Does not run when in gear

ERIC HOLMLUND

MEMBER
1994 JEEP CHEROKEE
6 CYL
4WD
AUTOMATIC
185,000 MILES

1994 jeep cherokee 4.0 L 6 cyl power loss then returns. The engine runs fine when reved up not in gear. Going in reverse runs fine. Put it in gear, step on the gas it accelerates for a quick second then dies, then accelerate for a quick second then dies. Codes retreaved where 12 followed by four 27 codes. Replaced crankshaft sensor, checked all vacuum lines, and connections. Once it gets rolling, ( with bucking) removing the gas causes the engine to die. Tried holding on the brake while in drive and stepping on the gas, revs up for a second then dies?

Saturday, November 20th, 2010 AT 8:52 PM

1 Reply

JACOBANDNICKOLAS

MECHANIC
110,176 POSTS

First, check the wiring and connections between the fuel injector and the power module (or SMEC) and the injector contol lines between the logic module and power module. Clean and regrease any corroded connectors with dielectric grease and repair any shorts.

Injector driver transistor failure - Check the injector signal from the power module. It should rise to aprox 12 volts when the injector is off and drop close to nearly 0 volts when the injector is on. If it is out of spec, chances are you need to replace the power module.

As far as the code 12, have you had the battery disconnected reciently?

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Saturday, November 20th, 2010 AT 9:00 PM