Let me just start by saying this is my first real post, and mainly haven't needed to post b4 'cause there's so much awesome info already on this site my questions have been answered!

Background: I just finished installing my newly-built 350 for my 85 Berlinetta. I'm running all the original emissions garbage and computer controlled Quadrajet (rebuilt) plus CC dist (rebuilt, with MSD ext coil and 6A). New 3-wire O2 sensor, new Random Tech cat, 3" exhaust, SLP headers. Running a Comp Cams XE268 set @ 0*. We already broke in the engine and set the valve lash while it was running.

On to the problem. We can't get the thing to run worth a darn at idle. Set base timing by grounding A&B on diag connector and the mark is so far advanced, it's under the water pump barely visible! That's the spot we found had the best vacuum, but it's still fluctuating wildly between 10-15 in HG producing very rough, surging idle. Then pulled the diag. ground and let the computer do its thing. I set the idle speed in gear with the lights on to about 750-800 rpms & kept throttle kicker solenoid unplugged. Vacuum remained lousy. Once I put it in park, idle jumped to 1050-1100 rpms with decent vacuum around 17-18 in. What is going on here??

Here's what we checked so far. Throwing NO codes. Checked M/C solenoid - 23 ohms, no shorts, clicks with key on. We double checked TDC on #1 and position of dist. CTS is working fine (diag computer shows temp reading). The one thing I did find wrong was the TPS. I could only get it down to 0.64 volts at idle of 750 and then lowered speed to 550 rpms and voltage stayed same. Could this simple device be causing all my problems? I've got a new one coming today and will post results but need more ideas to try.

Sorry for the long post, but wanted to get out as much info as possible.

 

hmm, i thought to set the timing on a computer controlled car, you had to unplug the connector by the firewall. At least thats how it was on my 87.

 

From what I've read, you can also just ground the B port on the diag connector. You can definitely hear the difference in the engine with it plugged in vs. out.

I can't believe nobody else has any ideas. I'm losing my faith in you guys.

 

I'm guessing you swapped the timing cover and put on a non-stock one; and some sort of bolt-on timing mark?

If so, it's in the completely wrong place. The stock timing mark is welded on to the center of the TC, right behind the water pump. That's why it shows up right behind the water pump when you adjust it to where the motor runs right.

I'd leave the TPS alone, if it were mine, and had that reading. Way too much maze changing it out, with no cheese at the end.

 

What balancer did you use versus what cover?

 

You may be onto something here. The balancer is just a Summit 8" for street use, int. balanced. The TC was off an old engine we had lying around. The timing marks are off to the driver's side with 0* starting about 25-30* from the top center of the pulley.

 

Was the timing tab on the cover in the center of the cover, like on the 305's? Sounds like a balancer with the mark at roughly 1:30 (designed for an aftermarket bolt on cover with a matching timing indicator location).

i guess, basically, where is the timing tab?

 

What we ended up doing was getting the engine set at TDC on #1 by removing the spark plug and feeling for the pressure while watching the valves move. Once there, we put a mark on the balancer which lined up with the 0* mark on the timing cover. The balancer mark was definitely not on the scribed 0* mark, but that really doesn't matter now, as long as we know where TDC is correct?

 

As long as it runs, and you know how it works, it doenst matter a bit. You may confuse the hell out of someone if you sell it that way though.

 

HAHA