LS V8 Stuttering @ High RPM

[Joe_theboob]

I have 2001 LS V8 w/ 95k miles. Recently it has been stuttering when the peddle is floored. If you nail it from a dead stop it runs strong up to about 5k rpm and say 50 mph - then it starts choking and cutting out. It doesn't seem to be a cylinder miss, it seems like they're all cutting out, the whole car jerks back and forth.

I am running Shell v-power and have had the injectors cleaned annually since it was new.

I've had to replace 2 of the coils in the past 18 months. So I don't believe it's another coil going bad (cause I know what that feels like). This things runs great at idle and lower speeds. It's just under a heavy load that it pukes... and then it needs the high RPM to puke.

any / all advice is appreciated.

[discnik]

Have the vehicle scanned for DTC codes. I think Auto Zone does this for free. The way your vehicle is acting there should be some trouble codes. This will give you an idea of where to start.

[shorod]

Have you ever changed the fuel filter? If you have access to a scan tool with the datastream mode, hook that up and check for the "fuel rail pressure" parameter. If the tool shows it, monitor that while running the car under load at high speed and make sure it stays within specifications.

Also, you may want to check the air filter and clean the Mass Air Flow (MAF) sensor with the CRC MAF Sensor Cleaner. I'm not sure how many stores stock this yet, but I've been able to find it at Advance Auto Parts.

-Rod

[discnik]

If the engine you have has the coil pac on each cyclinder with a cover over them, check the seal on the cover. Just talked to a friend having the same problem you described. Come to find out that with it raining, water had seaped into the right side bank under the cover gasket and had caused several misfires. Just an idea.

[Joe_theboob]

Thanks All - Have been to AutoZone and It's not throwing any codes. I bought a fuel filter, I just ahve to find where it's located on the car now...

I was thinking about buying a scan tool - I'll post a new thread on that question...

[Quik_LS]

the fuel filter is a simple swap - it in the driver's side fender well - behind the plastic liner - one screw and some r-clips.

It still sounds like coils to me...... they have to be pretty bad to actually throw a cel code. little misfires at higher rpms will not likely cause an engine light.

When you swapped the other two coils - did you find oil in the spark plug wells?

[shorod]

I'm not sure how many of the scan tools on the market have the "Component Parameter" feature, but if you end up with a scan tool that has this capability, you can check for misfire counts on individual cylinders, even if it does not set a check engine light. My AutoXray EZ-Scan 5000 and OTC Genisys both have this capability, and it has been quite helpful. Just be aware that a cylinder misfire does not mean that it is certainly a coil failure. It could also be a fuel injector issue or even low compression.

-Rod

[Joe_theboob]

No oil in the plug wells. I had the valve cover gaskets replaced 50k miles ago when they started leaking - no problem since.

Please excuse my ignorance... which is the fender? the front or back - I am guessing you mean the front behind the wheel ?- remove that big plastic liner between the tire and the engine?

[shorod]

Yep, that would be what he's talking about. The fender liner is the "wheel well" liner, black plastic between the wheel/suspension and the engine compartment.

-Rod

[LSGIRL]

Hi Guys

I have being having the same problems with my 2001 w/over 140,000 miles and it got so bad that it would even almost stall when I would try to pull off from a stop and then all of a sudden would build it's speed back up. I just got it out of the shop 1 day ago and it is still jerking when I pull off from a rest and continues as I try to build up speed. Everytime we have put it on the machine we would fix what the machine at Autozone says to fix. We had a tune up last October 2006 and just had one done again the other day and it still is doing the same thing but it doesn't stall anymore since he changed 4 of the coils. The mechanic also has told me that the gasket covers need to be changed out soon but that shouldn't be causing this problem. He suggests to change the other 4 coils out now. My husband has had the fuel injector cleaned, changed the fuel pump, change the fuel filter and has added a new 0xygen sensor. None of that worked and now the Autozone machine has detected that bank 2 is bad, so that is the #2 coil. We will now change all of them in hopes of fixing this on going problem. I just want a new car because it is a terrible feeling to know that you are putting your car in the shop and it still may not get fixed because the problem is so hard to detect and figure out. Also my horn does not work and one of my back windows.

