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HELP! - O2 Sensor[ALL/1998] posted by Bill on
Sunday, 28 December 1997, at 6:02 p.m.
I have an 86 740T. I wanted to check the O2 sensor, but I am a bit reluctant since I can't tell how to get the 3 wire connector off the sensor. I don't want to ruin it so can anyone tell me how it comes off? I see the three wires going into a rubber grommet which seems to be buried in a metal sleeve. I don't know where to pull safely.
Thanks,
Bill
Re: HELP! - O2 Sensor[ALL/1998] posted by Joseph Kmiec on
Sunday, 28 December 1997, at 10:30 p.m.
You don't need to take the wire off the sensor to check it. All connectors are by the firewall. There are three wires; two of them are the same - they are to heat the sensor - to check it just check for ohms or see if it buzz (for continuity) if it does it means the heating element of the sensor is OK; third wire goes to computer - to test it, it must be connected to sensor, just slide off the black cover and connect the voltmeter between that wire and the ground (when the engine is hot) the voltage should fluctuate between 0.2V and 0.7V very rapidly.
Joseph Kmiec
Re: HELP! - O2 Sensor[ALL/1998] posted by Bill on
Sunday, 28 December 1997, at 11:58 p.m.
Thanks for the help. I checked it out and the sensor is working just fine, going between 0.1 and 0.7 volts, inclusive. I wanted to check it as I am trying to track down a bit of an erratic idle problem. Not much, just enough to cause the engine to shudder a bit. Otherwise, it runs good as new.
Bill
Re: HELP! - O2 Sensor[ALL/1998] posted by Joseph Kmiec on
Monday, 29 December 1997, at 1:11 a.m.
Bill, I would go and replaced the Knock Sensor. There is no way of verifying if the knock sensor is good or not.
However, on my 740 '86 I replaced a knock sensor and I've noticed an improvement.
I check the resistance of the old sensor and it was 0.3 MegaOhms and the new one was 4.8 MegaOhms. That is all I can tell you. A new sensor is about $80 Cdn. at a dealer.
Joseph Kmiec
Re: HELP! - O2 Sensor[ALL/1998] posted by Lee Lowrey on
Monday, 29 December 1997, at 4:13 p.m.
Before replacing the knock sensor, do a thorough visual check of all your vacuum hoses -- they harden with age and crack easy. Then check for intake manifold leaks by listening for a slight hissing with the engine running -- yes, you will need to stick your head as close to the intake system as possible (watch that fan!). Tighten the eight nuts holding the manifold onto head, as long as the gasket appears to be in tact where it is visible. My wife's '89 740 was idling poorly and found a leaking intake manifold gasket was the culprit (new gaskets are +/- $18 at Volvo dealers). I found the leak in my wife's car by slipping a very thin feeler gauge in the gap between the intake manifold and head on her B240F. Sometimes rough idling can be cured with these simple and inexpensive fixes, before getting into the expense of knock sensors, oxygen sensors, air control valves, etc. Good luck!
Re: HELP! - O2 Sensor[ALL/1998] posted by Bob Floria on
Wednesday, 31 December 1997, at 10:22 a.m.
My o2 sensor went on my Volvo, The car died on the road.
The engine warning light went on, two days later it died.
So be very careful with the sensor.
Re: HELP! - O2 Sensor[ALL/1998] posted by Jim McDonald on
Wednesday, 31 December 1997, at 11:11 a.m.
Failure of the O2 sensor by itself will not prevent the car from running.
Re: HELP! - O2 Sensor[ALL/1998] posted by Jeff Schneider on
Saturday, 3 January 1998, at 10:28 p.m.
I purchased an '87 760 Turbo about two weeks ago (111,000 miles). This is my first experience with a Volvo and have found the BrickBoard to be extremely helpful. As with any used car that I buy, I am going over the entire car from front to back; to understand it and make certain that it is safe to let my wife use it with the kids.
I really would like to verify that the oxygen sensor is functioning properly. After the car is hot and idling, I get a reading of .87 to .89 volts. Based on the range in the posting of .2 to .7 volts, I guess that this would make mine bad. Is the range also .2 to .7 for an '87? If the sensor dies, which default signal is sent to the computer, error toward rich or error toward lean? What over impact will the faulty sensor have on the operation of the car? Although I've only had the car for two weeks, it seems that the mileage is fairly poor.
Does a new sensor come with the pigtail/harness attached? What is the best way to remove the sensor as it appears to be deeper than most sockets and what size is it? It appears that it would be difficult to get a box wrench on the sensor with a turbo. Pep Boys can order the sensor from Borg Warner for $99, is this a typical price and would you suggest any particular brand?
Another item, I cannot get the service light to reset. Is there any other "trick" to geting these to re-sett or do the re-set buttons ever go bad? Do you have to hold the button in for a specific amount of time or while doing something else at the same time?
Lastly, what is the average life expectancy of a turbo. What are the typical ways that they fail and are they ever driveable after they fail?
Re: HELP! - O2 Sensor[ALL/1998] posted by Jim McDonald on
Sunday, 4 January 1998, at 10:56 p.m.
The range quoted is not a range in which a single value is OK; it's the range across which the voltage should sweep constantly at ~ 10 HZ. .89 means the system is quite rich which is the fault condition, but it's not a bad O2 sensor. This will give poor mileage, but won't kill the engine. There's some other problem in your injection system.
There's a special socket for O2 sensors; ask for it.
I got an unheated[1 wire] sensor for $35 and a heated[3 wire] one for $55.
Get the cheapest one and splice the wire[s].
TURBO - Life Expectancy[ALL/1998] posted by Bill on
Tuesday, 6 January 1998, at 12:08 a.m.
Jeff,
My 86 740T turbo lasted 11 years (140,000mi). The bearings on the turbo shaft went out. Symptoms were NO power up a hill and a rattling noise from the turbo when accelerating or when under load. The car was driveable as long as I babied it. I drove it 50 miles to my mechanic that way.
The replacement should last longer as it is both oil and water cooled (original was only oil cooled). Also, to ensure the longest life from your turbo, follow everyone's suggestion about letting your car idle for about 60 seconds before turning it off, especially if you have been running it hard. Also, frequent oil changes will help.
Bill
Re: TURBO - Life Expectancy[ALL/1998] posted by Steve Seekins on
Tuesday, 6 January 1998, at 1:06 p.m.
In addition to the cooldown time for the turbos it is as least as important (if not more so) to warm them up before stressing them. The car should be idled for a couple of minutes after starting before loading he turbo, and you should not do any hard acceleration until the engine had been running for about 5 minutes.
The problem is that immediately after starting, the cold turbine is hit with very hot exhaust gas and if heated up too quickly (as when putting a lot of load on the engine) it can heat unevenly and warp the vanes. Besdt to let the car idle for about 2 minutes, then keep out of the boost range on the gage for another 3 minutes. After that, it should be fine. This is also a good habit to keep from placing severe temperature stresses on the rest of the engine as well.
Steve
Volvo Colub of America