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Dodge Shadow Idles Rough, Stalls

Q. Vincent, I desperately need some advice. I have an 1989 Dodge Shadow, 2.2 liter TBI, automatic transmission and no air conditioning. I used your advice on the transmission modulator and coolant sensor and all worked very well. Because the transmission was an older version without the torque converter lock-up, I fooled the computer with a resistor, 12V 33 ohms resistance I think.

Dodge Shadow Idles Rough, Stalls

Worked well, got rid of the idiot light, and no one has said anything yet about the resistor causing damage so I'm inclined to leave it as is. Your opinion?

My current problem revolves around throttle and idle. If I disconnect the Manifold Pressure/Vacuum Sensor (MAP) sensor, I can adjust the timing and throttle to get the car to idle, but it stumbles under load. Disconnecting the coolant sensor also produces a similar effect. With the MAP hooked up, it doesn't want to idle at all, although I have been successful a few times. Is the problem stemming from the MAP? Or is this only a result of another problem.

When I flip the throttle I get stumbling, like a flat spot, after about 2,000 rpm. Starting the car is very hard when cold, but a bit easier when warm. When cold it takes many restarts and a quick foot to keep it running. When driving, I can't get the car past 20 mph, and I'm not getting any computer codes except for 12 - Battery Disconnection and 55 - End of Codes.

Besides the MAP, I'm also a bit suspicious of the O2 sensor, only because the drivability is lacking when the engine is warm, but I'm puzzled with the lack of a suitable code. If I move the distributer counter clockwise, the flat spot becomes smaller, then the idle becomes really bad (often stalling), and the drivability doesn't improve.

I've replaced all the vacuum hoses, intake/exhaust manifold gasket, throttle body base gasket, coolant sensor, and EGR. I've also replaced the fuel filter, distributor. cap, wires, plugs, rotor, and set the timing, and I've been told the fuel pressure is adequate, tested by mechanic.

I took the car to a mechanic a few days ago to fix the stumble with poor results. The mechanic missed the previous leaking EGR, lost the lock nut on the idle set screw, and didn't put the radiator cap on proper and then told me the car was overheating when it gushed coolant in his parking lot.

As I'm in a small town, I would like to avoid any future trips to this mechanic. When I bought the car it was very rough running and poorly maintained. The body is in excellent condition, and if I can get the engine working proper it will be a good car for quite a few years.

Any ideas on what would make the car hesitate, stumble, stall, etc?

A. I think the mostly cause is either the MAP sensor or the Throttle Position Sensor (TPS).

To check the TPS you will need an analog (needle) type meter set to read ohms. Unplug the TPS connector and put the meter on pin N5and K7. Slowly open the throttle and there should be a slow, smooth change in resistance. If there are any sudden changes, the TPS has dead spots and is no good. These dead spots will cause your hesitation.

Do the same test with pins K7 and K8. Also be sure there is no continuity between any of the pins and the metal case of the TPS. If there is, the TPS is shorted and needs to be replaced. Also, with the key in the RUN position there should be about 5 volts at pin K7.

Dodge Shadow Idles Rough, Stalls

To check the MAP sensor, with the key in the RUN position there should be about 5 volts at pin K4. With a hand vacuum pump, apply vacuum to the MAP sensor and look for a smooth voltage change. If there is a large jump or no movement at all, the MAP sensor is bad and will need to be replaced.

Dodge Shadow Idles Rough, Stalls

Additional Information provided courtesy of ALLDATA

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