My name is Andrew I own a 2003 Pontiac Vibe 1.8 2wd. I have two issues my biggest is I have a hard start issue when the car is warm. I have check spark plugs, fuel pump I also looked for air leaks I just can’t figure it out it’s only when the car is warm and the more I drive it the worst it gets. I have 246,000 miles with no check engine lights and and Maintence has been kept up with oil changes spark plugs things like that. I go to school for automotive technology and I’m just stumped. I’ve went through the process of elimination and just can’t figure it out. Any and all responses are welcome.
Maybe a leaky fuel injector (too much fuel), or a fuel delivery problem when hot (too little fuel).
Try a fuel pressure gauge on the hot engine, try some injector cleaner. Then try replacing injectors maybe one at a time if you can't afford all or can't test them at school.
Compression test, cylinder leak down test, coolant leak pressure test, coil packs degrade with heat? Cold starts are fine? Valve clearance has been checked?
There was a TSB for the 1.5 generation vibes for hard start when engine is hot. It involves a PCM reflash. I can no longer access that information because that **** costs money, but you should be able to through prodemand etc. via for school. This TSB may not involve the '03-4 models.
HOWEVER, you may also try testing for a drop in fuel pressure after the ignition is shut off, just because it is also something that causes similar issues. I think that's probably not your problem and it's instead the PCM's programmed tuning, but for the sake of sharing some related info I'm going to vomit it all over your thread.
The Toyota fuel pumps hold residual pressure on the fuel rail with an integral diaphragm inside the pump itself. This is to prevent you having to prime the pressure again before starting. It should hold the pressure for several hours, so you hook up a pressure tester, run the car, turn the car off, record the pressure, take off for a few hours, and then recheck. The pressure should not fall.
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