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I am losing my mind over this issue so hopefully you can help. I built a new 383 LT1 and it runs fantastic normally, but on cold start-up it is having a persistent issue where it runs really rough and dumps white smoke with a strong fuel smell out the tail pipe. If I rev it a bit and start driving then it runs great. I can shut it down and start it up again a little later and it fires up without issues. However if it sits overnight and I start it, it is rough and smokey again. It always fires up immediately though. Clearly the engine is flooded or not getting appropriate spark. The car didn't seem to have this issue for the first few weeks with the new build but is consistent now.
Related engine info: LT1 383, Optispark, new plugs (NGK BR7), new 8mm wires, Bosch 42# injectors, new MSD coil, OEM ICM, AI200cc heads, cam specs: 235/243, .579/.597, 110LSA.... let me know if you have any more questions on the build.
It is clearly related to either engine/component temperature or time the engine is off since it only happens if I haven't driven the car for a while. Leaking fuel injectors makes the most since based on that but it is odd to me that all the plugs are so fouled which makes it seem that flooding condition impacts all cylinders.
Take a look at what I have trouble shot at so far and see what you think:
For reference, here is what my new spark plugs look liked after 4 starts and 95 miles of driving:
Last edited by 1quickTransAm; Nov 18, 2015 at 11:58 AM.
Does it make any sense that a new/reman Delco Opti could have an issue that would cause it to run rough on cold start but then be totally fine the whole rest of the time including revving to 7k RPM without issue?
Does it make any sense that a new/reman Delco Opti could have an issue that would cause it to run rough on cold start but then be totally fine the whole rest of the time including revving to 7k RPM without issue?
First of all, did you have any issues with the opti BEFORE the new 383 setup and tune? Is it a mail order/email tune or has it been dyno tuned? It very well might be tune related.
I would be skeptical of any "remanufactured" optispark, Delco or not..."remanufactured" parts usually means just they cleaned it up and hastily reassembled and "tested" it . It sucks optisparks are no longer made new by AC delco....at least MSD has stepped up and still produces NEW optisparks with lifetime warranty!
I had no issues with the old Opti before the build (revved engine to 6,200). With the new engine I can rev to 7,000 RPM and had an issue with a slight miss around 6,400 RPM and also a rough cold start like what I described, but a little less often. That makes me think it isn't he Opti.
The tune is a dyno tune from a pretty well respected LT1 tuner. I also drove the car back up to him earlier this week to double check everything.
I agree that it sucks that they don't make new Delco Opti's anymore as I would have gladly paid more for one.
No codes at all. However I do not have the Cranks Position Sensor anymore (dual roller timing set).
Last edited by 1quickTransAm; Nov 18, 2015 at 03:29 PM.
I had no issues with the old Opti before the build (revved engine to 6,200). With the new engine I can rev to 7,000 RPM and had an issue with a slight miss around 6,400 RPM and also a rough cold start like what I described, but a little less often. That makes me think it isn't he Opti.
Rough idling, smoking on startup, sputtering, misfires, weak plug spark are all optispark symptoms....jus sayin!
Seems to me if you did NOT have this issue before this particular "rebuilt" opti was installed....but now you do...well, that particular opti is highly suspect! Maybe try to return it for a refund/replacement?
I had a rough and smokey start twice with the old optispark, but every cold start with the new one.
It runs much rougher on cold start since installing the new opti, but I am not convinced that it is the opti vs another issue getting worse. The car runs great after a minute and then runs great with zero hint of issue. Is it possible for an opti to have issues when "cold" then be fine???
Last edited by 1quickTransAm; Nov 18, 2015 at 04:01 PM.
First start with the basics, why are your running a 7 plug for NA? this may be too cold for your start up, the motor needs to be on the rich side at start up like a carb with choke, the plug could be too cold for this then after it warms up its fine. what is your FP at start up, it could be the opposite, could be lean and the PCM is dumping fuel...
I run nitrous. I have run these plugs for years and never had an issue with the old engine, but the new engine has higher compression and much bigger cam so who knows. I never thought about that being an issue though so thanks!
I'll need to check the FP at start-up. I had figured that it was fine since it fires right up when I turn the key but it would be better to know the actual #.
I also noticed this morning when it was doing the usually running rough and smoking at start that my wideband gauge was showing a normal/slightly lean number of ~15:1 when it was idling rough about 10 seconds after starting.
Last edited by 1quickTransAm; Nov 19, 2015 at 09:48 AM.
I also want to highlight that it does feel like it is missing. I can distinctly feel gaps in the engine idle like spark isn't happening when it should.
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Cold Start = Runs Rough & Smoke 
It sucks optisparks are no longer made new by AC delco....at least MSD has stepped up and still produces NEW optisparks with lifetime warranty!
