I have a 97 V6 F150 2WD extended cab with ~160K miles. Recently my check engine light came on right around emissions inspection time. I had codes pulled and they are PO 171 and 174 for "System too lean" for Bank 1 and Bank 2. They recommended a new fuel filter, fuel induction service, and to replace the mass air flow sensor (which I replaced myself). I took the truck back in to the shop yesterday, and now they are telling me more codes are coming up (due to running the truck with the check engine light on, so that it "stressed" the systems even more--is this even possible?). Now PO 1537, Intake motor run controller (IMRC) is showing, and they've also found a hole near the CAT. I haven't had the fuel filter changed yet, and declined the fuel induction service, but now with more codes I'm looking at more costs. The truck is not my primary means of transportation and is paid for but the AC is also on the fritz (not sure why yet).

Any opinion as to whether I should take the chance and fix everything (not yet sure the total costs, maybe $1000-$1500) to keep the truck or just give it up at this time? I was hoping to get another year or two out of it. The body is in good shape. Any feedback on the problems decribed would also be helpful. Thanks

 

i would not go to that shop if they think the little yellow light is "stressing teh computer". normally the "lean" code means too much air for the amount of fuel you are using. that could be lpw fuel pressure, bad fuel pressure regulator, etc, but normally it has more to do with the air side. your looking for a air leak around the intake manifold. could be the gasekts, or could be vacuum hoses. most guys find the old hoses are dry rotted and cracked or burnt. look for small hoses that are connected to the EGR system, or close to exhasute manifold. Pull the hoses off one at a time and check condition.

 

Thanks! They are also saying I have a small leak near the catalytic converter. The check engine light has been on for some time now and I've had codes pulled several times. It always comes up as "system too lean, Bank 1 and 2". I've never had the code for the IMRC before. Could this small leak be associated with the problem? I changed the MAFS and intended to change the fuel filter. I don't believe the fuel filter has been changed for awhile.

 

pin hole in exhaust pipe probably not a problem. you looking for a leak on the suction side of the intake. look at the small black vacuum hoses and the intake manifold gasket area.

 

I agree, a leak in the exhaust may not be your problem certainly not for both banks. However, leaks in the exhaust can cause serious problems if they are in front of the O2 sensors. As stated though, this would not cause a lean code on both banks.

The most likely culprits are vacuum leaks, bad PCV valve, or a leaking intake manifold.

 

They did a smoke test and said they did not find a huge leak, but did find a small vacuum leak at the EGR valve.

As stated they said there is a hole in the CAT (or near it). Why would the IMRC code come up if that wasn't faulty? If there is a hole on or near the catalytic converter perhaps I should get that fixed first, change the fuel filter (probably needs it anyway), and reset the computer. They did not recommend fixing the small vacuum leak (at least that wasn't part of the original estimate). I'm not sure what a fuel induction service entails. I will check the hoses but they did not indicate a problem there.

If I go by what they are saying, I'm looking at ~$1500 repair for a truck I paid $7K for 5 years ago. That would include replacing the CAT. They believe the O2 sensor(s) may need replacing, but that is referred to the muffler shop.

 

A vacuum leak of any size is your culprit. Fixing that will probably resolve the lean codes.

 

Thanks. When you said that an exhaust leak ahead of the O2 sensor could cause "serious problems", what can of problems are you referring to? Should I then get the hole near the CAT fixed?

 

I had a dime sized hole in one of my cats for 6+ months and never got a CEL. I'd say, keep looking for vacuum leaks.

 

dude, go to a shop where they actually know what they are doing. These guys aren't making any sense at all.

 

I went to another shop. They found a loose (or dissconnected?) vacuum hose behind the engine. They said they can't see the hose, but they have to feel for it. Is there a vacuum hose on this model year that fits that description? They said it was missing a clip which they ordered.

Thanks for the feedback, guys. With this other shop the bill is a fraction of what it had been!

F150dot

 

PCV elbow.

Common failure.