Acceptable Fuel Trims? Still a vacuum leak?
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Champion
Joined: Feb 2010
Posts: 3,686
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From: Greenfield, Wisconsin
Acceptable Fuel Trims? Still a vacuum leak?
Hey guys,
I put on a used ported and polished TB a couple weeks ago and have had vacuum issues. I replaced the gasket on the initial install, but I installed it dry. I got a whistle and my RPMs would hang while coming to a stop, or when I put it in park they would rise to 1200rpm. Also, if I revved the engine while it was hot in nuetral the RPMs would hang. I replaced the throttle position sensor and idle control valve and still no change. The problem never existed before I put on this TB.
Now I have pulled the throttle body off probably 6 times to try different things. After stripping one of the stock bolts, and snapping a couple 8.8 grade bolts from the hardware store, it may be time to give up on this TB. I have finally got the idle to be ok by lubing up the gasket with some vasaeline, but Im not completly sure I have fixed the leak. My fuel trim still jumps around, sometimes to a combined -15 with short term and long term while at a stop in drive. While on the gas at a cruising speed, sometimes the mix will be richened by +5 otherwise leaned slightly with -3. There is no major concern while cruising.
What is the acceptable range for fuel trim on our trucks? Maybe Im just being too cautious and there is no longer a vacuum leak.
And can anyone tell me whats the difference between Short/Long Term Trim 01 and Short/Long Term Trim 02 is? Because my 02 trim looks fine, this is all in the 01 trim.
If my current trims arent acceptable, there are two possible causes. On the TB, there is an imperfection on the back of the TB where it seals to the manifold (my guess is its this) or its the shaft seals are leaking. If its either one, Ill be ordering a Fastman instead of being so damn cheap. Do you guys still think the TB I have right now is still causing a vacuum leak?
I put on a used ported and polished TB a couple weeks ago and have had vacuum issues. I replaced the gasket on the initial install, but I installed it dry. I got a whistle and my RPMs would hang while coming to a stop, or when I put it in park they would rise to 1200rpm. Also, if I revved the engine while it was hot in nuetral the RPMs would hang. I replaced the throttle position sensor and idle control valve and still no change. The problem never existed before I put on this TB.
Now I have pulled the throttle body off probably 6 times to try different things. After stripping one of the stock bolts, and snapping a couple 8.8 grade bolts from the hardware store, it may be time to give up on this TB. I have finally got the idle to be ok by lubing up the gasket with some vasaeline, but Im not completly sure I have fixed the leak. My fuel trim still jumps around, sometimes to a combined -15 with short term and long term while at a stop in drive. While on the gas at a cruising speed, sometimes the mix will be richened by +5 otherwise leaned slightly with -3. There is no major concern while cruising.
What is the acceptable range for fuel trim on our trucks? Maybe Im just being too cautious and there is no longer a vacuum leak.
And can anyone tell me whats the difference between Short/Long Term Trim 01 and Short/Long Term Trim 02 is? Because my 02 trim looks fine, this is all in the 01 trim.
If my current trims arent acceptable, there are two possible causes. On the TB, there is an imperfection on the back of the TB where it seals to the manifold (my guess is its this) or its the shaft seals are leaking. If its either one, Ill be ordering a Fastman instead of being so damn cheap. Do you guys still think the TB I have right now is still causing a vacuum leak?