LS swap Buick Skylark running issue PLEASE HELP

[Cyrperformance]

67 Buick Skylark, 2002 5.3 DBW PSI Conversion harness. Truck was running and driving good before engine and trans were pulled. Deleted VATS, and all necessary to get running. Installed Speedmaster low profile intake (not the best) and the engine fires up and sputters and backfires through intake. Can keep it running constant throttle pumping and get it to rev up then it will throw a P0068 MAF/MAP-Throttle Position Correlation code and rev up to between 2800 and 5000 and hang until clear codes tab is clicked in the scanner. I believe the answer is the intake causing large vacuum leak but want to get opinions before swapping to stock and buying new gaskets.

[mcfarlnd]

You could test the intake leak theory with some old fashion starting fluid...... Spray and see if RPM changes. Have you double checked your grounds? Not sure if I had that same code but, grounding issues caused me a lot of heartache when I built my harness. Also, you need to make sure the battery is grounded to the frame, frame to block, frame to a few spots on your cabin. Here are some notes I took and have on my phone (Note: this is for a blue/green connection harness)

Blue connector
1 BLK/WHT Ground
21 YEL/BLK CPS Ground
24 BLK/WHT Ground
27 BLK/WHT Ground
40 BLK/WHT Ground
64 BLK/WHT PCM Ground
67 BLK/WHT PCM Ground

19 75 - Pink - 12v+ KEY Power Source to PCM. Hot when Key is in the ON and CRANK positions.
20 57 - Orange - 12v+ BATTERY Power Source to PCM. Hot at all times.


Green connector
1 BLK/WHT PCM Ground
40 BLK/WHT PCM Ground

[Cyrperformance]

This is a PSI Conversion harness so there is only one ground to the back of the block for the sensors and one ground off the PCM connectors that I have the one bolted to the back of the cylinder head, then the battery cable direct to block, ground strap to a stud on the firewall that holds one end (other end directly to back of block) and the stud then goes through the firewall which is where I have all the internal cabin grounds to. Problem with the starting fluid right now is I have no one to keep it running while I am sprayer the fluid. I will have some help beginning of next week and will report back. Thanks

[mcfarlnd]

This is a PSI Conversion harness so there is only one ground to the back of the block for the sensors and one ground off the PCM connectors that I have the one bolted to the back of the cylinder head, then the battery cable direct to block, ground strap to a stud on the firewall that holds one end (other end directly to back of block) and the stud then goes through the firewall which is where I have all the internal cabin grounds to. Problem with the starting fluid right now is I have no one to keep it running while I am sprayer the fluid. I will have some help beginning of next week and will report back. Thanks

I understand you have used a PSI harness, i would recommend doing a continuity and ohm check on the grounds if the issue persists. Doing that check can be done with one person and a cold beer. I have received bad parts before is the only reason i suggested it. Everyone makes mistakes.

[Cyrperformance]

Gotcha, yeah I did the old test light backwards test to verify. Gonna swap the valley cover bolts out to countersunk heads, the intake is sitting tight against against the stock bolts to where a piece of paper will not fit (cheap intake).

[Sales@PSI]

67 Buick Skylark, 2002 5.3 DBW PSI Conversion harness. Truck was running and driving good before engine and trans were pulled. Deleted VATS, and all necessary to get running. Installed Speedmaster low profile intake (not the best) and the engine fires up and sputters and backfires through intake. Can keep it running constant throttle pumping and get it to rev up then it will throw a P0068 MAF/MAP-Throttle Position Correlation code and rev up to between 2800 and 5000 and hang until clear codes tab is clicked in the scanner. I believe the answer is the intake causing large vacuum leak but want to get opinions before swapping to stock and buying new gaskets.

Cyrperformance,

Give us a call at 732-444-3277 Ext 3 for Tech Support, we can help you diagnose your problem.

There a lot of variables, the intake manifold, the tune itself, etc.

thanks

[Cyrperformance]

Got it nailed! The intake was sitting on two or three of the valley cover bolts causing it to suck a ton of air at runners. I knew it wasn't the harness and tune is stock with normal deletes. The harness is a beautiful piece and i will only be using your product on our OEM swaps. Thanks

[Sales@PSI]

Got it nailed! The intake was sitting on two or three of the valley cover bolts causing it to suck a ton of air at runners. I knew it wasn't the harness and tune is stock with normal deletes. The harness is a beautiful piece and i will only be using your product on our OEM swaps. Thanks

Great, glad you figured it out! If you have any other problems/questions feel free to give us a call.

thanks

Jeremy
732-444-3277
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