My Rough Idle Story, So Far...

[WoodShoe]

didnt mean to throw you off track with my post. I have a 2000 deville motor in my STS, I figured it was the same as yours...

[submariner409]

WoodShoe, Please post a digital pic or two of your engine, taken from front center and driver's side. A 2000 and up Northstar does not have spark plug wires or a 4-coil pack on top of the rear cam cover.

Something is inconsistent with you replacing spark plug wires.

If your car is a 97 and you installed a 2000 running takeout, how did you rewire the ignition system connectors and sensors?

[SuperC]

So here we are...

Cleared codes last night, Cleaned TB, and ran it in the AM. No codes on normal operation with the exception of B0429 Current. With WOT I get the flashing SES that goes away, but no codes upon dx. I had to try again. I set the car up in diagnostic mode while driving and gave it WOT to get the blinking SES. Ran the diagnostic while driving and got P0300 = misfire. After SES is gone, while still on the highway, run the dx again and PCM will say "No Codes"

What's next?

-C

[submariner409]

Remove the engine beauty cover, start the car, and pull the vacuum connector off the top of the Fuel Pressure Regulator (FPR) on the right rear of the fuel injector rail.......the little round thing with a vacuum nipple on top, held together by a hairpin clip. Dry as a bone in there or gas/wet ? (Should be dry, wet indicates ruptured control diaphragm). Simple plug&play fix.

While you're in there, check all the vacuum lines again. Do you have a stethoscope? Listen to each fuel injector barrel for a nice, even tick, tick, tick at idle.

Go to a West Marine or big parts house and buy a 20 oz. jug of Chevron TECHRON, dump it and a load of 93 in the car.

[SuperC]

Yep gotta stethoscope... As strange as it may sound, I have one in my backpack. I'm gonna try your suggestions and I will let you know in a bit.

-C

[SuperC]

My report back: Some good, some bad.
1. Checked the FPR, dry as a bone

2. Listened to each fuel injector, and I heard clicks on each one, however I found that difficult to do. It was hard to get the chestpiece directly on the injector. I got the best results by placing the diaphragm on the wire harness of each one. I also listened around to hear what the other parts of the car sound like so I could discern from normal engine noise and the clicks

3. I cleaned the TB one more time, this time I grabbed a tooth brush and really got in there, she is nice and shiney!

4. Last, but not least... Double checked the plenum, box, ect hose clamps. I did find that the plenum clamp was not loose, but was not that tight, I got about 3 turns out of it.

What was the result you ask...
The Good: I ran it about 2 miles in traffic, stopped to get a bite to eat, let it run and it seems to run pretty darn good, I didn't have a ton of time to run it, so I don't want to say it's fixed, but so far, so good!

The Bad: Got it up on JTB (a highway) and punched it. At about 60 and WOT, bam! Blinking SES and this time is switched to constant SES, and upon Dx got the now, infamous, P0300, damn.

Lastly: Attached is a REALLY bad photo of the engine, but it will serve its purpose. I swear I hear a sucking sound in the back left hand corner (circled in red) of the motor. Now, where you guys are going to get frustrated with me. When I replaced the plenum, I did not replace the o-rings on the intake manifold. Unless there is something else back there which is a more likely culprit, I suspect I need to go back and replace those.

Your thoughts, if you please,
-C

[Ranger]

It was hard to get the chestpiece directly on the injector.

Remove the chest piece and replace it with a 6"-12" piece of copper tubing. I added a little rubber tip to mine, then put a hole in the center.

I swear I hear a sucking sound in the back left hand corner (circled in red) of the motor.

After making the aforementioned modification, probe around with the stethoscope and you'll find it.

[submariner409]

You're gonna hate me !!

In your circle there are two vacuum leak sources!: 1. The suction line for the PCV system, attached to a nipple in the recess in the manifold. 2. The overpressure (blowoff) relief valve in the center end of the intake manifold. Common vacuum leak. Remove the manifold again and remove/clean/install the flapper/spring loaded valve (2 designs). Install new gaskets.

[SuperC]

Ranger: I'll have to buy a new, cheap, stethoscope and follow your instructions!

SubM: Okay, think I have a grasp on what you want me to do. In most cases I can kinda figure things out. I'll have to order the gaskets from rock and while I am ordering is there anything else I should get, while I am at it? While doing the work is there anything I should keep an eye out for?

I am in the middle of studying for my dental boards right now, so... I will order the parts and this, as much as I don't want it to, is going to have to go on the back burner until next Thursday. After which, I will be back in Gainesville and I will have some time to replace/clean the items you mentioned.

Thanks,
-C

[Ranger]

Use a long slim tool and reach into the front of the manifold where the over pressurization valve is and push on it. that will push the valve (flapper) tighter. If that seals it and the noise goes away, you'll know that is where your problem is. You could also use a length of hose as a makeshift stethoscope.

[SuperC]

Okay guys, my fears were realized and the rough idle is back.

1. I pulled the manifold.
2. Cleaned the spring release valve system, it was pretty darn clean to start, but cleaned it nevertheless.
3. Ordered the FRONT coil because the problem started with a misfire on #3
4. Ordered new gaskets for the manifold

Everything should be here tomorrow morning.

A couple of notes:

1. On the passenger side of the manifold there is a small rubber tube like structure with a flange that was broken. I have no idea what this is, I am going to the dealership in the AM to see if they have one

2. I could have sworn that I saw metal "crumbles" in each of the valve areas. However, I picked a few out and the appeared just to be carbon deposits. It's pretty messy in there, but I am reluctant to attempt to clean in there seeing that I really have no idea what I am doing.

4. There was a small pooling of oil in the #2 and #8 valve area. My oil is a little high, I goofed a couple of days ago, I am going to change the oil tomorrow hopefully this will sold the problem.

3. I did not know how to clean in the recess where the PCV hose runs in the the manifold. I don't want to force the hose out, or spray anything in there with out knowing what I am doing. What should I do here?

I will say it a thousand more times, but THANK YOU SOOOOO much for all of you help!!!!!

Lastly, I passed my boards!!! So putting the caddy on hold for a bit worked out. I still have 2 (of 4) years 'till I am a dentist, but if you guys need tooth brushes, I am your man, that's the least I can do!!

Thanks again,
-C

[SuperC]

Went to the dealership, the parts guy didn't seem to know the deville too well, but we found the part... See #567 in the diagram. They did not have it, but it is on its way.



Now, where does this part go??? I am going to ask to take a look at a deville to see where in the heck it goes. The good news is that is EXACTLY where I heard the sucking noise, the bad news is this hose was completely missing!!! I have scoured the engine compartment and there is no sign of it. The broken parts do not look as if there was a hose connected to it. What gives?

-C

[SuperC]

Sorry I should have been more specific. I know that it connects to the manifold, but where does the other end of the hose connect?
-C

[Ranger]

The other end should go into the cam cover. I believe that is the "dirty air" PCV line.

[submariner409]

SuperC........506, 7, and 8 are the dirty air PCV system. Are they in fact installed on your car ?? 567 looks like some sort of metered or check valved vacuum source for something on the lower right bank of the engine. (See 568 ? That's a metered vacuum delay device, and 570 connects it to a constantly varying manifold vacuum.)

When the part comes in the plastic pack will have a device name and GM p/n on it.

Can't find the connector/pipe in my 2002 Alldata, but the thing may be a hookup for the evaporative canister purge system.