First, in a previous post you said you dropped the fuel pressure to 40#. That should be good, especially temporally, to eliminate excess pressure as the cause of the over rich condition. Is it still at 40# at idle?

I cannot imagine any sensor becoming damaged by a vacuum leak or a rich mixture. The only possibility that comes mind is if the O2 became fuel fouled or carboned up. But is should still run decently in the open loop mode.

The procedure you were reading about for setting the TPS, includes setting the minimum air adjustment, prior to setting the TPS. This is more of a fine tuning exercise you can make AFTER you get it to run. For now, check the TPS with the ignition on, engine off. Make sure it is at the published specs. That is all you have to do. Simply check and adjust the TPS voltage, as necessary.

If you have not messed with the IAC, it needs no adjustment. There really IS no adjustment for the IAC. IF it has been removed and reinstalled properly with the pintle retracted there is a procedure you can go through to allow it to self adjust, or it will adjust itself through normal driving. Again, if you haven't messed with it, there is nothing you can do to "adjust" it. It has no "settings". Yes, the IAC is a controlled vacuum leak. The ECM opens it to allow more air flow for higher idle speeds, as desired. The ECM also adjusts the fuel for the idle speed it has commanded.

First things first. Find and correct the vacuum leak. Then you can use the ECM and the check engine light in the field service mode to insure you are in closed loop and whether it's running rich or lean, if there is any doubt. Fix the easy stuff, first, then you can chase the harder problems.

RACE ON!!!

 

Yes, its still at 40psi

I did replace it due to an error code - 13 was the code and now that code is gone since I replaced the old one - The old O2 sensor really didn't look that bad - I have seen worse...

The only time I have ever messed with it was when I installed the T-Body, but I took the entire lower section off the orig. t-body and just installed it with a new gasket - It was never removed from the "case" (I don't know what the case is called)

I wont do anything else until I figuer out what the vacuum leak is from - I promise

Thanks!

 

RACE ON!!!

 

Was the 40 psi set with the vacuum hose 'ON' or 'OFF"?

There's a significant difference between the two.

Jake

 

YEA!!!!!!

Jake

 

I'm back..... Checked every vacuum hose on the car and found no leaks at all....

I did get an AutoXray 3000 today and checked the codes - found nothing.. I scanned the car "real time" and it says the car is running lean... WTF!!! I smell raw fuel - not as much as I did before, but it's still rich!

I did jumper the A&B wires on the ALDL plug and disconected the IAC causing the pintle to open all the way - that stopped the sucking noise - temporaly.. But when it came back I could hear and feel the suction from the hole on the front lower portion of the T-Body (where the IAC pintle opens and closes the air passage) is this normal? Would a vacuum leak from the intake or the plenum cause this?

The AFPR is set at 30 psi with the vacuum line connected (on) and 40 psi dis-connected (off)

Car still will not rev over 2000 rpm....

Now what

 

I'm not familiar with the 90 so will just ask, does it have a MAP? Maps can make a engine do crazy things. That sucking sound may be the IAC wide open gasping for breath. What could cause the Iac to open? A false reading from another sensor? The TPS can cause funny things to happen too. Check it to see if it increases the voltage smoothly through out it's range. I don't remember the numbers but seems like .054 to about 4.5. Maybe someone will jump in and correct me. Just some thoughts that may steer you in a different direction. It will be so simple when you find it. You put on a new TB, Is the TPS installed correctly? The Iac is trying to get the revs up at idle. Try adjusting the base idle up some. It's got to idle before it can run. Try the simple stuff. The injectors too big? Cats plugged? Happy hunting!

 

Let me play devil's advocate here. Everyone seems to be hung up on a vacume leak, and while that could be the problem, it could be elsewhere.

Known facts seem to be: Car ran fine for 40 miles. Major work and new parts installed. Running rich above 2000 RPM's. Air sucking sound. Sound lessens or goes away if vacume lines are removed.

Start with cheap and easy fixes and work up from there. You have recieved excellent responses so far, and I agree with the thought of not throwing dollars at it to fix things that ain't broke.

This sounds like an air intake restriction of some sort to me. Restriction could cause the "sucking" sound around the restriction and the sound would lessen if the vacume lines were removed and the manifold allowed to breath. Could something have been sucked up into the intake during that 40 mile trip or was there something left lying in the intake tract during the parts swap and forgotten. Another thing that will cause similar problems is an air leak between the MAF and the TB. If the intake tube is not tight or not installed correctly, the air is entering the system after the sensor and it thorow the computer into a "rich" condition. Had this happen on my Silverado and took me a few minutes to get it figured out.

Hope this helps. Keep us informed.

 

The PCV system draws fresh air through that hole and whenever the engine is running you will hear and feel sucking.

