FAQ: Rough / Slow / No Start - Symptoms, Causes, Solutions

111k miles, but at 100k had system flushed and new filter put in... \

Wondering if crank position sensor could be wacky...Manual says that if the PCM doesn't sense a pulse from the CPS that it will kill the fuel pump off within 2 seconds...

I did have the harmonic balancer changed, and it acts with the CPS...if there's a misalignment there, a problem could exist...

It sure is a mystery!

You'll have to quiz the mechanic that did the Harmonic Balancer.
In my mind, at that mileage, you should change both at the same time to prevent customer "Come Backs".

Natesriv wrote:

but at 100k had system flushed and new filter put in... \ It sure is a mystery!

I had my Trans Flushed at 79,000 and within 5,000 miles I was experiencing Trans Shudder and other anomalies, ended up approving a complete teardown and overhaul.
Not to say that is what you are experiencing. You would have to be more descriptive.
But since you're having a starting issue, I would get that taken care of first and see if the shudder goes away.

I'm gonna' disagree with Rick for a change... Low fuel level has nothing to do with getting dirt in the fuel line. The dirt is always on the bottom of the tank, and the fuel pump pickup is also always on the bottom of the tank.

As far as your condition goes, you have a no-idle situation, but you can drive the car under load. Fuel starvation wouldn't be the cause of this, because idling consumes the least amount of fuel...

I realize that it should throw yet another effing code, but something that DOES affect the idle but not driving would be the IAC, the Idle Air Controller. I was just playing with my scanner tests today, and if the IAC goes below 10%, the engine will die. Could be a job for Carb/TB cleaner, taking the IAC off.

Eldo's correct.
I didn't read the thread thru completely.
A plugged filter will cause more problems off idle and during cruise or high power demand.
But, The plastic canister and Venturi tube do draw from the bottom of the assembly.

I'm puzzled.

It's about this mileage (100K+) that we've seen CPS die off. Maybe it is the crank sensor. If you could get it someplace with a TechII you could check for crank sensor signal while cranking. Got to do that because the way the Riv is set up a bad crank sensor will not throw a code (althoug a code *is* listed).

They are not *that* expensive, but the only 'pain' is pulling the harmonic balacer to do the R&R of the crank sensor.

Albertj

I should note, once I got to the store, it idled and ran fine (a little high, but I had been holding my foot on the pedal to keep it up)

From what I read in the shop manual, the IAC and TPS shouldn't cause the car to NOT start..I had to push the pedal in quite a lot to get her to run. Then take foot off gas it died like I had turned it off..no shudder...just dead.

All this crap seems to have happened right after balancer replacement.

The tranny shudder I speak of is weird....

Like I said, at idle at stop lights, foot on brake, I'll get a very light rattlling sound (sorta like when you turn the wheel all the way and the power steering pump shudders)..like that...about every 5 -10 seconds...lasts about two seconds. Put in park, goes away, let off brake and move, it goes away..

Now also, while in drive at idle, if I turn the wheels it will really happen...

All these noises are loud enough to be heard with the hood up too..

The tranny shifts fine, I don't get any thump, or slag...

I would sure like that CPS replaced...

Natesriv wrote:

I should note, once I got to the store, it idled and ran fine (a little high, but I had been holding my foot on the pedal to keep it up)

From what I read in the shop manual, the IAC and TPS shouldn't cause the car to NOT start..I had to push the pedal in quite a lot to get her to run. Then take foot off gas it died like I had turned it off..no shudder...just dead.

I would sure like that CPS replaced...

I normally wouldn't contradict the manual, but an IAC that was plugged or wasn't opening would have to keep the car from starting, wouldn't it? That's what provides the idle! Until you touch the "real" throttle, all the air that makes the car start and provides the various idle speeds goes thru the IAC. The only other thing I can think of that would give the same symptoms would be an EGR that wasn't closing all the way.

Whenever I have problems like this I look back at what has been recently touched, loosened or repaired.
Regarding the Shudder, I think in a previous post you mentioned it felt like the steering pump itself was loose.
That could very well be the case with this vibration your feeling.
They would have had to loosen the pump assembly to do a water pump replacement and the bolt's could have been left loose.
Regarding your other issue, from what I've read I would suspect the Crank Position Sensor, the connector could have become dirty and / or loose while the other work was being performed.
This would cause an intermittent or continuous problem.

