01 EXPY Rough Idle - Just replaced full exhaust / CATs / O2 Sensors

[jtoro]

Hey guys -

I just replaced the entire exhaust system on my 2001 5.4 Expy - which was totally rusted out. Had been running for some time with holes in the CATs and manifolds, and finally got around to doing it. Replaced drivers side manifold, both down pipes with all 4 CATs, EGR pipe, new muffler / tail pipe. Also replaced all 4 O2 sensors.

Problem now is that I have a rough / surging idle. Feels like its running fine once it gets going. But the rpm surging from 500 - 1000 or so while idling hasn't gone away after 3 days. Curious what may be causing that. No Check engine light so far so codes to reference.

Any thought would be appreciated.

 

[1955moose]

Just because you have no check engine light doesn't mean you haven't got a code in your computer. Have you plugged a scanner into your diagnostic port. A lot of things can cause a surging idle, run codes, and report your findings.

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[1955moose]

After rereading your op, I'm assuming it idled fine before these repairs? If that's all was done, I'm betting a vacuum line got knocked off, or an issue with one of the new 02 sensors. Again run a scanner on it, theirs about 5 or more things that cause surging. Egr problem, injector problem, vacuum leak, and so on. It's probably something simple, if it ran smooth with major lean conditions from exaust. Did you keep old 02 sensors, just in case. I never throw out old parts till vehicle is sound and right.

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[jtoro]

Yea good point. Gonna run it somewhere tomorrrow to get it scanned. Yes - it was running smooth before with no rough idle. Ill see if any codes come up an reevaluate / recheck vacuum lines. Will update..thanks.

 

[jtoro]

Finally got it and scanned. P1000 not resetting. Been a week and almost a full tank of gas and still can't get it to reset just yet. Its pretty cold up in Maine and hitting the right temp for reset may be an issue for a bit. The rough idle has become less frequent but still happens. Checked all vacuum lines and nothing yet. Work in progress...

 

[1997SCEBFEX]

hope you find it.
how old is your IAC, could be sticking? easy fix with carb cleaner spray, or replace.
what about throttle position sensor; they're notorious for going on these.
I would also suspect unmetered air &/or vacuum leak somewhere.
I too hate doing work and another "gremlin" emerges.

 

[1955moose]

Repeat after me, I love getting dirty, and working on cars! Morning everybody!

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