: My Rough Idle Story, So Far...



SuperC
07-06-08, 11:54 PM
So I bought my 2000 base deville a couple of months ago and of course, right after I bought it, she developed the infamous rough idle.

After finding, and reading this forum, I decided to replace the plenum. Which, by the way, was a little intense for me. The first and last time I worked on an engine was shop class in high school 10 years ago. Nevertheless, I got that done and starter fluid detection yielded no leaks post installation.

Retrospectively, perhaps I was a little too hasty on the plenum replacement, I had a SES light blink while playing with someone in a mustang on 75. It went away and came back for a few hours and is now gone again. I did, however, have the codes pulled and I have a misfire on cylinder 3.

I am currently out of town and away from the everything I need to do a spark plug replacement. So, it looks like its gonna run me $300ish to have them changed. Which doesn't make me too mad, especially considering that you guys have said it is a PITA.

So, am I headed in the right direction here? Is there anything else I can do BEFORE I have this done? If this does not solve the problem, how can I trouble shoot other possibilities causing the rough idle, is there a way two determine whether or not the coil pack is functioning correctly?

By the way... 2000 Base, with 80K. The car was owned by an old lady, which she serviced regularly. However, I called the dealership and they said it was difficult to see what service has been done. Are they feeding me BS?
-C

Ranger
07-07-08, 12:25 AM
I called the dealership and they said it was difficult to see what service has been done. Are they feeding me BS?
Any service performed by a GM deal will be available to them. Any service performed by anyone else will not.

WoodShoe
07-07-08, 12:41 AM
youre paying someone 2 change your spark plugs? its not that much of a pain. you can do it in 30 min. Take off the coilpack if youre really annoyed with the clearance back there. other than that there is no problems. and i seriously doubt your coils have gone bad. i bet its the wires.

SuperC
07-07-08, 12:51 AM
Any service performed by a GM deal will be available to them. Any service performed by anyone else will not.

All work was done a the dealership, the car came from a family member. I guess the guy at the dealership was just being lazy... I'll call'em back and give'em hell this time, thanks for the input.
-C

SuperC
07-07-08, 12:59 AM
youre paying someone 2 change your spark plugs? its not that much of a pain. you can do it in 30 min. Take off the coilpack if youre really annoyed with the clearance back there. other than that there is no problems. and i seriously doubt your coils have gone bad. i bet its the wires.

Pain or not, I am in Jacksonville for two weeks (home base is gainesville) so unfortunately, I am gonna have to suck it up not to mention the rough idle has nearly driven me to drink.

That being said, since there are no spark plug wires, what exactly am I looking for in terms of "wires"? When I replaced the plenum, I pulled the fuel rails and also unplugged 8 wires. I am assuming this is what you are referring to. If so, out side of frayed wires, how can I determine if the wires are bad?

Forgive me for being ignorant, I am at the very beginning of a long learning process.

Thanks for your help!
-C

Crown Vic Owner
07-07-08, 03:45 AM
Stupid idea, DONT do this unless someone else OKs it, but could a piece of carbon nailed a plug?


WOT cleanup?

Submariner409
07-07-08, 11:09 AM
WoodShoe doesn't realize that 2000+ Northstars have coil-on-plug ignition and do not use plug wires...the wires you unsnapped are individual injector trigger wires from the PCM. The 8 ignition coils are triggered by wiring to each coil cassette ICM in one end.

If you need to get the dealer in JAX to change the plugs, go for it.......it can be a bear without a hoist and tools.

Make sure that your air intake ducting from the filter box to the throttlebody is correctly oriented and the clamps are tight. An air leak between the MAF and throttlebody can show up as a low-speed miss or stumble.

SuperC
07-07-08, 06:22 PM
Alright... Bad news...
Spark plugs and what they referred to as "boots/wires" were replaced. She feels better, no hesitation on WOT, but there is still definitely still a rough idle. I am going to run it tonight with a little more WOT on the highway and double check my connections around the MAF.

