85irocrebuildtpi

o.k., so the car is now running but we have a problem and it goes as follows:

we turn her over and bring her to an idle, maybe we bring her to 1500 - 2000 rpm's and she purrs nice and we let off the gas and she idles for a while....maybe a minute or two and than she chokes up and the idle drops way down but she than comes back up.

so she's idling but than drops down like she's being choked but she does come back up on her own. purrrrr, low decible purr almost choked out, than she bounces back and purrs.

you give her a shot of throttle and she revs and idles right out nice.

my guess and i would certainly appreciate any ideas is as follows:

1. I got a bad sensor?
2. the IAC is not set correctly.
3. I need to get her on a computer to get a read out.

so this is my problem...................

aklim

Clean the hell out of the TB and the IAC and the IAC housing. Reset it to about 10-20 IAC counts, reset TPS. See what happens. This is assuming you don't have a vacuum leak.

85irocrebuildtpi

alright guys, i'll break it down as i see it and like i said i dont know what the problem is and i got a motor i need to break in [HTML]see my post "HOW TO BREAK IN A MOTOR"[/HTML] so basically i will drive this car now before i turn the keys next. i am waiting on a warm day, tonight is 5 degrees to minus 10 and tomarrow is teens. so thursday warms up to 30 degrees is that enough to break her in, i think so.

so back to this small little problem, you touch the throttle and the car cherps

basic car

#1 ed wright FASTCHIP.COM
#2 rv cam 4 valve relief
350 - 4 bolt main
305 heads planed .010
flat top pistons
bored 4 plus .04
bosch no gap platnium 4 cast iron plugs
305 tpi
rebuilt TB to 52mm plus air foil
pulled maf screens 790cfm
msd wires 50 ohms
hypertech dist
24lb injectors
stock torque converter 1600rpm torque converter TPI huge in low RPM range
adjustable fuel regulator
non adjustable torque arm
panhard non
lower control arms non
auto 700r
3.42 gears
weld on subframe supports
fire wall bar
3 point upper strut brace
air/fuel gauge
new interior
new stereo 800 watt 2 10", 44owatt 6x9 plus 6 1/2", deck 4 x 6
--------------------------------------------------

thats the car

so the rebuilt 52mm TB is my focus, there is a break in period this guy says.
here is his site ask him some questions help me out the problem is like where Aklim has pointed out. goto--http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33558&item=7941539 751&rd=1.............can some1 hyperlink this for every1 i do not know how to-----------http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33558&item=7941539 751&rd=1

so is my TB dirty, or the new bearings not broken in....i don't know but think this is the area to look as aklim said.

aklim

I would use brake cleaner and clean out all the TB passages and the butterflys. Remove the IAC motor and clean that as best as you can. Remove the IAC housing and clean that. Reassemble and run car. Turn the set screw till the IAC counts are about 10-20 counts after the car has warmed up. Then Set TPS. Of course, make sure your timing is on or you will definately have to redo the setting procedure.

85irocrebuildtpi

tom bishop out of austin tx rebuilt my TB, he said as follows

Sounds like a fuel problem – i.e. too much or too little. Throttle body would give a consistent high or low idle if adjusted incorrectly




--------------------------------------------------------------------------------

From: DRowan7658@aol.com [mailtoRowan7658@aol.com]
Sent: Wednesday, December 15, 2004 5:31 AM
To: horsepowerguy@sbcglobal.net
Subject: hi i have a problem does it sound normal?



hi,



i have an 85 iroc and you rebuilt my TB to 52mm and bored air foil,



well i got the motor running and need to break her in so i am not firing her up again until i do that....thursday is going to be 30 degrees in vermont so i should be able to do it,



so, here is the problem....she idles up and runs for a little while than she chokes up and rpms drop and than she revs back up to idle....she is cycling like this.



your paperwork said there is a break in period with this part....can you give me any ideas.......i sure would appreciate it...the car is very nice and so close to running perfect..



thanks alot,



don

85 iroc, TPI

aklim

If the fuel pressure is right then the EPROM is the culprit then. What pressure are you getting?

85irocrebuildtpi

well, this was my main problem before and the fuel pressure regulator itself was the culprit. I will double check this pressure reading when i turn her over for break in today but if my memory is correct.

She cycles up to like 47psi on ignition turn and than drops to like 41psi when she is running but i will confirm this later today.

aklim

If fuel is ok like you have replied then you need to check the IAC counts with a scanner.

85irocrebuildtpi

so i lined up a mechanic with a genesis computer to check the IAC, can you tell me how he is suppose to do this so i can relay the info.

what about resetting the TPS?

thanks

just trying to get this done

aklim

OK. Lets say your engine is ok (no leaks of any sort), and your timing is set correctly (say 6 deg with the connector off) and lets say your TB is spotless and the IAC housing is spotless and so is the IAC pintle (pointed part), I would say that when you get to the screen that says IAC Counts after it is warm and in closed loop, it should be somewhere between 10 and 20 counts. If it is lower than that. you need to turn the set screw counterclockwise and if it is more than that, turn it clockwise. Adjust till it is somewhere between 10 and 20 counts. After that, you set the TPS. Of course, this is assuming your TPS is not way off.

You really should invest in your own scanner like an Auto X-ray or something like that.

85irocrebuildtpi

alright lets break down your advice with what i know is right.

no leaks in engine
timing forget it...its on
tom bishop did it and he does it all the time idle is not low or high as he stated it would be if TB was problem so i'll say no there

so here we go feeling confident...........

IAC HOUSING how do i check that? what could be wrong?
IAC PINTLE how do i check this?
TPS off alright now you really got me.........................

where is your shop? aklim...........

85irocrebuildtpi

aklim for 39 dollars some friends of mine will work on this for hours to make it right................... they spent 20,000 on this genesis computer.....................help me out

85irocrebuildtpi

i have not broken in the motor.....my genesis computer people tell me under 3000............ some1 tell me the RPM range to keep her in tomarrow

i only get 1 chance to make this motor.....................

85irocrebuildtpi

thought i'd take her to an xmas party....iroc racers and family to boot there....heheheheheheheheh

aklim

The IAC housing is under the TB and is held to the tb by 7 or 8 torx screws. You might have to change the gasket if you take it out. There is a coolant hose going and coming from it. You could bypass that if you wanted. I did. Take the torx screws out and clean the passages.

The IAC motor has a cone shaped thing at one end when you take it out. The cone part is the pintle. Make sure that is clean. When you take out the TB ahd have it in your hand. Look at the underside. You will see the IAC, Unscrew that. Clean that. Take off the torx screws. Clean that and the passages with brake cleaner as best as you can. Reassemble.


When you make idle adjustments with the screw, your TPS voltage will change. That set screw will move the linkage forward to open the throttle blades more or backward to close the throttle blades. Tht set screw is on the driver side. You will see a screw that does not allow the linkage to go any further when there is no tension. That is what you need to adjust. Of course, adjusting that will change your TPS voltage so after getting your IAC counts into the right zone. you will have to readjust the TPS. Like I said, if you did have to make a lot of adjustments, the TPS might be way off. Anyways, thjat is something to check after you get the IAC done.

I don't have a shop. My shop is my garage. If you were in Madison, I might be able to show you what I am talking about as far a swhat you are doing.