MRZ28HO

That is what I keep getting on the 6 cylinder scale in drive, plus code 44 (lean, duuh ). The plunger travel is .125 as per some rochester literature I have. Can it be the solenoid? I need more fuel.

Plus I have only 8" of Hg with all vacuum lines properly hooked up. I'm thinking the 268H is the problem with the 110 LSA and 218' duration (maybe too big for a mild 305). Any ideas?

Specs:
310 CID
E4ME
12' BTDC
1-1/2" headers
3" Flowmaster exhaust
Edelbrock Performer EGR
Comp Cams 268H
Crane 1.6 Roller Rockers

If you need more info, ... ask.

------------------
George P. Lara
1994 Z28 LT1 T56
1984 Z28 High Output
Member: SCCA, SCFB, SC3GFB

Ed Maher

You have some substantial sounding problems here. Something is very wrong.
That much dwell would indicat your computer is running full lean on purpose, which makes no sense if you're also getting a 44.
1/8" is the spc for travel on the MCS.
I don't think you're solenoid is the problem, if it was bad you'd be running grossly over-rich.
8" of vacuum is absolutely pathetic. My buddy had a 280 magnum in an otherwise stock L69 and he could still get 12" and really didn't cause that many problems, i mean everything still worked fine. In other words, that cam isn't your problem either.
Sorry, but i am completely stumped here. I'd solve that vacuum problem first, you have a severe vacuum leak somewhere. Maybe your timing is really retarded too. Perhaps the VAC sensor isn't hooked up right (it would screw your timing way up like this.) Past that, maybe your O2 sensor is bad, although that tends to send a 13? with a 44. I don't know why it would send 58' dwell if it is getting a lean O2 reading. I'd also measure the O2 value with a DVM to see what was actually coming out of it.
hop ethat gives you some ideas. Like i said, i can't help much, sounds liek you have a can of worms over there.
...ed

MRZ28HO

Guess I should go fishing with this can of worms. Well, the DVM hooked up to a new o2 was .200 @ idle when I had (mistakenly) the timing set at 40' BTDC. Then I readjusted everything and set the timing at 12' and the o2 readings came up to .550-.600. Hmm, thanks for ruling out the cam. Ok, now I also get a code 42 (EST) which I thought could be the distributor going out, but maybe it is the EST spark what-ever on the firewall. The vacuum sensor is per the vacuum diagram on my car (goes to the rear passenger side, base vacuum port) and gives a code if disconnected. What should the voltage be from the VAC sensor?

MRZ28HO

I think I may have figured out my low manifold vacuum. Let me explain, when I was checking for vacuum leaks I plugged the entire primary side of the carb. It did not stall until I really choked it. Then I checked my breather filter (it's a push on type with a tube for a hose), guess what, it had vacuum. That's odd, usually it will have a little bit of pressure, right? Now, could it be I have an internal vacuum leak? I used Fel-Pro gaskets with RTV surrounding the ports and water jackets. But then wouldn't the M/C solenoid have a rich dwell? That's what keeps thowing me off ...

Damon

The vacuum at the breather is coming from the PCV Valve on the other valve cover. That's what it's supposed to do- pull fresh air through the breather, through the crankcase, through the PCV valve and into the intake to be burned with the rest of the A/F mix. So I'm gonna pronounce that normal (you've got at least ONE thing goign for you!)

Now onto the rest of the problems. With the MV readings from the O2 now up to 600 I'm guessing your code 44 went away? I bet it did. Anyways, Ed knows the computer controlled QJets better than I do so I'll defer to him on that subject.

The EST is the whole spark advance/knock retard system that basically gives your distributor commands on how much to advance the spark at any given time under whatever conditions. Often, false knock will cause it to go ape-****. But that's not the only cause. It could be different stuff inside the distributor, the ESC module, or even the ECM itself. I don't know the ESC system very well on the carb'ed cars but on the TPI the diagnosis trees to figure out what's wrong with te ESC go on for 6 PAGES!!!

This is a job for DEALERSHIP MAN!! Seriously, it is unless you REALLY REALLY know your ****.

You may, however, want to try ONE THING first before you throw in the towel on the ESC problem. Bypass the knock sensor. Simple to do- unplug the wire going to the knock sensor (one wire- round shaped sensor is screwed into the block just above and in front of the starter) and run it through a 3900 Ohm resistor (Radio Shack- $.25) and then on to a frame/block ground. This effectively eliminates the knock sensor without the ECM knowing (and throwing a code). IF IF IF your problem all along was false knock, a malfunctioning knock sensor or a bad knock sensor module then this will make the ESC codes go away never to return. PLEASE keep in mind that this won't work in every instance, depending on what, exactly, is wrong in the ESC system but it's success rate has been about 50% in similar situations in my expereince.

How's your maifold vacuum doing? 8" is REALLY REALLY low. I suspect possible mechanical problems inside the motor if readjusting the timing hasn't brouhgt it back up. 18-20" would be about right with a stock cam.

------------------
94 Firebird Formula M6- No options but Z rated tires. No mods over $10. 13.5@105.
79 Malibu "beater" w/junkyard 400 SBC, tweaked QJet 4bbl, finally a decent set of heads, a few other tricks. A maddening 13.000001 @ 108 on the motor with little traction. No nitrous runs with the new heads yet.
Grandma's old 78 Malibu (33K miles!) soon to have the powertrain from the 79 put in it.

"One of the last remaining QJet tuners on Planet Earth!"

Ed Maher

If you're getting an EST code now, there's a good chance that that may be the root of everything. Like Damon said, EST is the box that actually sends the timing signal to the distributor. If that is going out, then your timing will be way off, and thus, lots of bad stuff will happen. Of course, it still seems crazy that you would get a lean code while the computer is trying to lean it out fully. I wouldn't rule out a bad ECM.
I've never gone through diagnosing a bad EST, but i wouod start there, and if it checks out OK then start looking at teh ECM.
...ed

MRZ28HO

Damon and Ed, thanks for the insight. As for the knock sensor, there is none and I get no codes (neat huh ). Code 44, I thought was also on idle, but when holding the throttle steedy at 2000 rpms it comes back (check engine light) and wont go away until I release the throttle. I think I will replace that danged EST just for the heck of it with a new AC-Delco unit (if I can find one).

OK now for the vacuum leak, here is my thinking let me know if it's a possibility. The heads were re-surfaced due to a very slight warpage (they were on my flat-top 357. ). I compared them to the original heads and it seems the machine shop milled them -.030". Now, I used GM's recommendation for hydraulic valve lash (1 full turn = .0416"). Could it be that the pushrods are too far in, so when the oil fills the lifter, the valves are staying open due to incorrect valve lash (I am thinking of going down to 1/2 turn = .020" to compensate for the -.030" milled heads), thus killing my manifold vacuum?

Plus on top of that, I think I mixed up the computers and chips from my Fed Emissioned '84 L69 A4 (old blue Z) and my CA emissioned '84 L69 A4 (red Z). I'll try that this weekend before I buy a "new" computer.