total power loss

[loucks3]

Just got a '92 Grand Prix SE 3.4 DOHC. its got 144k but its in great shape for its age and milage.the car runs and idles smooth but when it comes to power its no where near what i would expect from a 3.4 DOHC or even a v6. I also own a '93 Mitsubishi Diamante with a 3.0 DOHC and 120k on it that still will reach 130mph pretty quick, for its size.I know both engines are rated at about 200hp new, i figured somthing was wrong so the first thing i checked was the spark plugs for any signs of head gasket trouble.I thought i might be loosing some compression,but the spark plugs were fine.So i checked the coolant and it needed to be changed. After changing the coolant and bleeding the system i was warming the engine to feel it idle.I pushed the throttle to 3000rpm and it would not go any further,i had never reved it like that since i bought it so then i was really worried. So then i took it for a drive and the engine seemed to wake up suddenly there was power.I pushed it to about 50mph ,it reved fine past 3000rpm driving,but then the service engine soon light came on after about 20 minutes of running,so i shut it off.I figured thats kind of good ,because it will store a code,but then i drove it again to see if still had the power and the service engine soon light was off and the power was gone.Could it be as simple as the ECM or a bad spark plug wire,or is this American built 3.4 DOHC just tired? Theres not alot of these 3.4's around to get info on.Please help!!!!

[pocket-rocket]

The 3k rpms in neutral and park is normal. It is the rev limiter so if you let some jackass borrow the car, they can't over rev it with no load on it. I would check the timing belt on the car. The timing belts on these cars is pretty long. The front cams could be set perfect, but the rears could be pretty far out of spec due to the belt. I would also go to the nearest GM dealer and get a can (liquid, not spray type) of top engine cleaner. Do not do this in a garage! Do this in an open area. irst thing is let the car warm up. Then you get a good vacuum line with good vacuum, put it in the can. Most likely the engine will try to die, so hold the throttle open enough to keep the engine running, but not rev up real high (I guess you couldn't go past 3k doing this, lol). When it gets down to the bottom of the can, let the car die (but don't run the can dry). Let the car sit without the engine running for 15 minutes to let the TEC soak into the carbon buildup. Start engine (this will be tough to do for a while, but it will eventually start). The car will smoke like a bitch when it starts. Take the car out, varying the throttle while driving. When it stops smoking, your all done!

[Anonymous]

How much does tis can cost?

[pocket-rocket]

About $7 or 8 I think. Not more then $10 though. Well worth it vs tearing the engine down and cleaning it by hand since most cleaners on the shelf won't do snot for carbon build up. If you plan on doing this when doing plugs, I suggest doing this before changing plugs. I am not saying they will ruin new plugs, but better to do it on old plugs vs new ones.

[pocket-rocket]

Ok, here is the backup of the article that used to be on the site:

Carbon buildup can hurt performance, from the knock retard it can induce to the restriction in airflow and improper valve sealing in the combustion chamber. It is a good idea to go through this process as part of your tune up procedure.

Buy a can for top engine cleaner from your GM DEALER (other decarbon
fluids dont work as good). You want the liquid, not the spray. This is to be done outdoors ( a lot of smoke will occure). Part # should be 1050002



Start motor and let it reach normal operating temp.

Find a vaccum hose which has vaccum at all times (with engine running)

Open can

Stick vaccum hose in top engine cleaner

Hold the idle up as the car will try to stall

Let the car suck the fluid into the engine

Dont let the vaccum hose come out of the fluid,as if it does NO DECARBONIZING WILL OCCURE

Let about 90% of the can go into the car and then let it stall

Reconnect vaccum hose to vehicle.

let it sit for 10 minutes

Start car, car will smoke a lot

Drive around till smoke discontinues (better to try and use 30%, then 40% and then 50% and all the way up to 100% throttle)(meaning that you dont use one set gas pedal pressure)

[pocket-rocket]

I do have to add, my car didn't really want to stall out hard enough so we had to shut the car off with the key, so if you have a spare body around that isn't doing anything, you could grab them to make it easier. If you think your car won't die, and you don't have anyone around to help, put a pair of pliers on the ECM fuse and pull it when the level in the can gets low enough so you don't suck any air, wasting the whole deal.

[Cliff8928]

I'd do this right before an oil change aswell... I believe the directions do recommend an oil change after using the Top End Cleaner..

Cliff Scott
89 BerettaGT
89 Volvo740

[pontiac92gp]

so you only use 90% of can, then stall? what about other 10% ?

[pocket-rocket]

Dump it in the gas tank along with another full can of the stuff.

[demonte1997]

Does the TEC eat away at seals and gaskets?

[dykz34]

I would assume that it doesn't since its a GM part.

[loucks3]

Thanks I am going to do that.We also just checked the timing belt and it looks like thats going to have to be done!!