Troublesome Trouble Codes... P0171

aaron97

Cobra is King
Established Member
Joined
Nov 26, 2007
Messages
135
Location
Southern Louisiana
Okay. Here is the car, its a '97 Cobra with o/r x-pipe, MIL eliminators, flowmasters, 4.10's. Other than that its pretty much stock. I bought it a few months ago from a friend. Its got 95,000 miles on it and wasn't taken very good care of, but the price was right. The CEL has been on from the day he bought it, 3 years ago. So he just drove it around like that for 3 years and the car feels very slow for a Cobra. I haven't had much time to do anything to it, other than replacing the AC compressor. But now I am in the UAE and I left the Cobra with a friend so he could fix and drive it. He's a competent mechanic and owns an '04 & '05 GT so he is somewhat familiar with mustangs.

So here is where it started a week ago. He has a code reader so he downloaded the code and it was a P0171. So first we changed the front O2 sensors (because they have 95k on them). The P0171 came back. Also because the car is old we Seafoamed the intake. After Seafoaming and clearing the codes, the P0171 came back and now a P0174 came up. Common sense would tell you that if you got both codes, there must be a vacuum leak. So after a short check, it turns out the Seafoam worked too good and cleaned out all the gunk that had been sealing the intake. So we changed all the intake manifold gaskets and cleaned the IMRCs and checked the exhaust manifolds for leaks and tried again. This time the P0171 and P0174 came back and then a P1443. Good thing is all the lost power is back, now the car pulls smoothly all the way to redline. He checked the Charcoal Canister and all the vacuum lines, the EGR system , gas cap and PCV valves. Found a cracked up line and replaced it and the 1443 went away and hasn't come back but the P0171 & P0174 where still there. So we checked for intake leaks again and found small leaks at the ends of the IMRC's. So we pull the intake back apart and replaced the seals on the IMRC shaft and put it all back together.
After rebuilding the IMRC's and finding the IMRC cable had broken so he fixed that and now only the P0171 came back and its only tripping at idle. We're going to wait a couple days and put some miles on it and make sure only the P0171 is there. I'm going to have him check/clean the MAF and if that don't do anything, we are going to pull the fuel injectors and clean them or possible just replace them.

So that's it. After all this, we started with just a P0171 and have worked our way back to just a P0171. But after all this the Cobra acts like a completely different car, pulling hard from idle to redline. Unlike before. It still has an issue with the idle, after the engine is warmed up, and you drive it around. When you come to a stop the RPM comes down to about 1000-1100rpm and after about 5 seconds drops to 600-800rpm.

So has anyone had something like this before? Any help, advise or opinions would be greatly appreciated. Thanks.
 

STAMPEDE3

SAULS BROTHER
Super Moderator
Joined
Apr 5, 2003
Messages
27,023
Location
South Louisiana
You still have a vac leak is the most likely thing. Clean the MAF for good measure.

Pull the IMRCs and delete. Get it tuned.
 

Cookieman00x

Drunk Again.
Established Member
Joined
Apr 14, 2005
Messages
9,069
Location
S.E Pa
Thats a code that you are too lean...

+1 on what stampede3 said...

P0171 is lean bank 1
P0174 is lean bank 2

If you dont have the cash for the deletes.. Pull your intake, pull off the IMRC's and clean them real good with some brake cleaner. A tune though would definitley let you know where you stand as far as you air fuel ratio goes and let you know if you are running lean. It could also be clogged injectors..
 

aaron97

Cobra is King
Established Member
Joined
Nov 26, 2007
Messages
135
Location
Southern Louisiana
You still have a vac leak is the most likely thing. Clean the MAF for good measure.

Pull the IMRCs and delete. Get it tuned.