[shorod]

Welcome to the forum!

Bank 2 is not the same as cylinder #2. Bank 2 is the entire driver's side of the engine. Cylinder #2 is part of Bank #1. Is your LS also a V8, or do you have the V6? From a spark plug, valve cover gasket, and coil standpoint, the V8 is much easier to work on.

If your shop is telling you that you need valve cover gaskets, chances are they are what is causing the coils to misfire due to oil leaking from the valve covers into the spark plug wells, giving the coils an alternate path to discharge to rather than through the spark plugs. If there is any evidence of oil on the coils when removed, it is a waste of your money to keep replacing coils. Instead, your money would be better spend fixing the leaking valve cover gaskets and spark plug well seals.

As for the horn not working, that could be the clockspring, a relay, or the wiring. I doubt that both the high and low tone horns would both fail at the same time, so probably not the "horn" itself.

The non-functional back window - do you hear a motor trying to run when you press the switch? Do you get the same results from the driver's window switch as from the switch on the door itself?

-Rod

[LSGIRL]

I have a V8 and sorry about my lack of understanding of cars. Or I will blame my shade tree mechanic who informed me that if the printout said bank 2 default that means that coil #2 needed changing. He sounded as though he was lying when he said that.

I will bring the codes and post them tomorrow. Both of my back windows were fixed last year for $175 each. The motor had stopped working in them and now one of them has stopped again.

My mechanic took the steering wheel apart and they advised me that it could be 1 of 2 things that is wrong with it. They told me that if it was a part that has gone out in it that the part is $100+ and if they have to mess with the airbags to get to another area it would be more. I have never had any problems with this mechanic. He has always been cheaper than other places. He does what we ask him to do. I don't believe he's that good with figuring out problems in newer vehicles.

Could it be possible that the MAF sensor needs to be replaced? I saw that on someone elses posts here. Someone had told my husband that the MAF sensor can cause your car to not perform right and could also cause it to jerk and blow heat.

[shorod]

Yeah, the MAF could cause jerking, but that would often indicate an intermittant MAF, and a code should be set for that indicating such. The MAF should not cause it to blow hot air.

Loss of power and blowing heat would more likely be due to a cylinder head overtemp condition in the LS. The LS has a Cylinder Head Temperature (CHT) sensor that causes the engine to go into "heat pump" mode, disabling the unnecessary accessories (such as the A/C) and disable a couple of cylinder to allow them to pump air to help cool the engine. If this is occuring though, the PCM should have a stored code indicating CHT or an overtemp condition.

-Rod

[LSGIRL]

AutoZone printout
Troubleshooting P0175
Definition: Fuel Trim Bank 2 Condition
Explanation: The ECM has detected a rich or lean air/fuel ratio condition on engine bank 2
Probable Causes:
1. If bank on and two are set together suspect a fuel condition or MAF sensor fault
2. Failed H02S21
3. Ignition misfire condition
4. Fuel injector problem
5. Engine mechanical condition
The PCM has determined that during testing, the fuel system for rbank 2 was too rich. (Bank 1 identifies the location of cylinder #1, while bank 2 identifies the cylinders on the opposite bank)

Troubleshooting P0302
Definition: Cylinder misfire detected - cylinder number 2
Explanation: The powertrain control module monitors the crankshaft speed and has detected a misfire condition
Probable causes:
1. Ignition system fault-spark plugs
2. Vaccum leak
3. Injector fault
4. High or low fuel pressure
The PCM has determined that a misfire has occured in cylinder #2.

We have had all spark plugs changed for the second time within a year. The last time was last week.

Gaskets changed last year.

4 plugs changed last week

Fuel pump changed

Fuel injector cleaned

O2 sensor replaced last week

[shorod]

So when the spark plug was removed from cylinder #2, was the coil wet with oil or did the spark plug appear different from the others? You mention the spark plugs were changed, but was the coil for cylinder #2 every replaced?

Code P0302 is pretty telling. Sees like a good place to start. The confusing part is cylinder #2 is in bank 1 rather than bank 2. P0175 indicates bank 2 is too rich. The two codes may not be related.

-Rod