Low Rpm - Less Power When Warm

[Qwerty]

I have told my car's problem to many mechanics but I couldn't get a good solution for it. I think I will get some help from this forum.

The car had less power. When the temperature gauge reach the operating temperature (mid point) the power output goes further down. I suspect the rpm goes down when the engine is warm. Engine also starts to vibrate due to this low rpm (I could feel from the steering wheel).

To check whether if there any problems in the fuel system. I examined the spark plugs. Two of them had dry dark grey deposits and the others were fine. Then I did a fuel injector cleaning using a 3M product. Then the condition was better for around 3 days (engine delivered more power and the vibration was less). But now, it has started to develop the similar problems.

I did some research on the internet and there they suggested the fuel pressure regulator might be wrong. Can anybody help to run my car just fine?

[gunat]

Couple of questions:

1. Is it fuel injected?

2. How old is the car?

if fuel injected...check the fuel pump. The older the unit, the greater possibility of it failing due to fatigue. Have you tested the fuel pressure before it reaches the engine?

good luck

[Qwerty]

  gunat said:

Couple of questions:

1. Is it fuel injected?

2. How old is the car?

if fuel injected...check the fuel pump. The older the unit, the greater possibility of it failing due to fatigue. Have you tested the fuel pressure before it reaches the engine?

good luck

It is fuel injected. Car is 10 yrs old. Still I didn't test the fuel pressure. I thought doing it after I get some input from this forum.

[gunat]

Given the state of the spark plugs, i don't think you have ignition issues.

Fuel delivery might be your culprit...starvation can cause all the symptoms you describe. But you'll have to figure out the problem through process of elimination. If fuel is going to the engine without issue, you'll have to look again at the engine to see what could be wrong.

[Qwerty]

  gunat said:

Given the state of the spark plugs, i don't think you have ignition issues.

Fuel delivery might be your culprit...starvation can cause all the symptoms you describe. But you'll have to figure out the problem through process of elimination. If fuel is going to the engine without issue, you'll have to look again at the engine to see what could be wrong.

Thanks for the reply. If fuel delivery is the problem, can the fuel delivery differ depending on the engine temperature? Becaus the vibration and more power loss occurs when the engine is warm.

[Duncan]

Hi there

The problem as you describe it, could be due to several reasons. The one way of identifying the exact cause is through a process of elimination.

The milage of the vehicle would have been helpful. But never the less, have the following checked out before you attempt any major repairs.

(1) Have the fuel pressure checked. It could be that when the pump is warmed up it's efficiency decreases due various wear and tear conditions.

(2) Have the fuel filters and air filter checked. A blocked filter can also hinder the required fuel pressure and air pressure needed for the efficient running of the engine.

(3) Have the ignition system checked. As simple as it may sound, worn/damaged plug leads or HT cables can also creat similar problems.

(4) Have the engine compression tested. If the compression is being lost through worn or broken rings, at temperature when the chamber has expanded power is lost due to loss in compression.

(5) Is you engine consuming engine oil? This could also create the problem you mention.

Try the above and keep us posted.

Hope this is helpful.

Cheers

[Watchman]

Another simple posibility might be dirt in the gas tank.. since the injectors were cleaned and the engine ran well for a couple of days, i guess it could be more dirt coming down the fuel line and clogging it up at the end of the 3 days..

[Elvis_Pil]

Check the idle up sensor- when you start a car for the first time in the morning on a cold engine it usually idles a lot higher say around the 1100 mark in car like mine. However once the car heats up the idle should & will drop to say 700rpm. If the sensor is ka-putt it will fall below the 'safe' idle limit- thats when you fell vibrations & with car almost stalling.