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Discussion Starter · #1 · (Edited)
FYI, this will be a long read. I will appreciate any help that anyone can give me. I have officially guessed myself stupid. I'll cover the issues I'm having...I have no idea if they are related.

99 V6, mtx, returnless style fuel system, 98,000 miles.

I bought the car as a theft recovery in March or April of 2003. I believe I started driving it in the late summer, early fall by the time I got it repaired and titled. I put it up over the winter, so I really barely drove it at all in 03, and the only modifications it got were a short ram intake and B&M shifter.

In 2004 the original returnless fuel pump went, soon after I did the SVT lite upgrade (UIM and TB). As far as I can remember before that, things were fine with it, and it ran good. I purchased the redesigned pump for it and installed it myself (wasn't covered under the warranty due to the reconstructed title).

Shortly after installing the new pump, I began to notice this hesitation/surging sensation. It starts around 2500 rpm, and usually goes away when the IMRC opens, mostly in 2nd and 3rd gear...don't really feel it in 1st, 4th, or 5th. My first thought was that the fuel pump was bad, so I took it back to Ford. I was told the service department needed to determine it was bad before they would warranty it, so I booked it for service. The tech drove it with me and felt the problem. Upon hooking it up to the computer, he detected a pending lean condition code, and told me he couldn't warranty the fuel pump when the lean condition was present as that was most likely the problem, and suggested I replace some gaskets and try again. I replaced the gaskets and the code went away, but the hesitation didn't. I didn't feel like paying another service fee at Ford, so I let it go at that point.

Fast forward a couple years. Problem is still there, and I had replaced the IMRC, IACV, DPFE, injectors, plugs, fuel filter (again), fuel pressure sensor, and a couple O2 sensors that went bad. Mods now include MSDS headers/y pipe, trubendz high flow cat and Borla exhaust, and GMK CAI. I replaced just the fuel pump itself (not the sender or sump) and nothing changed.

This past spring/summer, the car started running a lot worse. I bought a new coil pack and plug wires for it, and changed the plugs again. Plug number one was destroyed. Very oil fouled, and just generally trashed. The new plug lasted about 800 miles before it looked the same way. With Trevor and DanG diagnosing a burned valve or broken oil ring, I swapped the engine for another 2.5, adding a Spec lightened flywheel, DMD, and SVT radiator at the same time. I could tell right off the bat this engine runs a lot better, and is running a lot cleaner, but the CEL came on for EGR insufficient and excessive at the same time, and the car was idling terribly. The inside of the UIM was pretty dirty, so I decided to do some more work. I had the UIM and TB hot tanked, and cleaned the LIM by hand. I replaced the IACV, EGR valve, and the DPFE sensor with the hoses, as well as cleaned out the EGR tube that connects to the header. I also bought a brand new fuel pump assembly and installed that. Upon reassembling it, the car wouldn't come down off fast idle, and it threw codes for Idle Overspeed error and EGR insufficient. I ordered new LIM and UIM gaskets and tore it down again, taking extra care to make sure there were no vacuum leaks, and that everything was connected properly. The idle was much better upon starting it up, and it ran pretty good...the hesistation/surging was barely noticeable. Within a few days though, everything has come back - the hesitation/surging is there (mostly noticeable in 2nd gear it seems and the CEL is back on for EGR insufficient.

I've replaced the ENTIRE EGR system. EGR valve, DPFE with hoses, IACV, and the UIM hot tanked and pressure washed. The inside is spotless, so I know nothing is clogging the EGR ports. I'm really, really, really out of ideas with this thing. I consider myself to be pretty logical and proficient, but I'm at my wits end with this.

A couple things: Would buying an XCAL2 and doing some datalogging show what is causing the hesitation/surging, or would it at least be evident on there? I don't know anything about tuning or options.

I don't know that these two problems are related (the P0401 code and the hesitating), thoughts?

Something I just thought of tonight on the way home from work. The main body wiring harness of the car that runs underneath the carpet under the passenger's seat was melted during the interior fire before I bought the car. Since a new harness was more than I paid for the car, the harness got repaired, and I'm sure it's very possible that one of the 46 wires in that harness (perhaps one to the fuel pump?) needs some attention, and I will try and tear into that with a multimeter this weekend.

Does anyone have any other ideas? I just can't see how I can still have the EGR code after all that's been replaced.

All of the parts are from Ford, BTW.

Just to give the mod list, here we go...

SVT LIM
SVT TB
SVT UIM (sent through the max extrude hone process)
GMK CAI
MSDS headers/ypipe
Trubendz high flow cat
Trubendz Borla dual system
Dual Mass Dampner
SVT radiator


I installed those new gaskets and got it back together last Sunday, and now the CEL is back on again, and the hesitating is back again. It seems that whenever the battery is disconnected for any amount of time (when the CEL gets turned off) it runs better until the CEL comes back on.

Thanks for any help or advice.
 

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Re: P0401 -- End of my rope!!!!

Question on the surging problem. Does it feel like if the car was almost pushed forward by some magical pressure on the gas pedal, but you haven't pushed it any harder than before?

