Stalling Honda could likely use throttle cleaning

Hey there, time traveller!
This article was published 18/07/2003 (8223 days ago), so information in it may no longer be current.

QUESTION — Nearly three months ago, my 1992 Honda Accord started to stall sometimes. This car has a 4 cylinder engine and automatic transmission. I have had it to the dealer and they could find no problems with it, but it still stalls occasionally. The engine only stalls when it is warm and I stop at a stop sign or traffic light. When the engine is cold, the car works fine. Can you help me out?

ANSWER — There are a number of sensors and inputs in an electronic fuel injection system that could cause the engine to stall, but many of these would set a trouble code in the computer. Your dealer could not find any problems so I can eliminate many causes.

Your problem is temperature related. The engine works fine when cold. The engine also operates on a “fast” idle when cold to decrease warm up time. This “fast” idle is controlled by the computer and an idle air control valve. The more air the valve lets into the engine, the faster the engine runs.

When the engine is warm, the computer almost completely closes the idle air control valve and most of the air required for engine idle goes past the throttle plates. I have seen many vehicles stall because airflow is restricted past the throttle plates. This may be caused by someone tampering with the throttle plate stop screw in an attempt to slow down engine idle speed. Changing the stop position only causes problems! Airflow past the throttle plates can also be restricted by gummy deposits.

During normal engine operation, oil and fuel vapours form gum deposits inside the throttle housing. Some cars are worse for this than others. The gum deposits can build up by the throttle plates enough to restrict air flow during idle. Then the vehicle may stall. Cleaning the deposits out is easy. Remove the rubber duct from the air cleaner to the throttle housing, open the throttle plates by hand, and wipe out the deposits with a cloth and combustion chamber cleaning solution. The cleaning solution can be purchased at any automotive parts store. One note of caution: Ford coats their throttle housing with Teflon to prevent build up and no cleaners should be used! This is printed on a decal on the housing but shouldn’t apply to your Honda.

QUESTION — The air conditioning in my 1990 Chevrolet car needed to be recharged because it is no longer blowing cold air. I took it into my local repair shop and they told me I should have the system converted to a new “R134a” refrigerant rather than spend the money refilling the system with “R12”. It is going to cost some money but they say it will be cheaper in the long run. Why should I convert?

ANSWER — R12 refrigerant production has been banned by law in North America because of the damage the refrigerant causes to the ozone layer. In the past, it was cheap to fill an air conditioning system with R12 because it only cost a few dollars a vehicle. Now the cost has increased to as much as $200 per vehicle just for the refrigerant! Converting to R134a refrigerant may be cheaper.

The cheapest conversions require only removing all the R12, refilling the system with R134a, and installing new service ports. The air conditioning may not work quite as well because R134a is not as efficient as R12. Other vehicles require replacement of the condensor and evaporator units to increase air conditioning efficiency. This will increase the cost of the conversion as well!

Finally, the compressor, compressor seal, or hoses may require changing because R134a has a smaller molecule than R12 and leaks out openings much easier. Different style seals and hoses are required. Many newer vehicles built in the 1990’s already have the improved hoses and seals do not require changing.

Balance the cost of converting to the cost of recharging the system with R12 refrigerant and it is cheaper in the long run to convert. Converting now will put you one step ahead of the game.

Jim Kerr is an experienced mechanic, instructor of automotive technology and freelance journalist. You can e-mail questions to Jim at the address below.

kerr.jim@sk.sympatico.ca