Mechanics

WEIRD EXHAUST TONE, HESITATION/LACK OF POWER

2007 Chevrolet Impala • 153,772 miles

I recently did a lower intake manifold gasket on my car and I replaced the plugs/wires, air filter, and all the gaskets along the way. After I was finished I started the car up and at first the car was really noisy in the top end but it quieted down after about 10-20 seconds, but it was still there.

I was worried I messed something up so after about 2000 miles I tore it down AGAIN, replaced gaskets with ac delcos, all the pushrods were in the correct location, no broken parts. As I was putting the pushrods back in I noticed one of the pushrods had a little stress mark on it, I put it all back together without changing it because it was on the front head so it is easy to get to. I go to start it and it was running just fine but it seemed to have a smooth idle but it felt like it was loping a little (no rpm fluctuations) and I still had a hesitation and no power.

basically my question is, can there only be one pushrod messed up? If it was bent wouldnt it cause a miss? Could it bend and not bend a valve? How could it bend?

I dont know anymore its driving me nuts though.

compression was good, lowest was on the cylinder with the weird looking pushrod but the numbers were like 205 to 195 so I didnt think it was bent.
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Pos07impala
February 22, 2012.




Forgot to add to. When im coasting along and I let my foot off the gas the rpms jump like 200-400

Tiny
Pos07impala
Feb 22, 2012.
Yes a push rod can be bent and not damage a valve and just one can be bent.I would scan for codes for the erratic tach. If I understand your post?You are concerned about the tick noise right?

Billymac
Feb 22, 2012.
Im more concerned about the power loss and hesitation, I was worried about the tick but after not finding any damage the second go on the LIM gasket I was more curious as to why its got no power

Tiny
Pos07impala
Feb 22, 2012.
And at idle my rpms drop to about 550 and returns to about 650-750 when I let off, I dont think its normal bc it was never noticeable, now I can visually see it drop. And when im coasting and the rpms jump I can kind of feel the engine go with it (if that makes sense?) Iv been told by alot of people its an electrical issue, but this never happend until I did the LIM gasket, so its driving me nuts having crap mpgs, no power, and a complete loss of driving excitement(complete frustration now)

Tiny
Pos07impala
Feb 22, 2012.
Well sounds like possibly a convertor restriction I would have it tested at exhaust shop

Billymac
Feb 22, 2012.
Is there any chance a bent pushrod can make the cat go bad?

Tiny
Pos07impala
Feb 22, 2012.
I see what you are saying. That you had no issues before you changed the gaskets. So why did you change the gaskets to begin with was it leaking?
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Billymac
Feb 22, 2012.
Before all of this I had a hesitation and about a 4-5mpg drop in economy, after about a week I had a big coolant leak comming from the coolant crossover, which at the time I thought was a headgasket leaking(also bc the intake manifold had some seepage). Once I got down and noticed the coolant leak was from the crossover and not the head I was really irritated since I bought all the gaskets/materials needed to do the head gaskets. So I went ahead and did the intake gaskets too thinking it would help get better mpg. On top of that I did the plugs/wires too, right after I did the job the first time I started said having problems.

Tiny
Pos07impala
Feb 22, 2012.
Ok if all vacums are on and in the right place no bent or kinked fuel lines all plugs plugged in correctly no codes in ecm check fuel pressure and ignition module

Billymac
Feb 22, 2012.

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