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2002 Toyota Corolla has a rough idle after replacing PCV valve

I have never done work on my car before except adding oil and a few other basic things. The vehicle has run great up until now, its just always had some oil consumption. The tail pipe is quite sooty and oily on the inside.

I did some research and it indicated that if there isn’t any colored smoke when running the engine, the PCV valve could be the cause of oil consumption. I took it to a local shop and they replaced the PCV valve (they wanted to do a $90 diagnostic but I sad no way). Its never had any kind of smoke coming out the tail pipe. Its definitely not an oil leak, I know that nature of such things because I’ve had a leaky car before. Its run great since but its been exactly a week since, and I noticed this morning that it has a “rough idle” when running. I’m not sure if I’m using such terms correctly but by rough idle I mean it chugs along.

I am getting wary of shops that just want to sell me unnecessary repairs and diagnostics but don’t know how to fix things myself. I’m a little afraid to try, I’d rather not be stranded at home. Could anyone recommend me on where to begin fixing things on my car? What tools I ought to get, where I should begin to learn?

Also if someone could figure out whats wrong with the Corolla atm that would be great.
I should mention the part they replaced the PCV with. Its a PCV1112DL.

It’s very possible that they accidentally disconnected a vacuum hose while they were fiddling around with the PCV.

First of all, any repair place that wants to run a diagnostic on a modern computer controlled vehicle is not out of line in my opinion. Most places waive that fee if they get to do the work. Most states will allow places like AutoZone to read codes. After getting codes the internet will let you see what they mean. As for do it yourself vehicle repair maybe one of the regular member mechanics can explain why that is not easy as it used to be.

To answer your second question, a decent 3/8" metric socket set is always handy. If your engine has a plastic cover, use the 10mm socket from the set to remove 4 small bolts and take the cover off. The PCV valve sits on the back right-hand side of the valve cover. If there is a loose hose, connect it back up and you’re good to go. There are You Tube videos on how to do the PCV valve replacement if needed. It is very easy to do and the part is under $10.

I should have mentioned that I watched a YT video of a guy doing this exact repair. So I am not unfamiliar with the position ,size, and shape of the part.

As for the diagnostic, I’ve never had this particular shop waive the fee and they never mentioned it. I didn’t want to pay $90 for something that would be replaced for $15. I thought if this part fixes the oil consumption, great, if not then I’m only $15 in the hole.

I will check the hose, thank you!

Next time ask if fee will be waived or find another shop.

An aftermarket PCV valve could cause the idle problem.
Get the original brand and part number of valve and see how that goes.
You can go to a Toyota dealer to be sure.
Re. oil consumption, this vintage Corolla is known to have an issue due to piston design.
There are various fixes that can be found by a internet search.
They range from an oil additive or piston soak to clean the ring grooves,
to removal and cleaning/modification/replacement of the pistons.

@circuitsmith above is spot on, a faulty pcv valve on almost any car will cause rough idling. The pcv valve pathway is sort of a designed-in vacuum leak. It’s not supposed to be allowing much flow at idle, and if it does, poor idling performance results. In some cases with a bad pcv valve, the engine will barely idle at all. If it is not the valve itself, I suppose it is possible they messed up replacing it somehow. It is a one-way device, so maybe the installed it backwards, or not in the pcv route where it is supposed to go. There’s a hose for where the fresh air comes in, and a hose where the crankcase air is drawn into the intake manifold. All that has to be correct. One quick check of the pcv system is to remove the oil cap and test if the oil cap hole in the valve covers draws enough air that it holds a piece of paper on it when the engine is running. It should. Make sure the oil cap is on tight like it should be and the oil cap gasket hasn’t fallen off too.

In my opinion you approached this wrong. It sounds to me that you simply told the mechanic to replace the PCV valve based on your own research. The mechanic only did what you told them to do, but apparently that was not the cause of abnormal oil consumption. Realizing this he simply offered to run a diagnostic to find out what, if anything, is wrong. You should have accepted his offer. $90 for a diagnosis is not bad.

Actually, there shouldn’t be hardly any smoke out the exhaust on a good tuned car.

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