Contour Enthusiasts Group Archives Forums General Troubleshooting Bunch of erratic engine behavior

Hi

I have a bunch of small issues with my 2.5l Duratec. They might be linked (or not) and hopefully I can have some help here.

1. Main problem: When cruising at low rpm (1700-2000 rpm), just barely touching the gaz pedal to hold speed, the car bugs (successively hesitation to acceleration). I have that since around the last 10 K miles. I had only I/E when it started. Lately, I held the car in that condition for a while intentionally, and the CEL came on with that:

P0401 EGR Flow Insufficient Detected

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Since then, I made the complete intake upgrade : SVT UIM & TB, 19 lbs injectors, 75 mm MAF, BAT intake tube, etc. Everything seemed pretty stable.

Lately, prob 1. seemed to increase, and I can add the following:

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2. Sometimes, If I'm stopped at a red light and press the gaz pedal to rev a bit and let go, the engine revs are falling under the normal idle rev and sometimes the engine stalls.

3. Sometimes when I release the gaz pedal and hold the clutch to slow down, particularly when it's hot outside, the revs will stick at high rpm (2000 rpm) for a LONG time (minutes) and then finally go down to 1500 rpm.. then after a while to 1000 rpm to finally reach the normal idle speed.

I don't know if everything is related, or if I have different issues to deal with. I would be glad to have your inputs.

I looked in vaccum leaks so far, but the intake was taken apart and re-assembled many times since the appearance of prob #1 so I guess I can scratch that cause. Could the EGR valve itself could be likely to cause most of those symptoms??

edit: Since the UIM is only there since 7-8K miles, that can't be because the EGR ports behind the TB are clogged. Problem 1 was there with both the old and the new UIM..

It seems that you replaced the UIM over 7000 miles ago. Is that correct? If so, have you gotten another CEL since you replaced the UIM? Also, did you check the EGR passages on the old UIM to see if they were clogged when you replaced it?

If you haven't received another CEL and the EGR passages on the old UIM were clogged, then I wouldn't worry about the P0401 anymore.

I also doubt that the EGR system (or lack thereof) would make the engine surge up and down the way you describe it. I had a P0401 and never had that problem.

Sounds like it could be either a MAF (mass air flow), an IAC (idle air control), or a vacuum problem, but it could be other things as well.

When you replaced the UIM and TB, did you put in new gaskets? Also, did you torque the UIM properly and in the right sequence? My understanding it that torque is important on these aluminum manifolds, since they can be bent if overtorqued.

ok.. I missed few precisions to shorten the story, but let me add few prcisions:

1- With the stock Intake + KKM kit (old setup) I had the bucking problem at low rpm, but never saw the CEL. I usually just down shifted a ratio to avoid staying in the 'sketchy' rpm zone.

2- The EGR ports were not clogged on my old UIM.

3- After replacing the whole intake, the problem stayed the same. No improvement. Since the MAF was replaced, I think we can remove it from the equation (unless the problem is in the connector.. I'll look at it). And only once I had the CEL trigerred and I saw it happening at the same moment I was holding the engine in the problematic condition (very light throttle, engine rpm below 2000 rpm, bucking..). I just reset the CEL, we'll see if it comes back.

4- I just come back from taking the EGR valve off the car and it seems fine. It is actuating when I put vacuum on the top.

IAC? That could make sens since my problem happens at very light throttle position.. Maybe it would also explain why the car dies when I gently pump the gaz pedal at a stop.

Could the DPFE cause the "bucking" at low rpm?

People told me to look at my fuel pump, but I would more believe the fuel pump (returnless system) to cause problem at high load/rpm.

Originally posted by spocket:

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The EGR ports were not clogged on my old UIM.

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So it seems that the P0401 hasn't been fixed at this time. Is that correct?

Originally posted by spocket:

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I just come back from taking the EGR valve off the car and it seems fine. It is actuating when I put vacuum on the top.

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My EGR valve opened when I applied vacuum also, but when I took a further look it was totally clogged. I took the EGR valve off the engine, opened the valve with vacuum, and then shone a flashlight in one end. I couldn't see any light coming out the other end (even in complete darkness). This showed me that the EGR valve was completely clogged.

Originally posted by spocket:

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Could the DPFE cause the "bucking" at low rpm?

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The DPFE is just a measuring device. It measures the amount of exhaust that is flowing through the EGR system (specifically the venturi tube).

The EVR (EGR vacuum regulator) is the device that actually opens and closes the EGR valve. It's possible that the EVR is erratically opening and closing the EGR valve. This could cause the engine to stumble. But this seems highly unlikely.

George I thought your clog was the EGR passage on the upper intake manifold?
TNX Paul

Originally posted by F111D F:

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I thought your clog was the EGR passage on the upper intake manifold?

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Actually, I ended up replacing most of the major components on the EGR system!

I originally took the the EGR valve off and cleaned it with TB cleaner, but the P0401 came back on.

I decided to replace the EGR valve and found that it was clogged up, even though the valve was opening and closing properly under vacuum. As I said in my previous message (above), I shone a flashlight in one end (when the valve was open) and there was no light coming out the other end. This showed me that even though the valve was opening and closing, it was clogged for all practical purposes. To verify my results, I tried the same test on the new EGR valve and you could see light come out the other end. I reset the CEL, but the P0401 came back on.

I then tested the EVR (with Alex Peper's Vehicle Explorer) and found that it was giving erratic readings, so I replaced it. I reset the CEL, but the P0401 came back on.

I then tested the DPFE (also with Alex Peper's Vehicle Explorer) and found that it was also giving bad readings, so I replaced it. I reset the CEL, but the P0401 came back on.

I finally found that the EGR passages on the UIM (behind the TB gasket) were totally clogged and cleaned them. I reset the CEL, and the P0401 never came back on! Problem solved. Drove to New York City and back over the weekend (over 800 miles) for a wedding. Still no P0401. Halleluhah!