Several Misfire codes, fuel pressure issue?
02-03-2011, 12:09 PM
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Several Misfire codes, fuel pressure issue?
Well, i am admitting defeat, and looking for help. I've got a fair amount of mechanicing experience, particularly with toyotas, but this one has me stumped. I have searched the forum, diagnosed everything i could, and replaced the obvious parts.
The Back Story:
I've got a 96 Limited with the 3.4 and 260k miles. I bought it last fall, and it ran like the day it was new. being the tinkerer that i am, i dove into it in december, and changed the plugs, wires and valve cover gaskets. Somewhere in this process, unknown to me, some unidentified piece of metal fell into the #6 cylinder. So when i started it up, it made all kinds of racket and i shut it down. the truck ran for less than 60 seconds total with whatever it was in there.
So i took the head off, fetched the small piece out, checked for damage to the valves, head, piston and block. other than some surface damage, there was no major damage. i reassembled everything, new head gasket of course, and the truck wouldnt start. It would crank over fine, but wouldnt run. had spark and everything, and eventually got it to start by pinching the fuel inlet hose closed while cranking. After a few rounds of this, it would start on its own, and now is back to drivable.
Where I'm stuck now:
I truck starts fine now, and drives pretty well. Once it warms up, it idles very rough, and the check engine light blinks. as soon as i pull out, the light goes back to solid, and the truck runs fine. The fuel mileage has suffered greatly. I changed the plugs and wires with Factory equipment, did a compression test and everything is pretty close together(only about a 10% difference from best to worst). I'm getting misfire codes for 4 cylinders, so i dont think its an injector issue. I havent changed the fuel pressure regulator yet, but im thinking that might be next.
Any thoughts or ideas?
Thanks in advance.
The Back Story:
I've got a 96 Limited with the 3.4 and 260k miles. I bought it last fall, and it ran like the day it was new. being the tinkerer that i am, i dove into it in december, and changed the plugs, wires and valve cover gaskets. Somewhere in this process, unknown to me, some unidentified piece of metal fell into the #6 cylinder. So when i started it up, it made all kinds of racket and i shut it down. the truck ran for less than 60 seconds total with whatever it was in there.
So i took the head off, fetched the small piece out, checked for damage to the valves, head, piston and block. other than some surface damage, there was no major damage. i reassembled everything, new head gasket of course, and the truck wouldnt start. It would crank over fine, but wouldnt run. had spark and everything, and eventually got it to start by pinching the fuel inlet hose closed while cranking. After a few rounds of this, it would start on its own, and now is back to drivable.
Where I'm stuck now:
I truck starts fine now, and drives pretty well. Once it warms up, it idles very rough, and the check engine light blinks. as soon as i pull out, the light goes back to solid, and the truck runs fine. The fuel mileage has suffered greatly. I changed the plugs and wires with Factory equipment, did a compression test and everything is pretty close together(only about a 10% difference from best to worst). I'm getting misfire codes for 4 cylinders, so i dont think its an injector issue. I havent changed the fuel pressure regulator yet, but im thinking that might be next.
Any thoughts or ideas?
Thanks in advance.
02-03-2011, 12:16 PM
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One observation:
Even per the diagram under the hood, the vacuum line for the fuel pressure regulator is plumbed into one of the resonator boxes on the intake tube. I cant understand how that would be a viable source of vacuum, and in fact there is no measurable vacuum there at idle. This is a big difference from what i am used to, as most FPRs get their vacuum source from the intake manifold.
Even per the diagram under the hood, the vacuum line for the fuel pressure regulator is plumbed into one of the resonator boxes on the intake tube. I cant understand how that would be a viable source of vacuum, and in fact there is no measurable vacuum there at idle. This is a big difference from what i am used to, as most FPRs get their vacuum source from the intake manifold.
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