If the car shows these symptoms when in neutral, then it is likely not an issue with the transmission.
Start with checking the basics. You mention it had been sitting for two years. The first thing I'd do is drain the entire fuel system. Fuel usually won't sit for that long without waxing. This is where the make-up of the fuel itself changes over time and causes it to lose it's flammable nature. It will also tend to clog and damage components within the system, including the fuel pump and injectors. You MUST clean the system and refill with fresh pump fuel before attempting any further diagnosis.
Testimonial: "When I replaced the fuel pump I had pumped all the old gas out of the tank. It now has a can of seafoam and bout 10 gallons of fresh gas now. Any other possiblitys? I haven't replaced the I/A sensor, crank or cam sensor yet. I have put another ground from block to body also. When I do get it to run it's almost like maybe it's loading up on gas because it does do some popping out of the exhaust sometimes. And you can never get it to idle more than 5 to 8 mins and then it finally starts idling more rough and then quits. After that it will fire but won't run until you let it sit for the night. I did get a code 37 off the dash for the TCC sylinoid."
SOURCE: 1993 pontiac grand prix 3.1 liter
the 3.1 had some EGR problems, EGR valve stuck open, blown diaphrams, Plugged passages Im not saying that is all your problems and I believe yours has whats called a linear EGR about $350.00 from the dealer (and that is the only place you ever consider buying such a critical part for the emissions system regardless of the cost)
That car is so antiquated as far as computers go that relying on the codes is nearly pointless! Map code can set because of low engine vacuum which you will have with a poor running engine, Check for 5 volt reference voltage at the TPS and MAP with the key on and engine off if no 5 volt reference I suspect a Computer. Computer Ground is on the Thermostat housing and needs to be clean and secure.
There is a legit test in the GM factory manual called the TAP TEST take the ECM (computer) and slap it with an open hand, if the symptoms change the ECM is bad it's very common in the early-mid 90s for the computers to go bad in one way or another the circuit boards come loose and suffer also from cold solder joints.
Make sure the wires are on the correct plugs and hopefuly you used factory plugs and wires and No split fire or bosch plugs only AC delco
Make sure you have good spark on all 6 cylinders.
Contact me at [email protected] with the results and any feedback or questions
SOURCE: 1995 dodge grand caravan,lot of mileage. rebuilt
I would start the engine and let it warm up. Once it is warm spray some WD-40 around the intake manifold gaskets and around all vacuum lines and fitting you can get to. If you hear the engine start to stumble, concentrate the spray on that area until you are able to pinpoint the fault.
SOURCE: Shakes while idling and sometimes stalls.
check for minor vacuum leak and map sensor,pcv,egr valve
SOURCE: 98 Chevrolet Silverado runs rough at half throttle and past.
try removing the EGR valve and clean inside of it and manifold
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When I put the new fuel pump in I had drained the system because of course like everything when it breaks down it always has a full tank of gas haha. The timing was good. The fuel pressure is between the book specs. The distributer and rotor look fairly decent, can't find any carbon tracks. Iv cleaned up the plugs cpl times and re gapped them and have also check the wires for damage. The sensors that I haven't replaced yet due to stuff gets spendy playing a guessing game, is the I/A sensor, crank and cam sensor. I am getting a code 37 off the dash for the TCC sylinoid. I have even put a new ground from the block too the body. I'm really starting to hate this truck! It is a 5.2 liter with the 46rh tranny.
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