CarTalk.com Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

PCV system problem

Hi everyone, I’ve got what I hope are two quick questions…

I just had the oil changed on my 2007 Grand Cherokee. While doing so, the mechanic said that he discovered that a tube/hose of the PCV system had come loose.

He said that as a result of this, the air filter had been bypassed and that my car had been running on un-filtered air for a while. He recommended a fuel injection service to take care of the junk that had entered my vehicle while the air filter had been supposedly bypassed.

I elected to postpone the recommended service until I did some research. I’ve done that research, and for the life of me, I can’t understand how a dysfunctional PCV system would lead to the air filter being bypassed. So I’ve got two questions:

  1. Can a dysfunctional PCV system lead to the air filter being bypassed?

  2. If so, would a fuel injection service remedy some of the problems that may result from an air filter being bypassed?

Thanks

An engine can inhale a small amount of unfiltered air due to a dislodged or broken PCV hose. However, I don’t see a fuel injection service as doing one thing to alleviate any real or perceived problem due to this.

The worst scenario is that if the conditions are extremely dusty where you live that some additionial engine wear could have taken place but (and just my humble opinion) I don’t think this is a big enough deal to worry about at all.

Agree with ok… Honestly not a big deal keep on trucking. If it bothers you that much put a can of cleaner in at your next fill up

Make mine another agreement with OK.

While a dislodged PCV tube technically bypasses the air filter, it’s a very small tube relative to the opening in the air filter box, and if the air filter were so restricted as to cause the easier path to be the PCV tube you’d feel it in your performance. Every time you tried to accelerate your negine would be starving for air.

That combined with the fact that the PCV tube is drawing from an underhood spot not open to regular dirt, dust, and road debris and it’s safe to say that you’re fine.

If you got a lot of dirt into the system through that opening, the only places it would accumulate would be the throttle body and the idle air control valve (if your car uses an IAC). If the engine still idles smoothly and comes off of idle normally, these areas are not too dirty, so keep on driving.

Even with a good air filter and tight connections, the throttle body and IAC usually need cleaning every 100k miles or so. You just take off the duct work spray aerosol cleaner through them.

Not clear what the mechanic means by “fuel injection service” unless he intends to clean the throttle body and IAC. The injectors themselves would be unaffected by dirt blowing past them.

As everyone else has said…and I’d just add that fuel injection services make a lot of money for the shop. They rarely do a thing for the car. If you really needed one you’d know it.

Amen, Cig.
“Induction system cleaning” as it’s often called, as well as “injector cleaning”, is one of the most common and least understood revenue generators for shops nowadays. And both are very rarely actually needed. When revenues get tight, innovators get creative.

I am gonna go out on a limb and say that your PCV hose was tight in the right place and this place was just after some extra $$. Scare tactic and it works with most consumers.

Let me fall in line with the general consensus here and say that there is little that can be done to correct whatever damage that might have been done by the open PCV system. Most likely there has been little if any damage. So now, if you put any faith in our opinions you must decide what your mechanics intentions were.