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Rough idle and "Check Engine Soon" light - FIXED

Post number 11 has been selected as best answered.

P0174 vacuum leak weak vacuum line elbow

Thank you Syber Tiger. I had the same problem on my 2003 Sport Trac with 75,000 miles, except I only got the P0174 code. I had my vehicle at my local dealer getting a oil change $5, and asked them about my CEL light coming on. They gave my trac an inspection, and told me I had a vacuum leak. They wanted to change my brakes out as well, total bill $1200. They figured $200 for the vacuum leak. I told them I would do the brakes myself, and thanks for the info. I had trouble finding the elbow as well, and had to modify a hose. Anyway, I reset the CEL and it's been off for 200 miles. Thanks for the post and the pictures, it has save me cash, which is desparately needed, especially this time of year. The word needs to get out about this common problem.
 



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Same happened to me a few years ago. I found a hose at PepBoys for approx $6. It has four 90 degree bends so if you mess up you have 3 extra chances to get it right. It also appears to be a sturdier replacement. I secured with two hose clamps as well.

The part number is (C) 72079 and it's marked "Curved Radiator Hose" or cooling bypass hose. Made by Dayco.

Here @ Rock Auto for $4.41 http://www.rockauto.com/dbphp/x,catalog,33,partnum,72079,d,DAYCO_72079.html

72079.jpg
 






still can't find a fix for the 02 4.0 wich seems to be different than the other 4.0 :mad:
 






I got a 97 Ford Explorer that has bad idle on a cold morning then as it warms up it smooths out. I am going to look at my lines and see if they are bad. Thanks for the info!
 






would this cause the little yellow wrench to appear lite up on the dash and send the car into limp mode?
 






I got a 97 Ford Explorer that has bad idle on a cold morning then as it warms up it smooths out. I am going to look at my lines and see if they are bad. Thanks for the info!

funny, mine doest the exact opposite
 






I'm having a ridiculous time trying to find the problem with my 2002 4.0 Eddie Bauer Edition. The issues I'm having all seem to be very closely related.
Does the 4.0 have the same 90 degree elbow? I can't seem to find it.
Here are the related issues
1. Is running rich, which effects cold starts occasionally, plus wastes gas
2. When Shifting from Park into Reverse, or Park into Drive, or from Drive into Reverse, the car does a huge lurch or surge, probably 1-2 feet. Applying the Brakes almost doesn't stop it (It feels exactly like I'm power braking it
3. When backing in and out of a parking space when I'm having to turn the wheel, the surging happens, and also the car will many times just die, or surge and die.
4. Gas mileage does seem less then stellar (which is probably partially due to it running rich)
5. Not throwing any Check Engine Lights, however, it does occasionally state that the Oil Pressure is low.

What has been addressed so far either by myself/dealership:
1. PCM Upgrade Completed: No change
2. IAC Replaced: No Change
3. MAF Replaced : No Change
4. Fuel Injectors Removed and Sonic Cleaned:
5. Fuel Injectors Flow Tested : No Change
6. Vacuum System Smoke Test: No visible leaks noticed.
7. Thermostat Changed: No Change

The Blue Oval Certified Dealership that I've been working with, is completely stumped, and cannot find the issue. It seems like I'm having problems that have plagued others, but the normal fixes just haven't done anything, and it's really starting to eat away at me. I'm trying to get this fixed up or at least identified tonight.

This forum has been really helpful reading through thus far, but I needed to have a meeting of the minds to help narrow this down. Thank you in advance for any assistance you might be able to provide.
 






Have a 2002 Explorer V6 and having very similar issues with the low idle (engine appear to almost die at some stops), Service Engine Soon light and fuel trim bank codes. Has anyone had this issue on the v6? I know most of this thread deals with issues on the 4.6L V8.
 






Have a 2002 Explorer V6 and having very similar issues with the low idle (engine appear to almost die at some stops), Service Engine Soon light and fuel trim bank codes. Has anyone had this issue on the v6? I know most of this thread deals with issues on the 4.6L V8.

What are the codes? I had a bad O2 sensor trigger fuel trim codes and lurching at idle.
 






where would it be on the 4.0? any pics please if avaliable

Mine is a 2002 also, look at the front of Intake on the passenger side, almost invisible under where the radiator hose goes up over the passenger valve cover (just behind the alternator). There is a hard plastic line running parallel to the valve cover and makes a hard right with the help of an UNDER ENGINEERED soft rubber elbow... Thanks Ford Motor Co...

