Had the CEL come on again today on the 96 Mystique six . Code P0174, bank 2 lean.
I checked the long term fuel trims on bank 1 and bank 2. At idle both are at 25. At 2000RPM I had about 17 on 2 and 7 on 1. I checked the PCV elbow hose and everything looks good - and would likely affect both banks?
Anything else to check before I pull the manifold (nasty job) and replace the gaskets??
O2 sensor on bank 2. It's dead and the computer is trying to compensate.
Al
No, the O2 sensors are both counting just fine. If I did not have the discrepency between long-term fuel trims between banks I'd say mabee an intermittent O2 failure, but when the O2s are all clocking properly I still have that trim discrepency -----
Seems to me one bank is keeping the injectors open a lot longer than the other. So why would the O2 sensors read the same? Pull the plugs and see if bank 2 is rich, if it is it's the O2 sensor giving false info to the ECM.
Al
Final mixture is the same - so the plugs burn the same. Problem is, the computer needs to richen one bank (longer pulse width) to maintain that mixture. This is due to unmeasured air getting into the one bank. I'm just trying to make sure there is no other way for this to happen other than a leaky manifold gasket/seal. The PCV system is a common problem, with the rubber elbow splitting. However, this would affect both banks, giving both P0171 and P0174. I'm only getting P0174, and upon checking the PCV system,everything looks good. Any other good ideas before I call the dealer and find out haw badly the gaskets are going to hurt my wallet? In two weeks the car will be driven by my daughter from Waterloo Ontario to Morden Manitoba and back for a friend's wedding - and I want it right before it leaves - don't need the CEL coming on in the middle of no-where, miles from home with 4 young ladies on board.
Ok, at least your still thinking. Now if it had a vacuum leak and the ECM upped the fuel to compensate, why is it not idling a lot faster? Think about that for a while:) Why not just switch the O2 sensors?
Al
Very simple answer to both questions. The idle is not faster because the idle control valve closes to maintain the engine speed. It is designed to do that. If it had a REAL bad leak, the idle control would NOT be able to compensate, and the O2 sensors WOULD indicate a lean running bank. At this point the computer has increased the fuel injection pulse width beyond a programmed (and relatively small) amount and has corrected the mixture to the point the O2 sensor sees it as OK.
As for why not change the O2 sensors - because they are (relatively) expensive, not REAL easy to change, and I KNOW it will not solve the problem. 36 years experience tells me that.
At this point the engine is still running fine - and passed the Ontario Driveclean test just last week (2 weeks after the light first came on, and 10 days before it came on this time) The light comes on if, on 2 CONSECUTIVE run cycles, with the vehicle at cruise speed for 3.4 minutes, the long term adaptive fuel trim richens the mixture by more than (something in the range of) 18%, more or less.
At this point it is not a serious issue, EXCEPT the car will be doing a 4300 Km round trip over the weekend 2 weeks from now - and I will not be with it to look after any problems. I don't need it breaking down somewhere between Waterloo Ontario and Morden Manitoba. I've been broken down in Flint Michigan before on a long weekend - and believe me it's no fun. For my daughter and her friends it would be a lot worse than a minor inconvenience - and finding a competent mechanic to work on a Mystique is not a trivial problem either - even under the best of conditions.
Further to breaking down in Flint - was labour day weekend 4 years ago, taking said daughter to University in Winnipeg for her first year. I had been in West Africa for a month, andknowing I had worn U-Joints in the Aerostar, had it taken into the shop to have them replaced. I got home a week before leaving for Winnipeg, and felt something was not right with the U-Joints, so back to the shop for the mechanic to double-check his work.Late friday afternoon of the labour day weekend,just outside of Flint, with my daughter at the wheel, one bearing cup on the rear U-Joint "left the building". The truck felt like it was about 8 inches off the road. We got towed into Flint - and could not find a shop who could look at it before Tuesday. Had the tow truck operator drop me in a parts store parking lot. I bought a new U-joint, a hammer, vice, and the only set of metric wrenches in the place (a short chinese set) and crawled under the truck. Could not get the bolts holding the joint to the yoke loose - bent the wrench into a "C" shape. Found a local chap with wrenches willing to help and still could not get them loose, so we knocked the joint apart ON THE TRUCK and replaced the 2 bearing cups that press into the shaft end holding the vice on my chest. We made sure the clips were in perfectly and continued on our way. Total delay something like 6 hours - half of which was waiting for the tow truck.
If my daughter was alone with the truck, it would have been Thursday before she got to school. If it was a problem with the Mysique, it may have been October.
Just ordered $156.00 Cnd worth of gaskets from the local Ford store - looks like I have some fun coming up.
Well,the $156 wasn't the end of it. That was only ONE upper and ONE lower gasket (needs 2 of each) and one injector seal (needs 6). Total came out to about $235 in parts. The lower gasket was blown in 4 places (3 on bank 2, 1 on bank 1) I put new plugs intoo, while I had the manifold off. A lot easier that way, but almost $50 more for the plugs. The secondary throttle assembly (runner control) was badly carboned but otherwise everything (gaskets NOT included) looked pretty good. With any luck no more CEL and code P0174 Started about 2pm - finished about 7:30 with a short rain break and a trip to each of the 2 Ford Stores in town to get the missing parts.
Let us know how it comes out, please.
Al
A little over 400km on it since re-assembly - and no CEL. It was coming on after 2 or 3 5km runs previously. The bottom gaskets were both visibly bad - with all 3 "secondaries" on bank 2 sucked in, as well as one primary, and one secondary on bank 1. I set the stops on the IRC so the butterflies cannot close completely
- my theory is high vacuum on decel with the butterflies closed contributed to the failure.
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