Cold idle problem gets worse and worser..

[Elessee]

cool... yeah. And hot, too.
But it was just following directions in the manual.
The longer you keep these cars, the more stuff goes on the blink. Gotta keep up with the big and small things, or else. The manuals do not cover everything.
Like a worn-out trunk key-cover not staying up so the key can be inserted with one hand. I put that off because I saw rivets, and everyone knows that rivets are intended to be "permanent". The job was easier than anticipated..

 

[OldSchool1]

Got pictures?

You should pictures of ALL of your repairs and start a separate thread for each one. If YOU'VE come across an issue then many others have and probably don't know how to correct it or just how easy the fix is.

 

[Elessee]

If you think it's worth it, sure. I will whip something up, and describe my fix.

 

[Elessee]

The car passed smog, so it'll be around for a couple more years and California's tax payers can delay paying me $1,000 when I finally sell it to the clunker retirement program... (after I strip a lot of little DC motors, solenoids and various other cool stuff. The car must have a driver's seat, so anyone who wants a passenger seat or a primo condition rear better say so when the time comes..).

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But the thing still idles funny, and is near the upper limit allowed in high hydrocarbons. I can feel a miss at idle. Actually, it feels like all the cylinders are misfiring. Something's wrong. It's not a rough idle. It's more of a constant, unstable, mild vibration. RPM sometimes varies maybe 50 rpm or so, up and down, over time..

From my reading, High hydrocarbons is raw, unburned fuel being exhausted. While some of that fuel might be "re-burned" in the cat converters, and thereby pass the emissions tests, the engine is STILL exhausting unburned fuel, and that bothers me. It's wasted power, and wasted fuel.

So, since it's not just one bad cylinder (I know what that feels like, and this aint it) it might be a constant lean-miss due to a vacuum leak or some other air-intake malfunction?

It could be ignition timing, as OldSchool suggests. The tank is empty and tomorrow I'll get some higher octane fuel.
I guess I gotta recheck the ignition timing as well, although this latest test that passed (from a different smog-test station) also notes "Ignition Timing B10". I am assuming the "B10" means 10 degrees BTDC. And I did see him fiddling with something near the distributor, and it was probably the SPOUT connector... but who knows..

As noted before, all the ignition components EXCEPT the coil, are new. I almost bought a new coil but.. well.. coils either work or they don't, in my experience..

Other than ignition, there's vacuum leaks, and maybe air pump problems? (nah.. smog pump puts air into the exhaust, so that's not it.)

The concept of lean-miss is new to me. How would the EEC permit a constant lean miss? What faulty components might allow that to happen? Dirty O2 sensors?

 

[Elessee]

A good night's sleep, it's a new day, I've done some more reading, and the correct path to take is a little clearer. I keep forgetting about the car's ability to diagnose itself (to a degree).
I'm going to run codes and maybe the clues will be there. KO Engine Running codes should show a "lean condition" if it really exists.

The plugs came out with worn center electrodes and therefore huge gaps, but otherwise looked clean and were in great shape. The car has plenty of power with no drivability problems.

Ultimately, diagnosing the problem might be out of my league. I'd really like to find a shop that is both willing and able to tune up this car, and will take the time to do it right. My regular mechanic is always too busy. Since I'm stuck with this car for the next couple years, I don't mind spending a few bucks to get a real professional diagnosis and tuneup.

 

[tomnh]

While checking the MAP sensor, I notice the engine "idles" much better with the MAP disconnected. "Idles" is in quotes because it doesn't idle at all unless my foot is on the gas.
However, the cold engine runs pretty smooth as low as 700 RPM with the MAP disconnected.

The MAP checks out as far as I can tell... its diaphragm is intact and its hose is OK.
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But a new problem with the dash temperature gauge caught my eye: It falls to zero and stays there when the engine is running. Or, when the key points to RUN / engine off..

Turn the key to OFF, or to Accessory, and the gauge reads around the 'N' in Normal, regardless of engine temp. Things weren't like this before. (Analog instrument cluster, btw)

The gauge's single-wire (red / white stripe) coolant temperature sender under the distributor is a thermistor, and as the engine cools, resistance rises as expected. So that sending unit seems to be OK.

Now I'm checking everything temperature related. There's gotta be around 5 different coolant temperature sending devices on this car.
Considering the original cold-start symptoms, and the Code 51 (ECT- Engine Coolant Temperature sensor) I'm starting to lean towards a bad wire or ground or similar involving coolant temperature.

After reading this, it sounds like my Mark.
1. change the engine coolant sensor to the right of the distributor (Drivers side). Mine was bad and it would jump all over the place. Fluid loss should be minimal,
2. Since it looks like you have done everything else, here is one more thing to try.
behind the intake are 2 connectors, the salt and pepper connectors. They are mounted to a clip at the top of the intake. Ford has always had a problem with the 5.0 and surging/stalling idle.
open the connectors. take a small pin and spread the male connectors open a bit. on the female connectors use a small pair of needle nose and squeeze them shut a bit.
Clean all 4 connectors with contact cleaner, add a bit of dielectric grease and plug them back in.
Remember our Marks are very sensitive to electrical problems. :shifty:

tomnh

 

[Elessee]

Thanks for the advice on the temp sender and about improving electrical contact inside those connections, tomnh.

Whatever caused this temperature gauge to act funny has since cleared itself up, and the gauge now reads properly.

This car got really sick, really fast. It was getting worse by the day. I almost didn't make it to the repair shop. New things were popping up right and left and I had no idea what to make of it.
On top of that, the car was due to be smogged and re-registered and it was a bad time for that..

Meanwhile, I was checking things out and posting all kinds of stuff that had nothing to do with the actual problem. As a result the whole thread is full of inaccurate stuff. ( Far as I know the root cause was a bad MAP sensor since that's the only part they replaced... But they did keep it for 9 days so maybe something else was involved.)
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I have a mind to go back and delete just about everything in this thread. I don't want to confuse or mislead readers of the future who are looking for a guide to fixing similar symptoms, and lack the knowledge to separate a little bit of wheat from a whole a lot of chaff.

hmm... seems like there is no "Edit" option available on posts older than about 3 days? I never noticed that before.. Oh well. I'll be more careful next time.