Just My Luck

[BMWburner]

The transmission repairs went smoothly, but now I have a new challenge at hand. I was going to clean my throttle body, and I pulled my filter assembly off, and crap. The most crap laden throttle plate I’ve ever seen. The throttle plate is actually stuck open a few degrees because there is so much junk in there. (Might explain the 1200 rpm idle.) So I asked myself, “How this could happen?” Well, it seems that the inside clip of the filter housing broke over the past week or two leaving one side of the assembly open about a sixteenth of an inch, the filter still grabbed the big stuff, but dust was free to take a ride through my Northstar. To add insult to injury GM no longer makes the half of the filter housing with the clips on it (apparently they once did) and there isn’t a salvage in a hundred miles with one lying around. I can buy the whole housing for about $150 shipped from GM parts direct, but pretty expensive for some molded plastic ($225 from the dealer). I guess I’m more worried about the engine. How could I let this happen to my baby. Christ, I’ve only had her about a month or so and I’ve already managed to seriously damage the engine. What can I do to undo some of the damage I’ve done. Replace the housing and clean the throttle body, that’s a given. I wondering if that 3M stuff that they spray into your intake under moderate throttle at a jiffy lube would help. I’ve always been under the impression that wasn’t the best for the engine, but neither is dirt.

This really sucks because I replaced the filter like two or three weeks ago and the clips were all fine. I just can’t imagine the filter housing just breaking like that, especially on a Cadillac.

Oh, well...... worse things have happened to me...........I guess.

–Ben

[Ranger]

I don't think you did any damage. Repair that housing one way or the other so as not to bypass the filter element. All the "crap" you are seeing in the TB is not dirt from the outside, but carbon from the EGR & PCV that accumulate after the engine is shut down. At that point there is no induction so that stuff just hangs around in the intake. The TB cools first and the air (along with the exhaust and crankcase gasses condense there first.

You can also bet money on that being the cause of your high idle. Get some carb cleaner, tooth brush and a rag and scrub the TB bore clean, along with the back side and the perimiter of the throttle plate.

[Scotty]

I have the same problem with my air filter housing, exactly and IT IS bothering me, and yes, I have gotten a big number from my local caddy dealer to replace it like $250....OUCH.... That is a great price I will buy one when I get a chance... Those housings become brittle from the heat and crack very much like the HVAC housing

THe first time I cleaned my TB and throttle plate mine was also really really gunked up with black carbon and YES I was idling high to the point where I would get a message on the dash "idle control service" or something like that.... Clean the hell out of it, but make sure you don't get a lot of cleaner down the throat, there is a potenial for hydrolock if you were to pour the cleaner in and it pooled... I have used GM upper engine cleaner Part Number 1050002 and a stiff nylon detail brush, hold the plate open and get the edges good. I bought a TB gasket and will remove the TB assembly the next time it hangs open and causes a high idle. Mike

PS, you didn't do any damage at all!

[Scotty]

By the way, your tranny is doing OK? Give us the details you are being to anti-climatic about it!

[Ranger]

I found that stuffing a rag into the manifold just beyond the TB will soak up most of the carb cleaner that is lileky to pool there. What little remains won't warm anything.

[BMWburner]

So I cleaned the crap out of my throttle body and my N* is running much better. I believe the problem with my idle variation is the actcuator (spelling?) sticking, or just being fickle and moving back and forth for no reason. After I reset the computer the first time the idle actuator wouldn't let the engine drop to dead idle when the torque converter disengaged, so you had to hold the brake down like a sonofabitch at stoplights, and you could cruise at 40 up a hill while getting "70" MPG on the display. However, you could kick down gears with like a quarter of the pedal travel, and while quite fun, was not practicle at all. I went out to the very industrial south side and and did four or five hard runs to 100 mph, to take advantage of the crazy throttle response, and to cure what ailed it. I pulled of in a factory's parking lot to take in the smell of hot Mobil 1 and pulled the negative terminal. I let it sit for ten min. or so before restroring power and it settled down. It varies less at idle like 300-400 RPM, but now feels less powerfull than I'm used to. Additionally, the traction controll wasn't efective at controlling wheel spin and I burnt out HARD when I gunned it out of the parking lot. It didn't even say "TRACTION ACTIVE" on the DIC and I must have burnt 20,000 miles off my brand new tires. (It was pretty cool though.)

We had a huge thunderstorm today so there was no class and I was reading my manual out of boredom and there is a dedicated reset procedure for the computer, make sure the wheels are straight, hold whatever buttons on the DIC and put it in park for X number of min. I assume that's why the wheel spin was not supressed. I'm gonna do one more srub job on the throttle body and do this "reset procedure" and take it from there.

I'm curious if anyone else has had trouble with the actuator.

