Well I've had a hunting idle for quite a while now. I've got a C&L with a Brenspeed tune. When getting off the throttle sometimes it will drop to the point it almost dies. It will rev up down up down and then usually sit somewhat still. It has never really died tho. It even has about a 50-75rpm fluctuation about every second once it settles down as well. I've tried everything to get this to go away becuase it makes my car look bad, ya know?

I've tried everything I can think of. I've cleaned the TB(actualy replaced it with a new because a certain over excited dog knocked it off my milk crate), cleaning the MAF, doing the idle relearn after a battery pull, new plugs. It seems better, but the more I think about it, I think it was more a placebo effect. The only variable left is the tune. But it's hard to believe that all 3(87,89,93) tunes have the same exact issue and that the issue isn't more widespread and that's what makes me think it may not be the tune. But there is always that possibility..... So is there anything I'm missing on the hunting idle checklist? I see most eliminate the issue after a TB cleaning. May have to get a hold of Brenspeed on this one......

 

Man.... nobody has any ideas?

 

I can't say with any certainty in your issue because I never had the C&L intake, but my Brenspeed Paxton tunes do the exact same thing. Coming off of cruising the engine may fall to ~500 RPM but then spring back and fluctuate ever so slightly when it stabilizes. Mine hasn't ever stalled either but I've done the same as you: cleaned the TB and the MAF. It does it on my 91 & 93 tunes for both pulleys. I think it may just be the way their tunes operate.

 

I know this sounds simple...but I had this problem and it was a leak in the intake. It was not sealed good and was sucking in unfiltered and unmonitored air. I am not familiar with the C&L, but if it is plastic and collapses under clamp pressure...it will leak. Worth a look

 

+1!! I had the same issue & found the clamp loose on the TB which allowed the TB to pull air. tightened it down & problem resolved. Check all your vaccum lines from TB & your CAI clamps. Hope that helps ya out man.

 

Check connections and clean the throttle body. A tiny bit of gunk can cause that hunting idle.

 

Air in-leakage and dirty TB are the primary causes. I'd also run a tank or 2 treated with SeaFoam to rule out an erratic injector pattern due to crud.

 

I have the exact same setup and had the exact same problem. If you have cleaned the MAF and TB sufficiently then try this. The issue seems to be with the rubber boot and the hose clamps between the TB and the plastic air intake. I ended up pressing the boot against the TB as hard as I could and then pressing the intake into the boot very firmly until it was jammed against the surface of the TB. This is where it gets interesting. If the intake shifts AT ALL, even the slightest droop or twitch, then start over. Once you get the intake firmly seated you can wrap the hose clamps around it. The 1st hose clamp needs to be around the lip of the TB, you can feel it. Make sure the hose clamp is squared up to the lip 360 degrees. It's easy to have the top seated correctly and then have the bottom off just a hair. Tighten the hose clamp down as hard as you can. Use a ratchet instead of a nut driver and tighten the living $&/@& out of it. Place the second clamp about 3/4" away so that it will be clamping the boot around the plastic intake. Snug this clamp down and check again to make sure you are squared up on the intake. Continue to tighten the clamp until the rubber boot just barely starts to distort. At this point the intake should be pretty solid. Move to the air filter and make sure it's on all the way, then tighten that clamp. Start the car and see if the idle is fixed. If it's not, then tighten the forward hose clamp (at the TB but on the intake) some more and try again. You might have to play with that front clamp to find the sweet spot for a good seal. Sorry to be so long winded but I wanted to be thorough. I chased this problem every day for over a week.

 

maybe its the Egr pressure valve sensor

 

Most likely tuning. The other suggestions are worth while and should be considered.

If Brenspeed looked at a datalog of your car while it was doing the hunting idle, it could probably cure the issue.