Engine low power?

Hi Two things to do have fuel pressure checked and clean MAF if 3.4 L in air intake plenum if 3.8L see diagram

This guide can help as well https://www.2carpros.com/articles/engine-has-low-power-output Please run down this guide and report back.

When the intake gasket was fixed, did they do this? Reference Number(s): 03-06-04-056,  Date of Issue:   September 29, 2003 Related Ref Number(s): 03-06-04-056 ARTICLE BEGINNING SERVICE INFORMATION A new gasket has been released for use in the above vehicles. The new gasket will seal better than the previous gasket. When changing this gasket, be sure to check the bottom of the throttle body for any flashing. Any flashing that protrudes more than 0.50 mm (0.020") should be filed by hand. Use caution that the sealing surface is not damaged. Flashing in the areas indicated between the arrows, ( Fig. 1 ), is the most critical as it can effect the sealing of the upper to lower intakes. Be sure that all surfaces are clean of any foreign material before installing new gasket. Fig. 1: Throttle Body PARTS INFORMATION BUICK: 2000-2003 LeSabre, Park Avenue, Regal with 3.8L V6 Engine (VIN K - RPO L36) CHEVROLET: 2000-2003 Impala, Monte Carlo with 3.8L V6 Engine (VIN K - RPO L36) PONTIAC: 2000-2003 Bonneville, Grand Prix with 3.8L V6 Engine (VIN K - RPO L36) SECTION: 06 - Engine/Propulsion System

It just started 3 days ago and getting worse. OBD2 reads code P0420. from 20 to 50 mph it seems to have a loss of power when I step on the gas. Do you suggest with code given the catalyst converter needs to be replaced?

Yep; the code and the lack of power at higher speed are typical of a plugged converter resulting in excessive back pressure.
Check exhaust backpressure to makes sure.
In your case it went bad probably because it had 157,000 miles on it, however a bad converter is sometime the result of another problem such as worn exhaust valve, leaky head gasket, cracked cylinder, bad coolant sensor, etc.

I have a 2003 chevy impala no code are on but it loss power when I step on the gas what can be the problem .i tried this egr valve mass air flow sensor tps coils ignition control module what can it be please need help

Check the fuel pressure. There is a test port on the fuel rail. Auto Zone or Advance Auto has fuel pressure test gauges they will loan out if you give them a deposit.

Problems started a few weeks ago. When accelerating car bogs down and slowly picks up speed.
From a stop it is good up to about 30 then the problem kicks in.
On the hi-way driving along is ok until the road goes up hill a little, speed slows down rpms jump up and down and car bucks.
If accelerating at this point it does nothing and sometimes will drop into neutral and tach out.
Also get random misfires every once in a while.
So far since the car has high miles I have replaced fuel filter, plugs, wires, coil packs, ignition control module and mass airflow sensor.
Also fuel pressure regulator had slow vacuum leak and was replaced.

What else is left to replace to try fixing this?

Seems the transmission is the issue and is slipping

transmision people say not transmision problem. car runs almost perfect with new mass airflow sensor unplugged. exact same problem with old and new sensor. only slugish at highway full throttle with unplugged.

When engine runs better with MAF unpluged then cam sensor is usually at fault. 3.4L or 3.8 L

I have a 2003 chevy impala no code are on but it loss power when I step on the gas what can be the problem .i tried this egr valve mass air flow sensor tps coils ignition control module what can it be please need help

sounds like a clogged cat converter. a shop can do a snap throttle vacuum test to verify.
also, have the fuel pressure checked as well.

Roy

Check the cat converter was not the problem I will check the fuel pressure in the morning

My car gets to 30 mph and then takes another mile to get to 35. The RPMs keep increasing (I can hear it), but the car goes no faster. If I raise my foot from the accelerator, I can 'force' the engine to downshift and I can get to 40-45. Then it stops accelerating altogether. I think 48 is the top I reached tonight on a 20 mile trip. The motor sounds like it's running OK, and I have no drips on my driveway. My dealership told me yesterday it was a plugged converter. I made an appointment to get it replaced on Monday, but tonight on the way home my check engine light came on. (had not doe this previously). When the problem first started my first thought was transmission because it acts like the motor wants to keep winding and nothing's getting to the drivetrain. Is it still safe to drive? The shop I need to get it to is about 30 miles from home. Please answer soon!!! Thanks Marci

