AutoTips     Symptoms - Solutions page

The purpose of this page is to list problems encountered with cars / trucks / automobiles and their less common solutions. It might be something other than a tune up that fixed a problem with poor gas milage, for example. If you have a symptom and solution you would care to share, please send e-mail to Please be concise, and include any details you think may help others, such as clues to the problem, remedies tried, etc. Thanks to the visitors to AutoTips who have shared their experiences.

Engine performance problems

NEW: From an AutoTips visitor

Symptom: Serious engine vibration on a 1989 V6 Plymouth Voyager at around 40-50 mph. Below that speed the vibration is not noticeable, and above 55 the vibration isn't as noticeable. Replacing engine mounts (3 on the Voyager) did not work, replacing shocks did not work. Checked the transmission, but no problems there.

Solution: Changed spark plugs, one plug was black with oil (rear of engine). Apparently, the engine was out of sync at higher speeds/RPMs. There was no noticeable knock at lower speeds or RPMs. After replacing the plug, there were no further problems.

NEW: From an AutoTips visitor

Symptom: Purchased a 1991 Chevy Caprice wagon. Nice V8 engine, good looking car, about 140,000 miles. About half way home the car slowed down and wouldn't accelerate... it would act like it was flooding. Lots of black smoke, and the smell of gas from the exhaust, but no rotten egg smell or rattle from the catalytic converter.

Solution: I replaced all the normal culprits, including O2 sensor, MAP sensor, spark plugs and wires, distributor cap and rotor... ALL of which did need to be replaced (makes me wonder about the maintenance on State vehicles...). After all of that, it still wasn't working correctly and I was about out of things to do. Then someone suggested drilling two small holes, one in front of the catalytic converter and one behind. The wind from the front hole blew leaves across my lawn. Sure enough, that was the problem. After replacing the catalytic converter and filling the holes I no longer have a problem.

Symptom - Intermittent rough idle on GM V-6 fuel injected engine.   Computer showed no error codes. Plug wires had tested ok, plugs had been replaced. Problem worse on hot days.

Solution - Replaced grommets around PCV valve. Grommets had become hard, and were leaking vacuum around PCV valve.

Symptom - Mazda with 4 cylinder dies at idle when warm, runs fine above idle, runs fine at fast idle when cold. Problem shows up after driving on dirt roads.

Solution - Cleaned idle air control valve by spraying mist of alcohol into air bypass valve opening in throttle body (carburetor cleaner was tried but didn't help as much as alcohol). This cleaned the passage around the idle air bypass valve. Problem continued to re-occur after driving on dusty roads. Hose to PCV valve was loose at valve, replaced factory PCV valve with Purlator PCV valve. The Purlator unit had a small flange at end of valve to improve hose seal. The air bypass valve supplies air to the engine at idle and is controlled by the computer. A second one provides air at fast idle when cold. That one was apparently ok, and is why it ran at fast idle. Leaking connection around PCV allowed dust from dirt roads to be sucked into throttle body - air bypass valve passage. Problem fixed.

Symptom - Intermittent engine cut out on late model Oldsmobile.  Engine would run fine- then act as if it were going to die, then pick back up. Problem occurred more frequently as engine warmed up. Computer error code showed misfire. Fuel injector cleaner tried, no help.

Solution - One of the spark plug wires showed corrosion at coil connection. That was cleaned, however that wire when tested showed to have intermittent connection from one end to the other. Individual plug wire replaced, problem fixed. (for more info on plug wires, see the AutoTips Plug Wire page )

Symptom - Gas milage drop in Ford F150 pickup truck after transmission rebuild. Milage had dropped from about 17 to 18 on highway to about 13 to 14.

Solution - Checking error codes ( with help from the book Sure You Can from Wells Mfg. Corp. or with a code scanner from Actron ) revealed problem with lock up torque converter.  When presented with the error codes, transmission shop opened up transmission and found wrong part had been installed, and lock up converter had not been working. A computer controlled solenoid locks up the torque converter to eliminate slippage and improve milage under certain speed and load conditions. When replaced, milage returned to normal.

Car body problems

Symptom:  GM mid-size car had rattle over bumps. Mechanics had looked under car, everything looked fine.

Solution: One mechanic found small piece from end of coil spring broken, still laying in support track. Removed piece, rattle gone.

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