Mechanics

BOGGING DOWN ON ACCELERATION

2002 Dodge Neon

Engine Performance problem
2002 Dodge Neon 4 cyl Two Wheel Drive Automatic 130000 miles

Symptoms: Car bogs (If I could call it something) down when I floor the accelerator to merge into the freeway or pass.
Troubleshooting: Replaced Spark Plugs, Wires, Coil, TPS, MAP, had injectors professionally cleaned, had pressure pump and regulator checked, no egr that I know and no leaks in the manifold that I could find. The engine has 180 lbs on 3 cylinders and 200 on one. I had the transmission oil emptied including converter and filter replaced. Did find the hose going from intake manifold to Brake booster insanely loose. Looked like it expanded or like there was something between the intake manifold spicket and the hose. Because the hose hole was way larger than the manifold spicket it was attached to. I placed a hose clamp on it and tightened very tight. The improvement was significant but the acceleration lag is still there. Mileage is very poor when I try and accelerate gives me 22 mpg. A great leap from 36 mpg when accelerate slowly. Please help me the mistery is killing me.
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Scorrea00
January 4, 2009.




Ok with all that you have done have you cleaned the mass air flow sensor? If not get a can of mass air flow cleaner and clean it first see if makes a difference. Now the air filter is clean? How is the exhaust flow? Is there any codes? Is the engine light on? How old is the fuel filter? Get back to me and we will take it from there.

Racefan966
Jan 5, 2009.
Have already cleaned the Mass Air Flow sensor. New air filter. Recently bought the car and it passed smog. Passing smog should eliminate a clogged Catalyc Converter or muffler? For safe measure I also replaced the muffler with a high flow muffler.

Connected it to an OBD and found no codes and there is no engine light on.

The 2002 dodge neon does not have a fuel filter that can be replaced like the common car. It is built into the fuel pump and is inside the gas tank. Replacing it entails replacing the fuel pump or so I read.

To dismiss the suspicion of a bad fuel pump I had the fuel line pressure and pressure valve tested by a mechanic. He said they were fine. Is it correct to assume the fuel filter in the pump is not plugged?
However, I don't know if the mechanic tested the fuel line under a SUDDEN load or even just at high rpm were my troubles begin " On sudden take off to pass.&Quot; Is there a test I could do on my own to check the fuel pump and filter without the use of pressure valve?

Tiny
Scorrea00
Jan 6, 2009.
Ok as with many dodge vehicles this one in this year don't have a replacable fuel filter thougth that would be the case. Ok did the mechanice say what the fuel pressure was under load? Did he do a driving fuel pressure test? Has it had a live scan to watch what the O2 sensors are doing? Have you checked for any other intake or throttle body vacuum leaks? Let me know what you can and we go from there.

Racefan966
Jan 7, 2009.
Ok,

I paid the mechanic to do a fuel pressure test and a fuel regulator test. However, he didn't give details such as what the pressure value was. Like a said don't know if he tested all of the above under a load or during a driving condition.

Are you asking me to go ask him if he did all of the above? Hope he can remember. He is a real you know what that is the reason I am here speaking to you. I work at Edwards AF base and he is the only mechanic in town.

As for the 02 sensors, also paid him to do an OBD scan from which he also told me everything was fine. Is it logical to assume the 02 sensors are fine since it did pass smog a few weeks ago?

As for the vaccum leaks I explained I have checked for vaccum leaks in the intake and throttle body for which I found one. Again, that leak was the hose going from the brake booster to the intake manifold.

In the past with carburated engines I would use carb cleaner to spray along the carburator, and vaccum lines to detect leaks.

Tiny
Scorrea00
Jan 7, 2009.
Ok it never safe to assume the O2 sensors are good but with the light not on we can't say they are bad either. As for vacuum leaks you can spray carb clean around the throttle body and intake and injector seats and see if it has any leaks.
I am sorry the mechanic is difficult to work with it would be nice if we could get the answers on the fuel pressure but we work without it too.
Have you tested the TPS? If not then we will do that next you will need a digital multi meter to do that. Get back to me and we go from there.

Racefan966
Jan 7, 2009.
Sir,

On my post I listed the TPS as one of the many parts replaced. I checked it with an Ohm meter and it was definitely bad. There was a noticeable improvement. Did this two weeks ago. But the lag is still there.

Here is the list of the items I replaced. Spark Plugs, Wires, Coil, TPS, MAP, Air Filter, oil change, cleaned Mass Air Flow an for good measure replaced the muffer with a high flow muffler and even a complete transmission oil change along with a transmission filter change.

Acceleration is smooth as long as my foot gradually but steadily and somewhat fast pushes down on it. Anything beyond that. Say a faster gas push to the floor board to merge on the freeway to ahead of traffic will create the lag condition.

I am sure this not normal vehicle operation.

Tiny
Scorrea00
Jan 7, 2009.
Still would like the TPS tested as it could be a slow one. I have had new ones not perform up to standard. We will also check the coolant temp sensor.
TPS first you have three wires to it and we need to make sure that there is 5 volts to it. Now the orange and dk blue wire should be.8 volts with key on engine off throttle closed. Now slowly raise the thottle it should slowly and steadely increase with no drops or glitches in voltage to 3.5 volts at wide open throttle. Let me know what happens here.
With the coolant temp sensor I want you to unplug it and check resistance across it and not the temp of the engine at the time. It would be prefered it you did this when the engine was cold that way the temp would be ambient temp. Give the resistance and the temp at the time.
Now I must ask has there been any performance mods done to this car? If so what are all of them.

Racefan966
Jan 8, 2009.
Will be looking into this weekend. Have been putting lots of OT at work lately. Will keep you posted.
Thank you

Tiny
Scorrea00
Jan 8, 2009.
Ok that will work just fine. I do not work on Sunday's so I will look for your post on Saturday ok. Thanks.
AD

Racefan966
Jan 9, 2009.
Hello,

Went ahead and change the coolant temp sensor and there was a noticeable improvement. It was $15 so just went ahead and replaced it.

Thank you!

Tiny
Scorrea00
Jan 12, 2009.

AD