It does sound like aplugged cat.If you want to see, loosen the exhaust pipe at the manifold, before the cat, if thecat is plugged it willl run , loud but it will run. The check engine light is most likely a "cat efficiency" code, they throw those codes when the cat is having problems

Hello. My Impala starting shifting very late, and you had to sort of feather the throttle to get it to shift at all. It did this for about a week, and while this was going on it started to loose power. I don't believe the power loss started until after the shifting problem. I replaced the TPS, and reset the code. The check engine light is now off, but I'm still experiancing a severe power loss. It seems to idle fine, if you rev it in park you can notice a little roughness, not really a hesitation so much, almost like a rev limiter is kicking in early, but that's not exactly it either. I've replaced the plugs and wires, and bench tested the coil packs, which appear to be ok. The exhaust seems to have pretty good pressure, so I'm not thinking it is the cat. I guess I'm now thinking it could be a fuel pump and/or filter, bad injector, maybe a bad fuel pressure regulator? I don't have a fuel pressure tester.
What do you think?

I think it would be a good idea to check the fuel pump pressure. Most parts stores will lend or rent them to you. If you can't find one, they sell them on this site under the test equipment store.

Let me know what you find. You may also want to check for intake leaks and actually check back pressure at the converter and before it.

My 2003 Impala has no acceleration. It idles and starts fine but when I start driving it has less acceleration the more I push the gas. If I run the RPM's too high it begins to made a detonation sound. I have replaced the fuel filter, air filter, and cleaned the mass air flow sensor. It also has good fuel pressure coming from the fuel pump. I did notice that the idle air control valve was dirty but it idles just fine. There are no codes coming up either. Please help!

after car is warmed up put car in first gear. put on brake so car dont move and floor it. what rpm does the engine stabilize at?

My 2003 Impala has no acceleration. It idles and starts fine but when I start driving it has less acceleration the more I push the gas. If I run the RPM's too high it begins to made a detonation sound. I have replaced the fuel filter, air filter, and cleaned the mass air flow sensor. It also has good fuel pressure coming from the fuel pump. I did notice that the idle air control valve was dirty but it idles just fine. There are no codes coming up either. Please help!

We drilled a hole in the exhaust pipe infront of the CC. Once we did that I started to get more power back. I guess I will have to replace it now.

my car start and run good but,it has no power

do you have check engine light on
if so scan it for codes
and come back with it here for more help
check mas air flow sensor
do an exhaust back pressure test (checking catalytic converter flow )
you can disconnect the exhaust before the cat and run car
good luck
let me know

My car runs fine in park once in gear and going down street it bogs down I replace the front set of wire and plugs because it was reading misfire in 3, a mechanic down the street took it for a test drive and came back and stated the engine was bad and needed to be replace, how did he determine this when all he did was drive around the block, the engine make no noise it just seems to be starving for air or bogging down. what could be wrong or is he right and does it need an engine.

Try loosening the exhaust before the cat converter, it may be partially plugged causing excessive backpressure when it it run

Yesterday, I started to drive up a steep hill. The engine pulled down real hard and would not hardly pull up the hill. It didn't appear to be missing out. As far as all cylinders firing ,it seemed to be ok on that part. If I put the accelerator all the way down on the hill it would shift down to low gear and the engine was accelerating as if I had shift the transmission to low gear manually while driving fast. The engine seems not to have the power it had when I got it. If I drive it on any other kind of terain, the engine seems to run good. What could cause this problem?

It could be a few things. First, make sure the catalytic converter isn't plugging. Also, check the fuel pump pressure to make sure it is within the manufacturer's specs.

My car is very slow to pick up speed when accelerating it kinda jerks and stalls. The check engine light comes on every once and a while, stays on for about a day and then goes back out. I think it may be my fuel injector because I am burning up gas a lot quicker than before. What do I need to do in order to clean it? Thank you for your help

Hi:
First, if the check engine light comes on, there will be a trouble code set in the computer. Most nationally recognized parts stores will scan it for free. Have it done, and let me know what you find.

