gio89kid

A while ago I asked a question about whether my rpms were operating in a normal range. It seems that the answer I got was that they were. But here is my concern...

I have a 2007 HHR 2LT with automatic transmision, I have added a K&N intake and Borla catback exhaust with a Dynomax VT muffler. That's it, its basically stock besides the intake and exhaust.

If I give it a little gas from a stop sometimes the car moves quick and smooth, other times you can hear the exhaust slowly bog up till it makes power, seems like hesitation to me.

Going up a steep grade which I drive daily, the mph's start to drop from constant 70 which is the speed limit, so to maintain that speed I give it a little gas when it drops, and this is the time my rpm woes happen...

If i give the gas very slowly the rpms will raise to the range of 3500 to 4000 and just hum there T 70mph until i let off the pedal.
If i give a little more gas it can go over my desired speed in the 4000 to 5000 rpm range.
If i depress the gas right away the transmission downshifts and the rpms surge close to or hit redline before shifting back up. (sometime usually only when passing)

I understand this may be normal, and only happens on this long steep freeway that I drive for a short time, but...

I love my car and want to make sure it lasts a lifetime, but I don't drive like a grandma hence the intake and exhaust but I am no maniac either that races and cuts people off and stuff, I would say i'm normal with a slight heavy foot.

This just happened to me today, and I want to make sure it never happens again...

I was driving up that big hill when I noticed a Semi-truck in the slow lane going way under the speed limit, I looked to my left lane and there was plenty of room to pass, but there were cars coming at fast lane speeds, so I put my blinker on and pushed on the pedal to maneuver around the truck and ensure I wasn't slowing down the incoming traffic, so that's when the transmission downshifted like it always does in those situations and the rpms went up, but this time they started bouncing and I quickly looked down and noticed the rpms were at the 6000rpm line and I quickly released the gas, it bounced about 5 times.

All I could think of was, what was happening to my car? I have never heard of anything like this happening before except race-cars on TV sound like that, when they are doing donuts. That na na na na na sound.

So I passed the truck and watched the temp the whole time going home in 95degree weather and the coolant went from 207 at its highest more like 205 and 195 the whole time and then went down to 183 cruising home, so the temp was fine, at home I checked the oil and coolant, both perfect.

I looked up bouncing rpm in google and came across rev limiter, I found a rev limiter is there to keep you from blowing up your engine. From what I found some people say rev limiter is there on purpose and people do it all the time, others say never hit the rev limiter or bad things happen.

I just want to know, is my car going to be ok hitting it one time in its life, and can this possibly be a transmission or torque converter problem?

I mean I have driven a toyota corolla with a 1.7L motor and it never goes above 3500 rpms just in general, maybe hitting 5000 max and that's still under its redline of 7000.

aradmahogany

Since its a 2LT you have the 2.4 correct? Now My HHR is completely stock. With the 2.4 the only out of ordinary thing I do is run the Recommended 91-93 octane. I am a driver very similar to you, but I wanted to clarify what you meant by "pushed the pedal". Did you floor it? I dont know if going up hill would be a factor with the RPM being held so high. I can tell you I have never floored my HHR, Nor has my engine seen anything north of 5,500 RPM and I still have plenty of passing power. If your engine seems to be choked up at WOT or under any hard acceleration there is probably something going on with all the aftermarket mods. They are fun, but can sometime create phantom problems. Could be as simple as you were at WOT or at least close at a steep incline and the engine was holding RPM due to that increased incline. To pass people, I usually only push the pedal down to about 3/4 throttle and it downshifts and takes off quite nicely.

gio89kid

Well I didn't feel the pedal hit the floor, and I never have.

But it was a quick movement from more than half depressed to maybe almost full.

And yes it's a 2.4L automatic.

I have never had a car go to redline before except this one, and I have put a K&N intake or drop in filter with a exhaust or muffler on each one.

I just feel like the computer should know to never go that high, especially since it's an automatic???

gio89kid

Plus those mods are equivalent to the GM performance upgrades that can be ordered from the dealer.

The exhaust is made by Borla but it's GM, and says GM all over it, and I put a quieter muffler on it cause it ended up a little to loud for me.

The K&N intake is basically equivalent to the GM intake available.

So basically if I bought the car new and ordered it with those performance parts, it would have came that way from the factory.

gio89kid

And you are correct, the car usually never goes that high, like 5500 max, like you said.

But it's only when I'm going up a hill, and depressing the pedal down, does it go to redline, unless I see it doing that, which I watch for now, then I let off.

But, in this case I was passing and paying attention to the other drivers and road, when I heard the bouncing and looked down.

My idea was something seems like it should be fixed? Cause I have never had a car do this and I have owned a 2.0 2.4 and this 2.4, and this is the only one that does it. I googled and found that a torque converter failure can cause high rpms and not much movement, but the car moves, it just has a little hesitation sometimes and doesn't like hills???

aradmahogany

Was the car accelerating at a decent rate while the RPM's were up there or was it just bouncing off the limiter and not going anywhere

gio89kid

Oh!
By the way, I forgot to mention...
This happens whether it's me driving up the hill to maintain the speed limit or pass someone, or the car driving itself with cruise control.

If I set the cruise control to my desired speed and not touch anything and it hits the hill, it downshifts and gives it more gas than I would have and the rpms go up in a way i don't like, so I usually never use cruise control on that hill, cause it just makes the engine seem like it's straining itself for nothing.

And of course if someone else drives the car, or I drive it slow, there is no problems.

So you are saying the intake and exhaust are to blame?

gio89kid

Yeah, the car accelerated all the way up to the bouncing when I let off.

aradmahogany

No if the mods were installed correctly they should be fine.I just didnt understand what was happening in the beginning; I dont understand why an auto would hold gear like that though. Maybe going up hill had something to do with it.

gio89kid

Hmm, yes. I will have to ask the dealer at my next oil change.

Other than that, the car is great.

It doesn't burn oil, or water. I maintain everything on it. Transmission fluid has been changed twice. It's got 156,000 miles on it and still running strong.

I love the car, I like the way it sounds with the added intake and exhaust, I just want it to last forever.