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SSRacer
06-24-2009, 09:00 PM
OK, here's what I got
2002 GAGT 3.4 Auto 96,000 miles
Plugs (AC Delco Iridium) & fuel filter are less than a year old
WAI with K&N filter cleaned recently, MAF cleaned at the same time
LIM and cat replaced years ago
Transmission fluid and filter change at around 50K
Oil and filter change a couple of months ago (mobile 1 synth high mileage 10W-30)
No SES or SVS lights

Here's the problem
Low end power is gone and I'm averaging about 20mpg
From a stand still the car just has no power anymore. It used to break the tires loose any time, but now it just lugs off the line even if I get on it (not talking racing or anything, just like getting out into traffic). Once up in the RPMs it gets up and goes pretty good, but the bottom end power is just gone. It doesn't feel like its bogging down, its just not going.

Idles fine and runs smooth.

Anybody have any ideas?

Mike Jung
06-24-2009, 09:15 PM
WAI & hot air = not good ?

Fuel injectors clean ?

SSRacer
06-24-2009, 09:28 PM
been probably 6 months since the last time I used any fuel system cleaner. Might giver that a shot since its cheap and easy.

TheWAI as been on for a couple of years and is better than the stock airbox.

Jhashwa
06-24-2009, 11:08 PM
Transmission shifting through all the gears on acceleration? Maybe its taking off in second or third gear.

burgett2103
06-24-2009, 11:11 PM
if you replaced all your plugs, may one of your plug wires be loose or not plugged in all the way?

SSRacer
06-25-2009, 08:09 AM
Transmission seems to be shifting fine, I don't think it's starting me in second. I may look into new plug wires because the ones on it are about 5 or 6 years old now, but I know I got them all on tight.

Wondering if it could be an O2 sensor issue

cardude007617
06-25-2009, 09:41 AM
yeah id replace the wires, toss a new o2 sensor in it seeing as how you are at 100k basically and even possibly look into a new IAT; theyre pretty inexpensive and i think a new one would be much more accurate than one that has seen 96,000 miles...

SSRacer
07-04-2009, 09:09 PM
New front O2 sensor didn't do much. SES light popped on tonight, so off to autozone I go to get it scanned tomorrow.

[ChaosweaveR]
07-04-2009, 11:53 PM
Post up what codes come up, since I work at Autozone myself. I have a feeling it maybe either the 02 sensor after the cat, and maybe the wires. Not to say a missfire, but a weak spark.

AaronGTR
07-05-2009, 09:02 AM
You are using the wrong oil too. You should be using 5w30. Technically using the thicker oil will create more pumping loss inside the engine and might cost you a couple hp... but nothing that would be noticeable like what you described. It's next to impossible to diagnose a problem like that over the internet without SES light and code or anything more specific to go on. You really need to see and drive the car in person and scan it.

SSRacer
07-05-2009, 10:04 AM
Well, the code was for the pre cat O2...that I just replaced a week ago with a bosch from autozone...guess I'll pull it back out and get a replacement, it has a 1 year warranty....grrrr

Mike Jung
07-05-2009, 10:14 AM
Bosch O2 sensors & spark plugs are crap for our cars (I keep on hearing).

mfuller
07-05-2009, 10:15 AM
Bosch O2 sensors don't work too well on these cars for one reason or another.
Stick with Denso or ACDelco (which I think is made by Denso).

SSRacer
07-05-2009, 10:44 AM
Great. So for those that work at autozone, what are my chances of just getting my money back instead of swapping for a new one or having them put the money toward a denso one, even thought that is special order

SSRacer
07-05-2009, 01:31 PM
Just took the bosch back to the zone. They wanted over $100 for a direct replacement denso so I just had the money put back on my car and I'll get it online. Also went ahead ans ordered a scanner from amazon so I can do this myself from now on

[ChaosweaveR]
07-05-2009, 03:24 PM
They're idiots at that store then. I looked up prices from my store, it is over $100, but they could have returned it under warranty, and put the return towards the Denso sensor, and you pay the difference. I've done it before. You would have paid about 35 bucks with tax. Give them a slap for me, will ya?

SSRacer
07-05-2009, 05:38 PM
I could have done that, but I got the denso from amazon for the same price as the bosch at the zone, so it will take a couple of days to get (but they would have had to order it too), but it didn't cost me any extra.

