Hello. I purchased a 2006 Volvo S40 last week for my daughter. It has 147,000 miles with the 2.4i (non-turbo) engine. The seller told me it just started misfiring within the last two weeks. It idles rough and even stalls out after driving it for a while. After you get going above 10 mph it runs fine. Whenever you get around 50-60 mph it will flash the check engine light and the hazard dummy light. It also hesitates/misfires going up inclines. I "thought" it would be a relatively simple fix. I took it to my local Autozone and they printed out two codes (PO300 & PO301). I swapped ignition coil one for ignition coil two: no change. I put a new plug in cylinder one: no change. I then swapped injector one for injector two: no change. I noticed that whenever I take the oil filler cap off I feel and hear suction and the engine idle increases. I'm not sure what to do next. Any help or guidance would be greatly appreciated.

 

A few possible causes - 1) bad gas... if you are still on the original tank try dropping in some "dry gas" and wait until the next fill up. Also consider swapping out the fuel filter 2) coils - since this car is new to you, if you are not sure when the coil packs were replaced, put new ones in (generally they start to become problematic after 100K miles). 3) fuel pressure. rent a guage and measure at the rail (there's a valve there) 4) check for vacuum leaks. Note that the connection betwen the oil filler and your idle is the PCV system which is vacuum driven. Normally when PCV systems clog you get positive pressure (ie place a rubber glove over the filler cap and it will inflate. Otherwise if it should pull in slightly).

 

Ok. I will try those things. Do you thing that since I swapped out ignition coils and got the same reading (PO301) I can rule out an ignition coil? I will try the gas, get ahold of a fuel pressure guage, and look/listen for a leak. I'm just really worried I might have a bad valve in cylinder one.

 

I would replace all ignition coils as a first order of business.

 

OK. So do you think it could have anything to do with the valves? Also I noticed this evening a small amount of antifreeze underneath the car. Maybe the size of a half dollar. I drove it 4 hours home last week and no leaks. And drove it the last 5 days off and on and no leaks. I was letting it idle a lot last night and kept taking off the oil filler cap trying to look over things. It doesn't smoke when it starts. Like I said earlier it idles up a little bit when I remove the oil filler cap. And of course it idles even rougher (almost wants to die) when I have it in park and turn the AC on. Just worried and trying to get it running good for my daughter.

 

When you say you swapped coils and injectors and there was no change, did you clear the codes and drive it and then check the codes again? Or do you mean no change as in it still misfired?

It certainly can be a valve issue. Do a compression test and cylinder leakage test and find out.

 

Sorry about that. I had the codes cleared and drove it around (took about 45 minutes to get the check engine light to stay on). The code PO301 came back on again. However, I cant remember if the code PO300 came back on or not. I will get do a compression test. Not sure what a cylinder leakage test is but will research that and have that performed, also. Trying to listen for a vacuum leak. Not sure if I hear one, but also not sure what one would sound like for this engine. It seems like to me when I first start it up and it is idling high it sounds fine. But then after the engine is warmed up (maybe 20-30 seconds) and the rpm's drop is when is just idles rough and even worse when I turn the AC on. I really appreciate the responses. Thanks!!

 

I doubt it's a fuel issue. That would cause issues across all cylinders. If the plug and coil are good, I would suspect a cylinder issue.

 

injector/injector seals? Not sure if a balky injector would throw a code on this model... A compression test seems in order.

 

Thanks for all the help. I will do a compression test ASAP and report back my findings. I am hoping (and praying) its something else.

 

What it the average compression for this 2.4?

 

O.K. Did a compression check. C1- 5-8 lbs (did it 5 times), C2- 130, C3- 130, C4- 120, C5-145. Accidentally started up the engine and C1 shot up to almost 150. Immediately shut it off. Intake 1 suction is a lot less then intake 2 (I noticed) when doing a compression check. Please advise what you guys would do at this point. Thanks!!

 

Cylinder leakage test on cylinder 1