1989 Power Ram W100...318 v8...MAP SENSOR question

[hokietiger]

Hi gang,

Will a failing MAP SENSOR in a 1989 W100 Power Ram (318 c.i./5.2 L with EFI throttle body) start causing idle issues?? (came up on engine codes when checked, along with IDLE CONTROL SOLENOID issues....I've done the following to my truck:

1. New plugs, air filter, pcv valve, wires, dist.cap/rotor, and new ignition pickup in distributor.
2. New fuel pump.
3. Cleaned and lubed the IDLE CONTROL SOLENOID
4. New vacuum hoses on MAP sensor.
5. Rebuilt throttle body with new gaskets and injector O-rings (also cleaned entire throttle body, all ports, and vacuum inlets with carb cleaner).

It seems the IDLE CONTROL SOLENOID works OK with no internal damage (took apart, inspected, and re-lubed).. However, it will move somewhat from low idle back to normal idle during idle in PARK. And, when I cleared the codes and restarted the motor, the new codes only indicated an IDLE AIR SOLENOID problem and not the MAP sensor....Strange!!

I'm at my wits end and now suspect the MAP sensor might be going bad......The truck starts up nicely and idles wonderfully at cold startup. Then, after warmup, it begins to idle sporadically from normal to low idle and will sometimes stall.

Help!!!

Mike

[oldestof11]

Yes. MAP (manifold absolute pressure) sensor detects incoming air pressure (vacuum) and adjusts the fuel to it to keep stoich.

[Remps]

When the idle control sensor went bad on my 90 D150 I took it off and ran without it, I just turned the idle up some. It was just temporary til I found a new sensor. Never thought about taking it apart and cleaning it at the time. Have you tried running it without the sensor to see if it acts up without it?

[hokietiger]

Well, after checking to see if a replacement MAP SENSOR and IDLE CONTROL SOLENOID would solve the issue, neither worked.
I still have a somewhat rough idle thats wants to occasionally die to a stall when pulling up to stop signs, red lights, etc.

Wonder if the new O-Rings on the fuel injectors are not fitting correctly??...Wonder if fuel injectors were the problem from the start??..Wonder if the FUEL SENDING UNIT in the gas tank is the problem??

I'm at my wits end with this and may just take her to a repair shop.

[DodgeFreak]

Have you looked into the O2 sensor at all?? Have you done a basic tune up. Plugs wires cap rotor?? Low fuel pressure could be an issue to...put a gauge on it....

[hokietiger]

Yes sir, here is what I've done so far:
1. Rebuilt / cleaned Throttle body with new gaskets and new O-rings for the fuel injectors.
2. New plugs, wires, distributor cap and rotor button, and new ignition pickup in the distributor cap.
3. New Idle control solenoid (adjacent to throttle body)
4. New fuel filter
5. New Air filter and PCV valve
6. New O2 sensor.

Also tested the MAP SENSOR (functions properly) and inspected almost all vacuum lines for leaks.
Viewed the fuel injection into the throttle body barrels while idling. Fuel sprayed evenly into the barrels even
just before the idle dropped and stalled the engine (telling me that a lack of fuel flow may not be the issue).

Ran a "key on-key off" code check and got #37 which indicates:

part throttle lock/unlock solenoid driver circuit (87-89 models) OR, solenoid coil circuit (85-89 Turbo I-IV models).

Wonder if the THROTTLE POSITION SENSOR could be an issue??....I would think that the FUEL SENDING UNIT in the gas tank
may also be an issue but, as mentioned above, I saw NO DIFFERENCE in fuel flow into the Throttle Body barrels when the truck stalled from a drop in the idle rpm.

Again, the truck cranks easily and idles nicely for about 20++ seconds then begins idling a little rough with abrupt, frequent drops in the idle rpm (almost near stall with an occasional stall). It could still be fuel injector issues because I just don't know enough to be completely accurate.

Thanks for all help possible !!

Mike