QuestionOnce again I am back with another question about the idle issue which I can't seem to resolve. I have been told it might be the electronic control unit (ECU). How can I check to see if the ECU is working or not? And where exactly is it located? Could the oxygen sensor be part of the problem? Thanks.
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Followup To
Question -
Thanks for your ideas. All of the basics have been taken care of and the screw on the throttle housing did not help. Anytime I first start the car, it idles rough and stalls. When I drive it, it runs fine. The idle is also very rough at stops. Could this be a defective air mass meter? If so, how do I test for that? Also, where is it located?
Thanks,
Tony
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Followup To
Question -
I am having trouble with my Volvo when idling. It seems about to stall, especially when I first start it no matter what time of day. I replaced the cold start sensor and cleaned the throttle plate. It is somewhat better but still rough. This has been an ongoing problem. The car has 135,000 miles and runs fine except when at a full stop, just idling. Do you have any suggestions? Can I raise the idle. If so, how?
Answer -
Tony,
The black plastic screw on the throttle housing will add a small amount of "base idle". Have the basics been taken care of? Cap, rotor, wires, plugs, air and fuel filter?
Answer -
Tony,
Sure a bad Mass air flow sensor will do many things ever a poor idle. Althought there are several electrical and ohm tests for the MAF the best is trying a known good one. If all else fails you may have to get the car to someone that can hook up the Volvo Sysytem tester (VST) to it and take some live readings. MAF is in the intake air tube and has a wire connector. Made of metal and clamped to the hoses.
Vacuum leaks can be the cause, even low compression or a burnt or stuck valve, injector not firing or a poor spray pattern, running to lean, cause idle problems. The car often runs "ok" off idle.
Peel back rubber boot from around air mass meter wiring connector.
Connect voltmeter between terminal 9 and ground .
Connect voltmeter between terminal 9 and terminal 36 .
Meter should show battery voltage in both cases. (Air mass meter terminal 36 is grounded at the intake manifold).
Check wiring from starter motor:
Connect voltmeter between ground and terminal 4 .
Crank engine.
Meter should show battery voltage .
Check fuel injectors:
Connect ohmmeter between fuel pump relay terminal 87 and ECM connector terminal 13 .
Correct resistance is approx. 4 ohms .
If meter shows:
approx. 5.3 ohms : either an injector or an injector wire is defective.
approx. 8 ohms : two injectors or injector wires are defective.
approx. 16 ohms : three injectors or injector wires are defective.
AnswerTony,
Right front kick panel you will find the control unit. There is no effective way to test the control unit. After testing all the compontants and either replacing them or finding they are free of fault you will need to try a "known good" control unit.
A defective O2 sensor will cause a poor idle. If you have a single wire O2 then there is a "recommended replacement" interval of 30K. If you have a three wire one then the only replacement is "as needed".
