Chevy & GMC Vans

So your idle air control valve, coolant temperature sensor and fuel pressure all check out ok?
What fuel pressure are you getting?
How's the spray pattern on your injectors?

no i have not done that stuff yet all i did was install a tach the coolant sensor on my 1992 TBI astro looks like a bear to get to!! help on that one and i have not looked at the IAC and how would you check fuel pressure on a 1992 astro with TBI??

If the 92 tbi is like mine, it will require a fitting placed between the tbi and fuel line in order to hook up the fuel pressure gage. It sounds like a pain but it's not that bad to do. Two things I suggest. get replacement O rings for the fuel line and buy or borrow a fuel pressure gage for low pressure systems. If the gage will read up to something like 200 psi, it may not give accurate readings in the low pressure ranges, which your tbi is -like 12 - 13 psi. I had a high pressure gage that was giving me a 20 psi reading which I knew couldn't be right. the 15 psi gage I have now shows 12- 12.5 psi.
I don't recall the coolant temp sensor being that hard to get to, but it's been a while since I replaced it. Might have to unhook the upper radiator hose to get it out of the way.
If you want to make this stuff seem easier, replace the spark plugs. It will give you a whole different perspective in the definition of pita.

yeah i already did a full tune-up the plugs included the plugs was not that hard just a couple of extensions and swival

Then the coolant temp sensor and fuel pressure check should be a snap for ya.

yes you are right i am leaning towards the coolant temp. sensor it is cheap and a lot easier than the fuel pressure gauge!! so when i get money and time i will look at the problem right now i am taking care of the little stuff on the van and christmas!! the reason i am leaning towards the sensor cause it only happens in closed loop.

I would be focusing on the O2 sensor & confirming its operation.
As you have determined, the fault occurs when it gets into closed loop. Try disconnecting the O2 sensor & see if your condition is gone. I have seen a lot of O2 sensors go bad & they can cause this type of condition.

okay i still have not had much time to check in to it yet but it has been cold here latley and i notice that when i cold start the van the engine idles at 1400 rpm for 2-3min then idles down to 1100 rpm stays there for a while then drops again to 1000 rpms until the van goes into closed loop then idles at 650-700 rpms this all when not in gear when in gear and the engine is in closed loop it idles at 450 rpms. will the engine running a little rich make it idle low when in closed loop and at the same time not foul the plugs the reason why i bring up it running cause since i got my exhasut it smells a little rich when reved.

yes.
it will foul your plugs eventually, and screw up your cat.

i am going to disconnect the o2 sensor and see if the problem still occurs but i have to wait until it warms up outside a little cause my van has been running really cold cause off the low temps. we have been haveing.

okay guys don't be mean you all just have to be patient with me please! okay i have been doing some more research on my low idle since not many people has had this problem it is now pointing more towards my IAC valve. now here is a quick question is this normal when it is cold like 40 or below when the engine is first cold start it idles at 1500 rpms for 2-4 mins. then idles down to 1100 rpms and idles there intill the engine warms up a little then once warmed up which takes some time here when it is cold. then when it warms up enough to go into closed loop it idles low in gear like 350 -400 rpms. the othere rpms that i talked about is when it is in park. now i talked to a couple of auto parts store and orallys seem pretty knowledgeable and they said that it is my IAC valve not letting enough air into the engine. now what ways can i test this IAC valve and i have been told that if i turn on the a/c the idle should go up a couple hundered rpms but i don't remember that happing but i have not used the a/c in a while so i am going to check that.

Bryan-Clean the carbon off IAC.OK???.

i was just going to replace it cause when the van is warmed up i beleive the idle air control valve motor stops working cause when the van is fully warmed up i turn the a/c on and the idle drops and does not go up but the engine continus to runs okay.

Ok Bryon,then replace it if that is what you think will get'er done.Don't make the same mistake I do all the time and just seek as many opinions as you can and never end up fixing it.Let us know how you made out.

Btw-Happy Holidays.

well i have the same problem exactly lets see if we can get it fixed maybe i'll head out there now and pull the dog house in the cold dark....

edit 1: fuel pressure checks out 60 before start 62-65 while running, off is 60 then drops to 55....? no arching egv and iac next (not as cold out as most nights ) back out i go

edit 2: in the time it took me to write that first edit pressure dropped to 40... i wonder how much lower it'll go but sortta looks like it's going to be fuel related for me good thing i bought this pressure tester when i thought my fuel pump was going... i'mma leave it to sit for a while then head back out see if it can hit 0

edit 3: in forty mins hit 25 psi it's now snowing so i'm going to put it back together and check the injectors another day...