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losing power at higher speeds
Posted 14 December 2004 - 11:14 AM
I think I've done everything that has been suggested in past threads. I rebuilt the engine in March and replaced all filters, fluids, plugs, wires, o2 sensor, etc. and timing is still good. I'm running regular gas so octane can't be too high.
Any suggestions of other things to look for? No idea how to navigate the emissions stuff but maybe that's the culprit? No sign of a vacuum leak anywhere...I went over the lines/hoses a month ago.
I'm just trying to think of what would affect power @ higher speeds but not slower. Can fuel pumps wear out gradually or is it an "all-or-nothing" component? I am getting a lot of blow-by...would lost compression produce this?
Posted 14 December 2004 - 11:38 AM
Check that the timing is advancing as you accelerate. Hook up the timing light and rev the engine while watching the timing marks. The marks should advance right out of the sight window. If the advance is not working, check to ensure the vacuum line is properly connected. If your disty has a retard mechanism too, make sure it's hooked up properly and the lines are not crossed. Advance side goes to port vacuum and retard side goes to manifold vacuum.
Fuel pumps can get tired but if your car is carburated, it doesn't take much pressure to make it work. Typically, if it fails, you'll know right away. Fuel injection can suffer from a tired pump as the requirements placed on the pump are much greater. If a system is needing 60psi and the pump can only deliver 55, it will probably still start up and idle but the driveability will suffer.
You may also want to remove that big aluminum wing bolted to the rear. I know they look cool but that's a lot of drag.
Posted 14 December 2004 - 11:56 AM
You can forget the vacume advance stuff.... it's an optical dizzy.
FUel starvation is a possibility. That would most likly show up as a sputter or missfire at higher RPMs. Is this just a lack of power or does it kinda sputter and missfire as you try to accelerate to 65 MPH?
Double check your spark plug gap. Often times plugs that come gapped are slightly off or completly wrong. Also the condition of your plugs can give you insight to how the combustion process is performing.
Maybe it's not your engine at all... maybe its your 3AT thats slipping at higher RPM / MPH ?
Posted 14 December 2004 - 01:43 PM
Posted 14 December 2004 - 05:29 PM
someone suggested a plugged cat.
brought it to an exhaust shop, they drilled a small hole in the exhaust pipe and checked back pressure- sure enough cat was plugged. they quoted me 200 to replace. i said no thanks. so they patched the hole they drilled and charged me 10 bucks for the test. i took it home and fixed it myself- gutted the cat.
no emissions testing where i live. not sure what the laws are in your neck of the woods.
Posted 14 December 2004 - 05:31 PM
had a geo once with no power. turns out it had 50 psi on every cylinder. no wonder it had no power. did not use any oil either. go figure.
Posted 14 December 2004 - 06:39 PM
I'll take a look at the plugs again (I could use some quick release plugs on this car as often as I do this). No misfiring or anything like that, just no go. Urp, don't like the sound of the bad cat option, but that will be plan B.
Is there a quick way to test the fuel pump? I can hear it running (groaning) so it had crossed my mind that it's dying, but then again it's always done that. Looks like it would be easy to replace, I'd just rather not drop the money.
thanks for replies
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