I'm asking because I get this same type of issue when I drive with very little pressure on the gas pedal of an ATX. I get it right about 2-2.5k RPM and usually about the time the transmission should shift to be "fuel economic friendly" but it just pushes forward then will change gears usually a little while after it does the surge. Most of the time around 3.5k RPM.
 

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Discussion Starter · #3 ·
Re: P0401 -- End of my rope!!!!

Nope, feels like I'm almost pumping the gas pedal, only not quite that severe (maybe between half throttle and the floor). The harder I'm accelerating, the more I feel it.
 

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Re: P0401 -- End of my rope!!!!

This might sound like a crazy idea and almost not do-able, but their should be a way to get something like this done. Have you ever thought about putting a camera with night vision into the engine bay and driving the car around? Pointing the camera from the drivers side fender towards the throttle body would probably be a good position for checking about a TB cable tension issue. You can also see the water pump belt cycle to see if you have a crankshaft issue, or you could place the camera to the other side of the car and watch the serpentine belt. The only other placings I could think of as for checking on that particular type of issue would be checking the axles for excessive spin. You will probably need to get someone to ride with you and watch a video monitor to see what the TB is doing while you are driving.

As for the P0401 being the cause of your surging/hesitation problem, I'd say no. The only thing that would cause is that you are pulling more clean air into the engine than normal, as you are losing the exhaust flow back into the engine. Yes it sounds stupid and doesn't make sense, but I've driven on a similar code with my Ford Taurus and did not have any surging problems.

I'm thinking either a slipping TB cable tension or a drive train problem. Even something as stupid as the break pads rubbing on a rotor due to a warped rotor could cause this problem for you. If you could grab a short video of you driving in the car with the problem, more would probably be able to help.
 

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Discussion Starter · #5 ·
Re: P0401 -- End of my rope!!!!

I'm pretty sure it's nothing related to the TB cable, especially since it only happens during a very certain time.

Pads, rotors, and one axle are all new.

I don't have a camera mount for the car...I'm not sure how well a video would pick up the problem, as it's more something you feel, not see.
 

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Re: P0401 -- End of my rope!!!!

my car is throwing the same p0401 error. except it drives like it always did, i dont feel a surge or anything. that one 'green' hose coming out of the top of the EGR (Michcougar told me wat its called but i forgot lol) was cut on my car! so i sealed it back, hopefully the light will stay off this time around...
 

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Re: P0401 -- End of my rope!!!!

DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient -----

Your Egr and DPFE are most likely ok, but have you checked out the little black folw control module that mounts on the back side of the intake(held on by 2 7mm bolts? Also check your vac line connections. If you aren't careful you could kink/break or just plain disconnect one. also if improper routing you could melt one on the EGR tube it's self.

Try disconnecting the DPFE and the flow control module (elecritcally) and see if your car runs alright. Odds are it's that little black part.

You car bucks or feels hesitant because you are flooding out the engine with EGR retarding the air fuel charge and making it not want to run.

You ask why does it only happen at 2500-3500 RPM? Well that is cruising range and when EGR is most active. Once you get out of that range it runs just fine? no?
 

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Re: P0401 -- End of my rope!!!!

I had the same problem right when i bought my car. and as jank said is was the flow control module. ford replaced it under warranty and i haven't had the problem since
 

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Discussion Starter · #10 ·
Re: P0401 -- End of my rope!!!!

Your Egr and DPFE are most likely ok, but have you checked out the little black folw control module that mounts on the back side of the intake(held on by 2 7mm bolts? Also check your vac line connections. If you aren't careful you could kink/break or just plain disconnect one. also if improper routing you could melt one on the EGR tube it's self.
I went over all of the vacuum lines with a fine tooth comb last Sunday when I tore it all back apart. I found no problems whatsoever. I ran air through them and couldn't find any leaks or clogs.

I have not done anything with that module...what does that do exactly? I have a used one here I can try.


Try disconnecting the DPFE and the flow control module (elecritcally) and see if your car runs alright. Odds are it's that little black part.
I will unhook them in the morning before I leave for work.



You ask why does it only happen at 2500-3500 RPM? Well that is cruising range and when EGR is most active. Once you get out of that range it runs just fine? no?

It actually runs ok in that RPM range if I'm just cruising in 4th or 5th gear too, and I've never felt the problem in 1st. It's most noticeable in 2nd for some odd reason, but I have felt it in third too.

Thanks for the advice.
 

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Re: P0401 -- End of my rope!!!!

DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient -----

Your Egr and DPFE are most likely ok, but have you checked out the little black folw control module that mounts on the back side of the intake(held on by 2 7mm bolts? Also check your vac line connections. If you aren't careful you could kink/break or just plain disconnect one. also if improper routing you could melt one on the EGR tube it's self.

Try disconnecting the DPFE and the flow control module (elecritcally) and see if your car runs alright. Odds are it's that little black part.

You car bucks or feels hesitant because you are flooding out the engine with EGR retarding the air fuel charge and making it not want to run.