Quote :

4: Car/Engine shudders on and off at idle in drive at lights...put in park..nothing, turn wheels while in idle in drive and shudder is much worse! Shudder can be heard! It's like a rattling rotation sound.. when I turn car off, the last noise is that sound for about a 1/10th second or so...

I know you say the MAF was replaced, but this describes almost exactly what you can expect if you unplug your MAF sensor. Need to somehow scan or otherwise test the MAF is working properly. If the sensor is bad but still plugged in, it may not set off the SES light. Best way to tell is to look at MAFF values on a scanner.

Next thought would be a vacuum leak, since the problem is at low RPM, and you were just in there working on it.

well...from when it would run, an I unplugged the MAF is stumpled, stuttered and died...

THis just died like I cut the fuel immediately....not a cough or stutter.

The IAC could be it, I took it off and cleaned...don't see any gunk clogging that opening.

The EGR and IAC and MAF would suprise me that none of them are throwning a code..

Now, if for any reason the fuel filter clogged, for just that brief time and keeping on the gas raised the pressure enough to allow fuel to pass may be a reason. I did notice on driving home that day that she wasn't quite as peppy...didn't stutter (which would indicate an irratic fuel pump or still clogged filter)

Right now she's at Meineke...If they do replace CPS I might go ahead and have them chack EGR too..

Lack of proper airflow can sure wreak havoc!

I'll let you guys know when I hear more.

Thanks amigos!

Hey guys, just an update. Got her back, they put a new fuel filter in and it runs better, but still sounds bad at idle in drive...

Listening to engine...I can hear the coil packs humming...And it's not a smooth hum...it's smooth, then gets inconsistent sounding...and engine feels different when that sound changes.

Should you be able to hear a coil pack hum? If so, shouldn't it be a steady hum at any speed?

I did have a CEL for the cylinder #3 awhile back after washing the engine... Just curious if a bad coil can cause an engine to run rough???


Thoughts?

Bad coil can cause rough running.

Do you have the FSM? I think there is a spec in there for measuring the resistance across the primary and secondary windings on a coil. You can use a meter and see what the resistances are. If resistance is off spec wha-la you found a bad coil.

Other than that it should not be too hard to take the coils *off* and clean the metal grounding plate that the coil pack sits on. It should have a thin layer of a compound on it. Sometimes people use 'tune up grease' which is dielectric and does not conduct. It inhibits corrosion and is OK in a thin layer. Too thick and it's a problem. You can wipe it off and replace it with"NoAlOx" grease (under $10) from the electrical section of a home center such as Home Depot. I use NoAlOx for connections such as ground planes that (a) one or more components are aluminum (b) are in humid/moist or other challenging areas. It is great for making sure that your circuit breakers connections in your house don't corrode (be sure to pull the main breaker before you go painting the stuff on the bus bars) NoAlOx keeps the aluminum from forming a nonconductive aluminum oxide layer. You might need to swab it off with a mag wheel cleaner on a rag first or burnish it with a scotchbrite pad - be sure to put the noalox on within a minute or so of the burnishing.

Albertj

[quote="Natesriv"
I can hear the coil packs humming...And it's not a smooth hum...it's smooth, then gets inconsistent sounding...and engine feels different when that sound changes.

Should you be able to hear a coil pack hum? If so, shouldn't it be a steady hum at any speed?

[/quote]

I have never heard a coil pack humming.
You sure its not the injectors making the noise?

Bert

I didn't read back far enough initially to pick up on the "Humming Coil Packs".
That's a new one, I've never heard a coil hum.
Injector's will make a ticking noise, not a hum.
I think you need to use a stethoscope or makeshift one, a screwdriver.
Put the metal tip to what you want to listen to and put the handle to your ear. Obviously a long bladed screwdriver can be beneficial for this purpose.
Move it around to different components even if you don't think you can hear anything coming from them.
Try to get used to the various / different noises and frequencies until you find the "Hummer."
Please report back with what you find. Take pic's if needed to explain better.

it's the packs, My ear right against it (not to get hair in belts!)

It's weird, sound sorta like one of those outdoor electrical boxes...

Car still runs okay, but idles in drive funny....

I haven't dug all the way down to the crank sensor, but that's what sets the firing rate of the coil packs...

