Taurus Car Club of America : Ford Taurus Forum banner

1 - 19 of 19 Posts

·
Registered
Joined
·
20 Posts
Discussion Starter · #1 ·
'99 Duratec, 115,000 miles.
Got the codes and found a hole in and replaced the PCV hose hidden under the throttlebody(Most common fix).
Codes came back.
Car starts, runs and idles perfect(rock steady @750 r.p.m.).
Searched for air leaks, even trying actelene gas all around the running engine(a little nerve-racking). Can find nothing.
Any ideas what might be causing these "lean bank" codes?
Thanks.
 

·
Registered
Joined
·
21 Posts
What about the upper intake manifold seals? Spray around the seals w/ the engine running and see if the idle changes.
 

·
Premium Member
Joined
·
1,283 Posts
Again, someone recommend the worthless spray to detect leaks technique. If that worked, the leak wound be obvious anyway. It is not uncommon for leaks to develop at the upper intake manifold. In that way, I'm glad you have to pull the upper intake to replace spark plugs, because it more or less makes it an easy choice to replace the gasket.

O2 sensors do not typically set lean codes, a leak or weak combustion are more likely. Low fuel pressure can also cause lean codes, so make sure you replace the fuel filter if it hasn't been done in a while. A dirty or fouled MAF sensor can also trigger lean codes.
 

·
Registered
Joined
·
74 Posts
It is not uncommon for leaks to develop at the upper intake manifold.

O2 sensors do not typically set lean codes, a leak or weak combustion are more likely. Low fuel pressure can also cause lean codes, so make sure you replace the fuel filter if it hasn't been done in a while. A dirty or fouled MAF sensor can also trigger lean codes.
Khan is right on target. Great suggestions.

The intake manifold gaskets on the dual intake runner systems get brittle, and will crack. If you plan to keep the car and haven't replaced the gaskets before, now is the time. Common issue on the 2.5L Duratecs on the Contour/Mystique. Every fall when temps cool there is a glut of lean codes on the contour boards. In many cases gently snugging the lower then upper manifold bolts offers a temporary fix. You must be CAREFUL about doing this as the block is aluminum and will strip if you over torque. NOTE: Torque specs for these bolts are listed in inch-pounds.

Check the vac hoses from the intake manifold, particularly the one that leads to the power brake booster.

Another common culprit is the valve cover vent hoses. The rubber connectors at the top of the valve covers are known to deteriorate.
 

·
Registered
Joined
·
21 Posts
Again, someone recommend the worthless spray to detect leaks technique. If that worked, the leak wound be obvious anyway. It is not uncommon for leaks to develop at the upper intake manifold. In that way, I'm glad you have to pull the upper intake to replace spark plugs, because it more or less makes it an easy choice to replace the gasket.

O2 sensors do not typically set lean codes, a leak or weak combustion are more likely. Low fuel pressure can also cause lean codes, so make sure you replace the fuel filter if it hasn't been done in a while. A dirty or fouled MAF sensor can also trigger lean codes.
That is my mistake, I did not fully read the original post where it says, "Searched for air leaks, even trying actelene gas all around the running engine(a little nerve-racking). Can find nothing." Sorry bro.
 

·
Premium Member
Joined
·
14,126 Posts
I wouldn't say that using a spy of some sort is worthless. I looked and looked for a vacuum leak once and finally found it using carb spray on the EGR valve. A quick tightening of the bolt fixed my vacuum leak.
 

·
Registered
Joined
·
74 Posts
By the way, check the accordian tube as well. They have been known to develop large cracks along the pleats over time. Yours may be due after 11 years.

My money is on the brake booster hose and/or fitting or the dirty MAF.
 

·
Registered
Joined
·
430 Posts
Motomech,
Fought those codes for awhile. As in your case my engine ran and idled fine. You need a scanner that has a live data function. If you have one or can borrow one, monitor your short term fuel trim levels, while monitoring these levels try the propane or brake cleaner methods. Take your time and try suspect areas slowly and watch the values on your scanner. It takes about 5 seconds or more for the sensors to respond. I was worried about using the propane and only cracked the valve a little. Got frustrated because I didn't find anything. I then turned it on full blast and that was when I found my leaks around the IMRC. If Short term trim levels do not change, disconnect and plug the main vacuum source on the firewall. This will isolate the engine from other potetial vacuum leaks such as EVAPS, brakes, and dash A/C controls. Good luck and let us know what you find.

