New Engine - Sputtering On Acceleration

[cutlassman]

Hey guys, kind of sad to see this community fade over the years, but hopefully some of you have some thoughts on this. I bit the bullet and put a new engine in my ‘92 CS Convertible, 3.1L. Most of the top parts were transferred over to the new block. Old engine ran fine before, but blew out the LIM and hydrolocked. Runs and idles great now, but above say 30 mph I get sputtering/misfiring on acceleration under load. Any ideas? ICM and coil packs only have a few thousand miles on them. New plugs with engine install. Wires are almost new. Car sat for several months with 3/4 tank, Stabil added, but the fuel is about 10 months old. Swapped TPS. No difference. Vacuum looks good. Older fuel? Fuel filter? Bad injector(s)? MAP? I’m going to take it back to the mechanic if I can’t figure it out myself. 

 

 

[rich_e777]

Bad belt/tensioner, dried out vacuum lines, failing injectors, worn out O2 sensor, ethanol gas, corroded battery/starter/alternator cables and grounds are all things ive experienced in the different versions of the 3.1 running poorly or not at all. A compression and fuel pressure test might be a good idea here.

[cutlassman]

9 hours ago, rich_e777 said:

Bad belt/tensioner, dried out vacuum lines, failing injectors, worn out O2 sensor, ethanol gas, corroded battery/starter/alternator cables and grounds are all things ive experienced in the different versions of the 3.1 running poorly or not at all. A compression and fuel pressure test might be a good idea here.

I’m leaning toward an injector issue. Belt and tensioner are new with the engine install. Vacuum lines are good. I’m going to replace the MAP and TPS. Definitely seems fuel or air related. 

[cutlassman]

SOLVED! It’s unreal, but the shop installed the wrong spark plugs! Gapped to 0.060” instead of 0.045”. I put the OEM plugs and it runs great. 
 

[Black92GS]

Wrong plugs altogether? Or correct plugs but gapped incorrectly? OEM plugs were always a requirement for these cars, and even 20 years ago, we had quite a few bad running engine posts where the fix was "replaced plugs with OEM".  

I've seen these things run nearly flawless on heavily worn OEM plugs with gaps closer to the 0.090" range...so I'm not sure the gap alone was the main issue.