TPS and ICM Question

[BodybyFisher]

Take the MAF off, the cable should not seem to have pressure on it, it should have a little play, the throttle plate should be closed.  

You are doing great.  Have patience.

[jndnaps]

1 minute ago, BodybyFisher said:

Take the MAF off, the cable should not seem to have pressure on it, it should have a little play, the throttle plate should be closed.  

You are doing great.  Have patience.

With the car running, or off? I've already checked a few times with it off and it's closed. 

[BodybyFisher]

With the engine off.  

Now that all P codes are gone, we can consider other issues

I am pretty confident that if this were a vacuum leak that would cause a 3,300 rpm idle, you would have lean codes.   @Logan do you agree with this?  Have you seen high idle conditions caused by a vacuum leak that didn't cause a lean code?

I have no question seen gunk, hold the throttle plate open and have an idle so high it was hard to hold back and dangerous.  Typically when that happened, I would QUICKLY, VERY QUICKLY  in neutral stomp the accelerator pedal to the floor and release it quickly to get it to seat and slow down.  My 96, would occasionally hang open from gunk on the throttle plate and have a high idle.  The first time it happened I got a P1525 Throttle Body Service Required code

With no P codes, that precludes electrical connections not connected to say your IAC.  

I dont necessarily believe the mechanic with his smoke test because if he did uncover a vacuum leak where is the lean code?

Check if the throttle linkage is on the stop and the cruise control cable is free and loose.  Take the cables off if you have to and move the TB by hand to see if its binding or hanging.

Patience, you are doing good.  If you want to call it a day, that's fine.  Let me know what you find.  

Where are you florida?

[rockfangd]

Sorry for the delay with my posts. Work too much. 

Great to hear you found the 1634 problem. I hope you closely inspected the rest of those wires in that plug. As soon as I saw the 0 on that pin that nailed it. 

You are doing very well. We will get this. 

Long shot I know but it bears to mention that vacuum leaks do not always cause a lean code.

That issue you resolved could cause all kinds of goofy issues. 

I highly suggest that you go over every vacuum hose, electrical connector, and bolt or nut that was touched throughout the process.

If you had a high idle problem that was IAC related it should throw a code also. Be patient as you are making progress

[BodybyFisher]

That is good to know @rockfangd I am sitting in bed with the 96 FSM now.  

@jndnaps check the pcv hose for cracks, the PVC for free movement.  The MAP has a vacuum connection to the intake check it

Check the brake booster 90° plastic adapter and hose for brakes. 

This symptom happened before you took the TB off and you replaced the oring and seal correct.

I still want you to check the anti-backfire valve in the intake

The attached photo, is out of the FSM.  It is a list of places that vacuum leaks occur some of which I mentioned above.

[jndnaps]

6 hours ago, BodybyFisher said:

With the engine off.  

Now that all P codes are gone, we can consider other issues

I am pretty confident that if this were a vacuum leak that would cause a 3,300 rpm idle, you would have lean codes.   @Logan do you agree with this?  Have you seen high idle conditions caused by a vacuum leak that didn't cause a lean code?

I have no question seen gunk, hold the throttle plate open and have an idle so high it was hard to hold back and dangerous.  Typically when that happened, I would QUICKLY, VERY QUICKLY  in neutral stomp the accelerator pedal to the floor and release it quickly to get it to seat and slow down.  My 96, would occasionally hang open from gunk on the throttle plate and have a high idle.  The first time it happened I got a P1525 Throttle Body Service Required code

With no P codes, that precludes electrical connections not connected to say your IAC.  

I dont necessarily believe the mechanic with his smoke test because if he did uncover a vacuum leak where is the lean code?

Check if the throttle linkage is on the stop and the cruise control cable is free and loose.  Take the cables off if you have to and move the TB by hand to see if its binding or hanging.

Patience, you are doing good.  If you want to call it a day, that's fine.  Let me know what you find.  

Where are you florida?

I've checked it a few times and it's always closed.

After cleaning the TB and the plate/butterfly, that thing was spotless. It looked brand new. I used TB cleaner and a toothbrush. I've also done what you did, put the car in neutral and mashed the gas and that did nothing. In fact, if anything it made it go higher. 

Not sure about how to do that. It seems to be at the stop, but I'll re check. Don't know how to remove the cables. I'll check and see if there are any videos.

Yes, I'm in very hot and sunny Florida.  

 

3 hours ago, rockfangd said:

Sorry for the delay with my posts. Work too much. 

Great to hear you found the 1634 problem. I hope you closely inspected the rest of those wires in that plug. As soon as I saw the 0 on that pin that nailed it. 

