Lean condition TSB's
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Senior User
Joined: Nov 2004
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From: Lancaster, PA
Lean condition TSB's
I was wondering if anybody with a 97' 4.0 has had to deal with this? My truck hesitates at low rpm when I accelerate, and trys to stall when first accelerating a cold engine, though it idles just fine until you put a load on it. I was looking at TSB's 01-20-5, 98-23-10, and 98-6-8. These all indicate lean conditions due to vaccum leaks, maf contamination, and faulty intake gaskets.
I have no cel's, no pinging, average 16-18mpg on 87 fuel and other than that the truck runs great. Code scanner comes out codeless. I guess my next step is to do a vaccum test. Any quick ways to test the MAF?
I have no cel's, no pinging, average 16-18mpg on 87 fuel and other than that the truck runs great. Code scanner comes out codeless. I guess my next step is to do a vaccum test. Any quick ways to test the MAF?
Last edited by pintopower8; Dec 14, 2006 at 08:02 AM.
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Joined: Jan 2003
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From: Connecticut
Yes, there are quite a few threads around wherein people indeed had to deal with lean codes exactly as they are described in Article Nos. 98-23-10 and 98-6-8.
If it were my '97 4.0L I would replace the fuel rail gasket (and upper intake gaskets) even without any sign of lean codes. The relevant TSB mentions rough idle and stalling which seem consistent with the symptoms you are describing.
https://www.ford-trucks.com/forums/s...11&postcount=9
You can't forget the basics either, though. When's the last time the truck had a tuneup? New fuel filter?
Have you ever cleaned the MAF?
If it were my '97 4.0L I would replace the fuel rail gasket (and upper intake gaskets) even without any sign of lean codes. The relevant TSB mentions rough idle and stalling which seem consistent with the symptoms you are describing.
https://www.ford-trucks.com/forums/s...11&postcount=9
You can't forget the basics either, though. When's the last time the truck had a tuneup? New fuel filter?
Have you ever cleaned the MAF?
Thread Starter
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Senior User
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From: Lancaster, PA
Oh yeah shes in tune, I am a technician for a Chrysler dealer (not sure why) new plugs, wires, MAF cleaned, air filter, fuel filter, oil, trans fluid, rear end. Like I said I'm getting decent city mileage. I have monitored my thermostat on the scanner and it seems to be operating just fine. When I get the opportunity some night I will take my truck in to work and do a good vaccum test on it and maybe test the MAF. I am not going to tear my intake all apart and buy a $100 MAf just because it could be bad. I will do what i can to narrow things down. Thanks for the response!
Post Fiend
Joined: Jan 2003
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From: Connecticut
Good luck with the troubleshooting, keep us posted.
BTW: You asked about testing the MAF sensor, it sounds like you might be in a position to perform this one:
http://www.lindertech.com/newsletters/nwk11~99.pdf
BTW: You asked about testing the MAF sensor, it sounds like you might be in a position to perform this one:
http://www.lindertech.com/newsletters/nwk11~99.pdf
Elder User
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From: Ventura ,ca. (near L.A.)
I would agree that you might have a vacuum leak. An easy way to check the intake gaskets, is to start up the truck and let it idle, and spray the area where the intake manifold meets the head with some Carb cleaner and if the idle speed changes when you're spraying then you have a leak or a crack. You might also want to spray down all the vacuum hoses and fittings under there to see if you can find the culprit. Dont forget the brake booster, it runs off vacuum too.
Hotshot
Joined: Aug 2002
Posts: 12,679
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From: BC, Canada
On the 4.0L any vacuum leaks just about always show up more when the engine is cold. If you can watch short fuel trims on your scan tool that helps find the leaks easier than just listening for it. With the engine cold, spray Carb Medic, or some other type of carb cleaner, where the upper plenum bolts to the lower manifolds on a SOHC, or where the upper plenum attaches to the fuel rail on a OHV, while watching the fuel trims. Usually if there is a leak you'll see the short fuel trim lean out lots when the carb cleaner hits the leak.
If you monitor the MAF PID you should usually see about .8-.9V at idle. Usually if there's a MAF problem it will read way off of that at idle, from what I've seen. Disconnecting the MAF will usually make it run better if it's really bad too.
If you monitor the MAF PID you should usually see about .8-.9V at idle. Usually if there's a MAF problem it will read way off of that at idle, from what I've seen. Disconnecting the MAF will usually make it run better if it's really bad too.
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Joined: Jul 2005
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From: Copenhagen, Denmark
I do not have a '97 but my '94 4.0 behaves like you describe it in cold weather (below approx. 50 F). It will stall if throttle is not applied very carefully from idle if truck has driven less than approx. 1 mile. After the engine speed has increased to above 1500 rpm there is no problem and full throttle may be applied without stalling. The funny thing is that idle is stable and there are no problems starting the engine.
After getting a code for lean left bank when running above 80 mph on the highway for more than 30 minuttes, I thought the maf was faulty and changed it. No change! I have also checked the fuel pressure and checked for vacuum leaks visually and with ether as outlined above.
Did you locate the problem?
After getting a code for lean left bank when running above 80 mph on the highway for more than 30 minuttes, I thought the maf was faulty and changed it. No change! I have also checked the fuel pressure and checked for vacuum leaks visually and with ether as outlined above.
Did you locate the problem?
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From: SW Va
I agree, it sounds like a cold vacuum leak problem & the upper & lower intake manafold gaskets on this vintage 4.0L engine belong high on your suspect list.
You could also rig a propane "sniffer" with a length of hose & a "sports inflation needle" attached as a probe, if your concerned about stress cracking the "composit" intake manafold, with strong leak check solvents.
Maybe even the throttle position sensor has a closed throttle, cold temp problem, so if the vacuum tests don't pan out, maybe consider taking a look at the TPS resistance profile.
Just some more things to ponder.
You could also rig a propane "sniffer" with a length of hose & a "sports inflation needle" attached as a probe, if your concerned about stress cracking the "composit" intake manafold, with strong leak check solvents.
Maybe even the throttle position sensor has a closed throttle, cold temp problem, so if the vacuum tests don't pan out, maybe consider taking a look at the TPS resistance profile.
Just some more things to ponder.
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