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chellaman · 05-28-2012, 12:41 PM

I am writing this from the madhouse.
Please can a doctor come and get me out of here!
Since a bad misfire and loss of power a year ago, I have spent half my life and a fortune on this problem.,
The motor has done 70,000 miles and runs like a dream when hot. It starts easily cold but runs very rich and lumpy until, at about 170 deg., it smooths out and runs lovely. The exhaust stinks of gasolene when cold, but there is no smoke of any color
The motor is converted to run on gas or LPG,. and the problem is exactly the same on both.
It has new nearly everything. Plugs, coils, EGR components, MAF sensor, O2 sensors, fuel filter, air filter. Have not changed injectors because they don't figure on LPG!
There is no transfer between oil and water, and it loses no water and burns very little oil.
The manifold vacuum is steady on 18-19 psi at idle, and responds otherwise as it should.
I have also done many spraying tests around the manifolds which showed nothing.
There are no codes at all, and all readings on a scanner seem normal.

The computer must be adding extra fuel when cold for a reason I cannot figure.
Then, magically at the hot temperature, something changes and it fuels normally.
My bank account is empty, my hair is all torn out, my wife has left me, and I sit crying in the corner.
Please, doctor, come and help me!!!!!!

bluepill · 05-28-2012, 12:45 PM

Did you own it BEFORE the LPG conversion? If so, did the problem exist before?

Do you know if the LPG conversion included a device to enrichen the mixture for starting in the LPG mode?

Have you checked Ford forums for this problem?

chellaman · 05-28-2012, 02:29 PM

Hi Bluepill.
I had the LPG conversion done when I bought it in 2004 at five years old.
I drove it for the next seven years over 35,000 miles without any such problem.
Don't know about a device to enrichen in LPG mode, but the problem is also there when on gasolene.
I tried Ford trucks a while ago, but got advice to change various sensors which I've done!
I think the main point is that the problem does not disappear until the motor is almost at normal operating temperature, long after any cold start device would have cut out!
And then it disappears completely, until the next cold start.
I was only an "expert" in the days when we had carburettors, coils and distributors, so I am not sure where to look next!

tderonne · 05-28-2012, 04:13 PM

It's a 1999 then? (Has EGR) Sounds like an EGR problem, what did you replace? I've seen both bad DPFE sensors and bad valves. Both replaced? Any codes now? Was the "misfire" problem setting codes? New coils and that is gone?

teddyu · 05-28-2012, 05:35 PM

The list of sensors that you've looked at seem to be missing the water temperature sensor. I believe that the water temperature sensor enrichens the mixture and increases the engine rpm during start up until the engine is warm. Just my two cents...

teddyu · 05-28-2012, 05:41 PM

Couldn't figure out how to edit the last post, but I think this thread would do better on the Ford Chassis Forum below.

Dunner · 05-28-2012, 06:03 PM

Sounds to me like the temperature sensor is working. If it didn't work, then there would be no change when it did warm up. Whether it is working right is another story. Disconnect it and see if it makes a difference.

teddyu · 05-28-2012, 08:38 PM

If I remember correctly, the temperature sensor or other another engine temperature sensor has a vacuum line and a ported line that effects the cold start fuel mixture. Been a longtime since I work on a 460. Just my two cents...

chellaman · 05-29-2012, 03:07 AM

Thankyou for the replies.
Yes, it is a 1999, and the EGR was not working when I had the original misfire. I replaced the valve, DPFE sensor and solenoid. I am sure the EGR system works now because the pipe gets very hot when driven. There were plug and coil codes originally but nothing since replacing the whole lot.
I am sure the water temperature sensor is working correctly, because it shows ambient when cold and gradually rises to a normal driving value of around 195deg.. I have to admit that I would change it for the sake of it if I could get to it, but you have to remove the inlet manifolds to get to it!!!!!! Cannot even reach to disconnct it!
No vacuum line on it. Just electrical connection.

My own feeling was an air leak, but the vacuum readings are great, and I have spent many days checking everything.
A friend also suggested an exhaust manifold leak, but I cannot detect any.
Like I said, it purrs when hot!

macantic · 05-29-2012, 05:15 AM

Yep! Your right,I was about to post the same thing.

Quote:

Originally Posted by teddyu

The list of sensors that you've looked at seem to be missing the water temperature sensor. I believe that the water temperature sensor enrichens the mixture and increases the engine rpm during start up until the engine is warm. Just my two cents...

Dunner · 05-29-2012, 06:54 AM

Quote:

Originally Posted by chellaman

I am sure the water temperature sensor is working correctly, because it shows ambient when cold and gradually rises to a normal driving value of around 195deg.

Quote:

Originally Posted by teddyu

The list of sensors that you've looked at seem to be missing the water temperature sensor. I believe that the water temperature sensor enrichens the mixture and increases the engine rpm during start up until the engine is warm. Just my two cents...

Quote:

Yep! Your right,I was about to post the same thing.

cb1000rider · 05-29-2012, 09:35 AM

I do EFI tuning, non-Ford. IMHO, the way to find this problem - other than replacing random parts, is to connect it to a OBD-II system that offers "real time" diagnostics.

As indicated above, you're looking for a sensor that is telling the motor that it's cold and as such is running in open-loop mode, ignoring the 02 sensor.

Beyond that, look for when it goes into closed loop mode and the mixture starts to even out. This is shown as dithering (moving back and forth across lean/rich with your stock narrowband 02).

I'd not even attempt to diagnose on LPG.

Mekanic · 05-29-2012, 09:46 AM

The coolant temp sensor could be bad, like CB1000ride said hook it to a OBD-II reader that can tell you what you need to see.

bluepill · 05-29-2012, 10:22 AM

Quote:

Originally Posted by chellaman

I am sure the water temperature sensor is working correctly, because it shows ambient when cold and gradually rises to a normal driving value of around 195deg..

How are you monitoring this? By the temp. guage? I am not familiar with the Ford system, but some systems use one sensor to drive the guage and another as input to the ECM. If it is the latter, you would need to either use a scan tool to read the coolant temp. input to the ECM, or at the least run the factory prescribed test of the sensor (usually ohms at various temperatures.)

One trick that I have used is to substitute a fixed value resistor for the sensor that is equal to the running temp. value. It might be too lean to do a clean cold start, but if it changes symptoms it's a pretty good bet that the sensor has a problem. If access to the sensor is difficult as you mention, it is sometimes easier to get at the wiring at the ECM end of the harness.

Last suggestion - If you can read up on the Ford strategy for cold enrichment it might point you in a good direction. It seems that closed loop operation is fine, so you need to concentrate on open loop fuel metering. What strategy is used to control the mixture in open loop that is disabled/changed when it switches to closed? What sensors have authority in open loop?