Well, we cleaned the MAF, checked the IAC, cleaned and leak checked the Injectors, and rechecked the manifolds. There is still a tiny leak at the IMRC bearing, but its tiny. We're going to try and fix that some how. Not trying to delete the IMRC's just yet. Unless someone knows a place in Phoenix that will tune it for a reasonable price afterwards. Right now our main concern is getting the car smog-legal again so we can get it registered. We checked the plugs and all are fine, ohm'd all the sensors and they are all good. A new fuel filter is going in tomorrow and we are still looking for a fuel pressure gauge so we can check the psi. We had two gauges and one reads at the lower end of what acceptable and the other gauge reads 8psi lower than that. So we're going to change the filter and see if there is a change in the psi. But that tiny leak at the IMRC bearing is still going to need to be fixed. So if we cant come up with something to temp fix the leak long enough to get it smogged, then i guess the Delete is the only option left, since there is no guarantee that swapping the IMRCs with other used IMRCs wont still have leaks.

One good thing out of all this work is that the car is outstanding again. Able to roast the 315's all the way into 3rd gear, when before it would barely brake them lose in 1st gear.
 

Cookieman00x

Drunk Again.
Established Member
Joined
Apr 14, 2005
Messages
9,069
Location
S.E Pa
I have an extra autometer fuel pressure guage... It works but the plastic/glass front was cracked... If you still need one to use for testing...
 

FunkyBoss

Member
Established Member
Joined
Nov 8, 2006
Messages
569
Location
Woodbridge, VA
I went through everything you just described, it took me a year to finally find the leak at the IMRC bearing. I deleted them myself, very easy to do with JB Weld and a die grinder. I've had them deleted now for over a month and still have no CEL with the factory tune.
 

aaron97

Cobra is King
Established Member
Joined
Nov 26, 2007
Messages
135
Location
Southern Louisiana
I went through everything you just described, it took me a year to finally find the leak at the IMRC bearing. I deleted them myself, very easy to do with JB Weld and a die grinder. I've had them deleted now for over a month and still have no CEL with the factory tune.

I think just to test it, we are going to RTV up the bearings and see if the code comes back, since the code is only tripping at idle. If that makes the code go away then I will probably do the delete and just do that spring trick i seen on here to fool the ECU into thinking the IMRCs are still there and working. Like i said, the main reason for most of this is to get the car to pass a AZ smog check. After that, I will have plenty of time to fix it right and then get it tuned.

How did you delete the IMRC's and still run the stock tune without a CEL?
 
Last edited:

STAMPEDE3

SAULS BROTHER
Super Moderator
Joined
Apr 5, 2003
Messages
27,023
Location
South Louisiana
I think just to test it, we are going to RTV up the bearings and see if the code comes back, since the code is only tripping at idle. If that makes the code go away then I will probably do the delete and just do that spring trick i seen on here to fool the ECU into thinking the IMRCs are still there and working. Like i said, the main reason for most of this is to get the car to pass a AZ smog check. After that, I will have plenty of time to fix it right and then get it tuned.

That sounds like a plan.:thumbsup:
 

aaron97

Cobra is King
Established Member
Joined
Nov 26, 2007
Messages
135
Location
Southern Louisiana
Well, the P0174 is back now. We put a new FPR, MAF and fuel filter. The pressure is 6psi low with the Vac' connected and 8 psi low with it disconnected. Was talking with an ASE guy I know, and he thinks that the IMRC bearings leaking may not be enough to trip the codes this consistently. The codes only pop at idle still, only twice out of the 30ish freeze frame data's that I looked at showed it tripping at about 2500 RPM. So next up I am going to change the fuel pump, which is also a good time for a 255lph upgrade. We found tons of places online to get sealed bearings, so if the pump dont fix the CEL's, we’ll just have to take the intake apart again to mic the inside and outside diameters of the bearings. Even if the pump fixes the codes I would still do the bearings or delete down the road shortly.

Here is the parts list so far...
Forward O2 sensors
Intake Manifold gasket set
Intake manifold & IMRC cleaned (looks like new on the inside)
IMRC cable replaced (driver side)
IMRC o-rings replaced (both sides)
New MAF
New Canister purge valve
Cleaned IAC (was gummed up and making humming noise)
Cleaned Injectors
FPR
Filter

Next up are....
Fuel pump
IMRC bearings

I was trying not to just throw money at this problem but that's just the way its ending up... Been about 3 weeks since we started trying to fix the issue.
 