Ed​
 

·
Premium Member
Joined
·
1,283 Posts
My car never had a lean code, but that vacuum fitting on the firewall had a crack in it, I suspect that probably happens a lot.
 

·
Registered
Joined
·
430 Posts
Moto,
If you plug the main vacuum source at the firewall DO NOT drive the car, this is just for testing. You will have very little brakes!
ED
 

·
Registered
Joined
·
3 Posts
I have a '97 wagon with the 3.0 4-Valve V-6, and I'm getting both codes. Runs very well and idle is perfectly smooth. Getting 23 mpg on hiway. Replaced fuel filter, pcv hoses, cleaned the MAF sensor, tested the EGR and replaced gasket, tested for manifold with carb cleaner, looked at every vacuum hose I can see. Any additional ideas?
 

·
Premium Member
Joined
·
6,641 Posts
Gotta be a vacuum leak if it isn't the PCV elbow. 99% of the time those codes on the duratec are the PCV elbow. Just replacing the hose and not the elbow may be a source to your issue. I had replaced mine and the replacement went bad shortly later. Check that elbow!!

Otherwise you have a vacuum leak. Do the gas torch test. Turn it on (unlit!!) and move it around the engine at idle. You'll find the leak eventually! When the engine idle rises, you've hit the leak. Or someone was playing a trick on you and stepped on the gas :D

Here is a good thread that has a lot of ideas: http://www.taurusclub.com/forum/82-maintenance-repair/172282-00-sable-p0171-p0174.html

Did you test fuel pressure?
 

·
Registered
Joined
·
23,363 Posts
Sam, he just has a u-shaped pcv hose under the throttle body on his 97 tec. No elbow like your set-up. There's a slew of vacuum hoses and connections on the back side of the intake to check.
 

·
Registered
Joined
·
3 Posts
Thanks Breeves and sheila,
I'll check more closely for a leak. But the weird thing is, sometimes the light doesn't go on for a week, even if I do nothing. Could it be a false positive?
Thanks.

Sam, he just has a u-shaped pcv hose under the throttle body on his 97 tec. No elbow like your set-up. There's a slew of vacuum hoses and connections on the back side of the intake to check.
 

·
Premium Member
Joined
·
6,641 Posts
Thanks for the clarification sheila. I missed it was a 97 (not that I knew there was a difference!). I'm going to get a maintenance manual and learn more about all of this stuff. I guess they got really cheap on the gen 4's. Seems like the skipped corners everywhere and tried to drive the costs down. The thing that bothers me the most is the drum brakes.

As to your false positive idea, I doubt it. You should check your fuel pressure when the light is off, then check it the SECOND the light turns back on. It could be a fuel pump going bad but hasn't died yet (just an idea!).

Other option is the leak is very small and the fuel trims aren't getting to the max level of 25% very often. So one day it may get there and the threshold is enough for it to go from a pending to a stored code. Then you keep driving and the trims go back down into normal range and the stored codes reset.

I would also check fuel trims. If they are higher than +5% or so at idle and hanging around there, that indicates a leak. Also did you drive differently when the light would turn on?
 

·
Registered
Joined
·
3 Posts
Thanks for the analysis Breeves.
In answer to your question, no, I didn't drive any differently when the light was on. It must be a very small air leak. Light has been off for two days now. When it does go on, it's always idling, in traffic. That points to an air leak rather than low fuel pressure, doesn't it?
 

·
Premium Member
Joined
·
6,641 Posts
It makes sense that it would go on in traffic. The fuel trims will only shoot up when you idle usually with a leak. What happens is it spikes momentarily at +25% and then will go back down. When you are in traffic, it probably does it many times causing it to go from pending to a stored code.

You probably do have a small leak somewhere. It truly isn't a big issue at this point. Just do a smoke test if you smoke, or do the propane torch test (unlit) and see if you can find a leak.
 
1 - 19 of 19 Posts
Top