C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

will an 85' run without maf?

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Old Oct 1, 2013 | 11:53 AM
  #21  
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Even without maf you better set tpi sensor to .54 volts . That tells the computer how far the throttle is open. I would think that is mandatory.

Last edited by xrav22; Oct 1, 2013 at 02:33 PM.
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Old Oct 1, 2013 | 01:04 PM
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i also have a vac leak somewhere not too sure where, i think a couple of emission lines are plugged into the wrong place
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Old Oct 1, 2013 | 01:05 PM
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the dizzy was set perfect. and i cant turn it too much more as the extrusion on the cap will start to hit the firewall
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Old Oct 1, 2013 | 01:07 PM
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its at about .48 right now my large volt meter isnt too accurate so im going to have to go buy a digi
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Old Oct 1, 2013 | 01:36 PM
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Originally Posted by 85corvettec4
the dizzy was set perfect. and i cant turn it too much more as the extrusion on the cap will start to hit the firewall
This has me even MORE certain that the rotor has skipped a tooth.

The "extrusion" off the side of the dizzy should be at a 90* angle to your plenum.

-Find your motor's Top Dead Center (take #1 spark plug out, feel for puff of air indicatiing compression stroke).

-After that's done, rotate your dizzy to 90* (pointing towards the drivers side)

-lift the rotor out and drop it in in such a way that it lines it up pointing between the #1 and #8 plug wires.
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Old Oct 1, 2013 | 03:21 PM
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thats how i had it set now its at about 100*
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Old Oct 1, 2013 | 03:25 PM
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did you disconnect the EST before doing all of that? Edit: Also move it forward (clockwise) one more tooth.
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Old Oct 1, 2013 | 03:25 PM
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took me 2 hours to finally get it right, and then finally it dropped into place!
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Old Oct 1, 2013 | 03:26 PM
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i havent set the timing yet, i got the car to run then calle dit quits for the night. ill have to pull it off and time it tonight
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Old Oct 1, 2013 | 03:26 PM
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i had it disconnected until i started it
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Old Oct 1, 2013 | 03:43 PM
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i dont think it will seat if i move it anymore. all the time i spent doing this was trying to get it to seat while the rotor was pointed at #1
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Old Oct 1, 2013 | 03:46 PM
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Get the timing RIGHT...if the cap wire hood, or extrusion is pointed at anywhere besides the brake booster,. you are off a tooth. Like Cliff said, it should be 90* to the plenum. Straight to the driver side.
Once that's straightened out, PLUG in the EST wire. That's only to be d/c when adjusting and setting with a lite.

Pull the fuses and clean, replace. Pull the bulb in the center display. You NEED that SES lite to work. Go see IF there are ANY stored codes...(when the lite gets fixed). You have zero chance of adjusting, tuning or diagnosing ANYTHING without the help of the onboard computer. These things are self diagnosing and can do what takes you all day, in .03 seconds.
If TPS is close to .5...that's close enough to start. Tune later after it runs.

Track the leaks. Major vac leaks will keep it from starting.

The electrical on this car is CRITICAL. if the woring harness is not good, clean plugs and grounds, ALL the gounds, including the several on the bolt by the OIL filter, it won't run. Not at all. The wire harness MUST be in good shape with EVERYTHING connected. The GROUNDS by the oil filter especially. You know what I'm talkin about...the 4 or 5 harness wires that all go on 1 bolt on the blocl or the trans bellhousing. Those are the ECM, EFI and control systems grounds. Nothing works without those. The jumper pole behind the battery is equally important for power source.
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Old Oct 1, 2013 | 03:49 PM
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it fires up instantly after about 1 crank. i put it in 90* but i had to turn it counter to get it to start. and i have an obd1 scanner.
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Old Oct 1, 2013 | 03:49 PM
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so pull out the distributor and try to turn it clockwise a tad?
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Old Oct 1, 2013 | 08:43 PM
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i can pump it up to 5000rpm but it wont take any slow acceleration. and it wont start with power to the dizzy. so should i try and turn the rotor/shaft clockwise a bit then set the diy back in position and retry?
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Old Oct 1, 2013 | 08:50 PM
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and with the wire plugged in it runs at 25*btdc
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Old Oct 1, 2013 | 08:59 PM
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With the wire plugged in, the timing advance will vary depending on what info the ECU receives.

I still maintain that you need to find top dead center and find the proper rotor tooth location. After that, get it set to 6*btdc without the wire, then reconnect.

Edit: Don't just turn the rotor, you have to lift it out and then align the gears. If your dizzy is now pointing the correct way it should run. Then get a timing light and rotate the distributor cap until the mark reads 6*. Some people run 7 or 8 degrees depending on their preference but factory timing is 6. After you get your timing set (and EST connected), if your engine still runs poorly, it's a vacuum leak.

Last edited by Ghast; Oct 1, 2013 at 09:06 PM.
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To will an 85' run without maf?

Old Oct 1, 2013 | 09:03 PM
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Originally Posted by Ghast
you have to lift it out and then align the gears
joy
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Old Oct 1, 2013 | 09:08 PM
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If you haven't lifted the rotor out before it started running bad, then never mind, but start googling top dead center. There's a nice tutorial done by MSD on YouTube.
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Old Oct 1, 2013 | 09:11 PM
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i had to pull it out and twist the oil pump for ovwer an hour before i got it lined up it wongt run with the dizzy wire unplugged
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