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Discussion Starter #1 (Edited)
I've been researching all the common problems with the early first generation Focus problems with stalling/running rough when cold. I tried all these things on my 2001 Focus SE 2.0 Zetec with 260k miles.

It starts but runs VERY rough when cold starting below 50-60F. It stalls, chugs and surges. When it surges or your press the throttle, it smooths out. It will smooth out and be fine for the rest of the day after about 5 minutes. It's been fine all summer but since it's cooling off, this will be a problem through winter.

I've replaced the Idle air control valve, MAF sensor, verified the PCV hose is not collapsed or leaking and found no other vaccuum leaks around the intake, throttle body on the back side of the engine. It also has new spark plugs and wires.

- No CEL, no codes
- Cold start reads about 40C for coolant temp on the ODO screen test cycle. Unsure if this is normal. Will read higher temps as it warms up, fans work and temp gauge works.
- No leaks in the PVC hose and the PCV valve is good
- Checked the hose from the brake booster to the intake, its ok too.

What do you all think? Can't keep throwing parts at it!!
 

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Bad engine during colder weather is odd (to me).

At 260K miles, I would suggest that you perform an engine cylinder compression test, in order to establish general engine health. This can be done by you, at your home, using a test set that is available from AutoZone (or other) for free. Tool Loan Program.

Also consider replacing the spark plugs OR plug wires, -if needed?

Lastly, even if not "cold weather" typical, I would suggest the Coil Pack might be a problem ONLY because of this parts' history of failing and causing so many types of engine problems with the Zetec.

Gd Luck
 

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Vacuum leak or ignition or general engine condition at that mileage, many engines will act like that at cold starting when they begin to run ragged from age.

The coil is important there, you change them as much as oil filters on these cars. Yank it and clean it and look for hairline cracks in the outer case and ALL OVER IT INCLUDING THE BOTTOM in bright light and change part if you find any cracks, even if it doesn't cure problem if motor still has good compression the likelihood of coil being bought for nothing is minute on a zetec.
 

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Discussion Starter #4 (Edited)
It's certainly a vaccuum issue. This morning it was surging to about 3000 rpm until it warmed up and it didn't stall out/chug like usual. I'm suspecting an intake manifold leak/gasket area leak, but I haven't been able to determine where yet. It's really the only remaining place this could be happening, unfortunately.
 

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Spray some WD40 around the vacuum lines one by one. If we see a increase in RPM's after spraying you can pinpoint your leak
 

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If the TB gasket fails at the idle bypass passage inside, that is an undetectable vacuum leak that can occur with cold running. You will NOT detect it spraying a half gallon of leak check.
 

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Discussion Starter #7
If the TB gasket fails at the idle bypass passage inside, that is an undetectable vacuum leak that can occur with cold running. You will NOT detect it spraying a half gallon of leak check.
This is good advice and I can probably check/replace the TB gasket. So assuming it's just the top end bolts to remove it, and they are accessible, that will be next.

Checking out my repair manual pdf, removing the intake manifold does not seem like something I want to get into in my parking lot.
 

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Discussion Starter #8
I thought about the TB gasket more. But it seems if the gasket failed between the intake and idle bypass valve, this shouldn't make a different at idle IF the throttle is closed, since the throttle plate is upstream from the gasket and couldn't let more air in anyway. Correct me if i'm wrong?
 

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Think about it some more. You'll figure it out. The leak goes right past the closed throttle to add to it.
 
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