Crown vic injection problems ????

[minimanmark]

Hi guys , my vic starts and runs great when cold , as soon as it warms up it idles very rough and will cut out , starts again fine , I have replaced ...plugs , leads , dissy cap / rotor arm , coil , and module on the dissy , makes no difference , it pops back though the exhaust on over run and light throttle , it's ok if you boot it .???????.

 

[TransAmDan]

Do you get any Service Engine Soon lights on the dashboard?

When the car warms up it goes into closed loop, the ECU takes readings from the Lamba/Oxygen sensors in the exhaust stream to know whether to add or remove fuel. Too much fuel or too little will cause running problems as you know. This closed loop adjusts the fuel many times a second, it outputs like a sine wave waveform of about 0.5 to 1Hz when all is running correct. you could test with a voltmeter if you can get access to the wire.

When you boot it, it goes into open loop mode ignoring the Lamda/Oxygen sensors.

So to me it sounds like its these sensors, you probably have two, one for each side of the V. However on my '89 Firebird I just had 1 in the Y-Pipe. They get dirty after 5 years or so of driving, many short journeys soots them up, but you can't really clean them.

 

[AmericanThunder]

Fuel pump or regulator going out?

 

[minimanmark]

Only have one oxygen sensor , right hand exhaust manifold , single wire , I have ordered engine temp sensor it's easy to get at , the oxygen sensor not so easy .....lol...

 

[minimanmark]

Forgot to say No lights on dash ....

 

[minimanmark]

The spark plugs are a light brown color , which indicates fuel mixture is right , Not sooty or white in color which would indicate over rich / lean mixture

 

[AmericanThunder]

I missed the part in your first post when you said it's ok when you boot it. Dan is right that the oxygen sensors are ignored in that scenario, but.... Your car is ODB1 with a single wire O2 sensor and I don't know if the open loop / closed loop works the same way.
Does the car hunt at idle or are the hydrocarbons high according to an emissions meter? Either would also point at the O2 sensor.
Otherwise I would start looking for a vacuum leak. The cold idle with additional fuel would mask it, whilst a full throttle blast would also dump in sufficient fuel to mask it. But a warm idle would draw in enough unmetered air to kill it.
Carb or fi?
Maf or SD?

 

[minimanmark]

It's an early throttle body injection , No MAF , no hunting at idle , idles fine until it warms up , then idle becomes very erratic and finally cuts out , will restart no problem ......

 

[AmericanThunder]

Vacuum leak I reckon. Good luck

 

[minimanmark]

Orderd 02 sensor and ecu engine temp sensor ....should be here Friday .....I can still buy parts for a 30 year old injection system ......excellent .....

 

[TransAmDan]

With all that extra ironing work you will be getting you will have loads of spare cash to put into the car

 

[Chriswrx123]

Hi re your dash lights i would check the light switch first then earths had the same happeren to me on the firebird took the whole dash out replaced all the bulbs still didn't work then checked the head light switch bingo! Many hours wasted lol for a five minute job