C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Backfiring in intake

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Old Mar 1, 2010 | 08:21 AM
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Default Backfiring in intake

I got this car running pretty good now but I am having some trouble when its still cold and i put it drive and take off it sputters and backfireds in the intake. After it warms up it runs like a rape date.
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Old Mar 1, 2010 | 08:36 AM
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What is the base timing set at?

Did you adjust the valvetrain with what you had to do to get the car running pretty good?

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Old Mar 1, 2010 | 01:06 PM
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No, I had put new injectors and cap, rotor, and plugs in the car thats it.
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Old Mar 1, 2010 | 06:22 PM
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I see - did you go back with the same poundage rated fuel injectors?

Sure you got the plug wires landed in the correct sequence on the cap?

Check the base timing...should be ~ 6 degree BTC

Normal temp should be over 180 before you really smack the gas.

Check for stored trouble codes there may be some insight there.

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Old Mar 2, 2010 | 07:11 AM
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Yes I used the same poundage injectors, And I am most positive the plug wires are correct my father was helping me and been a chevy guy forever. I will check the timing but it is only running like crap when cold I am not getting on it just getting out of my development.
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Old Mar 2, 2010 | 07:29 AM
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usally when ive had a backfire through the intake it was timing,or a lean fuel condition.
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Old Mar 2, 2010 | 01:19 PM
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It only does when its cold. like start up and go I am in MD right now and its pretty cold in the morning so I go out and start it 15 min before I go to work and its fine but still would like to have it work like it should
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Old Mar 3, 2010 | 09:00 AM
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Does it have cold start valve? If so that could be bad.
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Old Mar 3, 2010 | 02:02 PM
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What year vette/engine do you have? On the later vettes with LT1s you have to be certain you match the injector wires connectors to the correct injector.

It is almost impossible for the timing to be off on most Lt1s, unless someone programed your stock ECM.
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Old Mar 3, 2010 | 02:14 PM
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Let's go back to valve adjustment for a second. Run a compression test when the engine is stone cold and post the readings for all 8 lungs. You may have an intake valve misadjusted.....and when it warms up and the oil thins out, the issue goes away.

Have you had any ECM tuning done? If so, what was altered?
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Old Mar 4, 2010 | 07:33 AM
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do you have the coolant bypassed at the throttle body?ive heard that can be an issue in really cold climates.
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Old Mar 4, 2010 | 09:28 AM
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It is a 89 l98 and I dont know if there is a cold start valve if so where would it be located? The coolant bypass I never seen a coolant bypass and pretty sure it does not have one.
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Old Mar 4, 2010 | 10:17 AM
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The is no cold start valve on an 89. No need to look.
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Old Mar 4, 2010 | 10:29 AM
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Originally Posted by drayset1010
It is a 89 l98 and I dont know if there is a cold start valve if so where would it be located? The coolant bypass I never seen a coolant bypass and pretty sure it does not have one.
No extra cold start injector on the '89.....extra fuel/pulses at start up is delivered by the ECM causing a "rich" A/F mix....your car will not deliver the power your after until it goes into (coolant ~148 F and o2 sensor warms up to operating temp) and stays in "closed" loop when A/F is metered properly. Then once in closed loop it's ready for "drive it like you stole" time. This sequence is very normal for your year model. The "cold" weather my be extending your time it takes to go into "closed" loop....be patient with it.

Where did you get the injectors from?

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Old Mar 4, 2010 | 02:46 PM
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Not sure but I believe it was justfuelinjectirs.com They were cheap and had fast delivery
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Old Mar 4, 2010 | 03:03 PM
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Originally Posted by drayset1010
Not sure but I believe it was justfuelinjectirs.com They were cheap and had fast delivery
Your cold start bog seems pretty normal to me it will no doubt be less noticeable when the weather tips back a bit warmer.

FYI: Their website is way cool they offer flow rates for nearly every injector.http://www.justfuelinjectors.com/ser...flowchart/Page

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