Recap of what has been done:
1. New plenum/boot
2. New spark plugs/boots
3. Cleaned MAF with spray MAF cleaner

So correct my thinking on (if need be) on the next steps:
1. There was a misfire on #3, I am going to have autozone clear the codes just to make sure something else does not pop up.
2. Replace the fuel filter
3. Replace Rear coil pack (seeing that it is a misfire on three)

Do you guys think this is the correct order, or should I go straight for the coils?

Does anyone know what the part number is for the rear coil pack? is it ACD589 or ACD590 from Race Pages (http://www.racepages.com/products/?D=cadillac+ignition+coil&Ntt=cadillac+ignition+coil&Dx=mode+matchallpartial&Ntk=Main&Ntx=mode+matchallpartial&N=9836+4294967029&Nty=1)

Thanks,
-C

Submariner409
07-07-08, 06:36 PM
There was no need to clean the MAF. Leave it alone. Do some snooping around in Northstar Perf. and read up on throttlebody (TB) cleaning. An hour job, toothbrush, rags, Throttlebody cleaner, (NOT carb cleaner !!). DO NOT shoot cleaner into a wide open TB. Block the gas pedal fully to the floor and stuff a lint free rag past the butterfly to absorb excess cleaner which would otherwise pool in the manifold and possibly hydrolock a cylinder. Cheap insurance. Scrub away, dry it all, and pull the rag with a hook or long needlenose. Check every one of the plastic/rubber vacuum and supply lines to/from the TB and PCV connectors.

read the stickys at the top of these forums...you can pull, read, clear, store codes right in the driver's seat in the driveway......no need for scanners or shops.......it's all built in.

SuperC
07-07-08, 07:14 PM
Thanks SubM!

I Used the diagnostic, however I accidentally cleared all the codes before I had a chance to write them down.

What I did get was PCM codes
P0300 History
P1189 History
P1617 History

As you know, misfire and oil level sensors, the oil was low a day or two ago and I topped it off.

I am going to run the car to the specs on the GM driving cycle sometime tonight. I will also clean the TB, following your guidelines in the morning and I will post the outcome(s) tomorrow.

-C

tateos
07-07-08, 07:20 PM
What about crankshaft position sensors? They are a known problem on these 2000s.

Also, what about a bad fuel injector - that would cause a misfire.

Ranger
07-07-08, 09:38 PM
Forget the fuel filter. If it where dirty enough to cause a misfire at idle, it would fall flat on it's face when you attempted WOT.

SuperC
07-07-08, 11:10 PM
Some other things I forgot to mention which may/may not help you guys, help me, that is.

Prior to plenum replacement, had blinking SES after WOT, which would go away shortly thereafter. I am assuming that was the misfire in the history.

After plenum replacement and a little WOT, had a blinking SES and then steady SES until I got to Jax (about a 1.5hr drive). After she rested, SES went away. I have also noticed that the rough idle is worse when the A/C is on.

No SES since plug change today, but I have not had a chance to really run her yet.


As for the rest if the ideas, thanks! Keep'em comming
-C

Ranger
07-08-08, 12:02 AM
A blinking SES light means "Severe Misfire Detected".

SuperC
07-08-08, 05:28 AM
:confused:

After I got done studying, I took her out and ran her, per GM driving instructions from the Cadillac Dx Page.

1/2. Cold Start w/ AC and rear defrost = Rough idle which held pretty steady at about 800RPM
3/4. Acceleration 1/2 throttle and hold at 55mph = nothing to report, maybe some intermittent hesitation while accelerating.... maybe... too hard to tell
5. Deceleration = normal
6/7. Acceleration 3/4 throttle and hold at 55mph = about the same as part 3/4
8. Deceleration = normal

After which I gave it a GOOD WOT about 10-70mph, and noticed some fluctuant hesitation on acceleration and got the blinking SES (again) that went away after about 30s of 55mph. Got home and pulled codes and only got, IPM B0429 Current, which has absolutely NOTHING to do with my problem.

