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My 2001 SSEi Bonneville runs super fast like an SSEi should, but only when it's cold, first two minutes or so. Once it warms up, the monster under the hood acts like a non supercharged engine, what could this be? It runs smooth as can be, I don't see how this can be plugs, wires, etc.

Any advice would be very much appreciated.

Thanks,
Dan

Can you get your car scanned for codes? I would think a faulty IAT sensor would be the first place to look.

Thank you Roadtech195, I will have my mechanic shop check that.
Air Intake temperature sensor aha!!

Dan

If you're saying that you have less performance from the car when the engine warms up, a catalytic converter that is going bad can cause that.

Archon wrote:If you're saying that you have less performance from the car when the engine warms up, a catalytic converter that is going bad can cause that.

Easy way to check, when the car is cold (Very Important!!) crawl under the car, and shake the cat, and if it rattles, then it is bad.

If it does rattle, it definitely needs replacement. However, it is possible for the cat to be plugged, and not rattle.

Archon wrote:If it does rattle, it definitely needs replacement. However, it is possible for the cat to be plugged, and not rattle.

True, that happened on my mom's Suburban. But, if it does rattle, it for sure needs replacement.

You guys are great!
It is so nice to not feel alone and be at the mercy of the mechanic.
I think you guys might have nailed it with the catalytic converter,...
my 95 GMC van 350 V8 acted exactly the same way, it ran awesome
when it was cold, and after replacing the converter it ran warm like it did cold.

I did replace the air intake sensor on the Bonneville today, but it made no difference.
It was only twenty bucks so I figured what the heck.
It will be a few weeks before I can get it into the shop for a converter,
but I will post the results.
Thanks everyone!
Dan

I wouldn't jump on a converter just yet. That might be a problem, but it is always better to know for sure then to spend the money to replace a part and have no effect

Where do you live? There might be a member near by that has a scanner and could hook it up for you and see what is really going on

We really don't want to see you waste any more money and not fix the problem

thanks crash, I am in St. Louis Missouri.
Beautiful red Bonneville!!!

Maybe I could find someone local, that's an asweosme idea.
Dan

Check all the obvious and usual host of characters. Tune up items, exhaust for restriction etc.

Knock sensors don't become active until about 150F. If you have any KR it wouldn't show until you reached the minimum knock sensor temps.

Also, a muffler shop can do a back pressure test to see if the cat is plugged.

it could also use an intercooler the blower gets so hot under those things and then the engine is just suckin in warm crap air.

n/a silver bonne wrote:it could also use an intercooler the blower gets so hot under those things and then the engine is just suckin in warm crap air.

Wrong, an intercooler is necessary when you have numerous other mods present first, i don't think Rogue has one, and he makes 465 HP and 592 Ft-lbs. Plus, it is much harder to intercool these motors due to the fact that it is a roots-type S/C, not a Turbo, or even a Centrifugal supercharger.

those other mods mainly being a smaller pulley (spinning faster and creating more heat)

bonnevillain wrote:those other mods mainly being a smaller pulley (spinning faster and creating more heat)

true, that and added timing and upgraded cams causing more heat in the cylinder, which needs a source of cool(er) air, hence why you intercool it, forcing colder, denser air in, causing less heat.

00Beast wrote:

n/a silver bonne wrote:it could also use an intercooler the blower gets so hot under those things and then the engine is just suckin in warm crap air.

Wrong, an intercooler is necessary when you have numerous other mods present first, i don't think Rogue has one, and he makes 465 HP and 592 Ft-lbs. Plus, it is much harder to intercool these motors due to the fact that it is a roots-type S/C, not a Turbo, or even a Centrifugal supercharger.

Don't agree with the wrong statement here. Many of the well modded guys look back and wish they had intercooled much sooner. Swapping a blower from a Gen 3 to a Gen V (assuming S2 motors) is solely for the purpose of cooling the intake charge. The designation M90 on both Gen 3 and Gen V means it produces 90 cubic inches of air for each rotation of the pulley. The Gen V is known to be much more efficient which is read as a cooler charge of air since they displace the same amount of air per revolution.

Because of the hot air being forced into the engine (assuming warmed up and at WOT) from the supercharger the timing tables are unable to support high timing with a high cylinder air mass without predetonation. Intercooling reduces the air temperature to allow a greater amount of timing at the same cylinder airmass with less or no predetonation.

Todd aka Rogue has an intercooler.

Let's get this back on topic. Start a new thread in P&B if you want to talk about the benefits of an intercooler.

Thanks for the thoughts guys. Although I am pretty confident that it is not a catalytic converter because a converter would not get up to temperature in just a minute and a half, plus this has been doing this ever since I bought the car with 94,000, and now has 97, 000 miles. Indeed the converter is no doubt partially clogged after that many miles, but a radical loss of horsepower is probably due to some other sensor. I am going to get my mechanic to check for any codes. I will for sure report my findings back here since you guys are trying to be so helpful.

Thanks again,... stay posted.
Dan

I have a scanner and I'm in St. Louis.
PM sent.