Cookwithvette

Well, after a lot of trouble and head scratching things are looking up.
History:

First attempts at starting resulted in a stall after about 5 seconds. I added about 10 points to about the lower half of the fuel map (400-2500 RPM) and it would start but idled at 2000 and ran pretty rough. Once, while shutting it off it dieseled and began revving back up! :eek: Not only that but the exhaust was coming out of the throttle body. The engine was running backwards! :crazy: Turns out I have a couple MASSIVE vacuum leaks and unfortunately both were feeding nearly straight into one intake runner. #7 wasn't running explaining the roughness and allowed a lot of gas to pump into the exhaust. Your imagination can figure out the rest.

After discovering the leaks I disconnected that portion of the vacuum system and plugged the hose but the battle wasn't over. For some reason I was having terrible trouble getting the thing to stop surging. That's when things got weird. The Commander 950 system uses a base fuel map and adds or subtracts fuel input based on other conditions, coolant temp, air temp, change in throttle position, O2 sensor readings. Well, my data set for coolant enrichment disappeared. Everything went to 0. Same for cranking and afterstart enrichment and Idle Air Control values, all 0. Needless to say that caused a bit of head scratching until I realized what had happened.

Now I'm at a point were the car starts and runs at a reasonable RPM but still surges a bit and giving it throttle is... rough. Stumbles a little, backfires sometimes, etc... It's at this point that I realize the fuel and spark maps are changing "on their own." Every time I viewed them I got similar but different values. This turned out to be my laptop. :rolleyes:

After lugging the desktop out to the car and running an extension cord I was able to get the thing running right in a matter of 2 minutes. No joke. Now it starts easily, idles SO smooooooothly, and copes with being put into gear and taken out nicely. I even stood on the brake and brought the RPMs up while watching the computer. Fuel map is nearly dead on for most cells. I had the oxygen sensor mounted in the header collector and there was some wondering about wether or not I'd be able to get closed loop operation at idle. (Oxygen sensors need to be ~350 degrees to start working.) Well... I get it. My car hasn't even seen the road since the swap and just warming up at idle brings me to closed loop. :hurray:

So, why am I not on the road yet? Well... remember those vacuum leaks I mentioned? One is the brake booster. Brake is hard as a rock. The other is the front crash bar which, on 75s, is used as a vacuum reservoir. Reservoir I'm not too worried about. If I can't patch that I can always get an inexpensive canister from Summit or Jegs. What does worry me is the brake booster. That looks like a real sonofagun to get out of there. Oh, well. Needs to be done. Complaining won't fix it. My only real fear is finding the reason it went bad is the master cylinder is leaking. I don't want to mess with that at ALL.

Anyhow, just thought I'd bring you guys up to speed on what the demented cook has been up to. Take care!

cardo0

Now I can tell that computors have made you life a whole lot easier. :jester And saved you a whole lot'a money too. :lolg: But it's good to see your making progress with the new technology. :yesnod:
We all have multible troubles with these 30 year olds. Sometimes trying to replace just one bolt results in rebuilding the engine! Or transmission! Or suspension! :eek:

Cookwithvette

Hey man. Glad you chimed in. Keep meaning to email you but having a bad memory :rolleyes: I keep forgetting. :bb First, thank you very much for the check. It was very kind of you. Also, did the manifold arrive intact? I was a little worried about the box but it was the sturdiest I had. Tried to pack it fairly well with padding and such. I guess I'm just nervous when sending things long distances. Hope everything is okay. Take care!

cardo0

Yes the manifold arrived in beutifull shape and thank you very much. You could have saved a few $$ and shipped UPS ground. I had plently of time to kill and know youv'e been busy. That intake got here soo fast I figured it was something else. Must be that it's off a high performance motor it just wants to travel fast. :cool:

PatsLs1vette

Sounds like your on the right track now :yesnod: itsnt ig great what new technology can do for our older cars. :thumbs:

81vette

Glad you were able to get it all figured out. I've been wondering about installing the O2 sensor in the collector. I was going to install mine in the collector and run it open loop at idle if I had to, but it's good to know that it actually works there in closed loop. :thumbs:

Mark

Fevre

Hedman makes a reducer with the bung already welded in. Summit part number HED-21106 for 2 1/2" pipe and HED-21107 for 3".

SmokedTires

:hurray: Looks like your on the right track :yesnod: . You should be cruising again in no time :thumbs:

Cookwithvette

cardo0, That's good to hear. Thanks! :cheers:

Well, I realized today that my brake booster doesn't need to come out. The idiot who owned the car before me apparently replaced the master cylinder but didn't feel like putting a gasket back in when he re-installed it. So, that's fixed. Now it turns out I have a bad headlight relay, there's a cool $70. Oh well. Also may have a solution for the laptop that doesn't involve getting a new one. With any luck it will be here tomorrow and I may get to drive it. :hurray:

Take care guys! :cheers:

burners

Hey that's great news! Mine was running pretty good until the bearings spun. It was so smooth and it had a lot more power. My old q-jet was really shot. Isn't it cool to make a change on the computer and have the engine respond? Which fuel map are you using? Are you running the ignition control as well?

phoenix

Boy... glad that you are finally getting it running right.

I am hopefully going to crank mine up with the TPI in 2 weeks.

I am just putting the finishing touches on the new exhaust and Vintage air before wiring up the TPI. :)

Cookwithvette

Burners, Yeah, I saw your post about the motor biteing it. :( It is a good excuse to build bigger and badder though. It is pretty neat having the engine respond to changes on the computer. I'm having the computer control the timing. I'm using a Delco CC distributor and MSD coil. When I started using the desktop the engine was already up to temp so I loaded the ZZ430MPI.950 fuel map which wouldn't run it before and gave it a shot. Since it was up to temp O2 comp was able to keep it alive though it was surging and showing a hard lean condition. I upped the entire fuel map by 4 and felt the idle smooth out a bit. Now it's running a little on the rich side ~98 O2 comp. Backed the entire fuel map down by 2. Surge picked up a little. Went over to spark, knocked that down by 2 and WOW! Car just dropped into a perfect idle. Only about 2 minutes. So far I've put it in gear and brought the RPMs up and free revved it and it stayed right about in the middle.

I can't wait to drive it. I can't imagine what it's going to feel like with all those vacuum leaks gone. :lol:

phoenix, I'll be keeping an eye out for your post! :cheers: