2000 Grand Am GT low on power

[bfarroo]

This is the wifes car. Has 90,000 miles. Just did plugs, wires, fuel filter, cleaned the MAF sensor, and a top end cleaning.(Some air powered Snap-on machine that hooks up to the schroeder valve and runs a chemical/gas mix through the injectors and through the engine after pulling the fuse for the car's pump) Still seems to be down on power. It's most noticeable at highway speeds when you go to step on the gas to pass or go up a steep grade. My next guess is a plugged cat. How could I test that? if I use a IR heat gun will there be a large temp difference front to back? I though I remembered reading this somewhere. I'm assuming that it will throw a code of i pull out the cat and replace it with a straight pipe. We have owned the car since new and all maintenance has been kept up, oil changes at 3000 or less with synthetic blend or better. The intake and head gaskets were replaced around 70,000 by the dealer as the intake gasket was shot and the head gaskets were weeping. There is a little bit of a tick in the top end that doesn't sound the greatest and is most noticeable when you free rev the engine.

Let me know what you think,

[Orangetona]

I would try an O2 sensor. When that light comes on, you can probably hook it up to a code reader and hopefully itll tell you whats wrong.

[BadAssPerformance]

Sorry, nothing you can do, that's just what you get for letting your wife drive off-brand product :D

Which engine? With the valvetrain tick.. are you sure you dont have a lifter or cam lobe issue?

Things that could make any engine do that... plugged cat like you said... carboned up intake/TB... weak coil...

As long as you dont have E-test, if you replace the cat with a pipe, you can get a 'O2 simulator' from Summit, etc. to replace the OBD-II (rear) sensor.

[bfarroo]

It's the 3400, It doesn't currently throw any codes. I may have to look into the simulator if I pull the cat. I'm going to look around for one of those infrared thermometers as I don't currently have one and check over the cat. Any idea what a normal temperature reading would be? I know they have to pull some valve train parts when they do that intake gasket, I know at least the push rods. I'm wondering if they messed something up or something is loose although it went 15,000 miles before noticing this current problem. The TB is pretty gummed up I could probably pull that and clean it although I wouldn't think that would make that much of a power difference. I'd think it would be more idle and driveability but it can't hurt to clean it. I guess it could be a coil issue, stock gap is like 60 thou which looks huge compared to our TD's.

[Speedeuphoria]

Removing the cat does throw a code and the check engine light stays on. You can leave the sensor in free air I think and will not throw the code, although it may stop working if left under the car especially with water/snow. I though someone put it under the pass seat in a can/jar and left it hooked up

Autozone can read the codes for free.


I have a 99 GA 3400 and not had any major probs, 145k miles, my mother has an 03 GT w/ 95K and no probs. Well if you want to get tenical the blower motor resistor just went out on hers and on mine the fan does not blow till "3" on the dial but still works so I have no need to replace mine(and its a PITA for only a couple bolts).

Actually once and awhile it will studder soon after startup or right when you take off it will be low on power like not firing on all cyls(sounds kinda like your issue) I just replaced the plugs so not sure if that helped or not yet.

I did not know the gap was 60 thou, mine are whatever came on the plugs like 45 thou. I would try to lower the gap and if it helps, then try a coil if you want

[Orangetona]

If you replaced the plugs, make sure you replace them with ACs ive seen the 3.4L react badly to anything else. As well as other GM engines. Ive owned a few of these cars, my current one is an 02 GA SE 3.4L They are good cars aside the intake leaking and ABS problems. Also, a weakening coil can be your problem. Also, another thing to think of, the transmission on them are kinda sluggish also, especially when cruising youre running at about 1600 rpm at 55 mph. Also, every 3.4L ive owned has had a bit of valvetrain clicking. It seems like a normal thing with them, I dont think its anything to worry about.

If you cant fix it, go to www.gaownersclub.com and post in the help section there, they should be able to help also. Ive been a member there for a while. Theres some 'know it alls' but thats a factor on any board. Hope this helps.

JT, 3.4L is all that came in a 00 Grand Am GT.

[turbovanman]

Don't buy a temp gun, check cat temps is a waste of time.

The best way to test is a backpressure test, drill a hole for a fitting in front of the cat, hook up some brake line, coil it then hook to a vacuum/boost guage. Go for a drive, WOT it, you shouldn't see more than 4-5 psi of pressure, if you see more, exhaust is plugged up.

