I still have a vacuum leak on my 07 tundra after having the intake manifold gaskets, all breather hoses (including pcv hose) replaced. My fuel trims remain high (+10.2% to +17% on both banks) at idle and drops normal with acceleration. I already had the fuel pump replaced and that got rid of the higher fuel trims that stayed high and got rid of the p0171/p0174 I had before. I don’t have a check engine light with this current issue and the truck definitely struggles to accelerate from a stop or when needing to pass or pick up speed in general. It doesn’t idle rough and doesn’t have trouble starting. It’s been a struggle to find a mechanic that can accurately trace down this stubborn vac leak. Failed attempts even with smoke test and carb cleaner. The intake gaskets definitely needed replacing and I thought it would have helped but it didn’t. I was wondering what other areas can a vacuum leak occur?
You don’t have a vacuum leak. It’s fuel delivery. So bad fuel pressure, clogged injectors etc
@imperator I thought fuel delivery problem would be the fuel trims remaining high? Because my fuel trims actually drop to normal when I accelerate.
Vacuum leaks are most obvious at idle. It would idle rough. They don't affect the engine at open throttle.
The fact that yours struggles to accelerate and take off points to fuel shortage.
However, it IS strange that your fuel trims go normal (according to you that is. Does LTFT go close to 0%?) during hard acceleration when the symptoms are the worst. So maybe the oxygen sensors aren't giving a true reading. Check for problems with exhaust. Either blockages or leaks.
@imperator During acceleration the fuel trims go between +2% to +7%. At idle I see a bit over +10% and some days it’s just under +20%. No check engine light or codes when I check. But something is also affecting my gas mileage.
Of course it’s burning too much fuel. Not great for the cat.
A high positive fuel trim, especially when idling, can easily be caused by a fuel issue. Your fuel trims could still be better at a higher RPM and yet you still have a weak fuel supply.I thought fuel delivery problem would be the fuel trims remaining high? Because my fuel trims actually drop to normal when I accelerate.
Too much air is often "not getting enough gas"..