Oh, and by the way, I got the solenoids replaced, the fluid drained from everywhere and fresh filters for less than 250 bucks parts labor and tax included. My tranny pulls hard and shifts smoother than silk. I owe you guys big time.

--Ben

[Scotty]

VERY glad to year about your tranny! Mike

I am having a hard time figuring out what your current problem is, did the idle calm down?

[growe3]

Not sure if this will help , but...I have typed out the Idle Learn procedure and it is posted at my web storage site. I did this as it was easier than dragging the manual out to go through the procedure.

This was for a 93 or 94 STS, but I think the 95 is the same.

The file is at the bottom of the list.

Idle Learn Procedure

-George

[Scotty]

Thanks George, my 96 doesn't have a formal idle learn procedure it seems to handle it easier, but I recall my 91 had a formal procedure when something on the TB was changed.. Our guru provided MATT with an abbreviated method, I wish I saved it.... Thanks

[Ranger]

Wait a minute guys. Someone correct me if I am wrong but isn't the idle learn proceedure for the 4.9? The Northstar does not use an ISC motor. It uses an ISC valve on the side of the TB that controls idle speed by controling the amount of air that is allowed to bypass the throttle plate. I would pull that ISC valve and see what you can see. Maybe plow out the air passage, cleane the valve and connections. Maybe it needs to be replaced.

[Scotty]

Right you are Ranger! My oversite. You can see I was focused on my 91 however and assumed this as a 4.9, WHY? I don't know.. You know what they say about assume (*smurf* u me)

[Ranger]

Don't worry Scotty. Been there, done that.

[growe3]

Wait a minute guys. Someone correct me if I am wrong but isn't the idle learn proceedure for the 4.9? The Northstar does not use an ISC motor. It uses an ISC valve on the side of the TB that controls idle speed by controling the amount of air that is allowed to bypass the throttle plate. I would pull that ISC valve and see what you can see. Maybe plow out the air passage, cleane the valve and connections. Maybe it needs to be replaced.

The Idle Learn and Throttle Position Sensor Procedure that I made availible, is for the Northstar. I have used it several times on both of my 93 STS's.

It isn't hard just go through the list methodically.

I did it after throttle body cleaning and after replacing the headgaskets.

The Northstar does use an Idle Speed Control motor, at least on the 93 - 94 models, maybe something changed after that.

-George

[Ranger]

Thanks for clarifying that Growe3. Aparrently they changed from ISC motor to ISC valve at some point. I would suspect the idle learn proceedure is for the ISC motor not the ISC valve though.

[BMWburner]

So the idle controll unit, I think is't an actuator (a digitaly controlled stepper motor with worm gear moving a pin) is to blame. I sat and looked at the data for a while while it my STS was at idle and problem one is that the plate is stuck at -1 degrees by default, I was worried when I was opening and closing the plate that the angle might get off, but it might have been off to begin with. Problem two, the actuator is constantly the moving the plate at idle. That's where the variation in idle is comming from. I'm not sure if the actuator is messed up, the controller is messed up, or if the data it's being fed is messed up. Anyone seen one of these go bad? What sensors would feed the idle controll it's data? Where can I get a decent set of ideal values to compare PCM data to? I'm not getting any codes so I'm in the dark. I can't find any parts numbers for the idle controll unit online. Some thing tells me that this could get expensive if I wind up at my mechanics shop, so I'm gonna give this one more try.

--Ben

[growe3]

To idle smoothly, richen the fuel properly for smooth acceleration and cruise, the engine needs to know where the throttle blade is positioned.

One of the problems that you may have is the Throttle Position Sensor may need resetting. I know that you have been cleaning the throttle body opening, so if you are satisfied that it is clean and not binding, the Throttle Position Sensor needs to be reset and then the Idle Relearn Procedure performed.

Before starting, check that the intake manifold bolts (4) are tight, to be sure the manifold is not leaking, do not over tighten bolts. Check that all of the rubber hoses and nylon tubes are plugged in and not leaking. Do a visual inspection first, then with the engine idling place one end of a piece of hose to your ear and move the other end around over all of the hoses and tubes to listen for leaks; fix any problems before proceding.

The procedure that I noted is to first reset the Throttle Position Sensor. Once that is done you need to preform the Throttle Position Sensor/ Idle Relearn procedure.

-George

[Ranger]

Does the ISC motor ratchet when you shut down? I seem to recall that is an indication that it is going bad. I would suspect the same for the hunting while running. Just my $0.02.

[BMWburner]

My STS finally threw a code: Electronic Spark Timing (EST) Signal problem [EGR].

I had gotten this code before so I had my plugs and wires replaced. Coil pack? Or is this an issue in the digital realm. I'm curious what the benifit of a coil pack is over an old school distributor.

