1979 Volvo 264 2.66 liter V6 idle problem - Hot Rod Forum : Hotrodders Bulletin Board
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Old 07-19-2010, 05:37 PM
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1979 Volvo 264 2.66 liter V6 idle problem

I have a 1979 Volvo 264 that won't stay idling. When started cold it will idle well at about 900 RPM for about 30 seconds and then it starts to fall in RPM, goes back up, falls even more, goes back up less, etc until it dies. If i try to start it up again without waiting a while it picks up where it left off and goes up and down until dying, instead of idling well for a little bit like when started cold.

It accelerates beautifully. I drove it around the block to warm it up and it does not hesitate to accelerate or bog at all, but when stopping to turn it was extremely close to dying at idle.

For what it's worth, it is fuel injected. Also, I'm waiting for a service manual to come so I'm unsure of the exact anatomy of the car, although I have the owner's manual which is somewhat useful.

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Old 07-29-2010, 08:54 PM
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Sounds like a vacuum leak some where. The fact is starts good when cold tells me the thermo time switch must be spraying the cold start injector. It may not have a thermo time switch but it will have a cold start injector on an old model like that.I dont have a book or any info available to me at the moment but i am calling on memory only. Now it can be an air leak at the cylinder head to intake area or a split or fallen off vacuum hose.but I think it best to start at the air flow sensor.Its probably the old style with the door inside that opens as airflow opens it. It regulates the fuel. The more air the farther open the door hence the more fuel goes into the engine.SO check the hose from the airflow meter to the intake manifold first. Take it off carefully as it may be kinda soft from age and if it tears you will need another one. Any splits or cracks can allow air in and wont pull the airflow meter door open and will run lean as less fuel is delivered and will cause it to stall and surge. Probably not a big hole yet which is why it still accelerates ok.as the hole gets bigger it will idle worse.I have taped over some spots in a few of them in the past as a temporary measure and it has worked.
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Old 07-30-2010, 12:26 AM
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Thanks for the help! I'm going to check your suggestions and some other possible causes. As it happens I just received the service manual today so I'm finally able to get an idea of how all the systems work.
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Old 07-30-2010, 12:32 PM
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I had this problem on my father's volvo and it turned out that one of the intake hoses after the MAF sensor came unhooked and it wasn't sucking air through the sensor. I could also be that the sensor is bad and needs a new one.
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Old 08-04-2010, 06:51 PM
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I changed some vacuum hoses that were a bit cracked. It didn't seem to do anything, but it's good to have it replaced anyway. I've checked every connection I could find to the airflow sensor and they appear to be fine. Although, there is one that I can't seem to reach without taking the air sensor and fuel distributor off. I will try to check it if the other possibilities don't pan out.

However, the most interesting thing happened today. I found a couple more hoses that were cracked, one of which connected to what I'm pretty sure is the cold start injector. I took it off to inspect how badly it was cracked and found that the metal connector to the hose on the cold start injector was almost completely plugged with hard black stuff. I took the connector off, cleaned it out, and reattached everything. To my great joy, this is the first time I've noticed any difference in how it ran. I started it and it idled higher than normal - slightly above 1000 RPM, instead of 900 like before. I waited for about 40 seconds and it seemed to be steady, which is longer that it has ever lasted without starting to die. Then I revved it to get the temperature up. When I quickly took my foot off it bogged down almost to the point of dying, and it went up and down for a few seconds until it resumed idling steady. I revved it again and this time took my foot off gradually - it didn't bog and resumed idling well. Then I tried revving again, and it wouldn't idle steady again, regardless of if I released the peddle gradually or not.

So, I'm going to try two things tomorrow: I'm going to replace the cracked hoses, and I'm going to do some diagnostic tests that are outlined in the service manual to test the cold start injector and the thermal timer. I want to see that:
A: It is spraying correctly, and
B: The thermal timer shuts it off. The manual says it should spray for no longer than 12 seconds.

