rough idle backfiring after motor work
Thread Starter
Staging Lane
Joined: Sep 2005
Posts: 56
Likes: 0
From: plymouth,MN
rough idle backfiring after motor work i took the motor out put in a cam and rockers... and with open headers it ran alright rich but ok and when i put mufflers on now it backfires and wont idle and vibrates like crazy when your going below 3000 RPMS could it be that bad just because i need a tune deos anyone know where in minnesota to get a dyno tune. getting angry with this motor!!!
LT1 right???? Recheck and recheck and then triple check the wiring configuration on your optispark. You might have #2 going to #4 or some other wires on the wrong post of the opti.... Believe me it happens..... Happened to me and my car did the exact same thing. Swapped the wires and car stopped backfiring and ran like a raped ape from then on...
what cam did you go with. Most aftermarket cams require you to cut the dowel pin that inserts into the optispark. I made the mistake of not trimming the dowel pin and burned up 2 optis.... BTW it would run fine for a few minutes and get progressively worse, backfiring and sputtering like crazy, until the car eventually would just die and not crank over at all.
Thread Starter
Staging Lane
Joined: Sep 2005
Posts: 56
Likes: 0
From: plymouth,MN
the spark plug wires are right and when i adjusted teh valves i did that with the car running i finger tightened them then 180 degree turn then snugged the lock nut down... it is a comp cams cam that would really suck to take that off now... forgot to mention when the car is cold runs good warms up runs like **** could it be the temp sensor does anyone know where they are located on the block so i can double check that they are re hooked up...
yea an LT1 oh yea there is a rubbing sound when i hit the gas that is pretty loud were could that be coming from? was louder and now getting quieter and was gone for a while sounds pretty bad...
yea an LT1 oh yea there is a rubbing sound when i hit the gas that is pretty loud were could that be coming from? was louder and now getting quieter and was gone for a while sounds pretty bad...
temp sensor is on the drivers side between the 1 and 3 cylinder if i remember correctly. there is also one on the water pump. if they arent hooked up your temp gauge should not be working. at least mine didnt when i didnt have mine hooked up. if it only runs like crap when its warm check the o2s as well as they arent in the mix until the engine reaches operating temp. hope you find the problem
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also depends on how big the cam you put in it is if you're asking about tuning.... If it runs fine when it's cold then it means it's running fine when it's in closed loop (correct me if i'm wrong bc i always mix these up)... Then when it warms up to op temp it will switch to open loop and start accepting o2 correction from your o2 sensors..... so if there is a definite change in the way it runs it could be fouled out o2 sensors as well.... Cuz from what you say it runs like **** when it's accepting fuel trim from your o2 sensors....
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I would definitely think it has something to do with the distributer. I believe Autotraac does dyno tuning. They're located in the Minneapolis area. They will be able to identify the problem, and they work on custom vehicles all the time.
Teching In
Joined: Dec 2005
Posts: 5
Likes: 0
From: Georgia
i had the same problem it is the opti. check your wires. if two are swapped it will back fire. i did a whole engine swap in the summer and did the same thing. it is a pain in the a@# to route some of those wires. if you have been running the engine for a while you will need new plugs on the two swapped wires. also have you checked your catylitic converter. it will get very red and hot and you will melt the inside if you are back firing.
Originally Posted by 572BBC4thgen
If it runs fine when it's cold then it means it's running fine when it's in closed loop (correct me if i'm wrong bc i always mix these up)... Then when it warms up to op temp it will switch to open loop and start accepting o2 correction from your o2 sensors.....
I would definitely run it as little as possible until you figure out the problem. Check the valve adjustment instructions again to make sure you have the preload right. Some of the hydraulic rollers want ZERO preload, and if you put preload on them, they hold the valves a little open. Could get worse as the motor warms up.
Jim
Jim
