run rough? I have to start it up to move it in/out of the garage until I can put on the convertor/muffler this week. Pulled 2 of the spark plugs that I couldn't remove earlier and both were black...

Fuel pressure is around 50 on the adjustable FPR so I don't think that's it...

[e30polak]

What motor?

As Matt has stated before, the FPR has to be set to 3.5 bar.

If you have an obd1 s52 with 24# injectors and no cams, it will run rich (ask me how I know).

[BDSax]

i dont have an AFPR but i ran my car with open headers for a little plus 15 miles to go to the muffler shop to get a price, then back again. no problem

[yberther]

^^just loud as hell? i think I will end up doing this.

[BDSax]

yes, Very loud as hell

[flawdaboi407]

Im going to run my m30 with just downpipes when I take it to an exhaust shop. What are you getting done and how much are they charging? Good luck man.

[golde30]

do you have the o2 sensor hooked up?

i also drove my e30 6 miles though a metropolitan city(san francisco) open headers to the exhaust shop...omg it was soo loud ppl got scared and ran away. it was hilarious.

[trelms]

Im guessing its OBD1 and the O2 is before the cats... this would not make your car run rich.

Mass air sensor? what injectors are u running? what chip/map/fuel system?

[bwh13]

Sorry, forgot to be more specific...S52 w/OBD1 conversion, 540i MAF, pink top injectors, 413 ECU w/chip from Matt, Ebay headers. All new sensors, etc.

Car starts right up but doesn't seem to idle smoothly, and won't really accept thottle blips without hesitating...and it's damn loud inside the garage.

[EtaSport]

Check to be sure the maf is installed correctly as in look at the arrow. I thought there was no way in hell i could install the maf backwards, but i did and it ran as you describe. (open headers too)

[matt]

MAF backwards could cause this sort of issue, so could the lack of a real exhaust. It's possible that air from outside the exhaust could be coming up the exhaust between pulses and causing the O2 sensor to read lean (and richen the mixture).

50psi is correct on the FPR. Were your spark plugs brand new and they're black now? Were they wet with fuel after running?

[bwh13]

OK figured out what it was. I remembered I had to adjust the throttle cable to get it to idle, and realized that shouldn't have needed to be done since the IAC controls all idle functions on signal from the DME. I suspected the IAC was malfunctioning so I swapped it for a spare and it idles nice and smooth, throttle blips are clean and crisp.

Still loud as hell in the garage...

I have the exhaust almost figured out, running dual 2" pipes from the headers into a 2 to 1 catalytic converter and then into a short resonator before going to the rear muffler. Hopefully I'll be able to drive it by the end of the month!

Thanks for all your suggestions. It's almost done...11 months and counting.

[platanos]

Whats IAC and where is it located??

[bwh13]

Idle Air Control valve under the intake manifold. It regulates the air coming into the intake manifold at idle.

It's the oblong cylinder with the 2 large diameter hoses attached. 1 hose goes to the back side of the intake, the other to the air intake boot...