Backfireing under the hood on startup

cloud 9 wrote:

Last couple days whenever I start the Caprice it pops from under the hood when I give it any gas for the first 30 seconds it is running. After that she is fine, normal. Any input?????

LT1 car? if so..... sounds like an opti.....

Check your air intake elbow for holes, also check the MAF and IAC. Any Sticking valves?

OPTI!!!!!!!!!!!!!

So just cause it was easy and inexpensive I replaced the fuel filter. Still doing it though. Weird, it only does it for the first 60 seconds after cold start then runs and starts easy after warmed up, responsive as normal. I have looked all around the engine compartment nothing disconnected or cracked. I believe it has the original opti in it. 80k miles and 17+ years old, sounds like that may be my next option. Any other ideas before I get into it would be appreciated.

IMPALADAKID wrote:

OPTI!!!!!!!!!!!!!

bowtiepimp wrote:

IMPALADAKID wrote:

OPTI!!!!!!!!!!!!!

Sounds like possibly a "lean-pop" backfire.

Check for anything that delivers the necessary rich fuel mixture required when cold.

The computer needs to know various temps though-out the engine systems.

O2, coolant temps, A/F ratio, Etc. The FSM (factory service manual) has excellent procedures for tracking down the cause.

The normal hot engine fuel ratios will be too lean while flowing through the cold intake runners, condensing on the cool surfaces.

Put in a new coolant temp sensor. Everything ok now. Cheap fix, very happy. Thanks for the advise guys.

Nice!