I have a 1999 z28 camero w/ls1 all stock when motor is cold it will not rev. up. It acts like something is clogged.It has no error codes.Hesitates untill it is fully warmed up. runs fine at idle. changed fuel filter & air filter & spark plugs & wires no effect. Thanks for input.(I know its not a chevelle but advice i have received on this site is always alot of help) :beers:







1970 malibu Blown 502 w/TH400 & gearvendors od

A good factory repair manual is always a big help for stuff like this...

I would check out the IAT sensor and the CLT sensor as a first step. Both should be able to be checked out with a thermometer, multi-meter, and pot of water. As an alternative if you have one or can borrow one hook up an OBD monitor and read out the temperatures as it operates and look for strange readings.

May be worth check out TPS sensor too. The rub here is you need more fuel when the engine is cold as it sticks to the intake runners a lot more. Higher RPM needs more fuel. Those seem to be when you have a problem suggesting not getting enough fuel. So then you look for why you are not getting enough fuel, which becomes basically a question of why the EFI is not giving it. So you look to validate that the inputs to the EFI which cause it to adjust and enrichen the mixture are not telling lies.

That is it in a rather generic form ;)

Check for vacuum leaks. Could be leaning out the mixture, which would have a larger effect when cold.