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Author Topic: Odd loss of power issue  (Read 6160 times)
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zombienerd
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« on: June 06, 2014, 05:44:59 PM »

I have a 2004 Aztek with 170k on it.

From a dead stop, it accelerates fine up to 20mph, then loses power.  If you put your foot down, it will slowly accelerate, but only to 30mph or so.  This happens even if you manually set it into 2nd gear (or 3rd).

I figured it was the fuel filter, and changed it, with no luck.

The fuel pump is giving good pressure, and I don't suspect it, but who knows.

It feels as if the computer is killing the fuel to the engine, regardless of demand.

No Check Engine Light is on..  No codes found on the scanner.

Occasionally, it will not do this, and operates normally.  This has been happening on and off for about 3 weeks, with the past week straight being "on".

Does anyone have any idea what I can check next?  I'm at a loss.
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zombienerd
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« Reply #1 on: June 07, 2014, 01:43:53 PM »

After talking to a mechanic, I am lead to believe it is being caused by the catalytic converter... Has anyone else had one of these get plugged up?  Is this a common issue?
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zombienerd
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« Reply #2 on: June 07, 2014, 06:40:54 PM »

It was not the catalytic converter.  Had it removed and checked it out.. it's in almost new shape :/

The search continues.
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GTABill
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« Reply #3 on: June 07, 2014, 06:51:27 PM »

Keep us updated as I've got the same year with almost the same miles.
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2004 Blue Aztek (Blue Bobcat) 204K and counting
1991 Bright Red Trans Am GTA 41K miles as of 09/15..... 1st place at 09 & 14 Trans Am Nationals (Light Modified 82-92 class)
2006 Onyx Black GMC Sierra Denali (Wife's ride)
Finfan187
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« Reply #4 on: June 12, 2014, 12:02:50 PM »

Not sure if this is helpful or not, but I had a similar issue with my 1995 Honda Accord.  In addition to the very slow acceleration, it would idle really rough at times.  I ended up removing and cleaning the EGR valve which helped for about a day but eventually I changed the plugs and that seemed to do the trick. 
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2004 AWD Aztek
Formerly drove 2001 FWD
DetroitTek
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« Reply #5 on: December 11, 2014, 05:31:18 PM »

I have the same year same miles. Same problem. Can go 1/3 pedal and its fine. Past that it falls on its face rpms go up but no power and even sounds different. Fight threw it for a few miles and drives normal.
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04 Tek stock. 17 in wheels, leather heated seats, 6 disc in dash. 2015 Concours d'Lemons Michigan winner.
tt29mp
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« Reply #6 on: January 02, 2015, 10:56:24 PM »

I have a 2002 Aztek and I have just about done everything to it through the years. Last year it blew the headgasket and I followed the steps on this site and did the job myself for about 500.00. I had got several quotes of 1500-2500 to do the repair. It wasn't that bad at all and you will be surprised about the minimal about of tools that it takes to do the job. The only thing tough about it is laying across the engine to disassemble the top end of the engine. I did this job in the freezing cold with no heat in Pennsylvania. Now , about the lose of power issue. The first thing that i would check is the hose that is on the back of the upper intake manifold. If you take this off the nipple, the engine will just bog down and misfire. This hose has to do with the engine airflow and it is part of keeping the engine properly timed. PUll it off and run your hand all the way back to see if there are any holes or if it is loose in the back. You have to know that this engine doesn't have a distributor and all of the sensors have to be working properly for the engine to be timed correctly. If there is no issue with the catalytic convertor, then you should check the various sensors. They are relatively easy to check. All you have to do is put in gm 3400 engine and a website called "troubleshoot my vehicle.com" you will find all you need to know to check the sensors. Also, you need to check the coilpacks, you can do that with a multimeter and a 10.00 electronic spark plug tester. It looks like a spark plug with a clamp on the side. You have to take sometime and work through these things. take a note pad and not each component that you test, write down the readings. Also, take note that the number one spark plug is clear in the back on the left side of the engine as you are standing in front of it. When I took my engine down, I could not get the plug out. It is so difficult to get to if you don't remove several parts and roll the engine forward, that most people that don't take their vehicle to the mechanic dont change the back plugs. It is pretty easy if you know what to do. If you are having issues, email me at ttate67@excite.com and I will walk you through it.