AleroB888
07-05-2009, 09:34 PM
This is funny, I've had a Bosch O2 sensor in mine for 3 years, maybe I should put my old one back in. I thought it ran a little lean....
lol

[ChaosweaveR]
07-05-2009, 11:46 PM
I planned on getting the Denso's for mine once my sensors go. But knock on wood, 103k, and they're fine. I just need to get a dummy for the one after the cat. My SES light has been on ever since I got my new cat (P0420)

SSRacer
07-06-2009, 08:30 AM
On the bright side I can now change that sensor in about 5 minutes...lol

ltpats
07-06-2009, 08:51 AM
;1083181']They're idiots at that store then. I looked up prices from my store, it is over $100, but they could have returned it under warranty, and put the return towards the Denso sensor, and you pay the difference. I've done it before. You would have paid about 35 bucks with tax. Give them a slap for me, will ya?

35 bucks + what they refunded him, he still will be paying over 100 bucks for the Denso, not 35 bucks.

[ChaosweaveR]
07-06-2009, 10:39 AM
35 bucks + what they refunded him, he still will be paying over 100 bucks for the Denso, not 35 bucks.

How so? He got refunded his 80 something back, and it would be put towards the new one. Sean still has to pay close to 100 anyway, would have been easier to get the refund, and put it towards the Denso, and pay the difference, IMO.

AaronGTR
07-06-2009, 11:29 AM
I say why bother with a $100 denso O2 sensor? You can get a denso from rock auto for $49 or a ac delco one for $75.

ltpats
07-06-2009, 11:35 AM
;1083301']How so? He got refunded his 80 something back, and it would be put towards the new one. Sean still has to pay close to 100 anyway, would have been easier to get the refund, and put it towards the Denso, and pay the difference, IMO.

I guess my point was you can get them way cheaper than $100.00. Your post (the way I read it anyway) was saying that once he gets the refund and applys it to the Denso it will only cost him 35 bucks. What I was saying was yeah 35 + the 80 buck refund = over 100 bucks out of his pocket.

SSRacer
07-06-2009, 11:53 AM
The Bosch one from AZ was a little over $50. They just refunded it to my card at my request because their Denso was just over $100, so even if they had just put the refund toward teh Denso, I still would have been out $100 overall. I went home, got on Amazon.com and bought a Denso for $51 shipped.

In the end I spent $51 total for the O2 sensor.

Also ordered my own scanner from Amazon while I was at it....something I have wanted for a long time.

[ChaosweaveR]
07-06-2009, 11:59 AM
Geez, that's a big difference. Maybe I should go Amazon when I need one. And having your own scan tool is very handy, especially if you need an inspection soon. ;) and I didn't realize it was a credit purchase, so you can't even ring up the return and scan the new part. I knew it was still like 100 something, but I thought he could have just exchanged them (bosch for denso) either way, it's done. lol

SSRacer
07-06-2009, 12:27 PM
;1083314']And having your own scan tool is very handy, especially if you need an inspection soon. ;)

We haven't had inspections here for years...thank god...and even when we did, they were much less stringent than some states.

[ChaosweaveR]
07-06-2009, 07:38 PM
We haven't had inspections here for years...thank god...and even when we did, they were much less stringent than some states.

Lucky bastard. lol If I didn't have the NYS inspection, I would have re-newed my registration already. Arg.

Metalxen
07-07-2009, 06:13 PM
what type and how much was the scanner?

SSRacer
07-07-2009, 06:20 PM
I got this one:
http://www.amazon.com/gp/product/B000EVWDAK/ref=ox_ya_oh_product

it was $90 and change, but I signed up for the amazon visa and I'll get $30 back :D

Mike Jung
07-07-2009, 06:51 PM
I got this one:
http://www.amazon.com/gp/product/B000EVWDAK/ref=ox_ya_oh_product

it was $90 and change, but I signed up for the amazon visa and I'll get $30 back :D
That isn't a scanner; it is just a code reader.

SSRacer
07-07-2009, 06:57 PM
OK...sorry...code reader

[ChaosweaveR]
07-07-2009, 07:06 PM
That isn't a scanner; it is just a code reader.

Smartass. :hay:

SSRacer
07-07-2009, 07:12 PM
lol...yeah, I guess it will be completely useless now...lol

Won't be here until next week....stupid slow free super saver shipping...lmao

[ChaosweaveR]
07-07-2009, 07:28 PM
lol...yeah, I guess it will be completely useless now...lol

Won't be here until next week....stupid slow free super saver shipping...lmao

Is it brought in by mule?

SSRacer
07-07-2009, 08:14 PM
;1083543']Is it brought in by mule?

USPS....same difference...lol

aiixon
07-08-2009, 10:46 PM
lol...yeah, I guess it will be completely useless now...lol

Won't be here until next week....stupid slow free super saver shipping...lmao

When you sign up for Amazon Prime you get something like 3 months of 2-day shipping if my memory serves me right. I know you get at least SOME 2-day shipping for free.

