93 850NA first time PCV service - failure

Larva · Post by **Larva** » 03 Dec 2016, 11:42

I have this 93 850NA that I have owned since 2000, Has 72,000 miles and PCV has never been serviced. The car has always run good and never failed me prior to this.

I purchased the kit from FCP and spent a few frustrating afternoons doing the service. Having watched FCP's and Robert's you tube videos and read the posts on this site, it seemed to be straight forward and I followed many of the tips provided.

First, I didn't need it which surprised me as I rarely drive the car and its a short trip thing so I expected it to be loaded with crud, but it was clean. Since the car is 23 years old and I had the new parts, I installed them. I also cleaned the throttle body while I had it off. This model has the EGR on the intake manifold but I did not remove it from the manifold as it looked clean. I took photos along the way and used masking tape, labeled all the vacuum lines so I knew to reconnect in the manner they were removed. So I finally completed the job and the engine starts and runs but it misses horribly. I am quite frustrated as this should have been a simple job but it has and continues to be a headache.

I'd be grateful for any suggestions on where to begin trouble shooting to locate and rectify the cause of the rough running.

Post by **erikv11** » 03 Dec 2016, 12:09

Congrats on getting the work done (or almost done!). What you describe is pretty common for a first time PCV, sounds like a vacuum leak.

First place to look is the lower right corner of the intake manifold. There is a bracket there that gets in the way when you put on the IM, so there is a huge air leak.

Larva · Post by **Larva** » 03 Dec 2016, 12:17

Thanks for the quick response. My Volvo was not equipped with a bracket at the lower right corner of the intake manifold. Not sure when they started that feature or what it is for but its not on the 93 version.

Post by **cn90** » 03 Dec 2016, 15:41

After PCV Job and misfire...common issues are:

1. Vacuum leak, as erik said, check the I.M. fitment to be sure it is flush with the gasket.
2. Check all hoses from a to z. If necessary, look up photos on the web to verify.
3. Another culprit is the ICV Valve, if you forget to reconnect the hose to the ICV valve, you WILL get a bad misfire, even stalling (don't ask me how I know).

Basically go back to the job you just did and review every single step, trying to figure out where things go wrong.

PS: Also, post a few photos of the of your engine now, maybe someone with sharp eyes can spot the culprit(s) for you.

Post by **sleddriver** » 03 Dec 2016, 16:55

OP: Frustrating indeed. We've all been there! Take comfort.

If your manifold is indeed properly attached, then check all air connections for potential leaks downstream of the MAF. Also ensure that the MAF is plugged back in as well as any other sensors/wiring harnesses you may have disconnected.

You can also go after it with a home-made smoker using cigars, cigarrettes, incense, fireworks punks, etc. inside of a metal paint can with an aquarium air pump or you can just blow into the sealed can from a tube. These work great on finding vac leaks on our older cars.

Post by **erikv11** » 03 Dec 2016, 19:23

Similar to cn90's comment about the IAC valve, is the throttle position sensor (TPS) connected?

And, when you cleaned the throttle body, did you first remove the TPS? Or at least make sure no cleaning solvent got inside of it? On my first PCV job I ruined the TPS by getting carb cleaner inside it.

Larva · Post by **Larva** » 03 Dec 2016, 20:17

No, I did not remove the TPS when I cleaned the throttle body. I didn't know to protect the TPS and could very well have gotten the cleaner in it. Looks like that might be a hundred dollar mistake. Is there any way to check it prior to replacement?

Post by **erikv11** » 03 Dec 2016, 22:02

The TPS is a potentiometer, you can test it with a multimeter. I haven't done it so was looking for a demo and found this, it is overly long but interesting he suggests just cleaning it with a volatile cleaner.

I have a couple spares so would test it by just swapping one in but it looks pretty easy to at least check out the one you have. Just two small bolts and it comes off the throttle body, like 6 mm heads or something. If you need another, it is certainly reasonable to go with a junkyard part on this one.

Larva · Post by **Larva** » 04 Dec 2016, 08:37

Thanks for sticking with me on this issue.

Interesting that the guy in the video used brake cleaner and WD40 on his TPS and didn't damage it. I used CRC brand MAF cleaner and a tooth brush to clean my throttle body. Its not like I submerged it in some caustic cleaner. The local Pick n Pull has a few 850s in the yard and they want $10 for the TPS. I can get a new Bosch TPS off eBay for $32 delivered. I don't have any spares and I figure if I'm going to have to go to all the trouble of changing the TPS, I might as well spring the extra $22 for the new one and know that I've eliminated that as a possibility.

That being said, I kinda hate to start throwing new parts at the problem for troubleshooting. I'll get out to the garage today and double check the vacuum hoses and electrical connections. I'll also take some photos to post, as suggested by cn90, and see if anyone spots anything.

Post by **sleddriver** » 04 Dec 2016, 11:48

I'd suggest holding off on replacing the TPS. CRC cleaner is great stuff. Can't imagine it damaging the TPS. I've never damaged mine nor removed it when cleaning the TB. I've owned the sled now for 18yrs.

You may have to pull the IM and be sure the gasket is OK; Not folded over, crimped, etc. Having a T5 instead of an NA, I'm not sure how yours is plumbed. You will have much more area/room to work though. RSPI has mentioned a few times that IM vacuum leaks after this service are not uncommon for first-timers. Injecting smoke into the air intake snorkle will quickly show you where any such leak is occuring. Much simplier too as you're not undoing things that don't need it, getting more frustrated, and wasting time.

Also check both the connectors and wiring of both the camshaft and crankshaft position sensors as they can get roughed up. The insulation on both may have completely rotted off yours by now. If those wires touch, you'll have no signal. Engine will run rough, misfire, etc. may not even start.