I would guess you could have damaged the MAF cleaning it, seen that done before. How did you clean it?

Ox sensor won't affect WOT, neither will dirty TB but it will help idle and cruising.

Weak coil/coils would give you a misfire, not lack of power.

Even leaving the ox in the open air will still set the SES light, either put another cat in if its bad, or use a test pipe and O2 simulator as the comuter use's the rear ox for fuel trim top up.

It could also be a weak fuel pump, do a pressure and volume test, should fill 1 pint in 30 secs.

I disagree, GM plat plugs are crap, the little plat pellets always fall off. I use NGK or Autolite iridiums, awesome plugs, :thumb:

[Orangetona]

I disagree, GM plat plugs are crap, the little plat pellets always fall off. I use NGK or Autolite iridiums, awesome plugs, :thumb:

I was not talking about AC platinums. AC Iridium is the OE recommended replacement plug. In my system platinum AC is not even an option. I could not even tell you the plug number if it exists. However, the older 3.1L does.

Edit: the early 3.4L does have a rapidfire platinum my mistake. Yes, those #14 plugs are poop.

[black86glhs]

99% sure you have a bad Converter. Pull the O2 sensor in front of the converter and see if it runs better(doesn't run out of pull in the upper rpm). My friends Impala did the same thing before it really plugged up. I've seen it many times on both W & L/N bodies.

[bfarroo]

Don't buy a temp gun, check cat temps is a waste of time.

The best way to test is a backpressure test, drill a hole for a fitting in front of the cat, hook up some brake line, coil it then hook to a vacuum/boost guage. Go for a drive, WOT it, you shouldn't see more than 4-5 psi of pressure, if you see more, exhaust is plugged up.

I would guess you could have damaged the MAF cleaning it, seen that done before. How did you clean it?

Ox sensor won't affect WOT, neither will dirty TB but it will help idle and cruising.

Weak coil/coils would give you a misfire, not lack of power.

Even leaving the ox in the open air will still set the SES light, either put another cat in if its bad, or use a test pipe and O2 simulator as the comuter use's the rear ox for fuel trim top up.

It could also be a weak fuel pump, do a pressure and volume test, should fill 1 pint in 30 secs.

I disagree, GM plat plugs are crap, the little plat pellets always fall off. I use NGK or Autolite iridiums, awesome plugs, :thumb:

I cleaned the MAF with MAF cleaner per the instructions on the can. Also this was after the slugish performance started not before. The plugs are NGK Iridium plugs. I'll give the fuel system a check over. I also cleaned the TB yesterday buy it didn't seem to make to much of a difference although it does seem to idle a bit smoother. I'll try the pressure test when I get a chance also.

[turbovanman]

I cleaned the MAF with MAF cleaner per the instructions on the can. Also this was after the slugish performance started not before. The plugs are NGK Iridium plugs. I'll give the fuel system a check over. I also cleaned the TB yesterday buy it didn't seem to make to much of a difference although it does seem to idle a bit smoother. I'll try the pressure test when I get a chance also.

Ok, but HOW did you clean it? just spray it, or remove the mesh and use a toothbrush?

The best way to clean them is pry off the mesh cover-insert a screwdriver at the side and pry up-don't go into far or you'll hot the tiny wires, spray the little wires, get a toothbrush and very carefully clean off the film, then clean. I then blow off with an airgun, then finish off with some brakecleaner but if you have the proper cleaner, you'll be fine. Spraying it won't remove all the crap and that mesh blocks you from cleaning it properly. Disconnect the battery to clear out the learning cels, touch whichever terminal you undid to the other one, IE if you removed the neg, jump it to the pos, this clears out all the juice. Hook back up, and hopefully, its fixed. I've seen alot of dirty MAF sensors cause lots of issues, especially if you don't clear out the memory.

[bfarroo]

I'll try clearing the memory, I thought I could see the tiny sensor wires from the back of the sensor so I didn't see a need to remove the mesh. I also was wary of breaking something by getting to aggressive with a tooth brush so I just sprayed it off until everything was clean. I'll be out of town in Texas the next week so I'll have to work on it next weekend if I come up with any more ideas.

