ya, after setting timing, tps, cleaned IAC,new intake gaskets, still have slight miss in motor, but it's not there ALL the time.

Kind of a misfire that feels like a bad plug. Checked them, they're all good.
Pulled one plug wire off at a time and seemed like they were all firing ok.
Unplugged o2, drove car and it felt solid, no miss and pulled hard thru the gears.

Put vacuum gauge on it, reads about 15-16 inches, not quite in the 'Good' zone (around 20 maybe?), so I don't think there's a vac leak, but it says late timing for motor, it runs worse with more timing. I set timing at 6* with tan wire unplugged.

Anyway I'm stumped for now, any ideas?

 

When was the last time you changed the o2? It's supposed to be changed every 20,000 miles. That is the main sensor the ECM looks at to determine your air/fuel adjustments.

When it fails, it fails lean and commands rich. Basically making your car run like crap and get horrible fuel mileage. If the ECM can't see it, it defaults to the tables in the ROM.

You should have about 20" vacuum with the stock cam IIRC, start looking for a leak somewhere. When did you last change PCV? If the check valve in that goes bad, it's no longer a "controlled vacuum leak", it just becomes a vacuum leak. You're supposed to replace every other oil change for the PCV valve. It's only a couple bucks anyways.

Take care of those three things and see how much better it runs

 

thanks binky, yes new pcv and hose as well, the o2 was replaced last summer when it started to run bad, but I drove the car with it unplugged last year for awhile, maybe i'ts covered in soot like my tailpipes and intake were?

I know that pcv is working, I can hear it when the car is idling.

Mileage was pretty good on Suday when I drove it, but I'll pull the 02 and look at it today, if it's dirty should I clean it or replace?

I'll also look around at vac hoses for leaks. thanks.

 

You are definetly out of tune alittle. I have a LT4 cam in mine and I tuned it to pull 22psi of vacuum.

I would check into the o2 sensor again. That could be the problem. I haven't been around fuel injection for awhile so I'm not to good with it anymore.

 

cleaned o2, found a couple of so-so vac lines and replaced, still have that lumpy idle- although like I said, it's not there all the time.

Going to change fuel filter, maybe my fuel pressure lowers after running for about a minute or so, then goes to the lumpy idle.

Have 22 inches of vacuum going down the road, 15-16 at idle.

 

Like I said I pull over 20psi at 500rpm idle. And my cam is slightly bigger/more duration. I would keep checking for small things like you are. It is probably something cheap and easy to fix.

 

thanks for the tips....

anyway, I can't find another hose to check, I think I've done them all,

Changed fuel filter, added some fuel injector cleaner.

Sure sounds like a bad plug wire, but it runs so nice and smooth - for awhile, so It can't be ignition.

A buddy stopped in, said he had injectors taken out and professionally cleaned, said it cured his problem.

Any ways to check them still on the car?

Plus, I'd like to test my fuel press. regulator, how do you do that?