SSRacer
07-08-2009, 10:55 PM
When you sign up for Amazon Prime you get something like 3 months of 2-day shipping if my memory serves me right. I know you get at least SOME 2-day shipping for free.

Already done that once before...lol

[ChaosweaveR]
07-09-2009, 12:44 PM
USPS....same difference...lol

lol

SSRacer
07-09-2009, 06:50 PM
got my sca...I mean code reader today...lol.

AZ didn't clear the codes so it was still in there P0141. Cleared it and it hasn't come back with the original O2 in there yet. Hopefully the Denso will be here tomorrow

SSRacer
07-11-2009, 04:44 PM
Denso O2 has been installed :D

Mike Jung
07-11-2009, 05:59 PM
Denso O2 has been installed :D
& the result is ?

AceGAGT
07-11-2009, 08:02 PM
I seriously doubt it was the o2 sensor, they are continuously monitored by the pcm, if you cleared the code and the MIL didn't come back on immediately then your pre cat 02 is switching like it should, And i personally don't like the iridium spark plugs they don't have enough resistance in them so the spark they create isn't very strong. Try disconnecting your MAF sensor and seeing if the problem goes away, it might shift hard but it will still run and if your MAF is the problem the car will run stronger than with it connected.

AaronGTR
07-11-2009, 08:37 PM
I seriously doubt it was the o2 sensor, they are continuously monitored by the pcm, if you cleared the code and the MIL didn't come back on immediately then your pre cat 02 is switching like it should, And i personally don't like the iridium spark plugs they don't have enough resistance in them so the spark they create isn't very strong. Try disconnecting your MAF sensor and seeing if the problem goes away, it might shift hard but it will still run and if your MAF is the problem the car will run stronger than with it connected.


Wrong on many points. Just because the SES light doesn't come back on immediately after clearing a code does not mean it's working correctly. Many of the O2 sensor codes have to fail the diagnostic tests that set them under the same conditions for two consecutive trips. ;) Meaning he'd have to drive the car at least twice for the light to come back on, possibly more.

And there is nothing wrong with iridium plugs. And resistance does not create a strong spark either. More resistance=more power loss and less spark. The only reason they use iridium is because it resists melting to a higher temp than platinum so they can make the electrode smaller without it melting, and a smaller tip makes the spark jump easier with less voltage requirement. The reason they use platinum is because it heats up and stays hot at a lower temp so it burns off impurities and keeps the tip of the plug clean. Great for running 100,000 miles, bad for detonation resistance and making HP. Better to use iridium or copper plugs if tuning for power.

Lastly, disconnecting the MAF is NOT a good idea. The MAF sensor is the computers first and primary means of calculating fuel needs and engine load. If there was a problem with the MAF it would definitely have shown a trouble code for it by now. Some cars (like mine) won't even stay running without it connected. Some less modified cars will go into speed density mode and may run, but they will run much MUCH worse without it. They basically go into a default "limp" mode so you can drive the car long enough to get it somewhere to get the MAF fixed. These cars where not designed to run solely off the MAP, and the MAF is used for all kinds of other calculations in the PCM. Running without it for too long risks possible engine and transmission damage.

SSRacer
07-11-2009, 10:06 PM
Haven't really got on it yet to check the accelleration, but I have already driven longer with the denso than I did the bosch and no ses...lol

GAGT_99
07-12-2009, 01:27 AM
Try Seafoam. Put 1 in engine with new oil change & 1 in gas tank.

SSRacer
07-12-2009, 08:52 AM
I have seafomed...oil, gas and top end all within the last year

AceGAGT
07-13-2009, 08:45 PM
you need resistance to get the spark to cross the gap that is why they put insulation in the spark plugs, if the resistance was too low then the spark would be weak (fouled spark plugs) as it would take less voltage for the spark to cross the gap = weak spark which is the whole point of making sure your gap is within spec, think of lightning strikes, the air is resistance so it takes millions of volts for it to jump the gap = strong spark, and it doesn't always take 2 trips for the MIL to come back on, if it is a major input to the pcm then it will come on immediately which the 02 is so if it was a bad 02 then it would come back on immediately, because its constantly being monitored. The only reason it may take 2 trips for light to come back on is because when you clear the code you clear all of the monitors and it could take 2 or more trips for the monitor to run for certain systems but not the 02. And as long as you have a MAP sensor which Grand Ams do the car will still run. It will use on-board calibrations to keep it calculating incoming air using the tps and map voltage. And the 02 sensor calculates your fuel needs, by reading 02 left over from rich to lean mixtures to get the fuel trim right.

