Hello, still having trouble with my MAF car.

I'm running extremely rich at idle. So bad that I'm afraid to take it on the road or leave it run to long. My specks are at the bottom here but I'm wondering if I'm starting with the best bin by running my stock '87 350 bin. I need to lean this thing out enough at idle that I can run it but my computer thinks the car is lean so it add more fuel. What's the best way to stop this with my setup? Or if anyone has had a similar combo what is the best starting point? I fixed any vacuum leaks it had and backed the FP down to 42psi w/ no vacuum. I put in a new O2 sensor, reset the valve lash. Vacuum is pretty much in spec with what Comp says at 11 @ 800 rpm and 15 @ 11 rpm.

Spec: 383 w/ 10.5 to 1 comp and aluminum heads
Comp XR276HR cam with 4 degrees advance and 114 LSA
1.6 rockers, T-56, AS&M runners, Edelbrock base, 24# Ferd injectors
MAF car with $32B bin modified with Tunercat software.

If I don't get it running soon, here comes the carb.

 

If you lean it down and the BL's go up, then your too lean, as the computer sees things. Look to see if there are any vacuums leaks, or mechanical problems. If not, might try a new O2 sensor.

 

Grumpy, thanks for the reply. I was really hoping you specifically had some ideas for me. I double and triple checked for vacuum leaks, put in a new O2 sensor, and have been over the mechanical side a few times now. Should it be drivable at all with the stock chip and the above combo? I get no codes at all with it.

 

swith to the 6e code using the arap or any other bin you can get and use the maf tables to lean it out. that is the easiest way to do it. the first maf table will take care of the idle.

 

Well, you've said you leaned it down but the BLs went up. Which means it's actually too lean.

Just as an experiment try increasing the injector constant, and see if that doesn't clear things up. Go in say 1.5# increments, and do slowly. First seeing if the car idles, and just under light load test drives until your sure about where you are.

 

One more quick thing to try

Try unplugging the MAF sensor.

If the condition clears up, you know what to do next.

Mark

 

I'm not sure if you have the option to adjust pulse width for voltage in the $32b mask but that's a good place to play with adjusting the A/F ratio at idle.

 

isnt there a 3d table for airflow in 32B?

https://www.thirdgen.org/techbb2/sho...hreadid=133967

/N.

 

You may try messing with the closed loop rich/lean threshold vs airflow table. Not sure if its in 32B but is in 6E. Try setting it to around 450 to 400 mv from 0 to 16 gm/sec and see if it cleans your BLM's and exhuast smell at idle some. Not sure if it'll work for you, but I've been messing aroudn with it, with some success.

 

Thanks for all the help everyone. I started adjusting the injector constant and had it all the way up to #32 last fall before putting the car up for the winter. Then this year I read about the 3D Pulse Width/RPM/Load table and have been using it while putting the constant back to #26. I decided my plugs were shot after all this time running rich so I started researching running hotter plugs until I get my chip close. That's when I found out I was running the wrong plugs all together. I was still running NGK UR5s with a tapered seat and I believe my Canfield Aluminum heads want a flat seat with a washer. I bought some and will put them in this weekend and see if that helps.

 

Well the new plugs are in and I seem to be on the right track now. The car is running pretty smooth, pulling vacuum better, and BLMs and INT are getting close to the magic 128s. Grumpy, I must thank you again for suggesting a mechanical issue because it sent me checking again.

Here's an interesting one that I can't explain though, 7 of the plugs were completely black with carbon fouling and gas. One of them, number 5, was perfectly white with no carbon. Cylinder was firing though.