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Very rough idle....Some hesitation..


acklac7

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Ok I've had this problem for a while now, Im sorry to say that only now am I getting around to fixing it. Anyway the symptoms are the following:

Rough Idle....So rough you can see the steering wheel vibrating.

Some hesitation? or stumble?

When I go to accelerate there is like a chuggle at some speeds....And when I let off the gas it stumbles...Both symptoms occur randomly almost everyday.

I get about 1000 MPQ and do WOT's frequently...Never see any smoke...ever.

I have noticed while waiting in line at Mc'donalds, that my exhaust is clearly a different color/ more visible than everyone else's exhaust. Looked in the manual and found that fuel injector problems may cause discolored emissions as well as drivability problems.....Im thinking now I might be having problems with the injectors? I have already cleaned the EGR and took the serpentine belt off ( to see if the AC comp. was causing the rough idle)....No luck.

What do you all think? Should my next step be examining the fuel injectors? I read up on how to check them with a 9 volt battery but Im a little confused on where I would direct the spray while testing them.... Thanks in Advance.....

Oh yeah one other thing....Thanks (again) to everyone who helped me with the Trans. fiasco....As some of you may recall I was going to go to AAMCO but was advised that they probably weren't the best shop in town. I ended up going to a mom and pop shop, who did a good job at a good price. Although my flywheel cracked on the way home I am still satisfied with the work...The trans runs great! Anyway my stepdad got his Transmission rebuilt at AAMCO about 16 months ago. Two months after he got it back the rear main seal (?) blew and he had it repaired under warranty. Last week something blew on it again!!! He took it back to AAMCO and they told him that it was no longer under warranty and that it would be $2500 to fix!!! again!!!...Needless to say he got towed to the shop I went to yesterday...without the board I would have likely gone to the same AAMCO...thanks guys!

A.J.

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Lift your hood in the pitch dark and look AND listen for arching. Pull each plug wire and check it with an ohm meter, and record the results.. Sometimes the core burns out of the wires. A bad wire will be obvious. You can buy a digital volt/ohm meter at a radio shack and some home depots, etc. I would also check my coils, they are not that easy to check... if you pull a plug wire you are sure to get jolted.... if you pull the coil end sparks will fly everywhere, you really need to have an ignition spark tester see these, Mike

http://thetoolwarehouse.net/shop/TTW409.html

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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Good question!!...I'm going to go check right now....Also I have noticed a problem with my remote start system that may be relevant. About 1 out of every 30 times I go to start it (with the remote) the engine will crank and then I will hear a loud THUNK!!!! and then nothing...Sounds like its coming from inside the block :(....Any ideas?...Also I had the plugs and wires replaced around 50k...this was before my "mechanical days"...but I know at least 2 of them fouled....hope there not going bad agian

A.J.

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This sound exactly like my leaky EGR Valve problem on my old Ford. On that vehicle the EGR was 1/2 vacuum controlled and 1/2 electronic... I think that the Northstar EGR is 100% Electronic. You could Disconnect the EGR from its source and see how if it gets any better. Of course this will definitely generate an computer error...

Or just re & re with a good cleaning link here: EGR Cleaning Link

Good Luck!

caddy.jpg

Easin' down the highway in a new Cadillac,

I had a fine fox in front, I had three more in the back

ZZTOP, I'm Bad I'm Nationwide

Greg

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Good question!!...I'm going to go check right now....Also I have noticed a problem with my remote start system that may be relevant. About 1 out of every 30 times I go to start it (with the remote) the engine will crank and then I will hear a loud THUNK!!!! and then nothing...Sounds like its coming from inside the block :(....Any ideas?...Also I had the plugs and wires replaced around 50k...this was before my "mechanical days"...but I know at least 2 of them fouled....hope there not going bad agian

I was an installer in a past life......

The reason it does that is the wiring may be getting loose or corrosion/tape goo is interfering with the power wires in the column. Most places for speed will use wire taps (a BIG no-no) that work good for a short amount of time especially with the high-amp power wires. The reason for the abrupt stop is the remote start module (

all of them) for safety will shut down at anything (voltage drop,rpm problems) other than what it considers normal.

I would really blame the fouled plugs (from expirience) an just change them. $40 dollars and 30 mins tops the worst that happens is you won't have 2 fouled plugs and use a spray bottle filled with water, mist the wires and see if any are arcing,

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You said you changed plugs and wires at 50K. What is you milage now? OEM plugs and wires? I would initially think ignition but if plugs and wires are new then I would think twice. You said two fouled plugs. Are they off the same coil? If so that could be the culprit. If that is not it I would definately check the injectors. I'd first just lift the rail and turn on the ignition to pressurize the system without cranking and see if any of them leak. If you have to activate them, I don't think it really matters much where you aim them as long as the engine is cold. Any mist that gets on the engine will evaporate pretty quickly.

