Erratic idle(Intermittent) @ hot and cold temp...?

sd-slider

NOWUFFO
Joined
Feb 22, 2009
Verified all of these settings again with a new Scanmaster I bought and the readings are:

The O2 voltage @ idle(700-775) is .230-.780 over a 5 minute period
MAF appears to be holding steady @ 4/5, climbs to 15 @ 2000, and returns to 4/5 after revving to ~2000
TPS = .40
IAC = 27
BLM = 132
Int = 128-131 @ all RPM's

I noticed cruising home on the freeway @ 65 that the O2's would bounce anywhere from ~30 to ~800....

I have removed and cleaned the IAC, replaced the O2 sensor and still have an intermittent rough idle both while warming up and after an hour drive...and she smells a little rich and my gas mileage seems low...

Any ideas what may be causing any of these issues?

Thanks.
 
Eric, no loose vac lines or holes in IC hoses or anything? Let me know if you need any known good spares to help troubleshoot.
 
a TT chip is a good start. (theyre cheap enuf) and you didnt post voltage. keep an eye on that at idle and while driving. also fuel pump could be dying a slow death.
 
Eric, no loose vac lines or holes in IC hoses or anything? Let me know if you need any known good spares to help troubleshoot.

Thanks! It's hopefully something simple.



a TT chip is a good start. (theyre cheap enuf) and you didnt post voltage. keep an eye on that at idle and while driving. also fuel pump could be dying a slow death.

I have a TT streeter for 91 octane and hotwired Walbro 340, all with less than 1K on them. I replaced all of the vac lines last fall but I may have overlooked something. Voltage doesn't drop below 13.4.

I'll check all lines per the diagram and verify all connections and hoses. Any idea what the vac should be @ idle?

Thanks guys, this will at least get me moving.

=Eric

Mods to date: TT 91 Street chip, Hotwired Walbro 340, New Comp 980 springs, and free-flowing cat.
 
Went through all of the vacuum lines and I had replaced everything but the lines around the EGR. I also went through with a propane torch and slowly followed all of the lines and the intake gasket area's and didn't get any enrichment effects...:confused:

I took a trip to Autozone this morning for some more vac line and a PCV valve and when I went out to leave, the O2's at startup were ~375-425 with the rough idle re-appearing. Once I cruised back to the house, it seemed to work itself out...again.

For S&G's, I disconnected the EGR vac line to simulate a major leak and the O2's dropped below 100 and the idle went to shart.

I'm going to rig up my FP gauge and tape it to the windshield to verify FP is good across the board.
 
Maybe you can either cap all the vac fittings on the block, or put a solid gasket under the block to eliminate all the vacuum accessories. Or cap one at a time and narrow it that way. I had a hard vac line crack that goes under the dash to the AC/HEAT controls. Maybe capping them at the source (vac block) will narrow or eliminate some possibilities.
 
you didnt post voltage. keep an eye on that at idle and while driving. also fuel pump could be dying a slow death.

Strapped the FP gauge to the windshield and took a cruise tonite and did a few WOT blasts.

Voltage held steady ~13.7 and fuel pressure went up pound for pound with the boost(a whopping 15 lbs......:redface:). I still have the stock FPR and the pressure at idle with the vac line off was ~43, 35 with it on.

Didn't act up tonite...:)....:frown:

Side note: When she was warming up in the shop, the interior lights seemed to intermittently dip a little while getting up to temp....:confused:
 
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