(you know, the one that looks like the Griswold Family Truckster)...

with the 5.0 CFI EEC IV motor has a driveability problem only in very cold ambient temps (below 30 degrees F). After a cold start, when the engine idles you can literally hear and feel it running on four cylinders, (or running VERY lean) yet as soon as you slightly touch the throttle, it runs smoothly on all eight again. This is not an engine misfire condition. It feels exactly like one of the two injectors isn't firing, yet when the air cleaner is removed and I shine a bright light at the injectors while this is happening, both of them appear to be spraying. NO EEC IV CODES STORED at all. (Friend of mine at local Ford dealer has scanned EEC for me numerous times...) I'm the original owner of the vehicle and a "stickler" for maintenance, probably to the point of being ****, so I've gone thru all of the common replacement stuff--cap/rotor/wires/spark plugs (all genuine Motorcraft), even replaced the distributor, TFI module (genuine Motorcraft), and the O2 sensor to no avail. In milder weather, the problem never occurs---must be cold ambient temp. before it acts up. There's an air charge temp sensor at the back of the intake--I removed it for inspection and it was plugged up with carbon...I was able to carefully clean it, but that didn't change anything.......anyone have any ideas??

 

First of all ... congradulations on owning a SWEET RIDE! Any idea on how many of these are still on the road? It's gotta be a super low number. Our 1984s were made to last maybe 100,000 miles and then sent away.

I don't see your location listed but in Philly, we get freezing temperatures and starting problems around the same time. I don't know my 460's too well but I don't think they have an ambient temperature starting setting on the carbs or distributors that say, hey ... it's cold as sin so decrease air and rich the fuel and do this until the coolant temp is 160° f. What you're describing is very normal for my carbed cars.

Now, ofcorse there is sixteen owners out there that'll say, "my carbed 198x always starts the first time, everytime, no matter how cold." WE WANT TO HEAR FROM ~YOU~ GUYS AND GALS!

With the exception of a block heater, why does your 80's carbed car start so well in 32° and colder temperatures?

John "I'm-starting-some-stuff-again" Dancy

 

Oldschool I don't think his car is carbed. He said its a 5.0L (302ci) CFI injected

As for the problem, it sound like you done all that you can. Now sense I don't know the year I'm not to sure of this. Most fuel injected cars have either an air intake temp sensor or coolant temp sensor or both. They do the job of telling the computer to have the engine run a little rich until it warms up. If the sensor doesn't go open ckt, or short ckt. the computer doesn't know anything is wrong. Sometime these parts just go out of spec. and give the computer the wrong info.. I beat if you go on the internet you can find the spec. sheet at each temp. intervale, then you can check it with a ohmmeter of voltmeter. Good luck

 

cctxfish, you're right. It's a 302 (5.0) Central Fuel Injected motor (AKA "throttle body injection" by most people). This engine does have an air intake temp sensor (screws into intake right behind throttle body) and two coolant temp sensors, one of which tells the PCM what the engine coolant temp is. I still maintain, however, that if one of those sensors was operating out of its design parameters, the PCM would pick that up eventually. Am I making an incorrect assumption? I thought that even back then, sensor parameters (highest and lowest acceptable readings) were programmed into the PCM prom....or "calibrator". Like you, my thinking was that one of those two sensors was the problem....... but not according to the PCM, because there are no codes stored.

 

No, Let take a look at a problem that I was troubleshooting a while back. It was a dodge dukata, it would start-up just fine, but after about 1 min it would start running like crap, then after about another min it run just fine from then on. There were no trouble code at all.
When the engine strats it runs in, what is called "open loop" in which it doesn't react to all the sensors. Then after its warmed it goes into "closed loop" were it uses the sensor inputs. An heated oxygen sensor was not getting into operating spec in the time the computer was expecting, and was giving the computer the wrong info. You see the oxygen sensor works in the range of .1v to .9v, anythink out of these the computer knows as, 'out of spec' and will cuase a code. But, this bad sensor was at .8v when the computer started look for the info ie closed loop. At .9v the engine is running rich and at .1v lean, so the computer thought it was running to rich and leaned the fuel out causing the engine to run poorly.
So, it maybe that a sensor is out, but within spec not to cause a computer code.

 

OK, point well taken. I'll need to find correct readings for intake air temp sensor and ECM coolant temp sensor, then measure those sensors to see if they're within specs. Thanks for your help!!

 

Oh.
I thought that CFI stood for 'central fuel injected' at the carburator. I should have said throttle body My mistake

My 1984 Mark VII, OldSchool3, has the same set up.

Are you getting 14.5 or more volts across the battery immediately after a cold start?

Have you put a timing light on EACH wire to see if she's 'skipping' plugs?

I normally get stuck by those really obvious things until someone says to me, "Hey John, is the battery connected?"

 

when you mentioned "'skipping' plugs?" it caught my eye. Can that really happen?
While I have not yet done as you suggested and hooked my timing light up to each spark plug wire, the engine really does feel and sound like it's running on 4 cylinders..... it's a distinctly different sound and feel than misfiring. yet as soon as I touch the throttle, it's like it's "back on all 8 again" This Saturday, if the ambient temp is cold enough, I'll hook up my timing light to each plug wire just to check...

 

Okay mwatt,
But I still think its running lean.
This is going to be very difficult to troubleshoot (will it would be if it was here Texas), as that it only happens in cold weather and only at the start-ups. I'd say, take it to a good shop they should have a scan tool that can be connected to the ignition coil and record all the cylinders, if there is any anomaly they should be able to tell you what and which cylinders is cause it. Then again you could do it over 8 different mornings and save yourself some bucks.
Again I still think its running lean, but this test could eliminate or establish if its in the ignition system at all.