87 TBI

[DnStClr]

Yeah. Somebody else on here had a similar problem and found the Throttle Body gasket bad. It sounds like a bad idle air control too.

[GT1000000]

Thanks again,but unfortunately both the gasket and the IAC are new...had to try...also tried NEW computer,temp sensor,EST module...got a friend at the parts house...None have made any difference...
Still tryin',gt.

[VileZambonie]

What are your IAC counts? If you take off the oil cap does it make a difference? Are you sure you have no vacuum leaks? Brake booster is hooked up?

[GT1000000]

Last count noticed approximately 53-55,Haven't tried the oil cap...Booster is hooked up and the check valve is working, haven't actually checked for leaks, cause with the air cleaner off, the opening leading to the IAC in the throttle body almost sounds like a vacuum cleaner on steroids...besides spraying some brake clean around the intake and trying a long screwdriver like a stethoscope,nope,don't seem to  have any leaks, also when I disconnect the MAP vacuum signal to the MAP sensor and I keep the engine running, I also hooked up a vacuum gauge and at about a fast idle,1500-2000 rpm, I would get a nice steady vacuum reading, no bouncing or jitter... I'm the one getting bouncy and jittery,gt.
PS-Gonna tow it to a friends shop tomorrow,maybe he'll see something I'm not...

[VileZambonie]

A screwdriver to your ear will help pinpoint a mechanical noise not a vacuum leak. Sounds to me like that's your problem either internal or external somethings way off...

[Captkaos]

Are the injectors firing consistently?

[GT1000000]

Sorry,I meant a screwdriver with a piece of wd40 soaked paper towel on the end, have found a few vac leaks when the wet towel gets near or on makes a significant change in sound,sometimes whistles, sometimes kinda snores...as for the injectors,they are firing with a nice cone all the way to shut down...gt.

[DnStClr]

 Is there any way the wiring might be bad at the coolant temp sensor? I read where you installed a new one, but can't understand why the temp gauge didn't let you know the engine was overheating to the point where it fried all those valve seals and blew the head gasket originally. The reason I ask about the temp sensor wiring is because the computer gets a signal from that sensor and adjusts the idle air  motor so there's a proper idle.
 I read once where a guy couldn't get his car to idle properly unless he took off the gas cap! I guess the gas tank wasn't vented correctly or something.     

[GT1000000]

All good points, but the original overheat was a completely dumba.. move on my part...you know middle of the highway and you really don't want to stop till you get home and I used to have a coolant leak from what I found out to be the t-stat housing was warped at the base[since been replaced], and this was one of those times when the water level got below the sensor an it indicated everything was OK, I had forgotten to top up the rad before I hit the road,mind on other stuff, never glanced at the gauge...
Any how my buddy at the shop I took the truck to, checked and rechecked all prior and found everything to be in order, except one thing...Seems to be getting too much fuel and its loading up...since everything with the computer seems to be OK, we are now going to try a used TBI from the salvage yard. Didn't realize the TBI's were getting scarce,finally tracked one down at Cars-R Us, in Illinois. They are shipping one out to me...should get it by Mon or Tues. Hope that's the  problem,Will let you guys know...
Meanwhile THANKS again for all the ideas and inputs,gt.

[Captkaos]

Most auto parts stores carry these rebuilt.  They are easy to rebuild though.  I just went through chasing down problems on my Suburban.  I would guess the regulator on the back is probably shot if you are getting to much gas. 

[VileZambonie]

I thought you had a Holley throttle body?

[Captkaos]

You being GT1000000, right...

[GT1000000]

hey guys,
Just answering the Holley Question, No And Yes...No, I did not have a Holley TBI,it was just the Holley Pro-jection Intake...when I first installed it I had my eye toward someday putting a Holley TBI on it...And...Yes,we tried getting a used TBI,thinking that might be the problem,could'nt find a good one and have had bad memories with rebuilts,so I ordered the Holley Unit and I am back to nowhere...So...
I am in the process of towing the truck back to my shop and seriously considering a complete removal of the CCC/TBI system, but first I need some answers...
Q1-Q-jet carb best?
Q2-Do I need to replace the Ignition system with a 1-wire HEI?
Q3-The Transmission, what does the computer monitor there? Shift position?,and By completely eliminating the computer system, is that going to affect the tranny in any way?
Q4-Do I run power to the fuel pump relay from an Ignition On source?
Q5-Anything else?
I am going to install an adjustable Fuel pressure regulator with return.
I am getting a spread bore intake manifold,dual plane, good from idle -6000rpm.
Thanks again for all your help,gt.

[Captkaos]

It would be SO much easier to rebuild a TBI yourself.  They are the simplest setup as far as fuel systems go.  The only thing to them are gaskets, and the injector pod with consists of a diaphram a spring and 2 injectors.

1) I think Q-jets are best, right behind TBI's
2) You need a non computer controlled HEI.
3)700R4's are not computer controlled.
4)If you are keeping it, it needs to have power when the ignition is on.  Techincally you don't have to change it
5)Sure, why not fix what is wrong with the TBI, you are going backwards putting a carb on it...

[GT1000000]

Thanks Capt.
It is a TH400 and I just want to make sure it wont get fried if I go this route...
And yes I would love to fix what's wrong, but we[meaning the four "mechanics" who have looked at it] are a bunch of Dumba----s,cause we can't seem to figure it out...
One thing that continues to bother me is why??? if I connect the Map sensor vac hose correctly, the engine starts right away, idles for a moment, then dies...If I disconnect the vac signal to the map sensor, the engine cranks for a while before starting then seems too idlle pretty good, can even rev it and hold it at whatever rpms,but then after a little bit[30 seconds to well over a couple of minutes] it just seems to shut down,,, This I can do over and over again,thinking maybe the computer needs to wake up and re calibrate itself,but this doesn't seem to be the case...
If you can think of anything that might be causing this, besides everything we've already tried, I am open to suggestions,PLEASE...I would much rather keep the TBI, but I can't afford to be without my truck much longer,Thanks again,gt.
PS- as to rebuilding the TBI, it shouldn't be necessary now with the NEW Holley TBI,which I have on there NOW...