romandian

four years ago i put a centri blower on my 1999 c5 and tuned it myself. i never had any idling issues before, but last spring the car developed slight hunting that slowly got worse over time to the point where it would be undrivable (no changes to the tune), it would die at every stop light and even when getting off the gas while driving. this was in closed loop only, when cold on start up idle was fine and even if warm for a short while.

i repaced the pcv valve, no change, i put a fixed restrictor in, no change, i took it off (blocked the port), no change, i put in new oxygen sensors (one was getting a little slow anyway), no change, they now switch beatifully. i chaged back to tr6 plugs from br7ef (they looked good) and that fixed the issue in drive (so much concerning retracted plugs). not in park/neutral however. engine still hunts, a little less, though, it doesnt die. car behaves the same in cold and hot weather, btw.

where to lok next before i start making fancy changes to my tune? tps? doesnt make much sense.

mmartinez

I would clean the throttle body and MAF sensor, also do a search for idle relearn procedure. I have a 97 coupe with A&A kit with the vortech supercharger and experienced the occasional shutting down usually happened after opening it up and then coming to a stop light, the idle would just drop down to nothing and car would die, started right up afterwards every time. Hope this advise helps.

foggy

You might also be having leak thru at the throttle blade shafts as well.. SC pressure tends to wear out
the shaft bushing areas quickly

C5 Diag

El original

What condition is your air filter?

romandian

i forgot to mention: no maf, no ltfts. filter is new and huge (diy). the real question is: whats different when in park/neutral vs. drive? i dont think the bushings behave differently. btw, idle speed is set at 650 for both and no, increasing it doesnt make a difference.

the relearn subject is confusing. i see anything from pulling fused to car does it on its own. what do you have in mind exactly?

mmartinez

I did the relearn procedure that calls for pulling fuses, starting the car, turning of, reinserting the fuses, starting the car letting it come up to about 176 degrees, and going for a 30 mile ride that includes varying speeds. The exact steps of the idle relearn procedure are on the internet, I performed this procedure and it helped my 97 coupe.

romandian

i will try and do that, but i suspect it has to do with ltft cells, which are not used in my case.

tommypenguin

Have you lubricated your bpv? I had neglected this on my car, disassembled, cleaned, lubricated and put it back together. I also replaced he hose to bpv not sure which made the biggest difference but one of them helped a lot for my idle issues.

romandian

bpv=blow off valve? how did you lubricate it and why? i suspect it was leaking. but if idle is good in drive and only goes bad in part/neutral?

tommypenguin

Bpv = blowoff valve just kept selecting the wrong acronym from my phone, hardly anyone recircs with our cars so it's just a bov..

To lubricate I unscrewed the valve pulled out the spring and piston. Cleaned both, and bought a specific lube on Amazon made by turbosmart.

My condition was that I had an idle hunt issue where when driving when putting into neutral as rpms would return to set idle it would fall below where it died a few times or rpms would bounce back and drop in a loop. Sometimes it would return to set idle point other times is would hunt.

Here is a link to a thread about cleaning bpv.

https://www.corvetteforum.com/forums...-and-vids.html

romandian

thanks. ill plug the line and see how it is.

romandian

im still strugling with this. i will probably have to try and tune it out. but im reluctant to cover up some "hardware" issue with the tune, as this really came gradually from nowhere.

Sub8

Difference between park and drive is the load on the engine as you release the throttle.

Sounds like an air leak developed and has gotten worse. What does your fuel trim and AFR look like as its stalling?

romandian

well, obviously they are all over the place when engine is surging. i tried to establish what is lagging what, but its impossible.

Sub8

Get it to a stable idle, even if you need to use the throttle a little. Run it for 1 or 2 mins like that and log what's going on. Shift into D or close throttle and see what happens.

romandian

ill try that, thanks.