In the AM I will clean the TB, clear the codes again, and run it again and report back.

-C

WoodShoe
07-08-08, 10:13 AM
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
07-08-08, 10:59 AM
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
07-08-08, 12:57 PM
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
07-08-08, 06:13 PM
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
07-08-08, 07:32 PM
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
07-08-08, 09:52 PM
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

http://farm4.static.flickr.com/3281/2650705059_2a4712ffb1.jpg?v=0

Ranger
07-08-08, 10:02 PM
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
07-08-08, 10:07 PM
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
07-08-08, 10:31 PM
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
07-08-08, 11:30 PM
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
07-29-08, 04:18 AM
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
07-29-08, 12:28 PM
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.

http://farm4.static.flickr.com/3098/2714166782_dcfaa9e91a_b.jpg

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
07-29-08, 02:36 PM
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
07-29-08, 09:52 PM
The other end should go into the cam cover. I believe that is the "dirty air" PCV line.

Submariner409
07-29-08, 10:17 PM
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.

Ranger
07-29-08, 10:47 PM
I missed that. Thanks again Sub. Having the check valve in it make me wonder if that is not for the vacuum reservoir.

SuperC
07-30-08, 11:56 PM
You guys were right, the part that I bought did go on the 2000 N*! I took the part anyway and used it to cap off the nipple that was covered by the broken piece. New gaskets and coil and she runs like a champion!!! No hesitation, no SES no rough idle!!!!!!

FYI: I had two mechanics look at the part that was broken in a deville that was in the dealership and neither knew what it was or what it did.

I am not to sure how to test the coil. I did read the resistance between coils and got 10.5k ohms on both the new and the old coil. I am going to put the old one back in, just to see if it is the issue. If I can return it to Advance, it saves me $175.

Thank you guys again!!! I could have never done this without ya'll. This is SUCH a great resource.

Thanks,
-C

stngh8r
08-05-08, 03:07 PM
especially considering that you guys have said it is a PITA.
-C


Really? :confused: I thought it was the easiest V8 plug change I've ever done.

07srt8
08-20-08, 05:42 PM
SuperC

Was it the coil or the gasket?

Thanks

jeffboat1
03-11-09, 10:01 PM
I had the same syptoms and after doing several rechecks it turned out to be the wiring harness that connects to the back set of wires on by the firewall. it appeared to be connected but after pushing down on it i noticed that it was not.

andrewgrahamwebb
06-14-09, 11:16 AM
You guys were right, the part that I bought did go on the 2000 N*! I took the part anyway and used it to cap off the nipple that was covered by the broken piece. New gaskets and coil and she runs like a champion!!! No hesitation, no SES no rough idle!!!!!!

FYI: I had two mechanics look at the part that was broken in a deville that was in the dealership and neither knew what it was or what it did.

I am not to sure how to test the coil. I did read the resistance between coils and got 10.5k ohms on both the new and the old coil. I am going to put the old one back in, just to see if it is the issue. If I can return it to Advance, it saves me $175.

Thank you guys again!!! I could have never done this without ya'll. This is SUCH a great resource.

Thanks,
-C






Hi,

I have the same problem with my 2000 cadillac sts as you had, but I'm confused about part 567. I have the factory service manual, and in the manual it just shows a rubber cap on the intake manifold where part 567 goes. In your post you said that you didn't need it but used the part to cap off the nipple. Am I correct about this?

Additionally I cant find the plenum on rock auto -- I'm not sure if i need it, but can you buy one from them? I havn't taken the car apart yet, but can the plenum be replaced without taking the intake manifold off? I dont want to buy a second set of seals after the fact.

If you could please let me know, It would really help me out. Thank you,

Andrew Webb

Ranger
06-14-09, 05:21 PM
Additionally I cant find the plenum on rock auto -- I'm not sure if i need it, but can you buy one from them?
http://www.gmotors.com

can the plenum be replaced without taking the intake manifold off?

No.