Crate LS3 in a '99
Thread Starter
Racer
Joined: Jun 2019
Posts: 457
Likes: 54
From: Dallas, Oregon
Crate LS3 in a '99
I need some technical assistance. I put an LS3 (GM crate motor with the "hot cam") in my M6 '99 coupe, using the Lingenfelter converter for the crank and cam reluctors. Has the factory LS3 injectors, LS1 water pump, LS2 throttle body (GM), and LS1 oil pan & exhaust manifolds. Not intended to be a race car, the car just needed a new motor and this happened to come available.
Ran terrible at start up. Took it to a tuner (not many of them in my area); he wanted it cold but I couldn't arrange it. He made it run much better when warm, but cold running remained an issue. Took it to him to fix cold running and he did. Car runs on 92 octane, non-methanol, unleaded. Original fuel pump. No codes in DIC, no codes from OBD. My issue is that it surges at 1200-1700 RPM. For sure when at normal run temperature and maybe when cold (but it's not cold long enough to really know).
The tuner and one other smart guy say it's the cam - that it'll always do that. Another smart fellow says it the upstream sniffers jerking the PCM around between rich & lean, but has no solution. Forth smart guy says it can be fixed but might take major hours on a dyno to tune it out, thus costing BIG$$$$$. Happy to answer questions if if forgot some detail. Help??
Ran terrible at start up. Took it to a tuner (not many of them in my area); he wanted it cold but I couldn't arrange it. He made it run much better when warm, but cold running remained an issue. Took it to him to fix cold running and he did. Car runs on 92 octane, non-methanol, unleaded. Original fuel pump. No codes in DIC, no codes from OBD. My issue is that it surges at 1200-1700 RPM. For sure when at normal run temperature and maybe when cold (but it's not cold long enough to really know).
The tuner and one other smart guy say it's the cam - that it'll always do that. Another smart fellow says it the upstream sniffers jerking the PCM around between rich & lean, but has no solution. Forth smart guy says it can be fixed but might take major hours on a dyno to tune it out, thus costing BIG$$$$$. Happy to answer questions if if forgot some detail. Help??
Pro
Joined: Oct 2020
Posts: 529
Likes: 197
From: Columbus, MS
Are you sure you don't have a vacuum leak? There's not much for vacuum on these engines, but check the nipple at the back of the manifold. It's not hard to knock that loose when doing all the other stuff that comes with installing an engine.
Thread Starter
Racer
Joined: Jun 2019
Posts: 457
Likes: 54
From: Dallas, Oregon
No vacuum leaks that the tuner or my regular mechanic can find/identify.
Thread Starter
Racer
Joined: Jun 2019
Posts: 457
Likes: 54
From: Dallas, Oregon
I agree cam isn't huge and I've had bigger ones in other motors in the past. There are very few tuners in this area. Nearest ones after that are about 200 miles.
Drifting
Joined: May 2007
Posts: 1,552
Likes: 324
From: Mid Ohio
IMO... first make sure the physical parts are good. Do a smoke test on the intake side. And one on the exhaust side. If no leaks second I'd want to see MAF counts and 02 sensor counts to see if they are matching rpms or causing rpm changes.
Sounds like you have a fairly simple and known swap. IMO talk to ECS as they can do a mail order tune that'll get you running and not cost much
Sounds like you have a fairly simple and known swap. IMO talk to ECS as they can do a mail order tune that'll get you running and not cost much
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From: Portland OR
Thread Starter
Racer
Joined: Jun 2019
Posts: 457
Likes: 54
From: Dallas, Oregon
IMO... first make sure the physical parts are good. Do a smoke test on the intake side. And one on the exhaust side. If no leaks second I'd want to see MAF counts and 02 sensor counts to see if they are matching rpms or causing rpm changes.
Sounds like you have a fairly simple and known swap. IMO talk to ECS as they can do a mail order tune that'll get you running and not cost much
Sounds like you have a fairly simple and known swap. IMO talk to ECS as they can do a mail order tune that'll get you running and not cost much
Thread Starter
Racer
Joined: Jun 2019
Posts: 457
Likes: 54
From: Dallas, Oregon