skltnjak

hi,
i have a 2007 hhr 2.4L automatic. been having some engine issues, it seems sometimes when starting off from a stop the engine sounds like its struggling get up to speed, almost like there is a blockage somewhere or a clog.. but it doesnt happen all the time... somedays it runs like a dream and has some pep in its step... other days its like it doesnt have it in it to go another mile,
ive replaced the spark plugs, ran some injector cleaner through it changed the oil. still having problems. i have a check engine light on. the guy at the shop says its an o2 sensor OR the converter. something about a flow issue.. any help or tips to point me in the right direction would be great.

whopper

Without you posting the check engine light code, any suggestions would be a guess. So post the code and people will jump in with some good suggestions.

skltnjak

p0420

donbrew

That is an expensive one. It means that your catalytic converter MAY be shot.

Here is a good link to start with: P0420 Error Code: Catalyst System Efficiency Below Threshold (Bank 1)

I am currently tracking the same thing down. Best thing is to find a mechanic you can trust to actually trouble shoot the code, many will just replace the cat.

GM gets about $485 for the cat. Ebay around $190. 5 nuts involved in the R&R, less than an hour labor. IF that is the problem.

Your "bogging down" symptom sounds like melted cat. Which means something caused it to melt down and just replacing it will just cause another meltdown. You gotta fix the cause of the failure!

You could be lucky and just have a bad injector or one of the other causes.

thelastplace

Before you do ANYTHING, take your car to a 'national' auto parts store (NAPA, Advanced, Pep Boys, etc). They generally can diagnose the code, for free. Like anything else, second opinions are worth their weight in gold. You didn't mention the kind of gas you use. I'm not a 'brand' guy, but good quality REGULAR gas is a must. I have a 06 2.4 5M with 168,000 miles and NEVER have had a problem, and I drive mine hard.

donbrew

He already got the code from one of those clowns.

NEVER believe a diagnosis from an auto parts counterman reading a code. If they can read what they tell you is the descriptive name of the OBDII code number, which often has nothing to do with the problem.

Oldblue

one thing that caused my last cars cat to clog was a head gasket leak, anti-freeze was being burnt in the cylinder chamber and that clogged the cat, so new head gasket and new cat cured that problem.
I suggest you have a look at possible causes like this

donbrew

I am not ready to apply for sainthood yet, but I put some SeaFoam in my half full gas tank and ran it down. The p0420 that has been bugging me for several months has completely gone away for about 800 miles. Come to think of it, that's what cleared it the last time. I am hoping it's a very dirty injector.

donbrew

Follow up.: P0420 came back.

skltnjak

I tried the seafoam as well.. Before I did that one day the cel just went off.. Like no light or code. But came right back. I took it to a shop a little while ago they said that I had an oil leak, they said it was "seeping" from somewhere in the middle of the engine. Said to replace the seal they would have to "go down pretty far" into it. They never really said what was sleeping... Didn't hint at a head gasket or anything. It's weird. Oh I changed the oil recently I put the right amount back in it, right be low the full mark on the dip stick. When I check it now, after cleaning it off (the dip stick) it reads wayyyy above full. Kind of smells like gas as well.. I can only imagine bad things from this.