SXGT

OK so as of lately my car has a rougher idle than usual and the surging issue is back again, Now let me explain this to you and tell you what I think.

Idle is ruff, car seems fine when i hit the gas. Also the car puffs or poofs when I am going say 50mph and hold that speed constantly. Its the same poof sound you get when you are in 2nd gear and going down a hill, or slowing down with your foot off the gas, that empty chamber compression sound, like its really Lean.

so I was thinking I have a problem with either my fuel pump on low rpms, my fuel rail is bad, i have low fuel pressure or my car is running lean.

My car runs FINE through the RPM range when I put my foot on the gas, no power loss surge or anything. Its only at cruising. This makes me think its a fuel delivery issue. But I dont know enough about the mechanics of all of that to say for sure or not. What are the symptoms of a failing fuel pump or low fuel pressure? How do I increase my fuel pressure just slightly to see if that helps.

Also this could be an AIC issue/vacuum leak but that wouldn't explain the power surging or bucking feeling when going 50mph.


last, my mufflers are starting to rust off but I dont hear an exhaust leak. The metal housing wrapping around the glass pack could almost be pulled off I think, I dont know if an exhaust leak matters post muffler or not.

so the car seems very solid when going WOT, just bad idle, not so bad its going to die, but just shaky and sounds cammed. and then the surging or bucking feeling which I dont know what thats called.

Ideas? IAC was cleaned out with sea foam just 2 months ago but its the OEM part and has never been replaced. Also this might be my imagination but humidity seems to make the idle worse.

will post muffler pics tomorrow

uberstang1

If the car was running lean enough to cause you an idle problem, that means it would probably be lean through the whole power band. This more or less sounds like an IAC problem not a fuel delivery problem. Put a fuel pressure gauge on the shrader valve on the rails and that will determine if your starving for fuel, you can also pull a plug and see what it looks like. The car should have 40psi of fuel pressure with the vacum line removed from the FRP.

cliffyk

I agree, if you can run OK at higher loads and WOT it is not likely a fuel pump issue, however the fuel pressure regulator could be acting up--monitoring the rail pressure as suggested by uber' will let you know...

SXGT

checked the engine codes today

P1443 Evaporative Emission Control System - Vacuum System - Purge Control Solenoid or Purge Control Valve fault

P1131 Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1

A bad MAF should cause both banks to set a code, as would fuel pressure concerns. right?

Ive had that 1443 code since I bought the car, thats the sensor on the CAT, and I have a stock mid pipe.

SXGT

bump. not sure where to begin with this 02 senor thing.

cliffyk

Here is what the shop manual says about P1131, it has the same possible causes as P1130. It is common for failed sensors to report a lean condition as an O² sensor output of less than 0.45 V indicates a lean mixture, and failed sensors will output no voltage. The sensor in question here is the front, passenger side unit; HEGO-11 (Heated Exhaust Gas Oxygen sensor, bank 1 sensor 1).

On a car the age of yours I would first suspect an electrical wiring problem or a failed O² sensor.

You can bench test the sensor with a propane torch and a multimeter as described here.

P1443 (click here for more) is unrelated to the catalytic converters, also there are no sensors "on the cats". The catalytic converter efficiency is monitored by the rear O² sensors, those located just aft of the cats.

P1443 is related to the EVAP, EVAPorative emissions control system, that prevents the escape of fuel vapour into the atmosphere. In this case the DTC indicates very small or no flow through the EVAP canister purge valve caused by perhaps a blocked/collapsed hose or a stuck valve.

SXGT

i noticed that 1443 code goes away a lot in the winter time and is almost always on in the summer. Thank you for the links. I will look at them.

I had heard about using a blow torch to CLEAN the o2 sensors on the exhaust, any truth to that?

cliffyk

That is an outdated notion, harking back to when platinum/zirconia O² sensors were in their infancy and did not have built in heaters (these are known as 2-wire sensors). These early sensors depended on the exhaust gas temperature to keep them at operating temperature (1100 to 1200°F).

What happened was that in light load slow speed operation (a lot of in-town driving/short trips) the sensors ran "cold" (700 to 900°F, sometimes less¹) and could get coated with "soot" deposits that affected their operation. The deposits could be burned off with a propane torch to sometimes get a bit more life.

However with modern heated sensors (the heaters are 25 to 45W) this does not happen unless an engine is running very rich, or in an engine that uses a lot of oil--but more often that not a modern heated sensor will be stone cold dead from the abusive environment and trying to clean it with a torch is a waste of time.

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¹ - A P/Z sensor has to be heated to at least 660°F before it will generate any voltage at all; below that, from an electrical perspective, they just behave as a very large value resistor. For more than you probably want to know about P/Z sensors click here.

SXGT

i should have three oxygen senors on my intake yes? MAF. the one right after it and then the IAC has a senor on it yes? Why is there a **** on my IAC it turns but doesnt seem to do anything.

cliffyk

There are no oxygen sensors on the intake. The O² sensors "sense" the oxygen content of the exhaust gas and report that back to the PCM (Powertrain Control Module, Ford's name for the ECU; Engine Control Unit). The PCM uses that feedback to adjust the air/fuel ratio to maintain an average AFR of 14.7:1--which is the stoichiometric ratio for gasoline and air. I.e. that mixture that results in complete combustion.

There are four O² sensors, two "upstream" of the catalytic converters used for engine control as described above, and two "downstream" of the cats used for monitoring the efficiency of the converters.


The three "sensors" to which you refer are:

• The MAF, Mass Air Flow sensor, measures the amount of air flow--the mass in grams/second--and reports it to the PCM so that it will know how much fuel to inject;
  
  
• The "one after it" is the IAT, Intake Air Temperature sensor, as the name implies it measures the temperature of the intake air and reports it to the PCM. The PCM uses this information to tweak the amount of fuel to be injected and to adjust ignition timing;
  
  
• The IAC, Idle Air Control, is not a sensor nut rather a device; controlled by the PCM to adjust the amount of air (measured "metered" by the MAF) allowed to flow into the engine and bypassing the throttle valve. By controlling this air flow the PCM can control idle speed, more air = faster idle, less air = slower idle. The PCM use the IAC to maintain the idle speed, compensating for engine and air temperature, and additional loads such as the AC compressor, generator and power steering pump;

The "****" on the IAC is not an adjustment, it's just the breather cap for the vent/filter breather for the "backside" of the solenoid actuated plunger on the Hitachi sourced IAC valve:



The newer Nippondenso sourced IACs do not have this vent: