hey whenever i start my tahoe up first thing in the morning and the temp drops below 50 outside the truck starts but idles horrible sometimes it stalls and sometimes it saves it self but backfires and i can't figure out what it is because it's only when its cold. i have 102K on the truck almost all freeway and i just cleaned out the throttle body the other week and it woke up a little but still didnt fix the issue
does it have an exteneded crank? if so its probably a fuel pump going bad, or a fuel pressure regulator leaking down. get a fuel pressure guage, stick it on the truck, start and run it, then let it sit for 5 hours. go look at it, first check the guage before doing anything, is the fuel pressure still up above atleast 35 psi? if not, you have aleak down issue, and suspect it leaking through the pump, the regulator or an injector leaking down. its most likely an injector or bad fuel pressure regulator(really easy to change, and MAKE SHURE you get out the o ring of the old one), but on a 5.3L you can unbolt the rail, and lift all 8 injectors up with them still attached to the rail. with the injectors up, key the engine to on, and make shure fuel pressure builds, then visually make shure one injector is not leaking fuel out.... if it still has pressure, crank it and watch fuel pressurer while cranking. needs to be above 52 psi... if below you need a pump... install a new filter when you do a new pump, and only put in a delco, all the others are junk!
thanks man yesterday i cleaned out the MAF and the throttle body with some sensor safe cleaner and started it this morning and it ran fairly smooth but i wasnt as cold this morning so i try again tomorrow and keep you posted.
Fuel pump will normally act up when hot, not cold. Your vehicle is equiped with an engine coolant temp sensor. The computer uses this sensor for "cold start" situations. If the cts is not reading correctly, the computer will not allow enough fuel to the engine via the injectors for the engine to run correctly until it reaches opperating temp. This is the high tech version of the choke on a carb. I would check the cts reading with a scanner first. I will take a scanner to do this, the autozone code reader will not work.
we normally have the fuel pump problems on the first start oif the day due to fuel leakdown........ specially on 350's and 5.3L's
