I have done just about everything I can do trying to get my idle right, but nothing is working. I was just dead set that my valve weren't adjusted right, spent yesterday checking them, and it still isn't idling right.

in open loop it idles fine, map is around 50-53kPA, MAF is showing 8.4-9.4gm/sec, rpm is around 750w/ the hot cam hitting, o2s reading around 480mV, inj 1.8-2.0 duty cycle.

as soon as it goes into closed loop, the blms spiral down to 108, truck starts choking to death, map will read from 40-80 kPA (it's new, yes it's right), inj duty cycle hits 1.2-1.7, o2s reading around 500-590mV. The rpms will slowly get down to around 600, drop to 450, then the truck will kick over to closed loop, brush itself off, then go back to the death spiral. the cycle usually lasts about 2 minutes.

I have a brand new vented opti, crane cams HI-6R w/ LX-91 coil, huge K&N filter, temp stays around 188, shorty headers, have ran the truck in speed density mode for a while, seemed to like that, but still had the idle, i'm at a loss. i've checked for vacuum leaks, ran propane around everything, changed plugs, modified my bbk throttle body, etc etc.

I've had professional tuning, and it isn't helping, what's wrong with my motor??!?!?!?!?!?!?!?!

I have datalogs if someone please help, it's extremely jerky off the line, will about die, then rip your neck off when the engine catches, sometimes it will die at lights, getting tired of it and am at wits end.

 

I think your wording is off...it's running fine on OPEN loop and falls on it's face in CLOSED loop? Your O2 sensors take over your air/fuel ratio in part throttle driving. You need to monitor O2 sensors dynamically, then need to be bouncing back and forth rapidly (about 10 times a second) between 1XX and 8XX mV. Possibly you're running rich in closed loop and it's causing the engine to die. Is it a stock TB or aftermarket? I'd also check for vacuum leaks...you siad it runs pretty good in speed density mode but not with the MAF...a big vacuum leak will be unmetered air. Do you know if the MAF is any good?

 

hehe, oops, thanks, did have it worded wrong, corrected it.

I am wondering if the maf is ok or not. it shows to be pulling air through, and changes w/ the throttle. I pulled the screen, polished the inside of the maf a little, but didn't gut it or anything.. i cleaned the maf a long time ago w/ brake and electric motor cleaner, might have messed it up somehow. it runs fine in regular or speed density mode, just won't idle in either mode, seems to be worse in regular mode. I just don't understand how the vacuum is dying out in the intake like that, almost to atmospheric levels! I have checked for vacuum leaks, pulled everything off, plugged it, ran propane around everything, and still couldn't tell cause the idle is so messed up. My last resort is to pull the intake and put new gaskets in.. BUT, if it is a vacuum leak, why is the MAF showing so much air coming in?

it is a 52mm BBK pos(quality, machining, etc) throttle body, I am about to pull it off and put the stock tb back on there to see if things change. The o2s report the above at idle, but swing like monkeys on crack from 180-920mV going down the road. They are pretty new, have about 5k on them, and do get heated up and blown off quite often.

thanks for the reply.

 

Check the following:

IAC counts at idle - should be around 40ish in closed loop, Close the blades to get more IAC, Open the blades to get less IAC

BLM's in closed loop - If they bottom out to 108 you're pulling fuel like crazy and probably have issues with the MAF or the MAF calibration table or most probably both at the same time.

Steve

 

As stated above, sounds like your IAC isn't working properly. The IAC is fragile. I'd also check the TPS, should read approximately 0.5v with the throttle closed. What's your PCM idle speed set at?

 

Thanks guys, IAC is about a year old, runs fine, the counts are around 47-50ish, blades are as closed as they can get before binding in the bore, i've ran it w/ and w/o the maf, doesn't seem to make a difference, tried reducing the ve in the tables, but not much luck, the map goes from 50-80, it's just freakish, think when I get it back together I'm going to put the stock tb back on there to see if anything changes. tps is reading .69-4.59v. the TPS and MAF are about the only things I haven't changed out YET. looks like my stall converter money may be going towards one..

 

Since IAC is good, I'd borrow an MAF. If your MAF is bad, the PCM will try to run speed density. The VE table may be a bit too far off while running SD for the Hot Cam. I would try the MAF first, then try your stock TB second.

Steve

 

I've got Bryan Herter's tuning help (pcm4less.com), he's been really helpful and worthy of his reputation. I've tried reinstalling the stock program too, and man, like you said, it doesn't like it too much.

Since I am not in the "camaro crowd", I really don't have any friends close by that would let me run around w/ their maf. I might be able to get my hands on one, thanks for the suggestion, I'll try that out.

 

TTT, anyone want to check out my datalogs or should I post screen shots of rpm vs. map?

thanks.

 

i had a friend with the same problem it turned out that one of his
injectors did not have a good connection.

 

Thanks, I'll check that out as well. it does really fine taching all the way up to 6300, just at idle, seems like it looses pressure in the intake, almost all the way up to barometric pressure, figures itself out, about dies, comes back to life, idles normal, than starts the downward spiral all over again. you can hear massive vacuum coming from the tb while it's idling, almost sounds like a vacuum cleaner, i'm stumped. lol. I can take video, compress it, and send it to anyone along w/ datamaster or excel spreadsheets of the datalog, etc. HAAALLLPPP!!!!

 

YGM. I made some changes that I think will help.
Let me know how it goes. Your MAP is alittle high so you know what I am thinking. I will not say it.

Jeff D.

 

Thanks Jeff, I can't wait to try it out. Truck is still on jackstands, old crank hub about 3/4 of the way off (tight fit in s-10), i've been busy w/ family and holiday stuff so I haven't had a chance to get back on it. I want to get it back on the road, but really got burnt out on it right now (plus my little girl got a ps2 for christmas. ) I'll be back into it hopefully this week after work and will try to figure out what's going on w/ it. I really don't want to pull the intake, but that may be the route I take, may also replace the lifters while i'm in there, seems adjusting them helped a bit, but have one tapping.

Thanks again, will let you know what happens.