You are doing very well. We will get this. 

Long shot I know but it bears to mention that vacuum leaks do not always cause a lean code.

That issue you resolved could cause all kinds of goofy issues. 

I highly suggest that you go over every vacuum hose, electrical connector, and bolt or nut that was touched throughout the process.

If you had a high idle problem that was IAC related it should throw a code also. Be patient as you are making progress

Yes, there is one other wire, a pink one, that is a little scraped up. Will fix that one too. I've gone over a lot of stuff, but will do it again. 
 

2 hours ago, BodybyFisher said:

That is good to know @rockfangd I am sitting in bed with the 96 FSM now.  

@jndnaps check the pcv hose for cracks, the PVC for free movement.  The MAP has a vacuum connection to the intake check it

Check the brake booster 90° plastic adapter and hose for brakes. 

This symptom happened before you took the TB off and you replaced the oring and seal correct.

I still want you to check the anti-backfire valve in the intake

The attached photo, is out of the FSM.  It is a list of places that vacuum leaks occur some of which I mentioned above.

PVC is good and those hoses were replaced by the first shop that looked at it. I'll check the MAP. I checked the brake booster 90° plastic adapter and hose and even sprayed them with starting fluid. No real change of the idle. I can't get my fingers in there to check the anti backfire valve. But, I did spray it down with starting fluid and there was no difference in the idle. I did spray the starting fluid between the brake booster and the TB and I did notice the idle get higher in that area. Closer to the TB.  I ran out of starting fluid though. I was thinking of removing the TB again and this time remove the spacer and replace that O Ring. I didn't take the spacer off the first time. Also, that's the one area where the smoke was coming out when they did the smoke test. 

[BodybyFisher]

Yes definately pursue that.  I found a nice illustration of the area.

[Logan]

The high idle issue is likely related to the the TBI being removed. Maybe wrong gaskets. ....Personally I use brake cleaner or carb cleaner to find vacuum leaks....IMO starting fluid is a little too dicey for spraying around. 

Some codes will not set if other codes are present. 

Its possible there are additional chewed wires. Or maybe a broken coil return spring on the throttle body shaft.

Being a '96....the car will be using a IAC speed motor. Lacking a scan tool....There is a Kent Moore tool used to diagnose idle speed problems.  J-37027-A.

With the tool...you unplug the IAC....the tool works as a IAC driver. You can cycle the IAC open and closed independent of the PCM.....very easy to change engine speed with the tool.  So if the IAC is cycled all the way closed (low)....and there is still high idle speed....there is a vacuum leak. 

There is also a noid light that plugs into the vehicle side harness. The noid LEDs will blink green and red all the time to verify the PCM IAC drivers are ok and are trying to control idle speed. 

The tool comes with 2 noid lights depending on which type of IAC you have....the square 4 plug version or the flat plug in version. 

Most of the time I use the tool to pulse the IAC apart to clean the shaft. 

 

[BodybyFisher]

Very interesting tool @Logan thanks for sharing that.  Very interesting way to locate a vacuum leak.  I gotta get one of those!  

I hadn't realized the vacuum leak could be undetected as a lean condition when the idle was so severe.  It is great to know that.  

[BodybyFisher]

By the way, the FSM refers to a section 6C (Fuel), my 2 manual set does not include 6C, am I missing a volume?, is it something I can acquire?  

I often see references to 6C it would be nice to have it, I'll bet it is informational also, thx

[Logan]

Looking at my '93 Helm manual.....there is a 61 page section 6C. Fuel and air control system. 

Even more 6C info in the '94 Helm manual....60 pages for Northstar....63 pages for 4.9L.

Both are 2 volume sets.....section 6C is in the middle of each 'volume 1 powertrain' manual. 

[BodybyFisher]

39 minutes ago, Logan said:

Looking at my '93 Helm manual.....there is a 61 page section 6C. Fuel and air control system. 

Even more 6C info in the '94 Helm manual....60 pages for Northstar....63 pages for 4.9L.

Both are 2 volume sets.....section 6C is in the middle of each 'volume 1 powertrain' manual. 

That is interesting my 96 manual goes from 6B to 6D, no 6C, but my 94 manual does have 6C.  Great to know that I have a 94, 6C OBD1, I need to get a 96 6C OBD2.  Thanks it is good to know that it exists.  

[jndnaps]

13 hours ago, Logan said:

The high idle issue is likely related to the the TBI being removed. Maybe wrong gaskets. ....Personally I use brake cleaner or carb cleaner to find vacuum leaks....IMO starting fluid is a little too dicey for spraying around. 

Some codes will not set if other codes are present. 

