1992 1500 305H stalls when put in gear
 

Any suggestions on stalling when being put in gear - IAC is new and the TBI has been rebuilt w/ new injectors. possible low fuel pressure???

Here is a list of things that could be the cause:
If the replacement injectors are larger and you have an over rich mixture this could cause low idle and stalling.
A rich mixture because of bad sensor such as a O2 sensor.
A build up of deposits in the throttle bore below the throttle plates could cause a low minimum air rate, or the minimum air rate may need to be adjusted.
A bad IAC, or damaged IAC by installing it with plugger over extended.

Low fuel pressure is more likely to cause hard starting and lack of power. I doubt it is your problem.

If the truck runs very well except for the ilde/stall, my guess would be a low minimum air rate. The easiest was to adjust it is with a scan tool watching the IAC count at the correct RPM (engine at normal driving temp accessories off). This is only if there is no other running or drivability issues.

Sorry to but into your post but i have the same prob with my 91 5.7, I was told as well IAC, I went ahead and threw the $ 40.00 Iac in without testing the old one and found this (not) to be the source of my problem, from this point on I will be testing componants before just throwing $ away, the only trouble for me is just about everythoing else that could be the cause was replaced several months before i started to have the idle problems, since im at witts end i'm going to start from scratch and start testing even the newer components.
it sux, the truck runs great in everyother way, then i stop at a light and it wants to die on me. my haynes book gave me a whole list of possable causes, noting that the egr was the usual culprit, after checking for carbon and finding it clean i disconnected the egr and pluged everything off thinking thinking " yes ! thats got to be it" but then again the closer to operating temp she gets the worse the idle, now with the mile long list from the book and little precious free time i have ill be testing for weeks, to top it off i not only drive the truck to work i drive it "for" work maybe 300 miles a day, not to be a whinner as i interupt your post but this TBI idle thing really has me down.
im usually pretty good at pinpointing things and solving the problem but this thing has been going on for 6 weeks now with a lot of trial and error and im at my end.
if theres anything you can think of tech, or anyone else please let me know, id be so very greatfull.

If the "minimum air rate" is to low the engine will kill before the IAC can catch it when the throttle is closed.

The minimum air rate adjustment is the throttle plate closed stop. The IAC lets additional air in, to get the speed where the ECM wants it. Other air amounts (vacuum bleeds) were taken into account during it's design. The total air getting in the engine must be correct.

If your PCV valve got plugged up with sludge, no air would be pulled through it into the engine, and this would act like a low minimum air rate and could cause problems like your having.

For a quick test - add a small vacuum and see if it will idle without stalling.

fuzzypuppy - you said the closer to operation temp your truck gets the worse it idles. Could you have a bad coolant sensor, that is not seeing that the engine is getting warmer, so the mixture is to rich.

If your IAC was stuck at the slowest speed position (fully extended), and the engine is at normal operating temperature - transmission in park, you should be able to very slowly close the throttle and the engine should keep running. It would be running at the minimum air rate rpm spec.

The IAC and minimum air rate are only to be considered as a problem if the engine runs correctly in every other way.

Shouldn't any of these causes talked about set the check engine light? Or at least be in the memory? Thanks tech, you the man! Jeff.

If you guys download the diagnostic software "WINALDL", it will help diagnose the problem. I installed a TBI setup on my 85 and was able to troubleshoot it alot easier with the software. It will tell you what info the computer is getting, like IAC counts, temp. readings, O2 readings, TPS position. It really is helpful, takes out the guess work.

Thanks Jeff
If it gets rich or lean, to the point the computer can not compensate for it, a code will be set. A sensor failure should set a code - unless if fails in a believable range. For example, a O2 sensor can have readings that the computers excepts as valid, when in fact they are not accurate.

Yes, block learn information is in the memory. It will tell you if it has been runing rich or lean.

IAC and minimum air rate problems do not have trouble codes on these pre OBDll trucks. If the cause were a bad TPS, it should set a code.
For those reasons many people like greg0380 realize that looking at all the senor readings is easier and faster.
A good scan tool, in the hands of someone that has experience with it, is VERY valuable.