 

When you do the IAC restting procedure, that causes the pintel to extend to the fully closed position, not open. That gives the ECM a new base setting from which it sends current (measured in counts) to open the IAC just enough to maintain the desired idle speed. The counts should be in the range of 20/25 counts.

This sucking sound you're hearing gives me concern. That kind of sound is usually assoicated with a vacuum leak. I don't hear any such sucking sound around my MAF.

Have you had the IAC off the TB? If so, did you make sure to install the gasket when you replaced it? Is it tight?

You can see if there is an actual vacuum leak in that area by spraying some carb cleaner, water or propane gas (from an un-lit torch) directly at the area you hear the sound. If the engine speed changes or if you see any smoke out the tail pipe, the you'll know for sure there's a leak.

It could the the throttle body to plenum gasket that's leaking. As I said before, these engines are very sensitive to vacuum leaks. You MUST seal the engine if you ever expect it to run right.

Also, check to see if your throttle body has a small hose bib (a little tube extending downward) on the underside of the TB on the driver's side. On mine, this bib is a vacuum source for the gas tank venting system. There should be a hose attached to it or, if you aren't running the evac system, the bib should be plugged. You can buy little rubber caps in various sizes ina kit at most auto parts stores, or just use a rubber hose with a screw/bolt in the open end.

The only time I got a lean condition indication was when my 02 sensor failed. If you had a data logger you'd be able to actually see the 02 activity.

What I am suggesting is a data logger that gives you the sensor numbers, not error codes. You can pull error codes with a paper clip or jumper wire. You don't need anything else to get the codes.

I'm suggesting a data logger that you can connect to the ALDL and show what the sensor readings are as the engine is running. Readings like 02 sensor voltage and cross counts, IAC count setting, BLM and Integrator numbers, ignition timing, closed loop/open loops status, idle speed (both actual and desired), coolant temp (no, not the dash reading but the temp the ECM is using to make its calculations), TPS voltage, air fuel ratio, knock retard, fuel pump voltage, EGR duty cycle, air flow rate, etc.

If we had the numbers associated with those items, we can ID which one(s) are not as they should be. We all know that the 02 voltage readings, for example, should NOT remain in the .7/.8 range. They should cycle up and down from about .1 to .8 and back again. Each time the voltage cycled across .450, the cross count number should change. If we saw that the 02 voltage remained in the .7/.8 range, we'd know that 02 is malfunctioning, see what I mean?

You're our eyes and ears, we're depending on what you see, hear and do and how accurately you post it. Be specific and detailed in your posts, tell us step by step what you've done. Don't be brief or reluctant to make long posts, that's one reason we're here, to try to solve this. I don't have an aversion to reading.

Remember the old computer adage: Garbage In, Garbage Out. The more precise you are the better our chances of finding the cause.

Jake

 

BTW, 30/40 psi of fuel pressure isn't enough. According to TPIS, only the 85 calls for pressure even close to being that low.

Do you have an adjustable fuel pressure regulator?

Here's their listing:

1985 -------------34/40
1986 & 1987-------37/43
1988 thru 1990----41/47
1990 LT-5---------48/55
1991 thru 1993-----41/47

Jake

 

[SNIP=65coop]Yes, its still at 40psi. The only time I have ever messed with it was when I installed the T-Body, but I took the entire lower section off the orig. t-body and just installed it with a new gasket - It was never removed from the "case" (I don't know what the case is called)

I wont do anything else until I figuer out what the vacuum leak is from - I promise

Thanks![/SNIP]

If you replaced the lower plate on the throttle body and NOW you hear a sucking sound from that exact area, I'd take another look so see if the leak is there.

Using a very thin layer of Sensor Safe Silicone Sealant on the gasket can insure no vacuum leak.

You have to understand, in my many years of screwing on these suckas (just crossed 60 a few days ago) I've chased so many vacuum leaks that I've become sort of **** about them. I now use SSSS, teflon tape, or Permatex #2, etc., at any place that I even THINK a vacuum leak could occur. One ounce of prevention is worth a pound of cure.

In a perfect world, there are lots of gaskets that, according to the instructions, don't call it, but I refuse to take the chance any longer.

Jake

 

Ok - I'll answer the questions and then I will hook up the scanner and post the results.

Yes

I jumped the A & B terminal on the ALDL and then unpluged the IAC - This make the IAC "extend" and close the air gap

I would say "Yes" The TPS was set by a shop with a Snap On diagnostic tool and the T-Body was installed by me (not really a tough job) I just did a swap and put all the vacuum lines in the same place.. It did run good for about 40 miles before it fell on it's face..

Stock injectors with 80k miles, no cats - full Corsa exhaust with long tube headers.

Yes - I think your refering to removing the emission stuff major?

I doubt it.. But I'm willing to pull the upper plenum to see!!

No MAF on the '90

Yea, Thats is what I ment to say - It extended the pentle and closed the air opening.