Its possible there are additional chewed wires. Or maybe a broken coil return spring on the throttle body shaft.

Being a '96....the car will be using a IAC speed motor. Lacking a scan tool....There is a Kent Moore tool used to diagnose idle speed problems.  J-37027-A.

With the tool...you unplug the IAC....the tool works as a IAC driver. You can cycle the IAC open and closed independent of the PCM.....very easy to change engine speed with the tool.  So if the IAC is cycled all the way closed (low)....and there is still high idle speed....there is a vacuum leak. 

There is also a noid light that plugs into the vehicle side harness. The noid LEDs will blink green and red all the time to verify the PCM IAC drivers are ok and are trying to control idle speed. 

The tool comes with 2 noid lights depending on which type of IAC you have....the square 4 plug version or the flat plug in version. 

Most of the time I use the tool to pulse the IAC apart to clean the shaft. 

 

No sir, the high idle has been there for months. Before and after removing the TB for cleaning. Gasket is also correct and put on correct. I made sure to be extra careful with the gasket when Rock mentioned he installed one of his the wrong way. Took pics and compared the new one to the original that I removed in two pieces.  I probably should have removed the spacer and replaced the O Ring though. I'm gonna get a new can of brake cleaner and spray around the spacer again before I go back and remove the TB one more time. 

I'll go back and check more of the wiring and I'll check that return spring. I also changed the IAC and the TPS. Doesn't mean one or both are still bad. Wouldn't be the first time I got a new part that was bad. Also need to check if they're getting power. Probably need someone to tell me how to do that, too. LOL.. Let me ask you, you're saying an "IAC speed motor." is that the same as the "Idle Air Control Valve"? or is that another part? 

Thanks for the info! 

[Logan]

They are the same thing. The IAC is just a computer controlled vacuum leak. There are several different ones used over the years.  The rest of GM has been using these since the mid 80s. Only Cadillac was using the throttle control motor one. When OBDII came along Cadillac finally started using IACs.

Has the intake ever been off? 

Could be cracked or leaking intake or intake gasket. Or leaking blow off relief valve. 

Bad gasket on either side of the "crossover" part.

Leaking fuel injector O ring. 

Broken return spring on throttle body shaft or sticking cable. 

 

*The leak can be on the underside the intake....which you could never find by spraying around up top. 

Spraying around.....keep the spray liquid rather than vapor. If you find the leak the high idle will drop momentarily when you hit it with the brake/carb cleaner. ....and you should be able to repeat it every time you hit the leak. 

As mentioned.....starting fluid is a little too wild for finding intake leaks. I think you will have better luck with brake or carb cleaner. 

[BodybyFisher]

@jndnaps. I liked your reply above, it was spot on, I almost tried to reply to Logan as you did, but you did a terrific job better than I could have done.  

I want you to remove the TB, look closely for cracks, remove the spacer, inspect the o-ring and look for cracks, observe the tightness of the spacer screws when you remove them.  

Check to be sure the throttle plate closes fully, take notice before you remove it.  Does it close and sit on its linkage stop, does the cable bind, check cruise control cable.  

When the TB is off, remove the IAC be sure there is an oring.  

Look for cracks on the intake where the spacer screws attach.  

Remember, the oring must be replaced, so have one on hand, when you remove it, it will expand and not go back in.

[rockfangd]

If this continues after you get it back together you need to get a scantool hooked up to see what the IAC counts are. If IAC counts are 0 and  the idle is high there is for sure a vacuum leak. If IAC counts are high and the idle is high then likely the IAC is at fault.

Was the IAC replaced? If it was was it the correct one?

[BodybyFisher]

After you pull the intake, and replace the seals and check for cracks ??

[BodybyFisher]

29 minutes ago, rockfangd said:

If this continues after you get it back together you need to get a scantool hooked up to see what the IAC counts are. If IAC counts are 0 and  the idle is high there is for sure a vacuum leak. If IAC counts are high and the idle is high then likely the IAC is at fault.

Was the IAC replaced? If it was was it the correct one?

This may be possible (commanded IAC) through the dash with the real time read outs I'll look into the commands

[Logan]

Most GM products....but not all older OBDI ones.... you can override the IAC using a GM Tech 1 or GM Tech 2. 

It has to be a bidirectional scan tool with the ability to turn stuff on/off to command the IAC. 

After OBDII......about '97..'98....pretty much everything had IAC control thru a GM Tech 1 or 2 for leak testing. 

Older cars without the scan tool ability to control...or if you have no bidirectional scan tool....you used the above Kent Moore tool. 