SSRacer
07-13-2009, 09:21 PM
wow....lot of info there, thanks. The new O2 has been in for several days and a number of trips, no codes are showing up.

AleroB888
07-13-2009, 10:33 PM
you need resistance to get the spark to cross the gap that is why they put insulation in the spark plugs, if the resistance was too low then the spark would be weak ..............

I believe you've got it fundamentally wrong at this point....

Of course there has to be insulation in the plug, so it is not a dead short to ground, but the more resistance in the gap, as if the gap is made wider, the more voltage required to get a strong spark......
But the voltage at the gap is fairly constant. Then V = I x R, so when resistance increases, current in the gap goes down, therefore a weaker spark.

AaronGTR
07-14-2009, 01:04 PM
you need resistance to get the spark to cross the gap that is why they put insulation in the spark plugs, if the resistance was too low then the spark would be weak (fouled spark plugs) as it would take less voltage for the spark to cross the gap = weak spark which is the whole point of making sure your gap is within spec, think of lightning strikes, the air is resistance so it takes millions of volts for it to jump the gap = strong spark,

Hate to break it too you, but as Greg pointed out you've got the fundamentals wrong about how a spark plug works. They put insulation in spark plugs to keep the inner electrode where the current is traveling separate from the outer casing which is threaded into the cylinder head and provides the ground path. That is what forces the current to jump the gap. It has nowhere else to go. It has nothing to do with resistance. The electrical properties don't have anything to do with plug fouling either as you claim. That is completely determined by heat range of the plug. One of the primary factors that determines the heat range is the length of the insulator nose.

Read this and tell me where it says anything about resistance.

http://www.ngksparkplugs.com/tech (http://www.ngksparkplugs.com/tech_support/spark_plugs/index.asp?mode=nml)


and it doesn't always take 2 trips for the MIL to come back on, if it is a major input to the pcm then it will come on immediately which the 02 is so if it was a bad 02 then it would come back on immediately, because its constantly being monitored. The only reason it may take 2 trips for light to come back on is because when you clear the code you clear all of the monitors and it could take 2 or more trips for the monitor to run for certain systems but not the 02. And as long as you have a MAP sensor which Grand Ams do the car will still run. It will use on-board calibrations to keep it calculating incoming air using the tps and map voltage. And the 02 sensor calculates your fuel needs, by reading 02 left over from rich to lean mixtures to get the fuel trim right.\

Sorry, but you're wrong about this too. I'm not making this stuff up, I'm taking it directly out of my GM service manual. ;) I have a tuner and do my own pcm tuning too so, take that as you will.

The exact conditions for setting the dtc codes for the front O2 sensor depend on if the codes have to do with the operation of the sensor, or if the sensor is working but it's performance has degraded. Every code though, EVERY one listed in the manual, says it may store in the pcm but it does NOT turn on the MIL until the second trip!

You are right about the O2 sensor being monitored constantly, but not about the fault reporting. Also fyi the pcm doesn't use the O2 sensor at all during warm up or during acceleration enrichment, also called open loop, which is over 70% throttle. When you first start the car it primarily calculates fueling based on pre-set maps and signals from the MAF, TPS (throttle position), and ECT (engine coolant temp). Yet another reason it's important to have a MAF sensor. Under 70% throttle the PCM uses the O2 sensor as the primary means of determining injector pulse width and corrections needed to maintain 14.7:1 AFR, hence the short and long term fuel trims. Those correction numbers are still made to base tables that are first looked up by the MAF, TP, and ECT sensor values. If the MAF is missing it will continue to run only if your car isn't too modified. Modifications change the cars VE, and though you can alter the VE tables to lower your fuel trims and make the car run better, when the MAF is missing it only has 2 of the 3 original numbers it needs. It changes to some default fuel and spark timing tables based on those 2 numbers, and those default numbers may not be very close to your modified VE tables. Case in point, my car will not stay running with the MAF disconnected. The MAF is also used to determine engine load which is used in a lot of the transmission tables. That is why it shifts so hard when you put it in gear with the MAF unplugged. It has nothing to go by so it sets to a default line pressure, and that can damage your trans over time. I know it's a lot to process but stay with me here.

Now, about the MAP sensor you claim will keep the car running... it does NOT calculate incoming air. This is straight from the manual.

"The MAP sensor is used to determine manifold pressure changes while the linear EGR flow test diagnostic is being run. Refer to DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient, to determine engine vacuum for other diagnostics, and to determine barometric pressure (BARO)."

