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Continuing Bonneville Problems

HelP!!! I have had 96 Bonneville in shop (local community college automotive instructor vouched for the mechanics at this shop)several times in the last couple of months. Code read po300 and po171 before, now doing same thing AGAIN, and code is still po300. I started with a tune-up; plugs and wires replaced. Still had problem. I paid for diagnostics, was assured the shop’s diagnostics would pinpoint the problem, was told bad coil, had coil replaced and within a couple of days…same problem. Yes I should have taken it back to him, but I didn’t, so please don’t lecture me. I took it to a shop that was recommended by the local community college automotive instructor. Well guess what? I’m still having the exact same problem–car does okay until I drive approx. 40 miles,(where I am going to school) and if I do any amount of stop and go, or drive-thru’s, where I am sitting there, engine idling. New mechanics diagnosed and replaced lower intake gasket-upper also replaced–also heater hose, upper radiator hose, and alternator belt replaced. After I paid for all this, which is getting to be expensive, it took them FOREVER to start–actually, I had to leave it there, and get it the next day because they could not start it. Less than 10 days later, the car cut off at 10 o’clock at night on the bypass on my way home from class. Would not start back up–the next day I get a ride there and guess what? Starts back up no problem. However, new shop puts new fuel filter on, and now, little over a month later, having same problem with cutting off, but starting later. However, now, I have motor oil in my antifreeze reservoir, although I paid for the intake gasket repair which I understood would prevent this from happening. My funds are almost depleted from this and am I supposed to just keep paying out the nose for repairs that do not fix the problem? Please help if you think you know what it could be. At one point they said EGR valve, but the check engine light was not on, so they said they couldn’t be sure that’s what it was; they discovered the lower intake gasket probolem while changing the oil. H-e-l-p please!!! :[

This isn’t going to help, but if you have the 3.8 engine, they have a history of cracked intake manifolds. Replacing the gasket isn’t enough. Motor oil in your reservoir is a clue that you have a cracked manifold.

Thank you, Keith, for reply. When you say “this won’t help”, are you saying that this is expensive, or automotively fatal?

I meant that it won’t help you feel any better. It’s not cheap. What ever you paid to have the manifold gaskets replaced, it will be that much plus the cost of the manifold itself and a little extra to move over the throttle body and fuel rail.

You cannot use a junkyard part either, you want a new manifold with the newer design.

On the good side, everything else on this engine is rock solid, good for 200k miles at least with normal care. They also get remarkably good gas mileage for a car/engine this size. I mean, larger, more comfortable ride, more power and BETTER gas mileage than 4 cyl Accords/Camry’s.

I don’t know what symptoms your car is displaying. And I don’t recall what error codes our Bonneville was having. But here goes my story.

We had a '93 with the 3.8L that we had to stop driving because of stalling. We would be driving along and without warning the engine would cut-out. There was a baffle in the gas tank that had worked loose. It would intermittently block the fuel line and stall the engine. This drove my mechanic nuts. Cost me big bucks.

You reminded me of another problem. This car is flat out guzzling gas! The gas gauge does not work. Between the gas guzzling and all these “repairs”, I cannot even pay attention. But I appreciate everyone 's sharing their automotive knowledge with me. It helps me to not feel as helpless, even though I know that I am up the creek without a paddle–I live out in the boonies, and one really needs a car to get around, unless you’re a long distance athlete or crazy.

This is why a mechanic will install a fuel pressure gague and then tape it to the windshield so that it can be read by the person driving,while the car is being driven. As soon as your car would start to act up from the blocking baffel it would change the fuel pressure reading.