I have a 86 mustang with the 3.8 CFI. After getting fed up with drivability issues I pulled the CFI and dropped on a amazon chinese 2bbl that resembles a motorcraft carb. After running it, it sounded like it was running rich (carb was for a 351 so it should be a 1.21 venturi but who knows) So, I ordered an AEM a/f gauge/o2 sensor kit. Got it installed and it read 14.5 for about 10 seconds then went hard lean. I found a vacuum leak and fixed it. Even using the choke to flood out the engine is stays lean on the gauge and sometimes drops to 14:1 but really, just stays at hard lean. Feels and sounds too rich though. By quickly pumping the throttle it will drop to 14 or 13 so I thought, ok it is lean. BUT....spraying quick start in the carb when running drops the rpm which indicates rich. (I used the quick start to find the vac leak, it increased idle rpm when I hit the leak which indicates lean....ARG!!
So, I pulled the jets to compare them to other jets I have. That's when I found out the chinese carb doesn't have motorcraft threaded jets! Good news is, I have lots of holley and carter jets in the shop. Holley are too small diameter but the carter jets from the strip kit are the correct thread size and pitch! What I plan on doing tomorrow is popping in some massive (in comparison) 78 jets and see if I can get it to go too rich. (I have jets right up to 120!!)

The question, is there a possibility of the gauge reading too lean 18:1 even though it's actually running rich because I mounted the o2 sensor about 48" away from the port? The instructions said to move it to 36" or more if running a turbo due to heat. What happens if you run it that far or more without boost? Run too cool to read correctly?

Anyway, tailpipe smells rich but maybe I'm missing something. I'll be doing the jet swap tomorrow regardless but would like to hear other opinions.
Thanks

 

Why are you wasting time with a junk new part? Buy something quality first, then work on dialing it in. Too many unknown variables with imitation auto parts. The reason they're so cheap is they have no standards or QA/QC. Perfect example you noted. Jets dont use Ford standard threads. What else isn't held to a standard?

 

So...I put in 102 jets, the jets from my carter strip kit are shorter but right diameter and correct thread. Still running lean according to the gauge. Found some vacuum leaks and fixed them. No change. Said heck with it and installed the race carb from my 79 mustang stocker, WOW!! Lay tracks from a dead stop in gravel and would even give a chirp to the tires. (I installed a traction loc unit when I was drag racing it) OK, so I know it's a carb issue, forget the gauge, tune like I used to. Checked the vac setting on the power valve, too high (idle is about 20" vacuum and powervalve opens around 16-17. Pulled a powervalve from a new rebuild kit and installed that. Better but still blubbering fuel out of the booster cluster. Pulled the booster cluster and tried to put a ford one in. The ford has 4 emulsion tubes and the chinese one has 2 in the centre and the two on the outside are just air bleeds to the booster??? Tried to install the ford booster and the outside one bottom out so I trimmed them off just below the 4th hole. Installed the booster cluster and...bolt is different diameter and thread pitch. Used the chinese bolt to hold the ford cluster in with the 102 carter jets. MUCH better response but still too much fuel. PERFECT! Getting somewhere. Pulled the 102's and put in the smallest I had which were 68's (stock chinese ones are about 55-60 max) Working better!! Changed the accelerator arm from the highest hole (most fuel) to the lowest setting (least pump shot). NOW IT'S SOUNDING MORE CRISP! Now on pavement it will leave about 6-8" of black mark from both tires. On dirt it roasts the tires.

Gauge? Still reading hard lean. Turned the key on, let it cycle, it goes to 14.5 and then slowly rises until it's hard lean..and I didn't start the engine!! So, I have the o2 sensor back about 48" or so (convenient place to install) I think my next move is to move the o2 sensor to one primary pipe 12-14" from the manifold. This should only give air/fuel from one bank and with more temperature as well. Can't find anywhere saying what the correct install distance is, only "if running turbo, o2 sensor should be 36" from manifold to prevent o2 sensor damage from heat".

Has anyone else ran one of these AEM a/f gauges and where did you place the o2 sensor??

And Derf00, I'm in a severe rust belt and carbs are not in the junk yards around here. I found a couple on market place but all used/questionable carbs. I was going to rebuild one (why I bought the carb kit for $78.00 here) but then saw a brand new chinesium one for $120 and thought, "how bad can it be"?? (just noticed you're from AZ, that's where I got my race carb from Deano's carbs in Chandler AZ. Told me to send him a carb and he would rework it for racing but I didn't even have a good carb to send him. He had to get a carb locally, build/modify it, then send it to me.
All good though, I never take the easy way. Wife wouldn't go in my off road ranger because I rolled it with her as passenger. "put in a roll bar or I won't get back in" OK, simple enough, build a hoop like a jeep and....a month later I rolled out the truck with a complete exoskeleton because I don't like roll bars in a vehicle unless you're wearing a helmet. Get in an accident and wack your head on a roll bar can be deadly. Never take the easy way!! LOL! A few hours of bending tube and welding and I could of had a single hoop with 2 or 4 down legs like a jeep, but nooooo, got to do it the hard way! LOL!!!

So again, has anyone else ran one of these AEM a/f gauges and where did you place the o2 sensor?

 

Update, I got another bung and welded it into the drivers side primary pipe. Plugged the old hole and...NOTHING!! Still fires up, goes to 14-15 then climbs to infinity. Drove it around, hot and cold, lots of ide/full throttle, highway and back roads driving. Once it climbs to infinity, all I have is the 4 dashes where numbers should be.
So, apparently no one here has had/used/did anything with an A/F gauge so if no-one else responds, I guess I'll check other forums.
Thanks anyways.