97 taurus drivability problem???

1997 FORD TAURUS
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THE_UGLYDOG
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I have a 1997 Taurus, 3.0, Auto, 121000 miles. We just got it so I don't know it's history. I ran a scan on it with an Autotap scanner so I have some results. It originally had codes for low return voltage from the fuel pump and O2 sensors showing a bad cat. It acts like a bad cat, starts and runs fine, then when it heats up in about 20 miles, it loses power and will eventually stall. If it stalls or you shut it off and restart it, it runs fine for a couple of more minutes, then does it again.
The cats have been changed, fuel filter has been changed, the MAF sensor has been cleaned, air filter changed.
The MAF air flow reading and the TPS follow the opening of the throttle, the TPS shows a nice smooth graph with no hesitations or dead spots. The engine load is about 30% with the a/c on, the injector pulse width is about 25 until the problem starts, then it gets much wider and ranges up to 75.
The fuel pump doesn't shut off, the fuel pressure readings are within specs, about 32 running, about 40 not running, both the long and short term fuel trim readings follow along in a nice even pattern, with bank #2 having a slighly broader pattern than bank 1, till the problem starts, then the pattern widens from about -10 to +10 then drops to -10 and flatlines at 0. The car will still barely run. The graphs for misfire on all cylinders shows no misfires at all. There are no trouble codes. Any suggestions???
Jun 3, 2007 at 5:57 PM
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I'm still a little suspicious of the MAF sensor, and also wonder about a vacuum leak such as at the intake. I hate when no codes show. Check the baro reading and find what your area's sea level should be. Is it in spec when the problem happens?


https://www.2carpros.com/forum/automotive_pictures/30961_barochart_1.jpg

Jun 3, 2007 at 6:30 PM
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THE_UGLYDOG
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The graph for the MAF sensor corresponds to the throttle opening and follows the TPS graph almost exactly. I was thinking about a vacum leak maybe near the pressure regulator, i didn't find any hoses that seemed bad, I moved all of them around and nothing changed. I'll try a little carb cleaner around the intake to see if the idle changes. We're at sea level +30 feet here.
Jun 3, 2007 at 7:01 PM
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The graph is consistent when the problem is happening? I would still check the baro reading when the problem happens.

Did you use a fuel gauge to monitor the pressure when the problem happens out of curiousity?

I assume you know that the specs are the most critical when the problem is happening or nothing abnormal is likely to show.
Jun 3, 2007 at 7:24 PM
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THE_UGLYDOG
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Yes the graph for both the MAF and TPS are smooth and even,no jumps or dips, they follow the amount I push on the throttle and each other's pattern the same as they do when it's running OK.
How do I check the baro, I've never done that before? I'll do it tomorrow when I go back to my shop. I havent hooked up the fuel guage after the engine is hot, I'm a little afraid of high pressure fuel around a hot engine while driving it. I did get it to act up while running in the driveway yesterday so I'll get it to mess up then I'll hook up the guage with a hose and extinguisher standing by and I'll let you know the readings.
Thanks
Jun 4, 2007 at 6:53 AM
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Check the scanner's manual, I'm not familiar with that one. Maybe you can't?
Jun 4, 2007 at 4:52 PM
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THE_UGLYDOG
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The baro reading was a steady 30 at all times. I did get it to stall with the fuel pressure gauge hooked up. Just before the problem started I got a codeP0430 Cat low performance, then the fuel pressure started to drop, it went slowly down to 29, thats when the readings started to change for fuel trim and fuel injector pulse pattern, then the car started losing power, I disconnected the pressure regulator vacuum line and there was no change, I tapped the regulator a couple of times, no change, so I reconnected it, no change. Soon the pressure dropped to 19 and the fuel trim lines flatlined. I shut it off and restarted it and it was fine again for a while. I bet it's the fuel pump starting to go.... What do you think?
Jun 5, 2007 at 11:14 PM
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THE_UGLYDOG
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Oh I forgot, the Auto tap scanner. It uses your laptop or PDA and hooks up to the car, it has basic codes that it can read, advanced programs you can buy extra so you can tell what everything is doing including the transmission. You can put them into gauges, graphs what ever you want on the screen and monitor them as you do a road test or record them to read them later. It's the best thing I've bought in years. Price is great too.
Jun 5, 2007 at 11:22 PM
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Yeah, my bet is on the pump based on the results you have obtained. However, it is possible that the pump is losing power from a relay for example, causing the fuel to drop off. That's the tough thing about intermittants. You get to a point that you have make a decision on what repair to make. The fuel pump relay is part of the Constant Control Relay Module on the left side of the battery behind the headlight.