[turbovanman]

I'll try clearing the memory, I thought I could see the tiny sensor wires from the back of the sensor so I didn't see a need to remove the mesh. I also was wary of breaking something by getting to aggressive with a tooth brush so I just sprayed it off until everything was clean. I'll be out of town in Texas the next week so I'll have to work on it next weekend if I come up with any more ideas.

Spraying behind the wires does nothing, the air flow is thru the front and will coat the tiny wires. I just did a T-Bird on Thursday, they don't have the mesh but use special screws???????? Anyhow, took it out and they were black, turn it around, clean. So a light touch with a toothbrush, clear the memory and the power was back. :clap:

I hear you on the mesh but its actually worth a HP or 2 as it lets all the air hit the wires with not having the mesh redirect it.

[bfarroo]

I had some time this past weekend so I pulled the MAF sensor and took it apart and cleaned it thoroughly. I also installed a fitting before the cat to check for pressure. At idle there was 0 psi and the most I saw was 4 psi with the car floored at highway speed so I'm guessing the cat isn't plugged. I'm at a loss. I guess my next check would be to find someone with a scanner to check O2 voltage and make sure things there are in spec. I've been driving the car as much as I can and it seems to be worst at lower RPM's. I need to get the car in and get the trans flushed and a fluid/filter change although I can't imagine that causing the issue. Any other ideas?

[turbovanman]

Did you test fuel pressure and volume?

The only other thing it could be if the fuel pump is ok is dirty injectors, best way to clean is off the car but the next best is a seperate cleaner-you remove the fuel lines and run the cleaner thru the fuel rail, running the car. Ford CXC200 is the sh*t.

If you can find someone, have them check the ox sensor with a labscope, they can verify the operation, tell if its running lean and if the injectors are plugged.

[bfarroo]

I had a Friend with a snap-on injector cleaner and some special expensive cleaner do a injector cleaning for me. Not sure what the chemical was but the machine hooked into the fuel rail and you ran the car on this cleaner/gas mix. I haven't tested fuel pressure yet but I'll add it to my list. I may pull the plugs and see what they look like. The intake gasket was replaced under waranty a few years back but I've heard of dealerships using the same crap gasket and it going bad again :( it hasn't been using any amount of coolant but who knows.

[black86glhs]

4 psi isn't bad, but I rarely have seen over 3 on a good converter. Not saying this is definitely the case, but I still suspect it.
You are correct on the gaskets. That is how GM got rid of a lot of the crappy ones they had in stock. I used to do it before they had the new ones out, it was the only ones we had.

[bfarroo]

Yeah I suppose the dealer isn't going to go down to the local parts store and pick up a decent gasket when they can put the crap gasket back on it and soak you for another 700 dollars in 4 years.

[turbovanman]

Yeah I suppose the dealer isn't going to go down to the local parts store and pick up a decent gasket when they can put the crap gasket back on it and soak you for another 700 dollars in 4 years.


There is NO decent gasket, they are all the same. :o

[black86glhs]

There is NO decent gasket, they are all the same. :o
My friend Jason just did a 3.4 intake and the gaskets were metal with neoprene. I'll ask him what brand they were. I think they were Felpro, but I'll double check.

[bfarroo]

Yeah the felpro ones are the better ones, not made out of that plastic stuff like the factory ones are. So what's the lifespan on the factory gaskets?

[chilort]

Check for a recall.

I had an '02 Monte with the 3.8L. The cat clogged up about 2 seconds after I ran out of power train warranty. Turns out, after I paid to have a shop replace all of the exhaust system (because I wanted something better), GM recalled it. They ended up paying for the cheap'o cat I put on it, but if I would have had the work done in their shop, it would have been paid for by GM. Drat.

[turbovanman]

Yeah the felpro ones are the better ones, not made out of that plastic stuff like the factory ones are. So what's the lifespan on the factory gaskets?

Felpro around here are identical to factory gaskets, except a different colour. GM is blue, Felpro red, :confused:

Lifespan seems to be around 100-150 km's, although my Jimmy is at 190K and still ok?

[rich tideswell]

... plugged cat like you said... .

this was the exact problem with my buddys 2002. he has about 60k on his car

[black86glhs]

Felpro around here are identical to factory gaskets, except a different colour. GM is blue, Felpro red, :confused:

Lifespan seems to be around 100-150 km's, although my Jimmy is at 190K and still ok?
The ones he used, a few weeks ago, were the first ones I have seen with the metal around here in Akron. I like how they looked.