The two service manuals I have are frustratingly vague in some areas. There is a mysterious thing that is connected to the vacuum hoses that I suspect is a vacuum booster - however, there is not a single mention of it in both manuals that I can find. If it is a vacuum booster, would checking the gasket for cracks be a good idea? I attached a picture of it.
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Old 08-04-2010, 08:26 PM
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Quote:
Originally Posted by WW2dude
I changed some vacuum hoses that were a bit cracked. It didn't seem to do anything, but it's good to have it replaced anyway. I've checked every connection I could find to the airflow sensor and they appear to be fine. Although, there is one that I can't seem to reach without taking the air sensor and fuel distributor off. I will try to check it if the other possibilities don't pan out.

However, the most interesting thing happened today. I found a couple more hoses that were cracked, one of which connected to what I'm pretty sure is the cold start injector. I took it off to inspect how badly it was cracked and found that the metal connector to the hose on the cold start injector was almost completely plugged with hard black stuff. I took the connector off, cleaned it out, and reattached everything. To my great joy, this is the first time I've noticed any difference in how it ran. I started it and it idled higher than normal - slightly above 1000 RPM, instead of 900 like before. I waited for about 40 seconds and it seemed to be steady, which is longer that it has ever lasted without starting to die. Then I revved it to get the temperature up. When I quickly took my foot off it bogged down almost to the point of dying, and it went up and down for a few seconds until it resumed idling steady. I revved it again and this time took my foot off gradually - it didn't bog and resumed idling well. Then I tried revving again, and it wouldn't idle steady again, regardless of if I released the peddle gradually or not.

So, I'm going to try two things tomorrow: I'm going to replace the cracked hoses, and I'm going to do some diagnostic tests that are outlined in the service manual to test the cold start injector and the thermal timer. I want to see that:
A: It is spraying correctly, and
B: The thermal timer shuts it off. The manual says it should spray for no longer than 12 seconds.

The two service manuals I have are frustratingly vague in some areas. There is a mysterious thing that is connected to the vacuum hoses that I suspect is a vacuum booster - however, there is not a single mention of it in both manuals that I can find. If it is a vacuum booster, would checking the gasket for cracks be a good idea? I attached a picture of it.
I think that is a vacuum pump.not 100 percent sure. Dont remember seeing anything like that but that is what it looks like.could also be a control valve of some kind also. Dont know for sure.Remember the thermo time switch is just that. Its on time is relevant to the temperature of the engine coolant.It sounds very much like a vacuum leak somewhere. I looked at a lot of vacuum diagrams and I was unable to identify the device you posted the photo of. It could be a potential vacuum leak especially if it doent make vacuum. LOL I will keep looking for a diagram at which point I may come up with something more useful for you
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Old 08-04-2010, 08:28 PM
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Also if the cold start injector keeps spraying it will run rich you would see black smoke ( at least some) out the tailpipe. You could check it by simply unbolting it after you run it for a minute or two and see if it is still spraying.
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Old 08-04-2010, 08:40 PM
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You might also want to read up on how to check the 4 different system fuel pressures. Should be 4 it goes like this: rest pressure after system is shut off and wait about 5 minutes it should hold pressure see specs.
cold start pressure at startup running pressure after warmup and deadhead pressure ( max pressure) that the pump is capable of. read the precautions especially on dead head pressure as you dont want to hurt the pump.
I found a digram for the system and number 12 looks like the photo.It is the auxiliary air valve ( cold start up air regulator) anyhow this pdf ( download it so you have it) is at: http://www.bmfi.com.au/files/interjectKjetronic.pdf
Looks like good info.
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Old 08-04-2010, 09:06 PM
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WW2Dude,

I think that is a pressure regulator. Vacuum allows fuel to pass if it fails the engine will not start.

I think you need to clean the throttle plate with some spray cleaner. Also check the hose from the air cleaner to the mass air flow sensor. And the hose after the MAF sensor. If these are loose the engine can not regulate the amount of fuel needed to run correctly.