Joe

I had it scanned and P0300, P0125 and P0404 were the codes that came up but the light does not stay on. Thanks

PO300 - multiple random missfire

PO125 - Insufficient Coolant Temperature for Closed Loop Fuel Control

PO404 - Exhaust Gas Recirculation Circuit Range/Performance

It sounds like the car isn't warming up to lean out the fuel mixture. This sounds like a coolant temp sensor. That would explain the poor fuel mileage. That is what I would replace. Have that checked and replaced if needed.

Let me know if it helps.

Joe

How much does one of those run and how intensive is the work to put it on?

It's easy to replace. It should be near the thermostat. IT unbolts, disconnect the elect to it and replace. The part should be under 15 dollars.

Hey Joe,
So I could go buy the part and have someone put it in for me and that should fix my problem?

My wife has a 2003 chevy impala and was having the same problem with the slow acceleration. To make a long story short the problem was the cat converter. And the car only had a little over 80k miles on it. well its all fixed now and runs great. And for the P0125 code it could also be the thermostat instead of the temp sensor. Both parts are going to be under $15 each. I am going to replace the thermostat 1st and go from there. If that isn't it then I will replace the temp sensor.

I'll try to explain the issue as completely as I can.

First of all, no DTC codes at all.

The vehicle starts and idles fine. Upon startup there's a loud sucking noise coming from the airbox before the filter, which I know is normal because of the IAC during cold startup. At any point in neutral or park, cold or hot, the engine sounds fantastic, has great throttle response and revs up nice all the way to the limiter. I've replaced all the plugs, wires, and coils. I did a compression test when the plugs were out and it came out to 167-175 for all cylinders. Every plug looked fantastic, nice tan color, no fouling... beautiful.

If I start driving right away immediately after I start the vehicle, it accelerates through the gears and shifts smooth with what I would call normal acceleration. Feels like it should and if I could get it to stay that way, I'd be happy. However, after a couple of blocks, (or if I let the engine idle for a couple minutes before driving) the acceleration becomes very poor. There is a more hollow muffled sounding sucking noise (not even sure it's air, but that's the best way I can describe it...) during the poor acceleration. It seems to shift though the gears still, it just takes forever to get up to a speed to get the gears to shift. I'm actually not sure if it's even starting out in the proper gear. It doesn't slip during this, it's just like pressing the gas and it accelerates super slowly, there's no high rpm's as you would see in slipping.

If I press the accelerator maybe 2/3 of the way down so that it drops down a gear, the engine revs higher, the hollow sound goes away and it sounds more like it should. It accelerates much better, but I'm still not sure it's as good as it should be.

If I floor it so it drops down another gear, engine RPM's go way higher, but zero acceleration (transmission is slipping) with a loud rattling like marbles in a tin can. This rattling is worse the more the car is driven (or warms up I guess).

originally, I suspected the cat, but I'm not sure why it would be okay for the first couple blocks before it warms up. Also, in neutral, the engine sounds awesome with great response. Because of this, I"m beginning to think it's not a plugged cat. Even if it was clogging up after coming to temperature, it would be bad at idle too, I'm thinking. I'm also ruling out fuel delivery as it revs up great and very responsive. I haven't checked the rail pressure.

If I stop the vehicle and let it sit for a few minutes, then start it up and drive again, again it's good for a couple blocks and then starts doing the same thing again.

Would doing a transmission fluid and filter change (not flush) fix this? I'm thinking that there's some kind of restriction someplace that clears as the transmission fluid drains and then clogs up soon after starting the vehicle again. The fluid level is correct and the fluid isn't black, but it isn't red either. I'm confused because it seems so great for the first couple of blocks and when it starts having low power, it's not slipping until you floor it, it just bogs down under normal acceleration. If it's the PC solenoid, why does it take a couple blocks to see the problem?

Another question. will pulling the front O2 sensor allow enough air through the port to allow me to diagnose the catalytic converter? I don't really feel like disconnecting the whole pipe or manifold before the catalytic converter.

I plan to clean the MAF sensor, but looking at the readings on my OBD tool, the numbers don't seem out of line and there is no DTC and the engine seems to be running fine.

