2000 Gmc Jimmy 4x4 Tow Package 164000 Miles
Last month or Two, The Jimmy picks and chooses when it wants to start, some times it wont start, then other times it will start with no problems for a week or so then back to not wanting to start. When it Does run the power is normal, good acceleration, Terrible fuel Economy (low 13mpg city, 15 mpg highway always speeding). The check engine light Is on and these are the codes: PO171 Lean Bank 1, PO174 Lean Bank 2, PO304 Cylinder # 4 Misfire(usually not on, randomly comes and goes this code does)
Lately the ONLY to get it to run is turn the engine over, release the key it sometimes Runs for a few RPM's then real quick turn the key to start position and it will sputter for a second then actually run after I rev the engine to 3-4k rpms a few times, and then runs like a top, again once it starts it runs and drives fine.
The Check E light has been on and off since ive had the vehicle, and this is what i have done in the last 40kmiles:
Spider Injector upgraded version (was sputtering while acceleration and running Terrible at idle)
Fuel Pressure Regulator
Mass Flow sensor (ran smother and better power/acceleration)
All 3 O2 Sensors (ran smother and better power/acceleration)
Plugs (Iridium "Think" ACDelo ignition parts ), Cap/Rotor, Wires, Coil
Flush coolant system(chemical, flush then with flush kit several weekends in row, water kept coming out nasty AF, drained and refilled with 50/50 dex cool) Replaced Bottom Fan shroud, Fan, Fan Clutch, Water Pump, OEM Thermostat, Belt for pulleys, (used to like to jump over 210 mark quick at idle at lights or drive through and leak antifreeze), and Both hoses to and from Radiator.
Coolant temp sensor
Few other sensors that i cant remember
Think only vacuum line to brake booster
And other Wear and tear parts
Sorry for list, previous owner didn't know what maintenance was. Oh Yeah, do NOT buy at a mom and pop used car lot, trust me terrible idea.
Question is How do i make it Start Normally where i don't gave to play ballet with the key and ignition to get it to run?
Probably the Original Timing Belt, could the timing be off due to worn timing belt? Or????
Do you have a scan tool or scan app that can read live data?
There is no timing belt, so forget about that idea. There is a timing chain, but you're not describing any symptoms that would make me question the timing chain.
Run a full fuel pressure test. Also, has the fuel filter been changed? If no, or even if you're not sure, put a new filter in when your running the fuel pressure test at the fuel filter. You need to check the peak pressure during prime and the pressure 10 minutes after priming and turning the key off. Check both pressures/times at the schrader valve by the spider, and also at the fuel filter with the pump running straight into the gauge (optionally through the filter). Don't "Tee" into it at the filter, set the gauge up as the end of the line. At the schrader valve, you should have about 60psi peak during prime, and it should fall no lower than 50psi after 10 minutes with the key off immediately after priming. At the filter, directly into the gauge, it should read 75psi (ish) as peak during prime, and it should stay over 65psi after 10 minutes. It may be higher at the filter (measuring unregulated pump output pressure), but in 10 minutes, it should not lose more than 10psi.
Check for vacuum leaks. This is easier (and more precise) with a scan tool/scan app. Watch the upstream O2 sensor voltages ("sensor 1" on bank one and bank two) on graphs. With the engine warmed up (drive it first, then check for vacuum leaks), the sensors should fall into a nice oscillating rhythm. Spray Intake/Throttle body cleaner (NOT Carburetor cleaner!!!)
around the intake manifold gaskets, the vacuum fittings/lines, the MAP sensor and purge valve and around the injector spider. If there's any leak at all, it will make the O2 sensor voltage(s) swing way to the rich side when you hit the leak with the cleaner.
Obviously fix any vacuum leaks you find.
I really suspect you've got a fuel pressure issue, though.