Last edited:

aaron97

Cobra is King
Established Member
Joined
Nov 26, 2007
Messages
135
Location
Southern Louisiana
Okay here goes, all at idle.

Connected Vac on FPR: 30-45 PSI fuel press required, mine was 24 PSI
Disconnected Vac on FPR: 40-50 PSI fuel press required, mine was 32 PSI

Blocked off return to the tank: supposed to be super high compared to the other numbers, it was but it wouldn’t hold once the key was turned off so it is either bleeding back through the pump into the tank or leaking out the injectors, and since we don’t have a rich code or problems starting cause of flooding, we’ll go with the pump. So i ordered a BBK 255lph and it should be here in a couple days.
 

aaron97

Cobra is King
Established Member
Joined
Nov 26, 2007
Messages
135
Location
Southern Louisiana
Bushing leak on the IMRCs, What side is it on? Drivers or passenger?

All 4 bearings, front & back, both sides. Going to be replacing them is week i think, along with the fuel pump. I did some searching here and everyone seems to think you cant get replacement bearings. But after measuring them and doing a search for Sealed Bearings, turns out the bearings used on our IMRC's are standard use on Skateboards and Roller Skates. So we're going to pick up a set and change them out. I'll let everyone know how that goes, because it would be a cheap and easy fix to leaky bearings for those who dont want to delete the IMRC's.

STAMPERE3 - what part of South Louisiana are you from? I'm originally from Slidell.
 

Tx_Diablous

I build them she drives
Established Member
Joined
Jan 25, 2008
Messages
646
Location
Galveston Texas
You might want to try a spacer on the O2 sensor. Back it out of the stream about 1/16th to 1/8th. I have seen this work before but never needed to try it on the 4.6

:shrug:
 

98 svt

Well-Known Member
Established Member
Premium Member
Joined
May 16, 2005
Messages
23,963
Location
Massachoooosetts
Are you SURE you dont have an exhaust leak between the manifold and midpipe? That will trip the code.

There should be a gasket between the passenger's side manifold and midpipe.
 

98 svt

Well-Known Member
Established Member
Premium Member
Joined
May 16, 2005
Messages
23,963
Location
Massachoooosetts
Quick question....
Where the hell are the IMRC bearings? Never heard of them.

I'm cleaning my IMRCs soon, should I replace the bearings?

Any pics of where they're located?
 

aaron97

Cobra is King
Established Member
Joined
Nov 26, 2007
Messages
135
Location
Southern Louisiana
Are you SURE you dont have an exhaust leak between the manifold and midpipe? That will trip the code.

There should be a gasket between the passenger's side manifold and midpipe.
Well, I just have to assume my friend is sure, he said he looked several times and it wasn't leaking.

Quick question....
Where the hell are the IMRC bearings? Never heard of them.

I'm cleaning my IMRCs soon, should I replace the bearings?

Any pics of where they're located?
The bearing are at the ends of the shafts. If they aren't leaking then i would leave them alone. But i know mine are leaking a tiny bit, which is why i am going to try to replace them.

The fuel pump will be here on Tuesday, so I will let yall know how things go with the codes and fuel pressures once its all back together.
 

98 svt

Well-Known Member
Established Member
Premium Member
Joined
May 16, 2005
Messages
23,963
Location
Massachoooosetts
The bearing are at the ends of the shafts.


Keep us updated. I want to know what's needed and how rough it is.
I was getting that code last fall (pretty sure it's that code)
I plan on cleaning the imrc's before I even put it back on the road. So maybe I'll just swap them if it's easy enough.
 

FunkyBoss

Member
Established Member
Joined
Nov 8, 2006
Messages
569
Location
Woodbridge, VA
Do yourself a favor, save a bunch of time and just delete them. I only had one bearing leaking, which was the rear passanger side, and it threw both codes. I wouldn't really trust the skateboard bearing, but I hope it works out for you.
 

Users who are viewing this thread



Top