Any help would be truly appreciated. Thanks in advance.

Welcome to 2CarPros.

Honestly, are you sure the transmission is slipping and not the engine just revving without accelerating? I have to be honest, I feel it is the cat. The rattle you mentioned is most likely the insides of the catalytic converter. They can come apart internally and rattle. If it starts to block the air flow, you will lose power.

Here is a link that explains how to test a catalytic converter along with an additional one regarding symptoms:

https://www.2carpros.com/articles/bad-catalytic-converter-symptoms

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

When you read through the test, you will get to section 4 where it discusses removal of the O2 sensor. It doesn't work as well as removing the cat, but you should notice a difference when driving.

Let me know what you find.

Joe

Hi Joe, thank you for your reply! No I haven’t ruled out the catalytic converter at all, I’m just really confused as it idles and revs up so nice when it’s not in gear. The throttle response is so good when it’s not moving.

The confusing thing for me is the fact that it drives great for two blocks after startup. Plus the fact that when it is having poor acceleration it doesn’t act like the transmission is slipping at all really until you floor it. It’s mostly just bogging down.

It’s frustrating because half the symptoms seem to be bad catalytic converter and the other half are transmission.

I would have pulled the O2 sensor already but I hurt my back last week so I’ve been taking it easy. I hope to get back to it this weekend.

Thanks again for your reply. I’m hoping you’re right.

Took the O2 sensor out and went for a test drive. It ran much much better. Accelerated up through the gears just fine. Still not 100% but I’m sure it will be once I get the cat replaced.

Definitely the catalytic converter. Pricey but much better than a transmission!

Welcome back:

I had a feeling that was the issue, and so did you. You're right. Much cheaper than a transmission.

I don't know if you need them, but here are the directions for replacement. The attached pictures correlate with the directions. Also, see if you can find an aftermarket one that is direct fit. It should save you money. Just don't get the cheapest thing you find. I can't tell you how many times I have replaced new cats that end up with cracked welds. Ugh!!! I feel bad for the people, but remember, you get what you pay for. Stick with a brand name and a company you know will back you if something like that happens.

______________________________________________

CONVERTER
Catalytic Converter Replacement (3.8L)

Removal Procedure

Important: The 3-way catalytic converter is serviced by replacing the entire assembly. Always replace the gaskets when servicing the 3-way catalytic converter assembly. Never install the original gaskets
1. Raise and support the vehicle. Refer to Vehicle Lifting.


pic 1


. Disconnect the Heated Oxygen Sensor (HO2S) electrical connector.
3. Remove the exhaust manifold pipe stud nuts.


pic 2


4. Remove the catalytic converter nuts.


pic 3


5. Remove the catalytic converter hangers.
6. Remove the 3-way catalytic converter.
7. Remove the gasket from the exhaust pipe.
8. Remove the gasket from the exhaust manifold.
9. Clean and inspect the exhaust manifold and the exhaust pipe gasket mating surfaces.


pic 4


10. Remove the Heated Oxygen Sensor (HO2S).

Installation Procedure


pic 5


1. Install the Heated Oxygen Sensor (HO2S).


pic 6


2. Install a new gasket to the exhaust pipe studs.
3. Install a new gasket to the exhaust manifold.

Notice: Refer to Catalytic Converter Movement Notice in Service Precautions.

4. Install and support the 3-way catalytic converter.
5. Install the catalytic converter nuts.


pic 7


Notice: Refer to Fastener Notice in Service Precautions.

6. Install the exhaust manifold pipe stud nuts.
^ Tighten the exhaust manifold pipe stud nuts to 32 Nm (24 ft. lbs.).
^ Tighten the catalytic converter nuts to 60 Nm (44 ft. lbs.).


pic 8


7. Install the catalytic converter hangers.
8. Connect the Heated Oxygen Sensor (HO2S) electrical connector.
9. Lower the vehicle.
10. Inspect the exhaust system for leaks.

_____________________________________

When you get it repaired, let me know the final outcome. Also, I hope the back is feeling better. There is nothing worse than back problems.

Take care and come back anytime.

Joe