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Hi, my name is Kevin and I'm trip'n. 1990 Plymouth voyager 3.3 V6, 100 K miles. Symptomology; The engine starts and idles perfectly well but giving it gas just above idle under load it bogs, symptoms get worse as it warms up to the point you have to almost drive the car at idle because it will accept no pedal. I checked fuel pressure at idle at 65 lbs at the shrader, so I replaced the map sensor, TPS, the entire ECM, and the cat. I stripped the wiring harness from the ecm looking for bad grounds or bare touching wires and found nothing. Still doing the exact same thing. My next best guess is fuel pump or filter but after having done all the work I have already done with no results I am afraid to drop the tank and spend the money just to have it not fix it again. I bought the vehicle in this condition thinking I would just read the codes and fix it without a problem, so I got it cheap, but now I have already spent more money on parts than I payed for the car. I am hoping someone here can tell me what is going on with this thing, if I need to drop the tank so be it but I have a suspicion it's still electrical. HEEEEEEEEEEELP!!!!!
Please email me if you have a solution to my madness
[email protected]
Thank You Very Much!!!
 

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Welcome to Allpar.

Why did you replace the TPS and ECM?

65 psi is too high, it's supposed to be 55 psi. Sounds like perhaps a bad fuel pressure regulator. Pinch the rubber return hose with a pair of vise grips and see how it behaves. If the pressure jumps, the fuel pump is OK. if almost no change, it may be wearing out. Then unplug the vacuum line to the regulator and see what happens. This will create a condition similar to acceleration. Check for change in pressure.

What fault codes did you find?
 

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Are the spark plug tips black from carbon fouling? Are they the correct Champion type listed for the vehicle on the underhood label or service manual? (RN14PMP5?)
 

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Bob Lincoln said:
Welcome to Allpar.

Why did you replace the TPS and ECM?

65 psi is too high, it's supposed to be 55 psi. Sounds like perhaps a bad fuel pressure regulator. Pinch the rubber return hose with a pair of vise grips and see how it behaves. If the pressure jumps, the fuel pump is OK. if almost no change, it may be wearing out. Then unplug the vacuum line to the regulator and see what happens. This will create a condition similar to acceleration. Check for change in pressure.

What fault codes did you find?
I went to a shop and had the codes read, it came up 24 I think, voltage to high at tps or voltage to low at tps. Ihad already replaced the tps and the map at that time. He said the older vans did not have a code for a bad ecm but everything else checked out ok so he believed it to be the ECM....but it was not so I am leary to go back to that guy. Also a friend of mine who owns a shop said it was pretty common for the cats to go bad on these vans so that's why I replaced that. How would too much fuel pressure cause it to lean out? ?? wouldn't unplugging the vacuum line be the oposite of acceleration? I'm just trying to understand. I will do these tests, I guess maybe that regulator works backwards from what I thought. Thanks, I'll let you know what happens.
ImperialCrown said:
Are the spark plug tips black from carbon fouling? Are they the correct Champion type listed for the vehicle on the underhood label or service manual? (RN14PMP5?)
Haven't done a plug read, guess that would be a good idea. Thanks
 

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BASICS.. what did checking the codes tell you? as mentioned plugs, VACUUM , fuel pressure and pressure bleed down, crack the gas cap to vent tank, ECT, and confirm the fuel pressure specs.. I agree 65 sounds high
 

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Agree, it sounds like it's overfueling. Have you thrown any O2 sensor codes? A lot of times with fuel issues, the computer will start to think that the O2 sensors are failing because they're reading way high or low. In reality, they're just portraying what's actually going on: there's something wrong in the fuel system causing emissions to be off. The fact that it's not a misfire condition seems to indicate a problem with ALL the injectors or something that all the injectors are connected to, like the fuel rail.

I'm the tiniest bit tempted to look at the O2 sensors as possibly faulty, based soley on the fact that the problem gets worse as the engine warms up. The ECU runs two modes- open and closed loop- depending on whether the engine is warm or cold. A lot of times, O2 sensor problems can be pinpointed because the vehicle starts running lousy when warm. It's sort of like a lightswitch, though. The engine is fine and then as soon as the computer switches to closed loop, it starts getting bad data from the O2 sensors and makes the engine run poorly. That's way down on the list though, and you'll really need an oscilloscope to verify that the sensor(s) is/are bad. Start with the things others have mentioned first.

I would advise finding a different mechanic. Condemning the computer is a cop-out. There are a lot of diagnostics that need to be done before the ECU gets fingered with the blame. Chances are pretty good that he will tell you you got a "bad reman" and will want to replace the computer again. I've seen people go through three and four "bad" computers, at the cost of $100-200 a pop, due to simple things like a $30 Hall Effect pickup (2.2/2.5) or a wiring short. As a matter of fact, there ARE one or two fault codes that correspond to internal ECU failure. They rarely come up, as the computer is rarely the issue. The computers on these vehicles are fairly primitive, and a lot of times, things like MAP or O2 sensors fail to get detected, but they aren't so primitive that they can't figure out that some internal ECU component has bought the farm.
 

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How about the fuel filter?
 

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^Doubtful, since his fuel pressure seems to be too high.
 

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B10alia said:
^Doubtful, since his fuel pressure seems to be too high.
Cheap and easy to get at on this van. My 95 gave me fits when the filter was plugged. It ran perfectly until I got halfway to work. After I rounded the cloverleaf it wouldn't pick up. Shotgunned a fews part to no avail, then one day I decided to give the tailpipe a sniff and was surprised with no unusual smell. Anyway this van sounds like it's not getting enough fuel. Cheap and easy to get at.
 
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