[bfarroo]

So with 4 psi being questionable I'm thinking about picking up a universal cat and replacing the stock one. I figure I should be able to get what I spend on a cheapy aftermarket one back selling the old one. Is there any drawback to the cheaper cats at the parts store? We don't have emisions here so I won't have to bring it in for testing at all. I just need something so it doesn't throw any codes. I drove the car more this weekend and it almost feels like it chugs at low rpm. I may try and unbolt the cat and see if that makes a difference in power. If it's completely unbolted or partially will it still run ok?

[turbovanman]

Thats fine, just unbolt and go for a drive.

Cheapo cats are fine, just try to get a larger unit as they flow more.

[chilort]

I can't seem to find anything about a recall or warranty extension on the cat. This is really annoying because I am 100% positive my 2002 had a warranty extension. I know you may want to go with a high flow cat, but if you can get it replaced for free by the dealer .... stopping by and finding out for sure can't hurt.

[turbovanman]

They have a basic 5 year, 100,000 mile warranty on them or it could be 60,000 miles. It should be in the owners manual.

[chilort]

The PT for my '02 Monte was 8yr / 80,000 miles. But, they were having so many fail with 80,000.1 miles on them they extended the warranty. But I sure can't find anything about it on-line. And I don't own the car anymore and don't have any of the documentation sitting around.

http://farm1.static.flickr.com/230/446698126_2d8d820d2d.jpg

[DaveSkrab]

It certainly sounds like a restricted Cat. Though VERY rare, I've seen broken torque converter stator cause some lack of power issues (no torque multiplication)
Additionally, unplug the MAF sensor and go for a drive. This will help isolate the problem. Vehicle will default and not use any MAF reference.
Also, as Simon mentioned, check for good fuel pressure and flow.

[bfarroo]

I checked pressure an have 52 at idle and 60 with the vacuum line unhooked. The pressure went to 60 when stepping on the gas and didn't fall off at all so I don't think it's fuel related. I'm going to try unplugging the MAP tomorrow. This weekend the cat is getting replaced if I don't find anything else.

[turbovanman]

I checked pressure an have 52 at idle and 60 with the vacuum line unhooked. The pressure went to 60 when stepping on the gas and didn't fall off at all so I don't think it's fuel related. I'm going to try unplugging the MAP tomorrow. This weekend the cat is getting replaced if I don't find anything else.

You need to do a volume check, you can have pressure but no volume. 1 pint in 30 secs minimum.

[black86glhs]

You need to do a volume check, you can have pressure but no volume. 1 pint in 30 secs minimum.
A pint in 30 seconds....sounds like the beginning of a good night!:thumb:

[bfarroo]

If pressure doesn't drop off then there should be enough flow shouldn't there?

[black86glhs]

No. It can look like pressure is good, but the volume is not there. Sounds odd, but like Simon, I have seen this many times.

[bfarroo]

Spent some more time today looking over the car. The compression looks good. 120 on the first cycle then 180 on the second and slowly increases to 190 - 200 on all 6 cylinders. Ran it with the Mass Airflow sensor unplugged and it ran like crap so that didn't really tell me anything. I pulled the cat and it was slightly plugged, there were a few passages that I couldn't see through but nothing bad. I replaced it with a universal replacement anyway. I also put in a new oxygen sensor just because it's getting old and I was doing all the other routine maintenance stuff. It still seems low on power. I notice it most in 3rd gear when on the highway. The top end has a rattle in it that is slightly noticeable at highway speed when you step on it. Any possibility a knock sensor is pulling timing? I can feel a slight surge when stepping on the gas at highway speeds. The only other things I can think of are the Mass Airflow sensor or possibly a coil pack producing a weak spark. The engine also pulls 19in of vacuum at idle if that matters. I'm going to try and find out if there is a knock sensor and unplug it and take it for a ride and see if I notice anything.

[black86glhs]

Benji, the mass air flow is something to look at. Replaced the one in my wifes V6 Saturn and it made a difference. Her model Saturn is known for it, though. I would yank the valve covers and check the rockers. I have found broken or cracked ones beforeon 3100 and 3400 V6s in the past. It could also be one that isn't tight anymore(possible it wasn't torqued properly in the past). I forgot to check, but have the intake gaskets been done?