Motor swap driving me crazy!!!!

[Jackedup92]

so this is my first post on this forum hopefully someone can help me out as I have a few questions!! I have a 92 gmc 1500 4wd had the 5.7 350 tbi and it was knocking so swapped a 88-89 350 into it. Swapped everything over from the original motor to the new one including all the sensors and tbi.. here's where it gets weird. When I initially dropped the distributor in I went to set the timing and along with my grove in the balancer timing mark there was another mark painted on the balancer about an inch away from the oe mark. Now the donor motor was running a points style distributor and a carb on it so I dunno if that was there mark for the advance or what. Anyway I set the timing at 0degrees on my balancer grove mark with the est connector unhooked and pretty much it ran like crap at idle. When I give it throttle it ran smooth like it wasn't misfiring. When I Hooked the connector back up I could tell the computer was adjusting the timing while I had the light on it. So I started replacing sensors. Map, 02, and coolant temp sensor .so that brings me to this now, I had a friend helping me work on it and I finally got a trouble code to pop up. We checked it which it showed bad map sensor and proceeded to move forward. I believe that he forgot to pull the jumper pin out of the obd plug and we ran the truck a few times as it got worse and worse until it finally wouldn't run at all. Only then I noticed the jumper still in the plug!!! So my question is do y'all think it fried the brain while running it like that? I got another brain and it will fire and run for maybe 5 seconds then die?? If I try to give it gas it automatically dies??! Other question is that if I set my timing to the other mark it runs exactly the same and it puzzles the hell outta me!!!

 

[Jackedup92]

so this is my first post on this forum hopefully someone can help me out as I have a few questions!! I have a 92 gmc 1500 4wd had the 5.7 350 tbi and it was knocking so swapped a 88-89 350 into it. Swapped everything over from the original motor to the new one including all the sensors and tbi.. here's where it gets weird. When I initially dropped the distributor in I went to set the timing and along with my grove in the balancer timing mark there was another mark painted on the balancer about an inch away from the oe mark. Now the donor motor was running a points style distributor and a carb on it so I dunno if that was there mark for the advance or what. Anyway I set the timing at 0degrees on my balancer grove mark with the est connector unhooked and pretty much it ran like crap at idle. When I give it throttle it ran smooth like it wasn't misfiring. When I Hooked the connector back up I could tell the computer was adjusting the timing while I had the light on it. So I started replacing sensors. Map, 02, and coolant temp sensor .so that brings me to this now, I had a friend helping me work on it and I finally got a trouble code to pop up. We checked it which it showed bad map sensor and proceeded to move forward. I believe that he forgot to pull the jumper pin out of the obd plug and we ran the truck a few times as it got worse and worse until it finally wouldn't run at all. Only then I noticed the jumper still in the plug!!! So my question is do y'all think it fried the brain while running it like that? I got another brain and it will fire and run for maybe 5 seconds then die?? If I try to give it gas it automatically dies??! Other question is that if I set my timing to the other mark it runs exactly the same and it puzzles the hell outta me!!!

Ok so question is that if I ran the motor with the obd pins jumped like I was trying to find the codes could it have fried the brain? It ran for about 30-45 seconds then stopped now it won’t run and if it does hit it dies immediately??

 

[RichLo]

jumping the pins should cause issues running, they are just there for diagnostics. it would probably just be flashing the CEL at you when running.

Did you replace all of the sensors and wiring from the original motor from the truck to the new donor motor or are you still running some of the original 88-89 wiring and sensors?

 

[Jackedup92]

jumping the pins should cause issues running, they are just there for diagnostics. it would probably just be flashing the CEL at you when running.

Did you replace all of the sensors and wiring from the original motor from the truck to the new donor motor or are you still running some of the original 88-89 wiring and sensors?

Replaced everything from the old motor to the donor. Sensors, throttle body, had to swap over the entire front accessory bracket, everything I could see or think of got swapped. Initially when I first fired the truck up it ran ok it just wouldn’t idle right. When given throttle it seemed to run good like it wasn’t missing.. yet when trying to idle it bounced around between 750 and 950 rpms. That’s with the timing set at 0. I could idle it up with adjusting the timing at distributor but it would still eventually die or stall out when test driving.

 

[skylark]

Check that the balancer is on the mark. Pull the number one spark plug and rotate the engine by hand with a piece of wire on top of the piston. Feel for when it actually comes to Top Dead Center and see if the balancer lines up with your mark. It is possible that the balancer has rotated on the hub.

 

[Jackedup92]

Check that the balancer is on the mark. Pull the number one spark plug and rotate the engine by hand with a piece of wire on top of the piston. Feel for when it actually comes to Top Dead Center and see if the balancer lines up with your mark. It is possible that the balancer has rotated on the hub.

I definitely know I’m at top dead center on #1 on my compression stroke. I took the valve cover off and watched the valves but when I feel like the piston is actually at top dead center it’s kinda between my marks. The one from factory in the balancer and the one that someone drew on it. If I set it on the factory mark and lock the distributor down when I fire it up timing light shows 0 yet when I plug up my timing connected to let the ecm advance it it barely will stay running. Again I can give it throttle and hold it at about 12-1500 rpm and it runs smooth not missing but it’s just the idle.. now all of a sudden it doesn’t act like it’s getting fire all the time just intermittently. Gonna check a few sensors this weekend I will post what I find out. Thanks guys