There is a tsb on the fuel pump harness getting chaffed on the hose clamps for the pressure and return lines. Get a good look at them, if you drop the tank.

So I guess that leaves you with a few avenues. The ccrm is easier to get to, and you may be able to get inexpensive through a junkyard. At least it's narrowed down.
Jun 6, 2007 at 5:57 AM
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THE_UGLYDOG
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Hi Yes, I thought about that too. These have a relay pack that has the pump relay, a/c relay and something else, I don't remember what sealed inside. I swapped it for another identical pack from one of the cars that didn't have the problem and it kept acting up the same, so i guess that makes it the pump.
Thanks so much for your suggestions, you led me in the right direction pretty quick. I've had other pumps go bad before but they always just went out quick , like in one day and I was always able to see it right away on the gauge, this one has been doing this for a few weeks. I suppose since the fuel filter was mostly clogged when we got it, maybe it had overloaded the pump and that caused it to die when it runs for a while.
Jun 6, 2007 at 6:28 AM
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Pumps are funny like that. Couple thoughts, one, check the harness I mentioned and second, becareful with what brand of pump you get. May want to get an oem. There are some pumps on the market that suck....but not for long.
Good luck, and please follow up!
Jun 6, 2007 at 7:15 AM
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THE_UGLYDOG
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Hi Yes I'll definatly check the harness when the tank's down. Could the discount pumps cause a loss in fuel economy too, I noticed a 1.5 mpg drop in gas mileage after I changed the pump on one of our trucks.
Jun 6, 2007 at 7:29 AM
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I doubt there is a relationship between the pump and the fuel economy. The fuel regulator should control that as excess is returned to the tank. But who knows? As far as economy pumps go, I don't have much faith in too many aftermarket ones. Although delco is avaiable aftermarket as well as at a gm dealer. I have seen too many problems with airtex in particular and those at autozone. Be sure to change the filter and socK BTW, regardless if it was done recently.
Jun 6, 2007 at 6:23 PM
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MERLIN2021
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Hey Paul my 99 chaffed thru at the left front wheel well! 6 hours of tearing the interior apart to find a break outside!
Jun 7, 2007 at 4:30 PM
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And there ye have it, straight from an old ford guy!
Jun 7, 2007 at 5:58 PM
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THE_UGLYDOG
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Hi Paul,
I think its fixed now. I checked the wiring and found no problems, I replaced the entire pump assy. including the strainer with a Ford pump (it cost almost as much as we paid for the whole car), and a new filter. The old pump was a real rusty brown when I took it out, so I cleaned the tank out.
I ran it a couple of hundred miles so far, no problems, and it seems to run and even shift better the more I drive it. I think there may be a very slight problem with the TPS, there was a slight hesitation at off idle only one time, but not bad and it shows no codes, so its good enough. I can't thank you enough for your suggestions.
Richard
Jun 17, 2007 at 6:46 PM
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I'm happy for you. Thanks for completing the post, as it feels good to know things worked out.

Don't let the logic of what you pay for a car or what you can sell it for cloud your judgement of how much it costs to keep driving it.

Ya got repairs or payments....or both.
No one ride for free :wink:
Jun 17, 2007 at 8:42 PM