Yes, I took it off the other night to see if it was stuck or something.. and yes it is "spot tight" (I tightend it until I seen spots )

I did that as well as pulling each and every vacuum line to make sure there was either vacuum present or if anything changed - nothing... everything seemd to be doing what it was supposed to do.

That was my first thought - I checked everything I installed and it all seems to be correct.

Yes it does have the vacuum line your refering to and yes it is still connected to the venting system.

I do have one now (AutoXray 3000) and will be posting the data after this post.

Yes I do have a AFPR and I have had it set to those numbers - I was asked to lower it to see if it would help - it didn't...

It wasn't replaced - just "swapped" from the stock t-body to the BBK t-body (52mm) when I did the "bolt ons"

Just so you know who (or what) your dealing with - I have built many cars and have had a few 9 sec. Mustangs (Supercharged & Twin Turbo) that I built and did the all the work myself. I'm currently sitting behind a desk earning my living, but I still love to play with cars - not big HP cars anymore, just street cars.. I'm not saying I know everything, just that I'm not new to working on cars..

Thanks for the continued support - I figured you guys would give up on me and offer to buy the car so I would quit posting

I'll be back shortly with the results of the scan..

Thanks!

 

Ok -

This is what I got from the scanner -

Prom ID = 5101
Coolant Temp = 116.6 F
Start Up Coolant Temp = 74.7 F
Throttle Sensor = 0.49v
Throttle Angle = 0%
Engine RPM = 801
Vehical Speed = 0 mph
Oxygen Sensor = 44 mv
Cross Counts = 0
Block Learn = 128
Block Cell Learn = 4
Intergrator = 128
Idle Air Mtr Pos. = 160 steps
Desired Idle = 812 rpm
Map Sensor = 1.92v
Manifold Air Temp = 80.6 F
EGR Duty Cycle = 0.0%
CCP Duty Cycle = 0.0%
Battery Voltage = 13.5v
Fuel Pump Sensor = 14.0
Learned Idle Pos. = 40 steps
Oil Temp = 82.8 F
Spark Advance = 29.4
Knock Sensor = 2
Knock Retard = 0
Injector Pulse = 2.8 mS
Engine Run Time = 196 sec.
A/C = Requested
A/C Forced Off = No
Battery Voltage High = No
Shift Light = Off
TCC Status = Not Locked
Park / Neutral = Detected
Fan #1 = On
A/C Clutch = Enabled
Oxegen Sensor = Not Ready (showed both)
Fuel Cut off - Disabled
CCP Purge = Off
Air Divert = Solinoid On (on & off)
Air Switch = Solenoid On (on & off)
Fan #2 = Off
Learn Control = Disabled (both)
Rich Lean Flag = Lean (both)
Loop Status = Open (both)

Several of these values did change while it was running - If you need the spacifics on the value changes, let me know and I will post them as well.

While it was running this time, I held the throttle to the floor to see what would happen - it still ran, but did not rev... It was like it was getting too much fuel.. when I let off, it choked a little and then went back to a rough idle.

Does any of this help?

 

Turn off the AC.

You should be able to do the following with the ignition on and the engine not running with the scanner connected to the ECM.

Press the gas pedal to the floor, does the scanner show 100 percent throttle angle?

What is the voltage of the TPS when the pedal is held to the floor?

When the engine is running and you floor it, what is
the Map sensor voltage?

 

No, 99%

4.07v

4.84v to 4.86v

A/C off -

 

To give you something to do, what is the injector pulse with when you floor it?

What is the timing/spark advance when you floor it?

How old are your Cats?

Does the engine go close loop when it warms up?

 

7.6 to 8.4 - the rpm jumps up and down.

17.8 to 18.2

How warm? @ 192.2 it's still open

 

Should go closed loop when the temp. is around 160F and the O2 sensor has a good cross count.


The TPS voltage is a little low at WOT. Should be around 4.6 volts.

When you posted the results the engine was around 800 rpm and the spark advance was 29?

With your scanner, when the engine is running and you slowly press the gas pedal can you monitor the spark advance and see it slowly change?

And you're saying when it gets to wide open throttle the spark advance was around 17 degrees?

 

What would keep it from going closed?

Should I change it?

The results were when I set the scanner to "monitor" while it was running, I was also writting the values down while in "real time" mode and the idle was jumping from 660 to 750 and the spark advance was 15 to 24 - this scanner is new to me and i'm still learning how to work it...

at idle it's 24.8 as I slowly press on the gas it first drops to around 14 and then climbs to 45.5 before it chokes...

yea, it's spitting and sputtering and popping - it's hard to explain...

Any ideas?

I've bought alot of parts and I'm a little resistant to buy anything else until it's "pin pointed" but I think the distributor is shot - I wish I had another HEI car, I'd swap them just to see what happend....