Yes you are correct, it's not your charcoal canister. (and in a volvo that has never caused a poor idle problem)

But perhaps in another brand of car. I understand a flooded charcoal canister could cause a problem with a check engine light. I did see that once in a customers Korean car (don't remember the brand) but apparently if you try to put the maximum amount of fuel (by trying to add more fuel after the auto shut off works) you will fill the canister with gas and permanently damage it. Than can be an expensive fix. (that customer declined the repairs - and I don't know how it passed emissions after that . Perhaps the car was sold in an area that does not need an E test!)

 

Well instead of pulling the injectors, I had a gut feeling the injectors were part of the problem here, so I ordered some remanufactured Bosch Injectors off Ebay. Fairly simple job with three 10mms and then just prying the clip off, unplugging them and then plugging new ones in and reverse steps. The car ran better after. I'm going to give it a few days before I make a final decision as I can't see the fuel economy (need to drive it more), It still has a slight rough idle, but it doesn't drop low enough that it triggers the check engine light, nor does it get close to stalling. When I pulled the 4th injector (the one farthest away from me, I noticed part of the rubber seal was missing). I've attached some pictures of the injectors below. By chance when working on this I hit a small wire that connects to the exhaust manifold near the throttle body and by accidently hitting it came unplugged. I plugged it back in and noticed it is slightly broken (the break is wear, kind of like old dry rot in a hose). See attached photos.

 

Actually, it wasn't the rubber seal on the injector rather it's the end that almost feels like a spark plug in texture, but it was broke. I think that's why my engine was vibrating. It wasn't getting fuel in that cylinder and now that has gone away. What would be another route to solve the last of the rough idle? Is it work cleaning the throttle body and replacing the gasket? Seems rather inexpensive, but not sure how much that could contribute to a small rough idle (what is left of it).

 

If your engine is running equally at idle on 4 cylinders, firing evenly, no manifold vacuum leaks and such-

Then your "rough idle" can easily be caused by sagging engine mounts. (if they are the "hydraulic mounts")

The later 740/940 cars have "hydraulic" engine mounts. They are not a solid block of rubber like a 240 mount. When the gas pressure leaks out they sag - and - the car shakes when it's idling -

Those mounts seemed to last 8-10 years (just guessing, that's been a long time ago) before they became a problem. It was easy with the 740s/940s with a belt driven fan - the fan would be grinding away the bottom of the fan shroud!. Some cars would sag so bad the oil pan would rub on the subframe (volvo put a rubber pad on some cars there)

Do you have sagging engine mounts?

 

Well, I think I've identified the main issue and mt6127 was right, I'm pretty sure it's all related to the PCV system. I did the rubber glove test, and the pressure was coming out. It started by noticing leaks all over the engine. I bought this car as a way to hopefully get me back and forth to work so I didn't have to put miles on my m4, but also learn how to work on cars. Not really knowing where to turn, I figured I could at worst learn how to fix my valve cover gasket. I cleaned the valve covers and replaced the gasket. I drove it for a while and still noticed a small leak, but the leak was coming from the oil cap. So, I figured I'd just buy an oil cap as I know the seals go bad on those. The car definitely drove better after that, but still had a rough idle. I decided the next thing I could check was the Throttle Body. I was surprised when I took it off. It was filthy. I cleaned that out, put a new gasket, but noticed gunk was going all the way back into the air intake. First 5 miles it ran a lot better, but then the symptoms returned. I dug around on the internet and at this point I'm starting to understand the car more and saw the PCV test. It's such a simple test too.

My question now is, can I access this system without taking my intake manifold off? There were a few videos online, but the issue is, most are 240s. The best video I could find is this guy here with a 740 who manages to pull the flame trap out without taking the manifold off. . Going the route of taking the manifold off seems to have it's own issues, mainly one really large nut. Anyways, any tips or links to information here would be great. I'm glad I didn't start replacing lots of parts, thanks Honk, and went each step the cheapest route that ended up leading me to what appears to be the answer.

 

OK, lets talk about your PCV system. The oil trap #1 can (allegedly) get plugged, (easy to test, take oil cap off and blow into it) but from 1976-2018 my 2 shops never saw one that was plugged (on a b21/b23/b230) and we never replaced one. (i'm in the south - so maybe that has something to do with it.)

Typical PCV replacement parts. (no need to remove the intake manifold, Volvo engineers are not that evil)
#7 holder, 5 trap, 6 hose.
The #8 vacuum line goes to a metered orifice on the intake manifold. Use a drill bit to clean the carbon out clogging it (so there will be a slight vacuum on that hose.)

Oil cap leaks - I've sold thousands of oil cap seals. They get brittle, shrink and - leak. easiest $1 (well maybe $2 now) leak you will fix.

BTW - the rubber glove test started with the aluminum block DOHC engines - the PCV system on those seems to clog easily. (at least after 100x miles or so, worse it seems in colder climates)

Is this still trying to fix a rough idle? I noticed you have EGR. An EGR valve not closing will cause a rough idle. Does the EGR system still work? Apply vacuum (with hand held vacuum pump, or a hose connected to engine vacuum) to the valve with the engine idling, if the valve/system works the idle will get very bad. If idle does not change - either the pipe is clogged, or it's stuck open. Your PCV system will not cause a rough idle (unless there is a large un-metered air leak) Intake manifold gaskets are known to split (on one cylinder leg, try #1) Use carb cleaner spraying on the gasket area to see if any is sucked in (and changes the idle speed)

 

I figured I'd check the EGR first because it seemed simplest to check. I searched the internet and found pictures of what the EGR looks like but had trouble finding where it's located at. From what I could find, people said it's under the exhaust manifold. I looked and didn't see anything that looked like an EGR, but I also am not exactly sure what I'm looking for. Here is under my exhaust manifold.