 

[BodybyFisher]

19 minutes ago, Logan said:

Most GM products....but not all older OBDI ones.... you can override the IAC using a GM Tech 1 or GM Tech 2. 

It has to be a bidirectional scan tool with the ability to turn stuff on/off to command the IAC. 

After OBDII......about '97..'98....pretty much everything had IAC control thru a GM Tech 1 or 2 for leak testing. 

Older cars without the scan tool ability to control...or if you have no bidirectional scan tool....you used the above Kent Moore tool. 

 

@Logan I believe the 96 has the ability to display, real time parameters, does that sound right, I think I could do it on my 96

[Logan]

Don't know...."94-97 were kind of bastard years....as GM migrated to OBDII.....Cadillacs lost a lot of the hidden features available thru the IPC. It was more of a question of is this GM vehicle OBDI or II?...a few GM vehicles had OBDII  in '94-95.....What adapter do I need.....Do I need to use a VIM module.....etc.

For me....it was never a question about using the IPC diagnostics...It was always "Am I going to use the Tech 1 or the Tech 2?"

I always used a scan tool. A lot faster to do.

1998 and on.....it was very clear you were working on OBDII.

[jndnaps]

19 hours ago, Logan said:

They are the same thing. The IAC is just a computer controlled vacuum leak. There are several different ones used over the years.  The rest of GM has been using these since the mid 80s. Only Cadillac was using the throttle control motor one. When OBDII came along Cadillac finally started using IACs.

Has the intake ever been off? 

Could be cracked or leaking intake or intake gasket. Or leaking blow off relief valve. 

Bad gasket on either side of the "crossover" part.

Leaking fuel injector O ring. 

Broken return spring on throttle body shaft or sticking cable. 

 

*The leak can be on the underside the intake....which you could never find by spraying around up top. 

Spraying around.....keep the spray liquid rather than vapor. If you find the leak the high idle will drop momentarily when you hit it with the brake/carb cleaner. ....and you should be able to repeat it every time you hit the leak. 

As mentioned.....starting fluid is a little too wild for finding intake leaks. I think you will have better luck with brake or carb cleaner. 

The IAC on the right in the pic looks like the one it has. 

I've had the car for 13 years and the intake has never been off. I put about 45K miles on the 133K total miles on it. First time the TB has been taken off in those 13 years. 

I had the car at a local shop and a smoke test showed smoke coming out both sides of the intake. Shop thinks the intake is cracked, but won't know for sure till they remove it. 

12 hours ago, BodybyFisher said:

@jndnaps. I liked your reply above, it was spot on, I almost tried to reply to Logan as you did, but you did a terrific job better than I could have done.  

I want you to remove the TB, look closely for cracks, remove the spacer, inspect the o-ring and look for cracks, observe the tightness of the spacer screws when you remove them.  

Check to be sure the throttle plate closes fully, take notice before you remove it.  Does it close and sit on its linkage stop, does the cable bind, check cruise control cable.  

When the TB is off, remove the IAC be sure there is an oring.  

Look for cracks on the intake where the spacer screws attach.  

Remember, the oring must be replaced, so have one on hand, when you remove it, it will expand and not go back in.

OK.. Now the one thing I didn't do was torque the bolts down. I don't have a torque wrench. But, they're on good and tight. 

7 hours ago, rockfangd said:

If this continues after you get it back together you need to get a scantool hooked up to see what the IAC counts are. If IAC counts are 0 and  the idle is high there is for sure a vacuum leak. If IAC counts are high and the idle is high then likely the IAC is at fault.

Was the IAC replaced? If it was was it the correct one?

I don't have access to a scan tool. 

Yes, replaced the IAC with correct one and with the o ring. 

[BodybyFisher]

@jndnaps  you said above you didnt torque the bolts down, I assume you mean the throttle body bolts?  I am speaking about the 4 bolts attaching the spacer to the intake, where the oring is located.   Does that make sense?

[jndnaps]

6 minutes ago, BodybyFisher said:

@jndnaps  you said above you didnt torque the bolts down, I assume you mean the throttle body bolts?  I am speaking about the 4 bolts attaching the spacer to the intake, where the oring is located.   Does that make sense?

Yes, the ones for the TB.. 

[BodybyFisher]

I am less concerned with that, then I am about the 4 bolts connecting the spacer to the intake, and the oring.

If we assume that the smoke test was legitimate, do you have the video, can you post it? 

I know you are doing a lot of work, it may make sense to pull the intake altogether with the TB installed, throw it on a table and inspect and work on it there, replace the oring, intake seals, look for cracks, etc. 

Let me know, Ill write a procedure and pull the procedure from the FSM