I almost forgot about this, another major reason that vehicles don't respond well in acceleration is due to the spark plug wires being no good. They may look good, but most likely they are grounding themselves out on the engine block!!!! The easy way to check this is too get in a very dark place, start the vehicle, open the hood and look for little blue bolts of lighting arcing off metal parts around the wires. Sometimes you have to rev the engine up by hand, by pushing on the throttle to the right of the engine. I have overlooked this several times on numerous vehicles and just recently had the same issue with my aztek after putting the engine back together. Don't buy cheap wires!!!! I did and about 3 months later, they had it. Buy the ones that are at least 40-50 bucks and save yourself alot of headaches. Hope this helps.
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DetroitTek
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« Reply #7 on: January 04, 2015, 10:50:43 PM »

If the original poster is like mine it's a total intermittent problem. When the problem persists. When accelerating after 1/3 pedal travel power cuts off but car does not shut down. It's just gutless. Rpms will go up with more pedal travel but no power behind it. Back of the pedal to les than 1/3 and power comes back but only till you hit that 1/3 pedal 
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04 Tek stock. 17 in wheels, leather heated seats, 6 disc in dash. 2015 Concours d'Lemons Michigan winner.
Tom Moog
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« Reply #8 on: January 05, 2015, 02:53:29 PM »

The best way to see bad plug wires it to load the engine. Again, go to the dark place, but this time, take a friend. Have the friend put the vehicle in gear and hold the brake while pressing the accelerator down a little. When the engine loads up, you will see nice sparking action.
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Tom Moog

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Tronman
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« Reply #9 on: April 18, 2018, 10:45:38 PM »

I drove mine like this for over two years, til the coolant side of  the LIM gasket failed.  Thankfully I caught it real fast and didn't drive the car around with chocolate milk in its oil circuits.. also two exhaust manifold studs had broken so that cylinder was undoubtedly sucking air into the exhaust stream and altering the mixture that the computer thinks the engine's at.  So what was happening was that the engine was running lean-which makes the exhaust really hot.  Like it was melting the metal heat shields above the muffler!  So to protect the engine, converter, and the car from catching fire the computer puts the engine in OL Drive mode above a certain percentage of calculated load-this percentage seems to equal about a third of the throttle travel.

So now when I run it, it will for sure have no vacuum leaks-as I even had the heads milled and the valves all vacuum tested and they were fine.  I'm installing the Fel-Pro super thick rubber sealed metal LIM gasket, which is supposed to be the best solution to this common 3400 engine foible.

I'm looking forward to being able to put my foot down and feel the power again.
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Tronman
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« Reply #10 on: April 26, 2018, 07:03:55 PM »

Well poo.  Still LTFT of -25 (super lean) but the engine is making 24" of vacuum at 700 RPM.  It wouldn't have that kind of vacuum reading at idle if there were a leak large enough to cause that lean of a condition.  It makes over 25" of vac at 2500 RPM, too.

Here's a weird one tho:  live codes and data shows the computer only seeing 10" Hg at idle and 7-8 at speed.  The engine itself is always making lots of vacuum.  So..  maybe bad MAP sensor?  I'm also wondering if the fuel injectors could be to blame..  while I was in there, I hooked up the gauge and got 50 PSI to prime, and when you goose it, it goes up to 60, as when you pull the vac line off the regulator it also goes high.

I'm going to try running a direct vac line only from the engine to the MAP sensor.  I already used that plugged off vac line from the manifold that's right next to the fuel pressure regulator, to apply suction to said regulator.
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Buymyaztek
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« Reply #11 on: May 30, 2018, 08:11:13 PM »

Try disconnecting the mass air flow sensor and take it for a drive . If it runs better change the mass airflow senor! Also check all the pid values  on the scanner, make sure they are within the limits.
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Tronman
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« Reply #12 on: June 07, 2018, 11:49:24 AM »

Tried the MAF sensor unplug long ago, no joy.  I eventually replaced said MAF sensor, but it didn't make any difference.  Now it's idle as there still seems to be orange coolant filled motor oil and after two episodes of replacing heads (the machine shop missed a cracked head the first time!!) I'm kinda at a loss.  But that's for another thread..
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