QuestionQUESTION: I replaced: fuel pump, fuel filter, fuel pressure reg., MAP sensor, TPS, EGR solenoid, ICM, plugs & wires, cleaned throttle body & injector bowls and engine STILL bogs down at WOT and will not recover until throttle is released. It WILL accelerate to 70 mph+ with slow throttle advance. Also, new EGR solenoid doesn't allow vacuum to EGR at any throttle position (supply side working, delivery side tested with vac gauge). EGR diaphragm moves freely and holds under test. Ran direct to EGR from intake but engine still bogs at WOT. I haven't tested fuel psi at inlet (new fuel pump) but could the return line be collapsing? No codes other than a lean fuel when I tried to tow a horse trailer (engine bogged and gradually lost power down to 50 mph max. No knock or ping. I'm at my wits end!
ANSWER: Skip,
Sounds like you have fuel delivery/return problems or a timing issue. Have you checked the timing with a light to see where it's at? I would probably check that first, and if everything is good there, then I would dig into the fuel. There has to be a blockage or a collapsed tube somewhere, or injectors not coming full open. Check your fuel pressure at the inlet and check your return line for blockage/collapse. Also have your injectors bench tested to make sure they are flowing freely.
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QUESTION: I have duplicated the problem with a second set (used but correct size) of injectors. Haven't checked the timing yet. The fuel return line exiting the TB gets VERY hot after run at highway speed. There's a short length of rubber in the metal line (inlet & outlet) I can tee into to check pressure but have to drop the fuel tank to get at the back ends. How do I bench test injectors and any thoughts on the EGR solenoid situation? Thanks!
ANSWER: Skip,
You should be able to get a good idea from testing pressures at the rubber in the lines. If the return keeps climbing, you have a block. I wouldn't drop the tank just yet. You should be able to take the injectors to a parts store, like NAPA or something and have them bench test the injectors... call ahead to see if they have the capability. I called my Dad on this one, and he had an idea as well. My Dad says it sounds like a blocked exhaust, like maybe the honeycomb in the cat collapsed and isn't letting the exhaust flow. He said you would be able to drive and pick up speed slowly, but not under power or WOT because the exhaust has nowhere to go. The more I think about it, the more I like that idea as a fix for your problem. As for the EGR solenoid, He said that if the exhaust isn't going anywhere, you get no vacuum. I would reccomend unbolting the exhaust at the cat and seeing if it is blocked. You can also wire up the pipe and take it for a drive.... it's just going to be really, really loud. If the solenoid continues to not provide vacuum, you should be able to have it bench tested as well, sometimes parts are just bad from the factory. Check these things out, and let me know how you make out. If none of it works, I'll dig even deeper if I can. Good Luck!
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QUESTION: The cat converter was removed when I installed a new OEM muffler & tailpipe last year, but your Dad is right. It DOES mimic a clogged cat converter. Running open pipes is a problem now since the muffler is welded in place. I AM getting vacuum at all throttle positions on the baseplate (supply) side of the EGR solenoid (24 ----> 0 in. Hg) but not the outlet side (constant 0). WOT drops supply vacuum to about 7 in. Hg but it will not equalize. It just flutters until I back off the throttle. I could try another solenoid but something tells me the computer isn't sending voltage or receiving info to activate the EGR. I guess I should check for voltage, eh? Or does the EGR solenoid operate as a resistor and SEND impedance info to the computer? Guess I'll find out. Many thanks for the brainstorming effort. I'll track down a fuel pressure gauge tommorow and get back to you with the results.
AnswerSkip,
I don't know which way the solenoid runs as far as voltage, but it does sound like there is no signal one way or the other... Definately let me know how it checks out, I always like to learn something I didn't know before, and I guess I never had to check one to see if it operated on voltage or resistance. Thanks... Jim
