Ok, now that I'm home I can start getting annoyed with my car. Still has a part throttle low RPM stumble. Threw a MAP Voltage High code, replaced MAP, no more code. Still stumbling. Really noticable coming off of idle at part throttle, and is ever present rolling into WOT. Here's where it gets odd though. If I just crush the throttle, it doesn't stumble. Even sitting at idle, if I blip it, the engine will hesitate and stutter, but if I just smash it, it'll rev right up. EGR checks out, was throwing a code before the heads came off, but I did the "diaphram check" and all was well. New MAP, Accel 300+ with coil brand new, brand new vented opti, new plugs (old wires reused but had less than 1500 miles and were NOT burnt). Car also breaks up high in the RPM band (6000+) for seemingly no reason, and again no indicators. I'm totally stumped. Nothing is coming up on datamaster that would show a cause. I'm about ready to take the thing to a dealership (shudder) and let them have at it.

One thing though, my TB is a BBK 58mm, and at WOT the TPS volts are reading at 4.65, a tad bit high. Idle they are .92. Could this be a problem, or THE problem?

Other thing, the first time the car was on the dyno, the opti oil seal decided to do it's best rendetion of a sieve. Oil everywhere. Had to pull opti and clean off, replace seal, reinstall. I know the opti is known for the low RPM stumble, but could it also cause the high RPM break up?

Thanks, sorry about the long read. I'll buy ya a beer.

 

Sounds like it may be a fuel/air situation going on. Just a couple of questions. Why are you using such a big TB for such a doscile engine? They aren't recommended for less than 383 CI. Second, when was the last time you had the injectors cleaned professionally? What is your fuel pressure at idle and when the car is driven? How's the fuel filter? I still think you have a EGR problem with it is leaking air or sticking. Try swapping the EGR and TB from the good engine and check the other things I mentioned if that doesn't help.

 

Well, the 58MM was highly recommended by the guy who did my car, and he's rather knowledgable in the LT1 world. A/F is good, been tuning constantly with PCMforless. The Injectors are brand new SVO 30#, and the fuel filter is only a couple years old. When I pressed on the EGR valve, it was moving under a little pressure, but it was smooth and felt good. The stumble problem was non-existent before the Head/Cam package, and the guy who did my car said that it wasn't present the first time he had it on the dyno, only after the opti had to be pulled and put back on because of the bad oil seal. I'm pretty much just trying to rule out anything else other than the opti at this point.

 

Well, if your saying the stumble is NOT there under WOT, then take info consideration what sensor is not working at WOT, the o2's Those will most definitly mess with your a/f mix, i say change'em and see where you stand. I belive Jason Cromer has great prices on them.

 

Well, it actually is there. It breaks up above 6000 RPM and there's that TIP IN hesitation that I can't seem to get rid of either. The only time it didn't stumble when I smash it is in neutral, and before I get flamed I only let it get up to about 3000 before I let off. Other than that, if I'm rolling in gear and floor it, there's the momentary hesitation.

The O2's are only about 2 years old, 2K miles at most. Had datamaster running and been looking fine.

 

Mmmm... I got the exact same problem!! My car is not as modded as your car though. My O2's are OEM Delco and have only about 3k miles on them. I'll be scanning tomorrow and see what codes I get. I even thought it could be transmission related as otherwise it revs/pulls ok.

Let you know what I find at my end ...Laterzzz

 

Yeah, I'd like to know what you find out. Thanks!

 

Sorry to go a little off topic but I don't belive the '93s have the same prob with 02 sensors as the '94+s. Unless he has done the conversion.

 

Conversion?!?!? Are you crazy. I like my 93 specific stuff. Only conversion I've done is the opti. Speaking of, gonna find out next week what the deal is. Ordered an opti today.

 

I had a tip-in hesitation too. Mine was the EGR valve. I removed it and soaked it with brake cleaner and then blew it out with compressed air, several times. It never used to move before this.

Even though your diaphragm moves, it may still not be working fully. I'd try cleaning it and see how it goes. It's only two 1/2" nuts to remove.

 

I'll probably do that too, but I'm still going to do the Opti just in case. If it's not the opti, Hey, I've got a spare if either of the cars decided to dump.

 

maybe you should replace your wires

i know that's almost like telling someone to swim over niagra falls if they have an LT1, but... what else could it be?

i just went OVC and the car has never run so well. i had a miss from a burned wire. maybe one of yours has high resistance even if it doesn't look burned

 

Just finished scanning mine with DataMaster and FreeScan ...mmmm, NO codes and everything looking ok.
Hate it when this happens!!! Still have that small "shudder" between 1400 and 1900 rpms no matter in what gear. Torque Converter switch?? TPS values look ok.
I can email you the files if they help in any way.

Laterzzz...

 

I have the OVC setup, less than 1.5 years old, less than 2K miles. They're fine, I've double checked them.

Hopefully the opti is the problem, hopefully......

Zyber, I'd take ya up on the offer, but I wouldn't be able to help out. My datamaster files look just fine too, no codes, no problems......Of course, the opti has been notorious in the past for being bad and not throwing codes.