ABQjournal Car Clinic

December 18, 1999
Car Clinic
DEAR CAR CLINIC: I drive a 1991 Chevrolet Caprice. It seems to use a lot of oil, especially on trips.
For some time, it has been emitting puffs of white smoke from the tailpipe when first started after sitting overnight or when the engine is cold. Now, it is beginning to emit clouds of blue smoke when starting cold!
Do you have any suggestions as to what my problem might be? F.W.G., Rio Rancho
DEAR F.W.G.: Chevrolets are notorious for valve-guide problems and it sounds like that's what is going on in your case. Worn valve guides or bad valve guide seals allow oil to get into the combustion chamber on startup and decceleration.
Important questions to help diagnose your problem include: Are your spark plugs clean or do they have a sooty ash or heavy deposits on them? How many miles are on the engine? Has it ever been severely overheated? Has it been parked for a long time? How many miles a year does it get driven?
A compression test would also be helpful. Jim Maddox Jim's Automotive Inc., Albuquerque

DEAR CAR CLINIC: Our 1994 Ford Escort (1.9 liter four-cylinder with 56,000 miles) begins to overheat immediately while stopped at a light or in heavy traffic. But the temperature gauge drops back to normal range almost as quickly when we start moving again.
The cooling fan cycles on and off and the coolant level is OK.
Any suggestions? M.R., Magdalena
DEAR M.R.: The first things I'd check would be the radiator and hoses for any restrictions or blockages inside and the water pump for a possible slipped impeller. Slipped impellers are not common but they do occur.
You also want to be sure there is no air in the cooling system. Was it serviced recently? If so, it may have an air pocket in it causing the gauge to read hot when in fact is isn't. The cooling system can appear full and still have an air pocket.
I hope this was of some use to you. Rick Jones, Motor Call Mall, Los Lunas

DEAR CAR CLINIC: My wife's 1988 Merkur Scorpio (2.9-liter V-6, fuel injection, automatic transmission, 82,000 miles) idles at 1,800-2,000 rpm.
A diagnostic test shows code 67 NPS failed-closed, but there seems to be no problem with the switch.
I've replaced the oxygen sensor with no results.
When the electrical connector to the Idle Air Control unit (IAC) is unplugged, the idle drops to normal. The unit checks out OK electrically (no short to coil). Voltage to the unit measures 12V with the key on but jumps to 13.8V (alternator output voltage) when the engine is running and does not change or decrease.
I applied a variable DC voltage to the unit and it worked OK, that is, I could control the idle speed.
Which sensor sends electrical information to the IAC? If it's coming from the onboard computer, what's giving it the wrong data?
Thanks in advance. R.E.B., Albuquerque
DEAR R.E.B.: Your Merkur's idle control system problems are most likely computer-related.
The computer in this car uses tachometer readings and tries to maintain a set RPM regardless of engine load for example: air conditioner on, increased alternator load, in gear or out of gear. Cold idle speed is higher until the car warms up and the computer gets information from the engine coolant tempurature sensor. I would start there and check the sensor for the correct values both hot and cold.
The next step of diagnosis on your car is going to be replacing the computer with a known good unit. Unfortunately, there are no other alternatives for diagnosis. Jim Maddox, Jim's Automotive Inc., Albuquerque

Answers in this column are provided by Albuquerque-area automotive service shops. Got a question about your car, truck, van or RV? Describe your problem (please be brief!) and fax it to (505) 823-3994 or mail it to Car Clinic, Albuquerque Journal, P.O. Drawer J, Albuquerque, NM 87103. Or send your question via the Internet.