For what it's worth, this car was one owner and from the South/Mid Atlantic (Raleigh Car it's whole life).

Here's what the throttle body looked like before cleaning it out.




Of course, I want to find the source of the EGR/PCV first, but would it also be worthwhile cleaning out the air filter hose that goes to the throttle body? Some junk was clogged up in there too and I only got what I could from the opening. Thank you for the help so far.

 

That's perfectly normal and to be expected if not cleaned on a regular basis. Throttle body cleaning was part of every major service and a can of carb cleaner was charged on every major service ticket just for that purpose. Every 15k. Have cleaned thousands of them and none of them created a rough idle unless the idle motor was not working and the idle speed was way too low. Many throttles looked like that and the reason is - the pcv hose from the flametrap dumped those oil laden fumes - right in front of the throttle plate. A dirty throttle plate would simply make the base idle speed lower. The Idle motor (iac, air valve, whatever you want to call it) would in theory compensate for the lack of enough air passing the plate when dirty and keep the idle at a steady ~750 rpms.

EGR
There is a small pipe from the exhaust manifold that wraps around the back of the block and connects to the vacuum operated egr valve under the intake manifold. When the valve is open those exhaust gasses are dumped into the intake manifold through the pipe highlighted below. (the purpose is to reduce NOx emissions) You can safely disable that system and the car will run just fine. (and hopefully you have fixed the vacuum leak at that small hose shown in your picture by now)

 

[QUOTE=hoonk;529062]That's perfectly normal and to be expected if not cleaned on a regular basis. Throttle body cleaning was part of every major service and a can of carb cleaner was charged on every major service ticket just for that purpose. Every 15k. Have cleaned thousands of them and none of them created a rough idle unless the idle motor was not working and the idle speed was way too low. Many throttles looked like that and the reason is - the pcv hose from the flametrap dumped those oil laden fumes - right in front of the throttle plate. A dirty throttle plate would simply make the base idle speed lower. The Idle motor (iac, air valve, whatever you want to call it) would in theory compensate for the lack of enough air passing the plate when dirty and keep the idle at a steady ~750 rpms.

EGR
There is a small pipe from the exhaust manifold that wraps around the back of the block and connects to the vacuum operated egr valve under the intake manifold. When the valve is open those exhaust gasses are dumped into the intake manifold through the pipe highlighted below. (the purpose is to reduce NOx emissions) You can safely disable that system and the car will run just fine. (and hopefully you have fixed the vacuum leak at that small hose shown in your picture by now)




I used electrical tape for that vacuum leak. I wasn't sure how to fix it and my roommate suggested it for a temporary fix. What other options would I have to fix leaks like that? And when you say disable the system, do you mean just unplug that hose? Would that hose also be where I do the vacuum test?

 

[QUOTE=Wilfong;529063]A 1' long piece of vacuum hose (maybe free from the auto parts store, or off your roll) that fits both the plastic and the metal makes a permanent fix (the Volvo part might be a 3534790)


https://www.google.com/search?q=how+...hrome&ie=UTF-8

 

Honk, I know you sent the diagram, but to access the PCV system should I remove the throttle body and then go down from there? Also, this is kind of near/under the throttle body. What is this?

 

For the pcv - everything in the circle is between #3 and 4 intake runner - on top of the engine. Your photo is the idle motor/iac/airvalve/whatever you want to call it. DO NOT try to take the oil separator off (the #1 plastic box ) unless you prove it's completely clogged. And of the thousands of those engines my shops worked on - we never had to replace one. (the tube and oring under it - will be bricks, the tube goes into the oil pan and is attached inside the block, to get it out you have to take the pan off. )

 

Okay, I made some progress. I went searching first for the EGR valve this morning, just to see if I could locate it. I believe the thing in the far back is the EGR valve? While inspecting this, I noticed a vacuum line going to the thing in front (I'm not sure what it is) had the worst vacuum leak I've seen yet. So, for the meantime, I just put some electrical tape around it. I took it for a spin and it idled better. It still has small intermediate hiccups but I can tell it's come a long way. Now, back to the vacuum hoses. I'm not sure how to take them off. I feel like this should be pretty easy, and I'm making it more difficult than it should, but the one below that goes into the EGR seems to have some sort of bolt/nut? The 3534790 coupling would I just pull off the old one and then push this on it, i.e., is it that easy?

One other question: I'm sure you can see my engine is pretty messy with dirt/oil, etc. I saw a YouTube video where someone used plastic bags to put around all the electrical parts, alternator, ignition coil, fuel injectors, etc, and then used a degreaser and a bucket of water/hose to spray down the engine. Would you recommend that?

 

Yes that's the egr valve.

To find vacuum leaks - buy a can of carb cleaner, with the engine running spray areas that might be leaking - manifold gasket, injectors, vacuum ports and lines - any vacuum leak (when the carb cleaner is sprayed in it) will cause a change in the idle