Where should I look next?

--Ben

P.S. I'm losing power fast, I have to really hit it down a on ramp, not the typical Cadillac "float". Not to mention getting 14 miles to the gallon.

[KHE]

I'm curious what the benifit of a coil pack is over an old school distributor.

With a coil pack, there are no moving parts to wear out - distributor, rotor, cap, etc.

[Ranger]

My STS finally threw a code: Electronic Spark Timing (EST) Signal problem [EGR].

I had gotten this code before so I had my plugs and wires replaced. Coil pack? Or is this an issue in the digital realm. I'm curious what the benifit of a coil pack is over an old school distributor.

Where should I look next?

--Ben

P.S. I'm losing power fast, I have to really hit it down a on ramp, not the typical Cadillac "float". Not to mention getting 14 miles to the gallon.

Off the top of my head I would say the problem is in the ICM (ignition control module). Anyone agree?

[Scotty]

Electronic Spark Timing (EST) Signal problem [EGR] is this two codes? EGR? What were the code numbers, the code is easier to track with the number

Make sure none of your spark plug wires travel parallel to any injector or for that matter any wires for any distance, cross them at 90 degrees

[growe3]

With the poor fuel mileage mentioned, I would first check the fuel pressure, replace the fuel filter, and then check the FPR.

Remove the intake cover (all of the Torx screws, not the 4 hex head screws), then CAREFULLY (it is plastic and can break if handled roughly) lift the fuel rail off, and position out of the way. Unplug the coil plugs at both ends of the coil pack for safety, if the engine starts with the cover off it will runaway; due to uncontrolled air intake. Turn the key to the on position, and look for seepage from the FPR. Any fuel coming out of the nipple and it needs to be replaced. After replacing the intake cover be sure to plug the coil wire harness’ back in.

Do the fuel injector check using the onboard diagnostics, and note any changes; possible bad injector(s).

Clean the EGR passages, notches at the intake ports, and the runners along the intake face of the head.

Make sure the EGR valve is clean, that it is sealing to the manifold, and able to close properly. This doesn't have a big direct effect on mileage, but can make the engine run rough, as a consequence people tend to hit the gas harder out of frustration and thus can reduce the mileage indirectly.

Then assuming all of the vacuum lines are not leaking (and are correctly hooked up), my attention would be toward the PCM.

Do not forget the make sure that the battery cables are clean to bright metal and tight. Poor connections there will cause many intermittent problems.

-George

[BMWburner]

I'm getting the following codes:

P023 Electronic Spark Timing (EST) Signal problem [EGR]

and

P038 Open MAT Sensor Signal

What the hell is a MAT sensor? I've never heard of that before. Additionally, once the fuel rail was mentioned, I started thinking about the recall. My fuel rail has yet to be replaced with the cool stainless steel one. I was given the notice when I recieved the car and I mailed it in to GM to show that I was the current owner of the vehicle, but I've yet to hear back. Could this problem be related considering the high mileage? I'd hate to spend any time or money on a problem the dealer is obligated to fix. I might call the dealer about having the replacement done. I should just clear the codes if I can get it in soon and hope they just fix it.

--Ben

[Scotty]

The MAT is the Manifold Air Temperature Sensor. There is a connector that attaches to it that could be disconnected if you have an open, or the sensor is bad (open). I am looking at a 1991 Manual, so I can not give you details as to where it is on your 1995

The following picture shows how an E023 is set (also from a 91 manual). As Ranger stated the final item on the diagnostic tree is Replace Ignition Module. Mine was replaced before I bought my car.

[WarrenJ]

I am looking at a 1991 Manual, so I can not give you details as to where it is on your 1995.

But I might be able to help. You see, there is no MAT on a 1995 vehicle. Forgive me for being playful, but '95 vehicles used an IAT (Intake Air Temperature sensor). I have a 1995 FSM and would be pleased to provide any details you might find helpful.

Here is a 50KB photo of text from the FSM that describes the IAT and mentions it is "mounted in the air intake duct":

http://i7.photobucket.com/albums/y299/WBucket/IATSensor.jpg

Here is A THROTTLE BODY PHOTO that also contains text. It notes that the "throttle switch" as opposed to the TPS we are discussing is not servicable. The 144KB photo can be found here:

http://i7.photobucket.com/albums/y299/WBuc...ISCActuator.jpg

A text blurb (111KB) related to the Throttle Position Sensor is here:

http://i7.photobucket.com/albums/y299/WBuc...PSensorText.jpg

It seems to suggest that the PCM will "learn" all by its lonesome.

Regards,

Warren

P.S. I wish, like Scotty, I could scan rather than photograph these uploads, but I haven't found a way to do it without breaking the spine of the book. Maybe one day Scotty will give up the secret.