My truck had been sitting for about a week and ran fine before last weekend, but once i started it up I noticed that my usual rpms are roughly 1600 for a couple seconds... you know the warm up period, but instead the rpms peaked at 1200 and slowly went down to 700 with a slow surge. At this same time I noticed that my exhaust leak on my collector seemed to be louder. Could my exhaust leak be the reason for this poor performance? I've always had an exhaust leak there. It almost sounds like an ignition problem because once the rpms go up it runs fine.

 

I'm wondering if the exhaust leak is causing the O2 sensor to sense a lean condition. Fix the leak and see if the other problem goes away.

 

Thats what I was afriad of... I hate working on those stupid bolts...

 

I don't think a leaking exhaust manifold can do that. The flow will always be outward so it cannot change the O2 mix.

The leaking exhaust gas can melt wires and vac lines.

There's a large number of items which can make it idle poorly. Vac leak, intake manifold leak, ignition problems, timing problems, worn timing chain, IAC valve, IAC position sensor, the list is long so more exploration is needed.

 

He said it's down at the collector. I have read of a trick some people do to help their vehicle pass smog inspections, which is to induce a small exhaust leak downstream from the manifolds which causes a lean reading. I don't know if that's just on the tailpipe sniffer or on the O2 sensor as well, but that's what popped into my head when he mentioned the two items together.

But you're right, there are many more possible causes. Best to tackle one thing at a time.

 

I see, I just thought it was odd that the two happend at the same time. The worsened header collector leak and the engine running rough. Maybe the exhaust leak sounds louder because of the inconsistent flow? The exhaust seems like the mixture is too lean.. I'm know thinking that it is an ignition problem because once the rpms are up it dosen't seem to happen...

 

No reason to think it's ignition either. Most ignition problems will kill the engine outright. It could be an ignition timing issue. Plugs could be bad. But there's no reason to believe that but like everything else it needs checking.

Actually what you need to do FIRST is check the codes. While they often don't tell you what you need to know, it's still almost a waste of time to go poking around a vague problem like this without checking them first. Most auto parts places will check the codes for free for you.