However, my packs say 1-6 on them...making me wonder if they're OEM and 14 years old....

MSD makes some I might invest in...

If this keeps up I'm tearing the crank pulley off (The harmonic balancer) and replacing CPS...

I would probably remove them to see if I could find something that is causing the noise.
Verify that the small bolt that holds the wiring harness to the ICU ? is tight.

That was loose on a 00 Regal I used to have and it caused some very strange driveability problems.

Happy New Year!

Bert

they seem fine (did the screwdriver sound test)...it's the whir of the belts spinning I think I heard!

However, guys, I think I need a new s/c coupler. I read that if you can feel slack in the s/c pulley when you rotate back & forth it's time to change it. Mine has about 1/8" play.

Also, when I turn the car off, i hear it rattle right by the s/c. for about 1/10 a second...a rattle that sure sounds like the coupler "slipping" as the rpms hit zero ...the coupler?

So I wonder if my driveline shimmy I hear at idle in drive (at stoplights) could be the coupler rattling? BUT, it goes away in park (does s/c remain "disabled" in park?)

I think I'll replace the coupler, I have new oil and it looks really simple to do!

I have the same amount of play in my coupler. I checked it when I had the belts off to do a complete pulley change this summer.
But I am not experiencing the noise or rattle you describe.
I don't think a coupler with 1/8" play is bad enough to replace. But as you said they are easy enough to replace so it can't hurt to put in a new one and see if it solves any noise (rattle) issue you may have.

Natesriv wrote:

So I wonder if my driveline shimmy I hear at idle in drive (at stoplights) could be the coupler rattling? BUT, it goes away in park (does s/c remain "disabled" in park?)

Nate, don't quite know what you are trying to say here. Could you describe it another way, possibly.
"driveline shimmy at idle" is a bit confusing and what do you mean by S/C disabled in park.????

just bought coupler off eBay for $40 with shipping & oil.

I can't wait!

Now another question. Looking at the shape of the coupler. Does it "lock" into position, and when it's worn it can slip, or something?

Gracias amigos!

The holes in the coupler get elongated by the metal pins that drive it.
The coupler is meant to be sacrificial.

Who on EBay did you buy the kit from.?

And don't forget to pick up a small tube of "Anaerobic Gasket Maker" to seal the SC snout.
It is the only type of sealer recommended that does work between the aluminum snout and the aluminum SC housing. Also what GM recommends. It's available at all auto parts stores.

Rickw wrote:

Natesriv wrote:

So I wonder if my driveline shimmy I hear at idle in drive (at stoplights) could be the coupler rattling? BUT, it goes away in park (does s/c remain "disabled" in park?)

Nate, don't quite know what you are trying to say here. Could you describe it another way, possibly.
"driveline shimmy at idle" is a bit confusing and what do you mean by S/C disabled in park.????

sorry Rick, let me elaborate


Sitting at a light... I hear a rattling sound coming from accessory side of engine and feel a periodic shake/shudder. Car doesn't die, or lower RPM, just feel the "rattle" of it. Just bought s/c coupler so I wonder if it's the coupler causing it...

At first I thought it might be the torque converter (since sound went away in park) but I suspect it's the s/c coupler.... But the fact it has play means it's time to change it regardless.


So far in the last year and a half I've:
1: New struts and shocks in rear
2: New belts and pulleys
3: New tranny gasket
4: New valve cover gaskets
5: New (used) maf sensor
6: New (used) s/c bypass valve actuator
7: New tires
8: New waterpump
9: New harmonic balancer
10: New vacuum lines (the rubber parts, I had to DIY it as these parts are gone!)
11: New (used) traction control motor
12: New (used) power antenna
13: New plugs & wires
14: New fuel filter
15: Total fluid flush (all fluids)

This car will last another 10 years!

Wife wonders why I put $$ into her... Name a car today to match?

Rickw wrote:

The holes in the coupler get elongated by the metal pins that drive it.
The coupler is meant to be sacrificial.

Who on EBay did you buy the kit from.?

And don't forget to pick up a small tube of "Anaerobic Gasket Maker" to seal the SC snout.
It is the only type of sealer recommended that does work between the aluminum snout and the aluminum SC housing. Also what GM recommends. It's available at all auto parts stores.

Don't know? Had 100% rating and coupler is the green one, lasts longer.. Has the gasket part too.