got a stock sbc 350 with rochester/gm tbi and a howell harness and chip in my cj7. well, 2 howell chips now. with the 1st chip they sent, it idled rough and was rich. called howell, told them the codes etc and they burned a new chip and sent it out. now, 2nd chip, it's still running rich and slightly better idle but still a bit rough. so the new chip didn't resolve it. checked for vacuum leaks, no vacuum leaks have been found.

is this likely a chip problem that howell can fix? the guy at howell said sometimes it takes a few tries to get the right "burn" on the chip. anybody gone through this with them?

any other stuff i could/should investigate?

Check your EGR valve, your exhaust sensors, and temp sensors. Could also be your injector o-rings.


Just a thought

Also check to be sure that your fuel return line isn't too small.

I would think that Howell would have had you check that first before burning a chip though.

no egr (howell knows this), new o2 sensor from howell, new temp sensor from napa, and the injector o-rings are also new. hell, everything is new. fuel lines too... both of em.

I'd suggest putting a fuel pressure gauge on there--ECMs assume the correct fuel pressure is present. If it's too high (or low), a GM ECM (and I'll assume the Howell ECM) will adjust the fuel mixture, based on O2 input (only when in closed-loop); however, it can only adjust so far. So a scanner can tell you if the "long term" and "short term" fuel trim parameters are correct. From the numbers you can infer what your problem is, as well.
Can't see how anyone could burn you a new chip without having the trim numbers pulled from the ECM, and hope to have it right.

thanks bubba. i'm kinda playing middle man here so i don't know 100% of the info. i do know that the fuel pressure was 15 psi which howell said was too high. by the way, the fuel pump is from howell as well.

is it possible that an obstruction or restriction in the return line could cause the fuel pressure to be just a tab bit too high?

and what about a fuel pressure regulator? is there one in the throttle body unit? if so, could that be it?

15 psi is too high, and probably would cause a rich fuel mixture at less than wide open throttle. The return line should be without restrictions and at least 5/16 tube. A restriction in the line, or it being too small can also cause high fuel pressure.
The TBI does have a pressure regulator built in, that can be modified to be adjustable.
There is a site, I think "thirdgen", or something like that has a detailed wright-up regarding modification of the TBI's fuel pressure regulator.

Try this site for TBI regulator mod:
http://www.thirdgen.org/tbi-afpr

great, thanks for help bubba.

ok, tweaked the pressure reg. and it's now at 13 psi. return line is good, proper size and no restrictions or obstructions. valves were also adjusted slightly to try to improve the idle. it's still idling slightly high, above 1k, and stumbling; not smooth.

this is a brand new, supposed to be stock, rebuilt motor built by a local shop. never run before, never even had fluids in it. could it just be that it needs to be run a bit? anything else to try? i'm wondering if it has an aftermarket cam in it.. that could cause this couldn't it?