You ask why does it only happen at 2500-3500 RPM? Well that is cruising range and when EGR is most active. Once you get out of that range it runs just fine? no?
Happen to have a picture handy with a red circle or arrows showing the piece you are talking about?
 

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Discussion Starter · #14 ·
Re: P0401 -- End of my rope!!!!

Drove to work today with the DPFE and flow control modules unplugged (electronically), and it made no difference at all. It really seems like it's only happening in second gear now :confused:

I'll try and see if I can get someone to go with me and shoot some video of it today.
 

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Re: P0401 -- End of my rope!!!!

Check your TB position sensor signal while it's doing this via an XCal2 datalog or via an OBD-II logger. Rule that out and let's move on from there.
 

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Discussion Starter · #16 ·
Re: P0401 -- End of my rope!!!!

So first step would be ordering an XCal2 from Nautilus then, right? Because I have neither of those things.
 

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Re: P0401 -- End of my rope!!!!

Was board in class and came across a vehicle self diagnostic page. I went through it and this is what it returns for the symptoms in bold with underlining. Notice that some of this does not apply to the cougar and can be skipped in the process of trying to solve the problem. Most of it seems to be what you have already done, but figured I'd post it for the hell of it.

Code:
Diagnosis

Here's what we think may be wrong with your car and what may be causing it. The list goes from the most likely problem to the least likely. Check out our Product and How To pages for more information about particular parts.

Keep in mind, this is a general diagnosis. Your car may not have the parts we list as potential problems. If you're not sure if you car has a particular part, check your owner's manual.

[B][U]Feels+like
Engine+Surges
Accelerating
Engine[/U][/B]
 
[B]Priority	Action		Part Type				Cause[/B]
1 		Inspect		Fuel Filter				Clogged or dirty fuel filter
2 		Inspect		Air Filter				Restricted or clogged air filter.
3 		Inspect		Wireset					Damaged, worn, or deteriorating spark plug or coil wire(s).
4 		Inspect		Spark Plug				Fouled, damaged or broken spark plug(s).
5 		Inspect		Carburetor Float			Improperly adjusted/saturated or damaged carburetor float.
7 		Inspect		Timing Cover Stud Kit - Performance	Improperly adjusted or worn/malfunctioning power valve
8 		Inspect		Choke Pulloff				Worn, defective, or faulty choke pulloff(s).
9 		Inspect		Choke Thermostat			Stuck or improperly functioning choke thermostat.
10 		Inspect		Fuel System Pressure			Incorrect fuel pressure being delivered to carburetor or fuel injection system.
11 		Inspect		Fuel Pump				Improperly functioning fuel pump or circuits.
12 		Inspect		Oxygen Sensor				Damaged or faulty oxygen sensor or circuit.
13 		Inspect		Spark Plug Wire Loom - Performance	Improperly adjusted or worn/malfunctioning carburetor.
14 		Inspect 	Fuel Injector				Plugged, dirty or poorly connected fuel injector.
15 		Inspect		Hood Brace				Leaking, worn, or damaged intake manifold gasket
 

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Discussion Starter · #18 ·
Re: P0401 -- End of my rope!!!!

Yeah...I've been through about all of that that applies.

Thanks for taking the time to look it up though. I appreciate it!


Looks like I'll be doing a datalog in a couple weeks. I'll post up what I find.
 

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Re: P0401 -- End of my rope!!!!

Wade, have you checked your MAF? I know it is unrelated to the EGR code but it probably has everything to do with your hesitation and lean running condition. I was experiencing the EXACT same issues as you are, First I checked for a vacuum leak and found nothing, I replaced the plug wires and the hesitation was still there, swapped the MAF for a good one at Autozone cause I know the manager and the car ran PERFECT. The genius I work with suggested this from the get go and he was right. The plug wires had 148K miles on them so they needed replacing anyway.

Now on to the EGR code...There is a possibility you have gotten a bad part from the dealership. If you still have your reciept take it back and have them get you a new one under the 12 mo/12,000 mi warranty through Ford.
 

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Discussion Starter · #20 ·
Re: P0401 -- End of my rope!!!!

Wade, have you checked your MAF? I know it is unrelated to the EGR code but it probably has everything to do with your hesitation and lean running condition. I was experiencing the EXACT same issues as you are, First I checked for a vacuum leak and found nothing, I replaced the plug wires and the hesitation was still there, swapped the MAF for a good one at Autozone cause I know the manager and the car ran PERFECT. The genius I work with suggested this from the get go and he was right. The plug wires had 148K miles on them so they needed replacing anyway.

Now on to the EGR code...There is a possibility you have gotten a bad part from the dealership. If you still have your reciept take it back and have them get you a new one under the 12 mo/12,000 mi warranty through Ford.


Thanks Drew...I have cleaned the MAF with MAF cleaner....I just noticed somthing weird about my intake tract though...I'll grab a picture of it tomorrow.

So would it be the DPFE or the EGR causing the EGR Insufficient code?
 
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