QuestionMY '95 LHS (3.5L) has an intermitant miss (stumble) while in any drive mode (rolling, at a stop w/foot on brake, or under slight accel on a hill), but doesn't seem to occur while in Park or under heavy accel. I've changed the plugs, plug wires, fuel filter, coil pack, PCM, and MAP sensor. I also replaced the large (5/8"?) vacuum hose that runs from the back of the Intake Plenum to a module located near the firewall, drivers side. I tested all other sensors (except Cam sensor and O2 sensors) and they checked out okay. I had the car tested on diagnostics at a shop with no fault readings showing up. Mechanic drove vehicle and noticed the miss but couldn't trace the problem.
Also, my Cooling Fans won't turn on as well as the A/C clutch. Initially I found fault codes (23 and 35 I think, for Fan and A/C) by using the 'Check Engine' light on dash (Ignition key turned on-off 3 times, then counting flashes) and checked the wiring (for breaks), fuses, and relays. I swapped the Fan relay with the Wiper relay with no result (meaning the relay was good). I metered the wires coming into the relays and had 13v on both the contactor side and the power side. I then ohm'd the wires from the relay back to the PCM and everything checked out fine. I removed the Fan assembly and hot-wired each fan and they worked. I also ohm'd the wires from the Fans up to the Relays, all were good. I jumped the power taps (Relay pins) at the Junction block and fans came on.
I have the Haynes manual and have spent two entire weekends chasing these gremlins. HELP !
AnswerHi Timm,
I too have the Haynes, and the 23 is for the intake air temp sensor being out of range in its voltage. The 35 is for a problem with the low-speed fan relay circuit. Unfortunatley I don't have the full Chrysler shop manual for the car, and the Haynes wiring diagrams are incomplete on the fan circuit. If the fans aren't working when the temperature of the system gets warm enough to warrant it, and you have verified the circuits as you described, then I would wonder if the coolant temp sensor is reading the temperature of the coolant accurately (i.e. off-value but not so much as to set a code). Why not check that its resistance is 7,000-13,000 ohm when cold, and that it drops to 700-1,000 ohms when the temp of the coolant is at 200F, the normal level with a 195 thermostat; and it should go down below 700 ohms if the engine get even warmer. If that sensor were not responding properly that would explain the lack of fans. It also would impact the air/fuel ratio accuracy and that could explain the miss. It might also be the case the there is an air bubble at the sensor that is preventing it from being bathed in the coolant.
Did you check out the intake air sensor, similarly, if indeed you had the 23 code? The Haynes (chapter 6) gives its temp vs. ohms specs (and they are different from those of the coolant temp sensor). That sensor being off-value or not functional would also impact the air/fuel ratio, possibly leading to the "miss". So check those out and let me know what you learn.
As for the no compressor clutch and fans when you go to AC, that might well be due to either too low a refrigerant level in the system or a faulty pressure transducer which is the switch near the compressor that monitors the pressure for either under or over pressure conditions. Chrysler is said anecdotally to have had a problem with that transducer and may have had to redesign it in the mid '90s.
You are doing a good job on the problem. I think you will get to the bottome of this.
Roland
