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Discussion Starter #1
EDIT: See my 7/13/04 response below for latest update - it's not the fuel pump.

EDIT: See 1/4/04 response below - it does NOT appear to be the aftermarket air intake afterall --

After the weather cooled off and the stock air filter box was in place, the hesitation became much more pronounced and easy to reproduce (good when I go to the dealership soon)! The stumble happens in 2nd gear, 25 to 30 mph, and 3rd gear, 35 to 40 mph under heavy to wide open open throttle. It becomes intermittant and almost goes away after the engine warms up.


2001 Cougar, 2.5L engine, Manual transaxle, 14,000 mi.

For some time now I've been getting a "stumble" or hestiation at around 30 to 40 mph, 3 or 4 th gear, 3,000 to 4,000 RPM during aggressive acceleration. You can feel the stumble and hear it in the exhaust. The car runs great except for this stumble.

This happens in hot or cold weather and with the engine hot or cold; however, I also pick up a stumble at 10 to 20 mph 1 or 2 gear with the engine cold.

The fuel pressure is within specifications (35 to 60 psi) as checked with a pressure guage. There are no trouble codes (checked with an ODB II scanner) and no Malfunction Indicator Lamp (MIL)/check engine lamp.

This stumble occurs with the stock intake and air filter installed but, does seem to be more pronounced with the cone air filter/short ram installed.

The dealership couldn't "verify" the problem but upgraded/reflashed the Powertrain Control Module (PCM) to see if that would help - it didn't.

Any ideas or thoughts??
 

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I had a 96 T-Bird that run beautifully - except for the same type of hesitation. I am not sure what your problem may be, but I had all my plugs and wires replaced. In addition, I had the Transmission flushed.

I have no idea what was ever wrong with it, but it went away and road like it was off the show room floor after that.

Good Luck!
 
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I would love to know that answer too, been happening ever since i had my car and the problem got more noticable when I put on an intake. I work at a dealership and none of my Techs can find a problem...i.e fuel etc. If anyone has any experience with this please let me know.
 
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Hey check out The topic above that says some buddy please help! Thats my boy we're having the same problem! (So I think Anyways)
 

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Discussion Starter #6
Originally posted by: Cougarsales
I would love to know that answer too, been happening ever since i had my car and the problem got more noticeable when I put on an intake. I work at a dealership and none of my Techs can find a problem...i.e fuel etc. If anyone has any experience with this please let me know.
CougarSales --- it helps to know (although it's disappointing) that the technicians at your dealership can't find anything. If your work friends can't help you, what chance do the rest of us dealership outsiders have!! Any idea what your technicians have tried/tested so far? Do they have any ideas no matter how far fetched?? I'd hate to waste alot of time chasing a problem a Ford Technician can not figure out.

How about other Cougar owners out there with performance intakes. Are you experiencing problems also? Any fixes or ideas you've come across?

Thanks to all. It helps to know I'm not alone.
 
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no, they tried the normal routine, replace the fuel pump, egr and some other stuff. they suggested that it could be the intake, but "OHHH NOOO I say. It cant be the intake" and since my intake incorporates my nitrous set up, I have been reluctant to change back to the original intake.
 
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Hi,
My son is in the Navy, and while he has been away, I have been driving his cougar along with adding a couple christmas presents, was hoping he would be home, but........................soon, anyway,........ set of new Calli chrome rims and tires, and custom cougars, dual exhaust with flowmaster, he also as an injen intake, I have noticed the same lag when accelerating, it seems to be getting worse, if you find the problem ,, please please let me know!!!
 

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what your feeling is a problem common on the 01-02. Its a bucking caused from the fuel pump. It is not your intake. Simply bolting on an intake will not cause your car to do this unless the problem was already present.
 

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GMK has a good point...does it happen more often when you're low on fuel...1/4 tank or more mine used to do it until we replaced the fuel filter.
Something else...when you installed the intakes...did you disconnect the battery to allow the ECU to relearn the new air/fuel mixture?
 

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Yup and it will get worse and worse until the car is bearly driveable.

From what i understand you can remove the fuel pump and clean the lil Sock. this might just solve your problem. I have heard of many people replacing the pump without solving the problem.

Removing/replacing the oem pump is not terrible difficult and can be done from inside the car if you simply remove the rear seats and pull up that circular rubber cover.



regarding not resetting the ecu being the problem......I have done so many different intake setups on my car. Sometime i get lazy and don't reset the ecu. Even so it wont cause this type of problem, the only thing is the car wouldn't learn your mod as quickly, hence not much of an immediate power gain.

This problem could be associated with your intake if you have a vacuum leak. This could cause this type of problem. Ensure all lines are connected and tight. Make sure there are NO leaks and every nip is either plugged or connected to a vacuum line.
 

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Discussion Starter #12
Originally posted by: GrandMasterKhan
what your feeling is a problem common on the 01-02. Its a bucking caused from the fuel pump. It is not your intake. Simply bolting on an intake will not cause your car to do this unless the problem was already present.
You're right GMK and Y2Cougar, the problem is NOT the new intake!