It only uses the MAP to determine outside air pressure as a secondary modifier to the fuel tables. Just as it uses the intake air temp (IAT) sensor primarily for spark corrections, but also to determine air density as a secondary fuel table modifier. I also know this about the MAP from first hand experience. My tuner has an option for scaling the MAP signal so you can use a 2bar MAP, however after trying a 2bar MAP from a grand prix GTP I found that the Kpa signal was working perfectly but didn't affect my injector pulse at all. However the grand am lacks a piece of programming that the grand prix has that keeps the PCM from resetting barometric pressure over 100Kpa when the engine sees boost, and after I hit boost my baro would be set at 140kpa and my fueling at idle was all screwed up. ;)


Like I said I'm not making this stuff up, and I don't particularly like to argue (although some here might argue that point lol ), but I don't like people on the forum getting misinformation either.

AceGAGT
07-14-2009, 07:54 PM
Well I'm not as dumb as I look lol and i don't like to argue so all points taken.

SSRacer
07-14-2009, 08:42 PM
This discussion has not helped my headache any....lol

themanytoys15
07-15-2009, 12:31 AM
Well I'm not as dumb as I look lol and i don't like to argue so all points taken.

dont ever argue with arron, you'll never win, its like argueing with someone who always wants to be right, waste of Time!! anyway so what was the cause of the dam carrr lagging??!!! no one made a ****ing point here!! :asshat :leg dam mexicans!!

[ChaosweaveR]
07-15-2009, 10:45 AM
dont ever argue with arron, you'll never win, its like argueing with someone who always wants to be right, waste of Time!! anyway so what was the cause of the dam carrr lagging??!!! no one made a ****ing point here!! :asshat :leg dam mexicans!!

Are you normally this stupid?

AaronGTR
07-15-2009, 12:41 PM
dont ever argue with arron, you'll never win, its like argueing with someone who always wants to be right, waste of Time!! anyway so what was the cause of the dam carrr lagging??!!! no one made a ****ing point here!! :asshat :leg dam mexicans!!


Is there something wrong with actually knowing something about a car you've owned and worked on for 9 years? That's typically what happens and then you end up being right a lot of the time. Sorry that doesn't fly with you. :rolleyes:

AceGAGT
07-15-2009, 08:51 PM
I doubt any of this bitching and moaning is going to help the real problem. So Sean how is the car running.

SSRacer
07-15-2009, 10:11 PM
lol...its running fine. no more codes since the new O2. Haven't had a chance to get on it to test the throttle response due to the weather. Just filled it up with gas so I'll keep track of the mileage on this one. no idea if I have fixed the "problem" or not

Honestly most of my working on a car time is being spent getting the truck in shape at the moment. Replacing all the steering linkage this weekend, changing the oil and putting drop shackles on the back to level it out. Just put a new O2 in it as well. Have a feeling it needs a new cat with 130K, cause its more of a dog than it really should be...lol.

[ChaosweaveR]
07-15-2009, 11:24 PM
Maybe a new exhaust is in order for the Chevy, Sean. lol Flowmasters anyone?

SSRacer
07-16-2009, 10:21 AM
;1085067']Maybe a new exhaust is in order for the Chevy, Sean. lol Flowmasters anyone?

Believe me, If I had the money that would definitely be done already...

[ChaosweaveR]
07-16-2009, 11:42 AM
Shouldn't be that much. I helped a friend of mine with an Explorer with a 5.0 get Flowmasters. The muffler was 80 bucks, he spent 19 on two tips, and the Meineke where I've gotten my exhaust done charged him 90 for the install, and that was with dual exhaust.

SSRacer
07-16-2009, 12:38 PM
Think I am just gonna cut out the cat and replace it with a strait pipe for now so it can breathe since I can't afford a new cat. Just discovered a sticking rear drum, so looks like I will be replacing a wheel cylinder as well...

sdk_89
07-17-2009, 06:49 AM
sounds like a coil pack but if you got a ses light on you can take it up to auto zone and get it check out for free

AaronGTR
07-17-2009, 03:22 PM
sounds like a coil pack but if you got a ses light on you can take it up to auto zone and get it check out for free


welcome to the party late comer. If you read page two you'll see that he already has his own code scanner. ;)

SSRacer
07-17-2009, 03:36 PM
Yup...and there are currently no codes

SSRacer
07-20-2009, 11:18 PM
Update...been giving the truck a break and driving the car for a few days. Power seems to be back and she definitely has some pep in her step again, so hopefully the O2 was my only issue.