97 sierra z71 when the car is cold it runs like shit and eventually throws codes p0133 and p0300 o2 sensor and multiple cylinder missfire. sometimes it takes almost a ...

97 sierra z71

when the car is cold it runs like shit and eventually throws codes p0133 and p0300

o2 sensor and multiple cylinder missfire. sometimes it takes almost a minute of

cranking to start but onle and only when the car is cold. it sputters and misses a lot.

but once the car warms up for around 20 minutes, it runs perfect and if you continue to

drive for around 30 more minutes the SES light goes of and the car continues to run

good until of course i dont use it for about 2 days and it gets really cold.

any imputs?? someone mention a distrucutor cap but dont wanna go by parts without

being sure.

thanbks is advance

Have you checked to make sure it does not have a vacuum leak? Those engines are prone to their intake gaskets leaking.

no, i have not but i gues i can look up how to test that and do it.

but if it had a vacum leak; would it have a problem all the time and not just when is

cold?

You can spray brake cleaner around the intake manifold while it is running. If the idle changes, you have a leak. Sometimes they leak on the underside of the intake, in which case the brake cleaner test will not make a change in the running of the engine. Those intake manifold gaskets are made of plastic with a rubber insert and probably are expanding when the engine warms up, which seals the leak. Like I said, without seeing the truck myself, this is just an idea. I believe you can get a more durable metal and rubber gasket from Fel pro. They are pricy, but you should never have to do the job again.

i was out of the country for a while and finaly got a chance to check for the leak but im

not finding anything, but i think im spraying the break cleener in the wrong spots.

is there pics for this and the exact places you have to spray??

thanks again.

Spray it around where the intake meets the head, near the valve cover (on both sides). It may be leaking from the bottom side, in which case, spraying the brake cleaner will not make a change in the idle speed.

I ignore the problem as long as I could but the truck quick starting. There was no vacuum leaks. It ended up being the distributor rotor and rotor cap. I replaced it and the problem went away an truck runs like new now.

That's good to hear. A lot easier repair than the intake gaskets, for sure.