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I was thinking about the possiblity that who ever installed the wires may have used dielectric grease on the wires, a common practice. I found this in my manual and have stopped the practice...

If the stuff was used on your wires you could be arching now...

post-3-1116283103_thumb.jpg

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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I was thinking about the possiblity that who ever installed the wires may have used dielectric grease on the wires, a common practice. I found this in my manual and have stopped the practice...

If the stuff was used on your wires you could be arching now...

Scotty,

What is FHC? I did use some dielectric grease....Sounds bad. :angry:

The saddest thing in life is wasted talent

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I was thinking about the possiblity that who ever installed the wires may have used dielectric grease on the wires, a common practice.  I found this in my manual and have stopped the practice...

If the stuff was used on your wires you could be arching now...

Scotty,

What is FHC? I did use some dielectric grease....Sounds bad. :angry:

They say NOT to use Silicone grease and 3M's site describes Dielectric Grease as this:

3M™ Silicone Paste (Dielectric Grease)

I got this from Popular Mechanics on FHC:

Finally, when you're just about ready to push the boot onto the plug, you may remember all the trouble you had getting it off. If so, you'll be tempted to smear a film of silicone dielectric grease on the inside of the boot, or spray on an aerosol "boot-release" lubricant, so the wire unplugs easily the next time.

And most of the time you'll be correct–but unfortunately, new technology is changing right to wrong. A new "lifetime" boot-release lubricant called type FHC is just coming into original equipment use. We've seen it first on the General Motors 4.0- and 4.6-liter Northstar V8s in Cadillacs and the Olds Aurora. It is not compatible with silicone grease, and if you add that grease over it, "tracks" of a carbon compound may form inside the boot.

http://www.popularmechanics.com/automotive...html?page=2&c=y

YEA BABY now I understand! Our old habits can get us in trouble! Adallak, you will not need to worry about this with your 4.9...I used it all the time with my 91..

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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YEA BABY now I understand! Our old habits can get us in trouble! Adallak, you will not need to worry about this with your 4.9...I used it all the time with my 91..

Scotty, the matter is that I just put new set of ACDelco wires. The boots had some stuff (greenish lubricant) and my new plugs were covered with dielectis grease. Go figure... :blink:

The saddest thing in life is wasted talent

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Well after an hour or so of showing my rear end off to the neighborhood and having a few "come on you mother..." conversations with the spark plugs I finally got them checked out.

Most of the plugs looked fine...One looks like it maybe in trouble. I wasn't really sure what to look for so I took a few pictures...Also there is oil at the top of one of the "ports" (see the pic)...I this normal? I found one plug that is blackened/bad that had a tad bit of oil gummed up around it...All of the other "ports" were oil free.

Scotty...There was definitely grease on a few of the plugs...Didn't look for it on all of them because, at the time, I didn't think it was a big deal....maybe the grease is causing the problem?

Larry...The car has 80,000 miles on it. I had the dealership do the plugs and wires @ roughly 50,000...I believe they were OEM plugs and wires before and they are OEM plugs and wires now. As to why they failed before.....I wish I knew...didn't really get into working on cars until I found this site :)

OynxSTS- I already had cleaned the EGR thoroughly, and I ran a test through the PCM to determine if the EGR or the EGR pipes were clogged...The test "said" everything was functioning normally........

Can't get the darn pics off the camera...Ill post them later on tonight...hopefully.

A.J.

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Each of the spark plug holes has an oil seal to stop oil from coming in from the CAM area. It sounds like you have a bad seal on that plug hole. Did you dry all of the plugs and boots and start it, you may have corrected it.. Look close at the boots for carbon tracking, or burns

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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YEA BABY now I understand! Our old habits can get us in trouble! Adallak, you will not need to worry about this with your 4.9...I used it all the time with my 91..

Scotty, the matter is that I just put new set of ACDelco wires. The boots had some stuff (greenish lubricant) and my new plugs were covered with dielectis grease. Go figure... :blink:

I suppose if AC DELCO has incorporated this FHC into their ignition wires across the board, you may also have the problem. But we don't know that your replacement wires were treated with FHC...

You would think that they would insert a NOTE in the new wires directing you NOT to use SILICONE GREASE if they were treated with FHC given that its standard practice to use Silicone Grease... Right?

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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YEA BABY now I understand! Our old habits can get us in trouble! Adallak, you will not need to worry about this with your 4.9...I used it all the time with my 91..

Scotty, the matter is that I just put new set of ACDelco wires. The boots had some stuff (greenish lubricant) and my new plugs were covered with dielectis grease. Go figure... :blink:

I suppose if AC DELCO has incorporated this FHC into their ignition wires across the board, you may also have the problem. But we don't know that your replacement wires were treated with FHC...

You would think that they would insert a NOTE in the new wires directing you NOT to use SILICONE GREASE if they were treated with FHC given that its standard practice to use Silicone Grease... Right?