Happy Hunting

Scholman(retired)
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Old 08-06-2010, 03:27 PM
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Thanks to everyone for the help. That PDF may come in handy, thanks Latech. I'm going to check everything I can that's been suggested. I think I may have found the problem today, but first: I checked the cold start injector. I ran the car until it had problems idling and then disconnected the power to it. It made no difference, so I don't think it's spraying too long. I think I've tracked down every vacuum hose and replaced all that had cracks. I checked by hand The one I mentioned before that went to the air flow sensor from the auxiliary air valve. I couldn't see it, but I felt the rest of the hose that I couldn't see and it seems to be metal the whole way to the air flow sensor. It only uses a short rubber hose for the initial bend from the auxiliary air valve. That doesn't rule out a leak somewhere in there, it may have come loose, but I think it's unlikely.

Now to the interesting bit: The car has a single O2 sensor. It's a single-wire unheated type and thus takes awhile before it becomes active. I ruled this out as a cause of the problem before because:
A: The car started idling poorly before the O2 sensor should be active
B: I disconnected the power to the O2 sensor and it made no difference

Today i realized that ever since I cleaned that plugged up hole to the cold start injector, it runs much longer before it has a problem, and it may be heating up enough to make the O2 sensor a factor. So I ran it for about 4 minutes today, heating it up until the thermostat was about at the middle. At this point the car would not idle unless I revved it and released the peddle very gradually, and even then only some of the time. Once it was steady though, it would stay like that, until I revved it again. Then I revved it and released the peddle fast so that it started the usual up and down thing. I then quickly disconnected the power to the O2 sensor and the engine stabilized instantly. I repeated this multiple times. Sometimes, when the engine was stable and the O2 sensor disconnected, simply plugging it in would instantly cause it to bog down and up.

So, it looks like it may have been a combination of things, but I won't know for sure it's the only problem until I replace it. The manuals say the sensor should be replaced every 15,000 miles and I don't know when it was last replaced. The car has about 85,000 miles on it. I'm not going to stop here though, I'm going to continue checking things while I wait for a replacement.
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Old 08-09-2010, 03:44 PM
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I replaced the O2 sensor with a brand new one today. It didn't fix the problem, but it did change it dramatically. Now it doesn't have a problem idling, it just runs very uneven and low. When it was started cold it ran at about 1000 RPM, but when it warmed up it settled around 600-700 RPM, which is lower than the recommended 900. During idle, it would suddenly surge up to around 900... then back to 700, and back and forth, like it was making rash adjustments to something. It didn't threaten to die though, it just stayed "reliably" uneven. When pressing the peddle down, it would hesitate and lazily make its way up. so basically, the engine runs uneven. I tried unplugging the O2 sensor and like before it runs with no problem when it is disconnected, idles fine and does not hesitate. I again tried plugging it in while it was running at idle and it instantly went down in RPM and ran uneven.

Since the new O2 sensor makes the car run different, but not well, it leads me to suspect that the old sensor was indeed broken, but it was not the only problem. I read that when the O2 sensor is unplugged (or not heated up enough to be active) the system reverts to a rich mixture. Since it runs well when unplugged, could the rich mixture be covering up a problem in the rest of the system?
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Old 08-09-2010, 05:29 PM
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WW2Dude,

The O2 does not receive voltage it creates it. The computer reads this voltage as either rich or lean and corrects the fuel accordingly.

Now for the erratic idle. I would check for vacuum leaks again.

Scholman
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Old 08-11-2010, 05:05 PM
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I double checked all the vacuum hoses and they are all in good condition

I received a replacement air and fuel filter today that I ordered along with the O2 sensor (separate shipment), and it did the trick. It's kind of embarrassing that such a simple thing was the cause, but it was only one piece of the puzzle. It was a combination of: blocked cold start injector, broken O2 sensor, and soiled filters. Thanks everyone for all the help and advice.
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