1985 Corvette

I was afraid of that. I got it off gearhead efi forums from their list of downloadable bins. I didn't see where it said stock configurations, so that's my fault for not verifying. Next question: anyone know where one can find a stock AYPY bin? No telling what else is off on this bin. I'll mess with it some more in the meantime.

THE 383 admiral

I just looked at bins from.
http://www.eecis.udel.edu/~davis/z28/
they also have a AYPY with the same timing. The ARAP was identical. I do not believe these reading's
If that is stock?? Wipe out the table and replace the timing with the 89z TPI 350 personally read AUJM .bin timing. I just read that bin. Also change RPM'S 400 - 800 To 20deg

THE 383 admiral

Any progress with your start up - initial settings.

1985 Corvette

Hi 383,

I wanted to follow up with a few issues I have run into. The 58mm TB is a Professional Products piece. It was an ebay score that came with all sensors and I noticed the TPS was not a slotted design. I spent some time slotting the TPS because achieving .54 voltage reading in its original state meant the blades were closed completely. I have done some reading on a "drill mod" in the IAC passage way that is lacking on many aftermarket TBs.

Start up requires coaxing of the throttle but after a few moments, it idles on its own. I've been piddling with the timing......but trying to get it to 10 degrees chokes it down in the 600 rpm and lower area...by the time I get it to 10 degrees it's long dead. Maybe shoot for more timing? I shut the car off, disconnect the power adn wait for about 30 seconds. I plug in the tan w/ black stripe wire for the ECM and start it up and I run into the same issue again with needing to coax it for a few seconds of light throttle.

After that, it lopes and idles at a nice 850 rpm area. Sounds fantastic! It's just that I've got some little kinks to work out. My next step needs to be a data log cable. I'm looking to have the car back on the road in the next few months.

THE 383 admiral

Excellent update. You are now progressing in the right direction.
You should easily be able to get your timing in the 8 - 10 Deg range @ 600 - 875 RPM's as of now i would guess the pp TB is giving you issues. I know my HSR combo loved more timing on my previous build i had it dialed at 14 - 16 Deg. I'm sure you could bump your timing to 12 Deg with the MR. Data logging will supply you with all of your needs. From crank, start, idle, inj duty cycle & so on. Keep up the pace. You are so close to completing your project & goal.

bjankuski

Check your IAC counts, you may have to open the throttle body by adjusting the throttle blade set screw to get the IAC count near 20 counts when the car is warmed up and idling. Timing on a modified engine can usually be at 15 to 20 degrees at idle, and you may have to hold the throttle open to set the base timing at 6 degrees with the timing connector disconnected.

1985 Corvette

I definitely need to do some data logging or I'll be chasing my tail on this one forever. The TB came from a reputable ebay seller that had a variety of TPI parts. He mentioned, "everything is set just bolt it on" but it may have been set for a 350. I tried it as-is out of the box but the 383 was not having it unless I cracked the blades, which threw off the TPS reading in the .68 voltage readout area. Even after adjusting for the .54 with the slotted TPS, the engine shakes and fusses quite a bit once I get close to 600 rpm from rotating the distributor. But in the 800-900 rpm area it is great and the engine is no longer vibrating and shaking. Amazing that 200 rpm difference is the difference in a smooth runner and a shaking, stumbling mess.



The base timing of 6 degrees is for the factory configuration, right? The base timing constitutes the idle? If I set the base timing and everything else is handled by the ECM right? Would the base timing be the 10 or so degrees I'm after? Not trying to be dense, just want to make sure I'm on the same page. As to the IAC counts, gotta do my homework on using Tunerpro RT to read those. Looks like Moates will be getting more of my business for a cable and a few other bits.

Another question: the cooling fan is on when I key on and it runs constantly, whether the engine is cold or running. I've got to go back in and take a look at the updated bin but can anyone recommend the best place to go for in the file first? It may end up being a faulty sensor somewhere but I don't remember this being an issue prior to altering the bin file from stock. This is an AC delete restoration.

Fuel pressure is at 50 PSI with the idle at 850 rpm or so. Are others experiencing that pressure level as well? Thanks for all the help, guys! I put fresh rubber on all four wheels and I just have to get it registered for Florida and we can finally start doing some actual driving instead of driveway guess and tune.

Cliff Harris

The ECM sets the timing at idle to 20° by adding 14° to the 6° base timing. Changing the base timing will affect that. The ECM assumes the base timing is 6° (it's one of the settings so it can be changed) and adds the 14° to it.

The ECM uses the IAC to adjust the idle speed by changing the amount of air going through the throttle body. If the IAC counts are too low then the ECM loses control of the idle and it gets lost. If you see an IAC count of zero it means the ECM has tried to take out as much air as possible but couldn't get to where it needed to be. That's a sure sign of a vacuum leak (air is bypassing the MAF).

There is a high pressure switch that tells the ECM that the A/C is on. That connection needs to be shorted out to stop the fan from running.

1985 Corvette

Just wanted to do a little update that most of my "tuning" progress has fallen off the map for now thanks to a rear main seal leak I am trying to remedy. I did want to touch on one thing I noticed and that's the ability to blip the throttle and get a healthy rev. If I slowly roll into the throttle, the engine revs no problem. If I do a quick blip of the throttle, the engine just sounds like its being upset/choked from its idle rpm and I get no rev and then it falls back into its normal idling.

I know a lot of my issues won't be resolved until I get it on the road and drive the damn thing but thanks for all the feedback. Once I get the leak and clutch interference issues resolved, I'll be back at it and update some more on progress or setbacks. Hopefully someone can pick up a thing or two from this in the future.