Need diagnosis
 

1995 Dodge Grand Caravan SE
3.3L, fwd
~180,000 miles

Over the past several months I have had drastically reduced fuel economy.

A couple of times over the winter I turned the key and the van did not start (did turn over, no ignition) until I turned the key off and back on.

As the weather is warming up, my symptoms are getting worse.

It started idling a bit rough.

I changed the evaporative canister purge solenoid (old was original, making lots of noise).

Symptoms continued. Changed my PCV valve (also original). Symptoms continued.

Rough idling increased with occasional jerking while driving.

Changed spark plugs (had done so a few years back but couldn't get to one of the six. This time got them all. Also ran fuel system cleaner through. No improvement (and possibly worse).

Changed the fuel filter. Again, no improvement.

Cleaned the throttle body. Again, no improvement.

With much warmer weather (today near 70) engine jerk was horrible. Leaving a parking garage stuck it slow traffic, engine was super rough at very low RPMs and if I very lightly touched the gas, it would lurch, then drag, then lurch, then drag... additionally, when driving at normal speeds it might lurch when accelerating through the low 40s and mid 50s. Have also had more instances of not starting on the first try.

There are no "key codes". The check engine light never comes on, but when turning the van off the engine might shudder and cause the check gauges light to come on for a second.

I running out of options. What else could it possibly be? I replaced the fuel pump a little less than 4 years ago. I am hoping it is not that again.

One of the problems we found in 1995 was the knock sensor causing a misfire at times. the fix back then was to unplug the sensor and wire tie the connector out of the way. I would also look at the wires going to the crank sensor and if you need to open harness, do so. Because the wires could be shorted in the harness.

Thanks. I'll check those out in the morning. Will disconnecting the knock sensor affect performance at all?

Have the fuel pressure checked both before and after starting. Starting on second/third try sounds like you have a leak bleeding pressure down. Possibly the pressure regulator, pump or fuel injector are leaking. Stumbling on acceleration indicates a possible weak fuel pump.

Let's see...

Knock sensor: don't have one, so that's not the problem. Apparently only on 91 or older or turbo engines. I did look, there's just a rusty hole where it would be.

Crank sensor: I had a brake fluid spill a few months ago, and the crank sensor harness was completely saturated when I just checked it. I cleaned both halves out as best I could using compressed air, kleenex, toothpicks, and q-tips.

Also had a miniscule leak at the hose ends of my new fuel filter, so I tightened up the clamps for those some more.

Ran it for a few minutes and at first it looked promising but then started shuddering again.

Open wire harness to the crank sensor and check for wires shorted together.

Any tips on how to open it? It is mostly black, but there are red bits on the inside between the contacts. I couldn't see anywhere that readily suggested "Pry me open here". Also, any tips for removing any more residual brake fluid that might be inside (certain cleaner, or soaking or whatnot)?

Just cut the tape with a razor blade. And pull the wire apart.

Weather and time off of work not on my side at the moment.

However, I can now definitively confirm outside temperature has a major effect on its performance.

Yesterday it was around 70 degrees, and the engine ran TERRIBLY. Jerking all over the place (though smooth once I finally got up to 60 MPH, and worse again once I slowed back down). Seems to be rather prominent when reversing also.

Last night it was just below 50 degrees, and I was able to drive perfectly fine with only one minor shudder toward the very end of the night.

Its hard to diagnose without seeing the vehicle and without a scanner on it too. It could be even a temp sensor or fuel pressure.