Inherited car problems, fun for the whole family?

September 8, 2007 11:31 AM

Inherited car problems, fun for the whole family?

I was helping my mother with her car, which developed some problems. It is a late 80s Buick LeSabre, the official car of all grandmothers. I notice some issues and wonder if they are related or dependent.

First off, when the car is coasting, no throttle, it runs fine. When I very lightly touch on the accellerator, it violently vibrates, but if i push a little harder the vibration disappears.
Is this a air flow issue? I notice the exhaust smells rich.

When I look under the hood, i see sometimes the belt tensioner moves back and forth and clicks, perhaps a loose belt as well?

Another fine issue I notice is the engine is bogged down and the transmission shifts hard. I put on the gas and the engine works hard and sounds fine, but the car's excellaration is very poor. I have to let off the gas and wait for the transmission to shift before putting the gas back on.
Is this also related to the throttle,vibration issue?

Does anyone rent Ozone generators?

Thanks.

posted by torpark to travel & transportation (7 comments total)

Transmission. You're gonna need a mechanic.
posted by rhizome at 1:19 PM on September 8, 2007

"... Is this a air flow issue? I notice the exhaust smells rich."

More likely a vacuum leak. You open the throttle a bit, a the resultant drop in vacuum, plus the additional vacuum loss from initial throttle plate opening is enough to drop the vacuum retard to the distributor, and you get a tendency to pre-ignition, or missing, which will seem like "vibration" and result in rich exhaust.

"... perhaps a loose belt as well?" Perhaps. Most V-belts should deflect no more than 1/2 inch when pushed with a force of about 20 pounds midway in their longest run between pulleys. Loose belts generally squeal, due to slippping, and the belt surfaces appear shiny and feel slick, due to past slippage. Belts are cheap and easy to replace.

"... Is this also related to the throttle,vibration issue?" Depending on the exact year and drivetrain of your car, the engine and, perhaps, the transmission are controlled electronically by either an Engine Control Module or a Powertrain Control Module. It's possible this car has a defective PCM, but since that is going to cost more than the car is worth to replace, I'd look for more basic issues to resolve first. An engine vacuum leak could conceivably prevent passing gear kick down by the transmission, under heavy acceleration, and it's pretty common for 20 year old rubber hoses on cars to be in poor condition. I'd go through all the engine's vacuum hoses, replacing any that look iffy, and have the transmission fluid and internal filter changed, before I went any further.

"Does anyone rent Ozone generators?" Probably.
posted by paulsc at 1:35 PM on September 8, 2007 [1 favorite]

paulsc is on the money re the vacuum leak. Have fun finding it, American cars of that era seem to have miles of rubber hoses.
posted by buggzzee23 at 2:28 PM on September 8, 2007

As an added note, I'm pretty sure it feels like I am getting misfirings, in addition to transmission shuddering at low RPMs. I'm going to change the wires in the least, but I am also wondering if the misfiring symptom is consistent with an engine vacuum leak.
posted by torpark at 8:10 PM on September 8, 2007

I don't think it's a vacuum leak. Poor acceleration and a rough idle might be due to extreme carbon buildup in the cylinders, because granny never womps on the gas and takes it to yellowline before shifting. Doing so once in a while is essential to burn out the carbon and keep things running smoothly.

The decreased combustion chamber volume will make predetonation (knock) more likely, so see if a tank of high-octane fuel (which resists knock) smooths it out. Also, since the engine has a knock sensor and the computer adjusts timing to compensate, it's probably running with a lot of spark retard, which further explains the lack of power. Also, an incomplete burn means poor acceleration, poor efficiency, and a rich-smelling exhaust.

Pull a sparkplug and peek in there with a borescope. Five bucks says it looks more like a coalmine than a combustion chamber. This is a common pathology among grannymobiles.

The shaking at light throttle is probably because the engine mounts are shot. It's pushing 20 years old, those rubber parts are due to fall apart even if it was never driven.

As for ozone generators, check the phone book under "mold remediation".
posted by Myself at 8:50 PM on September 8, 2007

Update: Found out that apparently all this trouble started one day in winter, two years ago. It was below freezing, and my mother had to rush a family member to the hospital. Prior to that it was fine, and after that was when the problems appeared. So I am inclined to think it is a single issue problem.
posted by torpark at 1:09 AM on September 10, 2007

Solution: We were all wrong. All the above problems were caused by the 2,4 Ignition Coil being burned up. I replaced it, and the spark wires, for a total cost of $50. Now the engine runs smooth, the transmission shifts clean and quiet, and the fuel efficiency is back up, as is the power.

Thanks for the suggestions everyone!
posted by torpark at 5:12 PM on September 10, 2007