Thank you for your help Tech, The temp sensor was good though it tested within range, it is 6 mos old but was worth a try anyways, since as i mentioned im going to start from scratch in testing,
But as you mentioned in your previous post, my truck does run fine in every other way, and as of yet it has not 'stalled' on me, just irratic idle, also as you coined a perfect term "hunts for idle" or surges a bit when sitting at a light, most times it just idles irraticly, but at times the idle will surge up and down, not really bad but enough that i have to make sure to keep good pressure on the brake, usualy when it surges as i mentioned i pop it in neutral tap the gas peddal a bit and it will then settle down to the funky idle again.
No, Red71 no trouble codes, damn I wish it would set one, at least then id have a clue where to start.
most sensors and emission controls are either new or have been tested as good, the Iac i thought was ok since i did get the idle kick up when i turned on the a/c, but since it was the last unchecked sensor i threw one in. then walked away discouraged once the closed loop cycle ended and the funky idle returned.
Except for the IAC a few cans of TB cleaner and several doses of fuel treatment the throttle body has not been touched (except to check torque), I guess ill try and clean the throats of the TB as you have mentioned to another poster.
If that fails I will start from scratch, I have noticed (though it could just be my imagination) that my injectors pulse louder than i remember, but i have dismised this because the truck runs great in every other way, and cold starts are normal.
one other thing i noted in checking the exaust several times since this all began i have not noticed it running rich, maybe slightly at clod startup but not at all other wise.
All these things gentelman are why i'am so perplexed,
I thank you for your help, and input, every reply gives me ideas and things to try,
im glad a board like this exists, its one of the better uses i have for the internet.
funny i cant go to any of my friends for help on this since they always come to me for help on thier cars, and i am right on 90% of the time. oh well huh. thanks again

The fuel being used could also be a problem. In the area I live, it is mandated that Ethanol is added to the gasoline all year long. A few years ago it started out only being mandated for the winter months. Ethanol is corn alcohol. The law is supposed to help the farmers and lower polution at the same time. In the winter all the alcohol eliminates the need for fuel deicer. In the summer many people notice their engine idles better when they buy non-ethanol fuel outside the metro area. Gas stations outside our seven county metro area are not covered by the fuel mandate.

fuzzypuppy your in California. I don't know what they are mandated to add to the fuel there. Pollution issues may be mandating fuel that causes problems.

Many thanks.
 

I never thought about the fuel Tech, very well could be a portion of the problem, never noticed it in years past but they could be mixing up an especialy nasty batch this year, here in so.cal the Air Quality Managment District, "AQMD", have mandated that every year untill 2008 I think emmisions must be reduced by a certain % more than the previous year.
theres good and bad things with that, but either way i gotta live with both.
As for today, I finaly had a couple of hours to actually work on my problem truck, installed a tach that has been sitting in my garage for months because no time to install it, I took this as my first step in re-checking all possabilities so i would have some actual # to look to for any small improvments.
I did find one trouble spot though, the vacume lines that go to the charcole canister and egr were switched at the TB, I dont know how long its been this way but it didnt seem to make any diffrence at all after i put it right. just piece of mind that they are as they should be now, and there is at least one check mark on my long list of items to consider and test.
one thing I have noticed is that there are a whole bunch of trucks out there with the same problem that I have, on this board as well as others, the only problem is they seldome follow up with thier solutions, if indeed they ever did solve thier problem. On princapale and curtisy i vow to post whatever cause I find. i figure it to be considerate of the people who's time you took when requesting help, the next person may be able to solve thier problem just by looking through a few old posts.
Just a thought anyhow,
I thank you again TECH for your time and input,

I totally agree with you on followups. When people ask me questions in person, I always tell them, I want to here back good or bad.

I also have noticed there is alot of TBI idle problems on message boards. My guess is there is a mix of problems and causes, but people are not concerned until it kills. I am always amazed, when I drive someones vehicle that has many problems, and the owner only cares about one of them.