Computer problem
1994 Dodge Caravan 6 cyl Two Wheel Drive Automatic 125000 miles
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I have a 1994 Dodge Grand Caravan ES with a 3.8L engine, and it starts but will not run. The Caravan ran well for 100 mile trip, and then I went to work and parked it, came back eight hours later and tried to start the van, and it would turn over, but did not idle without constantly goosing the gas pedal up and down, the moment the gas pedal was released the engine would die. The Caravan went from running perfectly fine to not running at all on the same day, which leads me to suspect an electrical component has failed. I checked for codes with the on /off (three times) and all I get is a 55. I have an Auto Xray scanner and it shows no stored codes. I have unplugged the battery to reset the PCM and this did not fix it. I checked all relevant fuses ( 16 & 20 under dash, and all under hood) I have checked the coil pack (proper primary and secondary resistance), I have strong spark on all plugs (pulled plug and viewed spark), I have fuel (pulled the Schrader valve on the fuel rail and pumped fuel into a jar), I examined fuel for water or contaminants (none found), I bought a fuel pressure gage and checked with KOEO and get 46psi ( Service manual says 48psi spec, suspect gage a little off), fuel pressure with engine on stays at 46psi ( with vacuum to regulator removed) I've checked for any restrictions in the exhaust pipe (none found, even disconnected exhaust pipe before catalytic converter to see if that may have collapsed and restricted air follow - did not fix), checked the air cleaner, and also tried to start the car with the air cleaner tube off (still will not run). When I say that it will start but will not run, it's as if the timing is off or the engine is starving for fuel or air, it will even begin to backfire at the intake manifold, but it will not stay running, and is not anywhere near close to even idling. I spray starter fluid in air intake and start the engine and it does run smoothly very briefly (maybe 1-2 seconds) before it acts starved again. This should indicate good air flow and spark. It raises the question of why the fuel flow is not consistent. I checked the relays by 12V energizing them and checking continuity (ASD and fuel pump and they work properly, even rotated other relays to be sure). I even jumpered the ASD and fuel pump relay to put in energized state - no help. I suspect the PCM, which I have removed and looked at the connectors for corrosion or dirt (I cleaned them anyway). I disconnect sensors (AIS & evap canister) and the scanner picks up the new codes and I can clear them, so that part of the PCM seems to work. I do not know if the camshaft position sensor or the crankshaft position sensor could be a possibility. But I do not understand if the PCM checks those in the first five seconds of cranking. Is the PCM not energizing the fuel injectors? I am baffled what to do next, other than to go buy a PCM and put it in. What do you think?