I have a 1992 camaro z28 that was an original 305/5speed but now has a crate vortec 350 that we put l98 aluminum heads on, an lt1 cam and a Holley stealth ram. Ever since the swap was completed it won’t take fuel and stumbles and falls under any throttle but idles fine. Any help would be much appreciated as we cannot figure out why it’s doing this.

 

You need to datalog once you do a starter tune.
Im assuming you went with 22#hr injectors ?
https://www.thirdgen.org/forums/elec...a-logging.html

 

We had a new chip burnt and we ran 24#hr but also tried 19#hr and they didn’t do any better

 

We had Scott Hanson burn a chip for us and recommended 24lbs Bosch gen 3 injectors. It revs to about 2800 and starts cutting out horribly, almost like it’s not advancing time.
I put the stock chip back in, changed back to 19lbs injectors.
Nothing changes. We had it at a local mechanic to tweak the exhaust because of an exhaust leak and asked him to take a look at it. He double checked to make sure the rocker arms were adjusted properly, checking timing, intake leaks etc. I’m honestly out of ideas.

 

Has a new icm been tried ?
has the fuel pressure checked ?

 

Installed a new petronix icm, fuel pressure stays steady @45 psi. Also ohm’d the coil, checked to make sure all the grounds were connected. I’ve unhooked the time wire and tried the timing at 0, 4 btdc and 4 atdc. At one point, I could turn the distributor manually while it was running and it seemed to take fuel better but upon shutting it off, it was so far out of time it would barely turn over.

 

Any major differences with the tunes and injectors with how it performs?
Has the coil been changed sounds like it might be breaking up.

 

Does it do the same with the factory chip? It wont run great, but my guess is it wont do what you're currently experiencing.

I agree with Tuned though... need to datalog it.

 

Anyone else thinking that it sounds like maybe someone should go back, roll it over to the compression stroke on #1, make sure the distributor isn't 180* out, doublecheck the firing order, etc? Because that's the first thing that comes to my mind...

 

Certainly worth checking. But it would barely start at all with a distributor that's 180 out, let alone idle fine. Maybe it's off by one tooth though?

 

180 out and all the plug wires moved around they can sorta work... Why are you looking at me like that? LOL Briefly drove a car like that, then decided dropping a distributor back in right wasn't a big deal and corrected it. Ran better right, ran wrong well enough to idle.

 

The coil is less than a year old, but I’ll probably run by the local parts store and grab one just to check. There is no difference running wise with either chip. I even tried an old hypertech chip I had laying around. Yesterday I put #1 up on the compression stroke and verified that it wasn’t 180 out.( that had crossed my mind as well).

 

Maybe it's off by one tooth though?[/QUOTE]

that is possible, I’ll try a new coil and if that doesn’t work I’ll pull the distributor. Btw, thanks everyone for the input so far.

 

Any chance you could datalog with Tunerpro? As they say a datalog can be worth a thousand words....

 

I was finally able to record a little bit of data while looking at the list on tuner pro. Target afr was in the red at 14.68 at idle, I’m guessing because of the 19lbs fuel injectors we put in just to see if it made a difference. Tried a new coil with zero improvement.

 

Maybe post the log here... does it include when the anomaly occurs?

 

I’m going to be at work the next few days. I’ll see if my son can post it up.

 

BTW, does the calibration you're running account for the 45 extra cubic inches on the displacement?

 

Yes. We have 1 chip for the 305 that was previously in it and a 2nd that is for the 350. I’ve tried them both.

 

 

How could one tell if the chip was burned for a lt1 cam?

 

Your BLM's are starting to bottom out at 108 as you get into closed loop and the operating temperature increases. Indicates that either there's a malfunction some place, or the bin is commanding too much fuel and the O2 sensor is telling the ECM to trim it back out (only problem is at 108, the ECM is out of adjustment and you actually end up with a rich mixture).

My guess is if you're that rich on normal fueling, you're probably overly rich everywhere else (AE, PE, Open Loop, etc). In these fueling modes, there is no correction via O2 sensor. Overly rich AE will cause stumbling on throttle transitions (even stalling if it's rich enough)...

Not sure what was done to the bin...

 

Is it possibly the ECM its self that is bad since it does the same thing with both chips?

 

Everything in the data suggests the ECM is responding properly to the sensor inputs it's being provided. So I'm skeptical the ECM is bad.

Have you tried this combination yet: Your factory (I'm assuming they were factory) 19 lb injectors with the factory chip? That engine combination should start up and idle decently with a factory calibration and factory injectors.

 

Yes, the 19lbs injectors are what we have in it now. We have swapped injectors and tried both chips with each set of injectors. It will idle pretty good with either set up but starts missing and won’t rev past 3000-3200 rpm. It acts the same under a load while driving. I’m beginning to wonder if we may have pinched a wire or something when we installed the engine.

 

There could be something going on with the passenger side that the O2 can't see....

You said you tried the chip with the 24lb setting while running 19lb injectors? Do you have that data? What does the latest 5-4.xdl file represent?

 

The file I had uploaded was the 305 chip w/the 19lbs injectors. If I don’t work this weekend, I’ll swap over to the chip for the 24lbs injectors and data log that as well.