89 Bonneville acceleration problem

Hi all: This is my first post. I have an 89 Bonneville with a 3.8 and 180,000 miles. I know something about cars, but most things I leave to a mechanic. I'd like to change the sparkplugs, but want to find out if other things can be causing my problem before I get my hands dirty.

The car hesitates when I accelerate from a stop. The hesitation is almost a stutter. I do a lot of city driving, and the hesitation disappears when I get to 25-30 mph. At highway speed, there is no perceptible hesitation, though on my last trip of about 400 miles, I noticed that the mpg was down about 3 miles per gallon. Usually my beast gets close to 29 mpg on the highway; on this trip it was about 26. I changed the plug wires in August, by the way, and was very careful to do one at a time.

I do have an unrelated (or related?) problem with the oil pressure, but the mechanic who did an oil change in December said that the sensor was probably bad and that I should just ignore the oil pressure gauge. There is no ticking or noise from the engine that would indicate that the oil pump is going.

Questions:
Could my problem be related to dirty injectors or some other issue like timing?

Is it difficult for a semi-non-mechanic to do the plug changes? I've done it before, but only on a VW way back when. I've bought the plugs and a gap tool. I'm most concerned about stripping the thread or overtightening the plugs.

Is it difficult to reach the sparkplugs at the back of the engine? And are there
any special issues with those rear plugs (or the front ones, for that matter) that I should know about?

Any other suggestions welcome.

Thanks in advance.
John

Welcome to AF!!

It is not difficult to change plugs but it is sometimes hard to get to them. Just take your time and make sure the engine is cold. You will probably need a universal for your extension to get you in a proper alignment to remove the plugs. You will want to use antisieze on the threads.

As for the injectors, use a good quality injector cleaner in the fuel tank and that should help clean them. You may want to replace the fuel filter to make sure that it is clean and not restricting fuel flow.

Your fuel consumption problem may be related to a lazy O2 sensor. Replace it with a new one, "Don't use Bosch" as they are junk.

Finally, never ignore the oil pressure guage. Change the sending unit, not hard to do but it will give you a good indication that is going on inside your lubrication system. If the pressure is still low you may have a wear issue due to the high mileage.

Hi GTP Dad: Thanks for the advice. My fuel pump and fuel filter are new from October. You're right about the oil pressure sensor. I usually use the car only once a week or so. I'll get to the oil pressure sending unit (no Bosch) as soon as I can. It went in early December. Before then, the pressure went up nicely as I accelerated.

But more questions:

Is antiseize a thread lubricant?

When you mention a universal, do you mean the long plug socket or the extension on the ratchet or something else?

On the O2 sensor: Is it the thing I see sticking out on the top side of the exhaust manifold going back from the engine? Or is it somewhere else? Assuming it's on the exhaust manifold: Is it a simple job of disconnect the battery cable, remove the wires from the sensor, unscrew the old sensor and then screw in the new one, reattach the wires, and reconnect the battery?

Regards,
John

Antiseize is just that. It keeps the plugs from becoming stuck in the heads. Dissimilar metals will corrode through electrolosis and the plugs will be very difficult to get out. It does lubricate the threads somewhat.

As for the O2 sensor. It should be located on the downpipe behind the engine. You may actually have two but the one on the back of the engine controls fuel mixture and will affect gas mileage. Purchase and O2 sensor socket. Then unplug the old one, remove it and reinstall. The new one will have antiseize on the threads so you won't need to add additional.

As for the universal, this is a universal joint for the extension. You can find them at most stores that sell tools. This will allow you to work at odd angles but still be able to use the ratchet.

my mom and dad has park avenues and they got the 3.8 in them..should just need socket and 1 exstenion for plugs.and the o2 they got special socket for that..there cheap at autozone or about any parts store. good luck

GTP DAD and Scrapper: Thanks for the additional info; very helpful. I hope to do the plugs and hopefully the O2 sensor as soon as the weather clears up.

John