QuestionDear Anthony,
My 1989 Plymouth Laser R/S Turbo manual shift has 197,000 miles. I still get 26 to 29 MPG. No mods whatsoever, I never had problems. It had new alternator, new exhaust pipe and muffler 4 months before I got the first problem. The car starts instantly even in the cold New Hampshire winter mornings. However, recently I have a severe bucking problem after the car is parked overnight which comes and goes and lasts about 2 to 3 miles of driving. After 3 miles eases up and the symptoms disappear. This happens each and every morning.
I have the same mechanic for 20 years and I fully trust him. After the problem started, he changed ignition wires, air and gas line filters, timing and balancing belts, and ignition coil as well. He hooked up a diagnostic computer while he was also experiencing the bucking but he got no diagnostics. My observations are: Pulling out of the drive way the car loses power and starts bucking to the degree that I have to brace my neck on the back rest. No engine warning lights come on, no ECU clicking can be heard either. When I vary the throttle it stops bucking and usually it is better with less throttle but keeping the throttle steady for more than 4 seconds the bucking comes back. During the power loss I noticed the turbo kicks in and the original booster gauge goes to the end of the scale as if the turbo tries to assist with the power loss. My mechanic has an eclipse to be junked and his is willing to try different components. However, I am against witch hunting. Also about a year ago I noticed when I shift to neutral the RPMs remain around 1,800 and only if I bring the car to a complete the RPMs will go down between 750 and 800. I love my car and its MPG performance. Do you suggest any plan of action or it is time for me to start looking for another vehicle?
Sincerely,
Elias Batis
133 Princeton Road
Nashua NH, 03064
Email: Elias.Batis@Hummingbird.com
AnswerElias,
There are a few causes for your problem. It's caused by a problem with the air coming into your engine and the components that regulate it.
The first thing to look for is a disconnected air hose. Having a turbo model means you have a large array of vacuum lines and hoses. You should make sure each one is connected and see if you can find any visible rips. The best method would be to have your mechanic perform a boost leak test.
The next thing to have tested is your Idle Speed Controller (ISC). The car's computer attempts to control the idle speed by opening or closing the ISC. The valve on the ISC allows extra air to bypass the throttle plate. You'll want to have your ISC tested. Another components that lets air bypass with the throttle body is the fast idle air valve (FIAV). This should only be active when engine is cold, but if it's always open, it can cause stumbling.
Next, the Exhaust Gas Recirculation (EGR) valve should be checked. This valve is located under the throttle body and if it's malfunctioning will cause stumbling.
Last, you should have your throttle body cleaned throughly. A dirty throttle body will hinder air flow and can cause the throttle plate to stick. Here is a general list of items your mechanic should check:
- Air/vacuum hoses
- ISC
- EGR valve
- PCV valve
- Base Idle Setting Screw (BISS)
- FIAV
- Throttle body
Also, having the turbo model means you should be using premium gasoline. If you've been mainly using regular gas, you should switch to premium (91 octane or higher). Unless your mechanic has an '89 or '90 turbo Eclipse, he CANNOT swap parts between your Laser and the Eclipse he has. Many of the air intake components are different for every other year of Eclipse.
Good luck!
