My 1990 740 GL 4 cylinder has excessive vibration when idling at a red light.
Increasing idle helps but then it's to high when starting vehicle or idling in park.
Any suggestions on what to do?
1990 740 GL virbation problem
Sounds like a missing cylinder. Start changing spark plugs. Change to NGK, Volvo just loves those plugs! If it does not help, get a new distributer and a new set of ignition wires for the spark plugs. Look also for all small rubber tubes connected to the intake, one missing or leaking, and it will behave like you describe.
Don't just start replacing parts, the cost could be very high!!!
An engine vibration at idle is usually caused by a cylinder not firing, but there are many reasons that can cause this. My first question is how much work are you able to do yourself, if you do not have the knowledge or tools it would probably be much faster and cheaper to take it to a mechanic that you trust.
If you are mechanically inclined then there are some regualr maintenance items that you should do:
1) do replace the spark plugs as LaRy mensioned and yes NGK work great.
2) clean the throttle body, deposits can cause rough idle.
3) upon a test drive if the "vibration" is still there I would suggest a compression test, check the continuity and resistence of the plug wires (only replace if needed), visually check the distributor cap & rotor for burning, arching, wear, and replace only the parts needed
4) the problem could also be dirty injectors, try an injector cleaner that goes in the gas, but if the injectors are really dirty a more aggesive cleaninf by a shop will be required.
An engine vibration at idle is usually caused by a cylinder not firing, but there are many reasons that can cause this. My first question is how much work are you able to do yourself, if you do not have the knowledge or tools it would probably be much faster and cheaper to take it to a mechanic that you trust.
If you are mechanically inclined then there are some regualr maintenance items that you should do:
1) do replace the spark plugs as LaRy mensioned and yes NGK work great.
2) clean the throttle body, deposits can cause rough idle.
3) upon a test drive if the "vibration" is still there I would suggest a compression test, check the continuity and resistence of the plug wires (only replace if needed), visually check the distributor cap & rotor for burning, arching, wear, and replace only the parts needed
4) the problem could also be dirty injectors, try an injector cleaner that goes in the gas, but if the injectors are really dirty a more aggesive cleaninf by a shop will be required.
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