93 Jimmy. Whining from rear and the truck dies.

08-11-2013, 02:51 AM
So, I've already made a few threads on this particular truck (4.3L fuel injected 93 jimmy.) My main problem was big backfiring and shuddering after driving for 30 minutes or so. After it began to act up like that I would park, and let it sit for 20 minutes or so. Upon, restart it wouldn't turn on right away and I would have to hold the key down until it slowly came back to life quietly (quietly as in I would have to guess when the truck was started because I couldn't tell when I had the key down). Another thing to note about the prior sentence is once you coaxed it back to life and killed it to restart again it would fire up fine. Well here are the repairs I have made so far: New alternator, temp sender, couple sparkplugs and I mean to change the rest, and a fuel filter. I changed the temp sender and fuel filter today, and the backfiring has seemed to stop as well as acceleration being smoother and not quite so fast on the deceleration. In other words, the power increase from a new fuel filter was noticeable (water really won't run through the old one and I had to really blow on the end to get air to come out so obviously clogged up.) The problem of holding the key down to restart also vanished but popped up with a new one instead. Rather than force it to come back to life the truck will just kill itself within 5 seconds upon restart once or twice after sitting for 10 minutes before it actually stays on to be able to drive. Right before it kills itself the fuel pump (I am assuming) has it's normal whine but suddenly gets loud and the car dies and in text form it sounds something like this mmmmmmmmmmmmmmmmmmmmmmmmmmm and dies. Now my step father said he replaced it about 2 years ago. and a year of that it sat because of tranny problems that have been fixed. One more thing of note is an extremely faint *pop*.....*pop pop*... *pop* from the exhaust. The pop is only really noticeable when standing outside and near the vehicle. Thank you and hopefully I did not overload with info.

Edit: the startup problems ONLY occur when letting it sit for 5 minutes or more. If I run it for a while, park it, and immediately restart it starts perfect, but not when sitting.

08-11-2013, 10:25 AM
Is this a Vortec engine or throttle body?

08-12-2013, 12:05 AM
It is the fuel injected vortec. Another thing is that the truck no starts up rough until gas is applied to get it warm after changing that fuel filter. I had to drive my girlfriend along that same long route this morning and this time no trouble restarting the vehicle once I got home. However, for the sake of speculation and saying that this morning was a fluke what could it be? I have also noticed brown "poop" on the top of the radiator, but no fear since the oil is brown from wear but not cloudy or muddy because of coolant and nor is the coolant a milkshake consistency. Rub the brown gunk in between your fingers and dries quickly into a coppery/rusty smelling powder. I dumped cleaner in and now the coolant is brown, but the radiator is showing nothing on the walls so that is good. However, after driving for a bit and the oil dipstick is pulled you can see very faint smoke for about 30 seconds before it stops. My theory is that the clogged filter caused the engine to run lean, running lean caused the pvc valves and vacuums to get crapped up and after a while of driving it caused the restarting issues and prior misfires. If that sounds plausible let me know.

08-12-2013, 09:09 AM
Get a fuel preesure gage on the fuel rail port you need 60# min. The other issues will not cause the pump to be noisy, running lean has no affect on any vacuum operated components.

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