This one ranks right up there with the failing OD clutch hub snap ring that has been failing for the last 25 years. It could be fixed with the full circle spiral lock (same part that is an upgrade for the TH400)...

Ranks right up there with the CHINESE bolts that hold the doors on my FOX mustangs, that break off at the head...

Thanks Ford Motor Co... Where Quality is Job #1...
 






Rough Idle PO171&174

This thread sure saved me too. Could that elbow be buried a little more? Made a hose and no more problem . Thanks, Dakota
 






The guys at the ford parts counter were like "you had better use this factory part, a coolant bypass hose will break down from the oil. It's a different type of rubber"... I'm like DUDE!!!!!!!!!!!! there are gobs of these vehicles that are failing like this....... because FORD used the RIGHT kind of rubber????? I'm thinking my $3.50 coolant bypass hose will last longer than the $40.00 factory assembly (8 yrs).... :D
 






wich one am i gonna replace?

1.jpg
 






Thanks much for the info. I found the leak myself yesterday, but hell of a time finding a replacement. Temp fixed it last night with a sliced section of coolant hose and a few band clamps. Easier to plug vacuum than pressure leaks.

Found the part at Rockauto.com for around $17.

Thanks...
 






03 XLT, Have most of the problems you have except for the oil light. No codes are coming up for me. Just replaced the PCV valve and soon will be getting a transmission flush. My mechanic said " It isn't giving out codes and nothing is leaking, so just drive it". But it is irriatating the hell out of me. I don't think I will buy Ford again, this is my 2nd bad one. Damn.




QUOTE=bmwsteve;2418895]I'm having a ridiculous time trying to find the problem with my 2002 4.0 Eddie Bauer Edition. The issues I'm having all seem to be very closely related.
Does the 4.0 have the same 90 degree elbow? I can't seem to find it.
Here are the related issues
1. Is running rich, which effects cold starts occasionally, plus wastes gas
2. When Shifting from Park into Reverse, or Park into Drive, or from Drive into Reverse, the car does a huge lurch or surge, probably 1-2 feet. Applying the Brakes almost doesn't stop it (It feels exactly like I'm power braking it
3. When backing in and out of a parking space when I'm having to turn the wheel, the surging happens, and also the car will many times just die, or surge and die.
4. Gas mileage does seem less then stellar (which is probably partially due to it running rich)
5. Not throwing any Check Engine Lights, however, it does occasionally state that the Oil Pressure is low.

What has been addressed so far either by myself/dealership:
1. PCM Upgrade Completed: No change
2. IAC Replaced: No Change
3. MAF Replaced : No Change
4. Fuel Injectors Removed and Sonic Cleaned:
5. Fuel Injectors Flow Tested : No Change
6. Vacuum System Smoke Test: No visible leaks noticed.
7. Thermostat Changed: No Change

The Blue Oval Certified Dealership that I've been working with, is completely stumped, and cannot find the issue. It seems like I'm having problems that have plagued others, but the normal fixes just haven't done anything, and it's really starting to eat away at me. I'm trying to get this fixed up or at least identified tonight.

This forum has been really helpful reading through thus far, but I needed to have a meeting of the minds to help narrow this down. Thank you in advance for any assistance you might be able to provide.[/QUOTE]
 






This post did help me a lot as well, but my situation ended up a bit different. My issue was the heat riser intake o-ring that was grabbing air while running. Making the engine difficult to maintain a constant even idle. Just like was mentioned above.

Thought it would be nice to share my example too!
 






This post did help me a lot as well, but my situation ended up a bit different. My issue was the heat riser intake o-ring that was grabbing air while running. Making the engine difficult to maintain a constant even idle. Just like was mentioned above.

Thought it would be nice to share my example too!

Did you have any codes that led you to this solution?
 






Wow, I'm just now getting back to reading this thread after numerous postings. I'm glad a lot of people were helped by this thread. It is such a common problem on a number of Ford products not just the Explorer.

I think most of the folks substituting a different hose by chopping up a hose for some other application should be good to go. I just went with the factory part as it really didn't cost that much in the whole scheme of things.

Happy motoring everyone!
 









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My car had codes 174, 300 and 316, idled rough and felt like it wanted to stall at stop lights. Got the parts at Ford today. The pvc hose was $29.53 and the pvc valve was $19.31. I guess we pay extra here in NJ. All codes cleared and idling smoothly again. Thanks for the detailed writeup and pictures SyberTiger!
 






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