I put the stock air box back on, reset the Powertrain Control Module (PCM) by unhooking the battery (I always do this when changing something) and the stumble is there.

It became very pronounced when the 30 to 40 degree weather hit. The stumble occurs in 2nd gear (25 to 30 mph) and 3rd gear (35 to 40 mph) under heavy to wide open throttle. The problem becomes much less pronounced after the engine warms up!

The problem is exactly the same regardless of the amount or type of fuel in the tank. I checked the fuel pump pressure with a gauge and it is well within the 35 to 60 psi specification (16,000 miles on the car).

I'm going back to the dealership in the next week or two and will take a test drive with the service manager and/or technician. I'll easily be able to reproduce the problem; so, they won't be able to ignore it.

I'm glad it's not the high flow intake but, this makes it that much tougher to find/fix the problem.

I'll let you know what the dealership finds!!
 

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Have you replaced your fuel filter and run some good fuel injection cleaner? I was having the same problem but this seems to have fixed it. :thumbsup: Remember you need good cleaner not that cheap $2 gumout crap. I used the Outlaw performance fuel injector cleaner and it made a HUGE difference. In fact I liked it so much I got some for my mom's van and she was really suprised how noticeable the change was. Outlaw fuel injector cleaner
 

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I think i know what your talking about, but my car doesn't do it all the time. It only does it when i first start the car at the beginning of the day, hot or cold outside. Actually it doesn't even do it all the time, or i'm just used to it. It kind of hesitates, goes, hesitates, and than goes. I kind of have to put on the gas a little, but not floor it for it to do it. Would that be the same thing? I'll try that fuel injection cleaner and see if it works.
 

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Best engine cleaner that ever was is BG 44K. You can't get it at stores, but if you have a nearby dealership/service department that is BG certified, they will sell it at their parts counter. It's about $15 for an 11-oz can. CAN. It would destroy a plastic bottle, so they had to put it in a can.

It flat-out rules.
 

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Hmmm.... doesn't sound like the fuel pump problem. Even if it was, don't replace the filter, just clean the damn sock! (done this a few times... the first time wasting money on buying a new pump -- which wasn't the problem).

Maybe you have a broken or loose mount, and the engine can counter-vibrate within a certain rev-range sapping power and causing that stumble? I have a stumble too, and am in the process of diagnosing it. Maybe you have a bad plug with a weak spark which doesn't fire under certain conditions leading to this problem during certain RPM portions, expressed in as dif speeds in dif gears.

Massiv.
 

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Discussion Starter #17
Originally posted by: BigDaddyTiberius
Have you replaced your fuel filter and run some good fuel injection cleaner? I was having the same problem but this seems to have fixed it. :thumbsup: Remember you need good cleaner not that cheap $2 gumout crap. I used the Outlaw performance fuel injector cleaner and it made a HUGE difference. In fact I liked it so much I got some for my mom's van and she was really suprised how noticeable the change was. Outlaw fuel injector cleaner
Thanks to all for the suggestions.

I plan on taking my Coug to the dealership next week and, I plan on being a bit persistant (read: pain the ass) with them if they have problems fixing it (I'm under warranty until May). If after some dealership time they can't fix it properly, I plan on trying the injector cleaner and fuel filter. The thing that's buggin me is the car has been very well maintained, filled with only quality petrol, and only has 16,000 miles on it!! This crap should not be happening already!!

Again thanks and I'll keep you posted of my dealership experience - I'm really hoping for a fix!!
 

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my car has done this since the day i picked it up...dealership also cant find a problem..they know it exists cause they rode with me but they cant seem to find what causes it...their suggestion to me was to keep taking it back about every 2-3 months so there was plenty of documentation on the problem....that would solve any warranty running out issues. They said with plenty of documentation of the problem it would be no problem to "good faith" the repair after the warranty was out

i know this doesnt help your problem..but deffinetly something to keep in mind
 

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Discussion Starter #19
ACCELERATION STUMBLE UPDATE - 2/18/04

After starting this post, I finally got my car into the dealership last week.

They FINALLY were able to reproduce the 35 to 40 mph stumble (cold engine, steady 30 mph in 3rd gear, then go to wide open throttle). This stumble occurs intermittantly in the hot engine.

They tested the electronic engine control (EEC) system and found diagnostic trouble code (DTC) P0304 - Cylinder 4 Misfire Detected. How they found this I don't know because I hooked up my scanner the day I took it in and found no active or pending DTCs. However, they may have forced the code by performing a scanner induced "output test." Most consumer scanners can't do this.

Anyway, they removed/inspected all spark plugs, replaced plug and wire #4, tested the fuel pump pressure (OK at 45 psi which is consistant with when I checked it), performed a leak down test (OK), performed an injector flow test (OK), and cleaned the Mass Air Flow (MAF) sensor.

They test drove it the next cold morning and called it fixed. I drove it the following morning and called it a valient effort but the stumble is exactly the same as before.

I'm going back to the dealership next week to let them try again. I'm going to remain hopeful, patient, and cooperative as these types of problems can be a pain in the ass to diagnose.

I'll report back again (hopefully with an F'in fix!).
 
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