The instructions only indicate cleaning the ceramic portion of the plug before re-installing the boot on the re-use plugs. There is also DO NOT list, and nothing about dielectric grease.

The saddest thing in life is wasted talent

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Ok I changed out the suspect bad plug and still am getting a rough idle...It MAY be a little better...but that could just be me. Any way here are the pics of the bad plug..and another one that I belive is good, along with the gummed up oil, and oil in the upper part of the port.

Another thing I noticed: Say I rev it up to 2000 in park, On the way back down it will "surge" @ 1000 rpm....jump up to 1200 and then fall down again...During the whole deceleration process you can feel the car shake in the seat...Do you think another plug is bad? is the plug in the picture (the black one) definitely bad?..Most of the other ones appeared to be white....What next...check the wires? thanks!

post-3-1116359199_thumb.jpg

A.J.

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it certainly sounds like you have an ignition wire problem, you need to check each one with an ohm meter given the grease was used. it sounds like you are getting intermittant firing.

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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Ya, I'd change ALL the plugs and ALL the wires...then re-check it.

Jason(2001 STS, White Diamond)

"When you turn your car on...does it return the favor?"

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  • 1 month later...

Just giving an update....About a month ago I put a can of seafoam in the gas,changed one plug, and added some Marvel mystery oil (for PM)....Also found out the EGR port on the throttle body was severely clogged. In addition I performed the "WOT maneuver" in 2nd, going up to 80, then back to 55...Previously all I did was let her rip on the on-ramp...never did the actual "procedure". Well the end result is that the stumbling has almost completely gone away, along with the hesitation. The rough idle is still there and hopefully I can diagnose that soon....Trying to spread repairs out if ya know what I mean...I'll be sure and post when I diagnose the idle problem..Thanks again…A.J.

A.J.

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Another update....After driving about 3 dozen times on the same 45mph road to work I noticed that there is still a "stumble"...however it only occurs between 50-53 miles per hour....I now believe that what I am/have been feeling is the TCC (Torque converter clutch) engaging/disengaging....Funny it only seems to become noticable while driving between 50-53 mph on a road that has frequent changes in gradient...Above 60 I dont have any problems, below 50 I don't have any problems...just right between 50-53 mph, and only while going up/down a slope..No trouble codes yet...Hopefully this is normal and I just missed something in the manual....Still haven't got around to the plugs and wires...Blower motor wiped out my "service fund"..lol

A.J.

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When it is running rough do a "Power Balance Check" where you go into the diagnostics and shut the fuel injectors off one cylinder at a time. If there is no change in the idle quality or RPM then that cylinder is one of your problems. I ran this on 94 Concours and found 2 cylinders giving me problems. I traced them back to the same coil and found the problem. I change the coil and all was back to normal. No codes ever showed up for me for a bad coil. The "Power Balance Check" is in my manual under the fuel and air control system section.

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When it is running rough do a "Power Balance Check" where you go into the diagnostics and shut the fuel injectors off one cylinder at a time. If there is no change in the idle quality or RPM then that cylinder is one of your problems. I ran this on 94 Concours and found 2 cylinders giving me problems. I traced them back to the same coil and found the problem. I change the coil and all was back to normal. No codes ever showed up for me for a bad coil. The "Power Balance Check" is in my manual under the fuel and air control system section.

PAULT,

Did you use tachometer? I tried the power ballance check (overdrive ES04, ISC motor unplugged, "warmer" - to chose the injector, "cooler" - to turne the chosen unjector off) but could not notice any RPM change. My idle is slightly rough too.

The saddest thing in life is wasted talent

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When it is running

Did you use tachometer? I tried the power ballance check (overdrive ES04, ISC motor unplugged, "warmer" - to chose the injector, "cooler" - to turne the chosen unjector off) but could not notice any RPM change. My idle is slightly rough too.

I used the tach and had to run it more than once to finally get consistant results. Then it consistantly settled on 2 cylinders. Is your tack digital or analog? Mine was digital and the change in RPM was only about 50-75. Concentrate on the cylinders that do not change.

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When it is running

Did you use tachometer? I tried the power ballance check (overdrive ES04, ISC motor unplugged, "warmer" - to chose the injector, "cooler"  - to turne the chosen unjector off) but could not notice any RPM change. My idle is slightly rough too.

I used the tach and had to run it more than once to finally get consistant results. Then it consistantly settled on 2 cylinders. Is your tack digital or analog? Mine was digital and the change in RPM was only about 50-75. Concentrate on the cylinders that do not change.

I can get RPM only through the DIC but in diagnostics it does not show RPM... It's next to impossible to notice 50 rpm drop without tachometer. Perhaps i need to run the test several times in some quite location, not on the street as I did. Thanks.

The saddest thing in life is wasted talent

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