Poor acceleration with blinking SES light under load

[waupachino]

I have a 00 GTP and I am experiencing poor acceleration and a blinking SES light under load. It won't set a code. While trying to diagnose the problem, I put the emergency brake on with my foot on the brake to bring the motor up to where the problem starts. After which I shut the vehicle off and took a look at the Catalytic Converter. It wasn't glowing red, but it did seem to be cooking. Would you think the Catalytic Converter is the problem?

[BNaylor]

How many miles do you have?

A blinking SES/CEL light even with no DTC codes set is a misfire condition detected. Typically a secondary ignition problem like bad spark plugs or ignition wires or possibly coil pack. Since you did the plugs the ignition wires are suspect.

CAT convertors are always cooking since they operate at over 1000 degrees F but if defective can cause a random misfire condition. You could run an exhaust backpressure test to make sure it is not clogged or damaged internally. A muffler shop can perform the test or sometimes an engine vacuum test will show something.

Also, what brand and heat range spark plugs?

[richtazz]

The blinking SES light indicates a misfire condition. This could be caused by worn out tune-up parts or an exhaust restriction.

How long has it been since you tuned the car up (plugs, wires, fuel and PCV), and if done recently, what brand parts did you install?

A simple vacuum check will tell you if the converter is blocked, or you could have an exhaust system back pressure test done. Another thing you can try is to temporarily remove the upstream oxygen sensor and see if the car runs better. If it does, your exhaust is restricted, most likely because of the converter.

You beat me by a minute Bob,

[waupachino]

The plugs have recently been replaced, they are AC Delco Irredium. The wires have not been replaced. The car has 154,000 on the Odometer. The main reason I am leaning to the Catalytic Converter is because this only occurs under heavy load while accelerating and the fact that when I looked under the car it seemed as if the Cat was cooking.

[BNaylor]

Are these the original wires? The stock OEM AC Delco wires are good only to about 100K miles and after that should be replaced. A bad wire or more than one will show under load too.

One sign of a clogged CAT is it will feel like running into a brick wall at around 4K rpms or higher. Too bad you are out of the CAT convertor/emissions warranty.

[waupachino]

Originally Posted by BNaylor

Are these the original wires? The stock OEM AC Delco wires are good only to about 100K miles and after that should be replaced. A bad wire or more than one will show under load too.

One sign of a clogged CAT is it will feel like running into a brick wall at around 4K rpms or higher. Too bad you are out of the CAT convertor/emissions warranty.

Not sure if the wires have ever been replaced or not. I believe the coil packs have been replaced at some point. It definitely feels like it has run out of power above 4K RPM. That is almost excatly where it started when I had it up against the brake.

[BNaylor]

Checkout this old thread in which the engine vacuum test mentioned by Rich and me actually detected the CAT convertor was bad. All you need is an inexpensive automotive vacuum gauge (0-30 in-hg).

Click here

[waupachino]

Thank you for the help. I am going to test for a bad Catalytic Converter. Just to be clear, a bad Catalytic Converter could cause a blinking SES without setting any codes correct? I had a local auto parts store check for codes yesterday and there weren't any.

[BNaylor]

That is correct but it will vary. When the CAT convertor in my GTP went bad a long time ago round 75K miles I had a blinking SES light under load but no DTCs stored. No random or fixed misfire DTCs. No CAT convertor efficiency DTC like P0420 either from the post CAT 02 sensor. Some are fortunate and get DTCs which helps most of the time. Also, it depends on which scanner is used and its capabilities on pulling up GM specific extended DTCs. Good luck and let us know how it turns out.

[waupachino]

Well it's not the Catalytic Converter. I had a friend at an exhaust shop do the back pressure test and he said it is fine. Good news is it finally set code and is P0301 misfire in Cylinder #1. So I guess now it is wires, coil, fuel injector, or ignition module is this correct?

[waupachino]

I put a bottle of Techron fuel injector cleaner in yesterday, to soon to tell if that will work. I started the car in the dark to see any sparks jumping and sure enough cylinder #1 is sparking. I am going to replace all the wires with AC Delco, that is what is currently on the car. I will update the results. Any better recommendations for wires?

[BNaylor]

If stock stay with the AC Delco Premium Silicone 7mm wires. Other alternatives are the Taylor Spiro Pro 8mm and MSD. I use the MSD 8.5mm wires.

With the aftermarket brands above you can get different colors like blue or red.

[tblake]

I think the reason your Cat converter was cooking was because you have a problem with the ignition system for number one cylinder. If you think about it, when the spark doesnt reach the combustion chamber, there is raw fuel that isnt spent that all gets pumped right into the exhaust. The cat converters job is to burn up all this raw fuel in order to eliminate excessive Hydrocarbon emissions. The cat converter was extremely hot because it had to burn up all that raw fuel from #1. Its a good thing you are adressing this issue immediatly to avoid cat converter failure.

Havnt you guys seen cars drive by at night with glowing red exhaust? Thats because their motor has an ignition missfire and their cat converter glows because its working overtime trying to use up all that raw fuel.

[waupachino]

Well I picked up a set of AC Delco wires $41, not bad. Did you know they have a lifetime warranty on them? The set on the car is AC Delco also, maybe I should look into sending the old set back. Good tip on the Di-Electric grease, I didn't think of that. I replaced the wire on Cylinder #1 and it seems to have fixed the problem. I am currently at work so the other 5 wires will have to wait until later.

[BNaylor]

Thanks for the feedback. Reading off an old box for AC Delco Premium Silicone 7mm ignition wires PN: 746BB you have a limited lifetime warranty by GM to the original retail customer as long as the purchaser owns the vehicle in which the ignition wire set was originally installed. For VIN "1" L67 SII 3800 PN: 726RR. Alot of disinformation at that other auto forum. ...........

Plus the AC Delco new wire set comes with enough dielectric silicone grease and don't over do it. Any excess may eventually drip down to the heads and exhaust manifolds since alot of heat is generated. The grease not only cuts down on possible stray high voltage and carbon tracking but helps makes the boots easier to remove from the spark plugs for the next time or future service. Especially helpful on the rear bank plugs since they are a PITA.