erratic idle and shudder on load
 

My 93 e150 started acting up one morning. I replaced a bunch of things and improved some of the running but it is still having problems. I will go through the whole scenario.

Symptoms:

At first start in the morning, the van runs fine-smooth and good power. Within 3-5 minutes, it starts to "miss"-slightly at first, but getting worse as it continues to warm up.

In park, it runs smoothly. In drive, but sitting still at idle, there is an intermittent miss that causes a just noticeable shudder.

On acceleration, the engine firing sounds quite loud in the exhaust system, and a slight, intermittent shudder, especially at steady highway speeds.

As the engine heats up, the shudder becomes very pronounced, especially when going uphill, or on load. Just before the gear shifts up, it smooths out, then after shift, it is usually a very heavy clunking shudder. Revving downshifts and smooths out the clunky shudder into a small, rapid, rhythmic shudder, like a steady misfire.

What I have done:

replaced distr. cap, rotor, plug wires, coil, ICM, fuel filter

I found and repaired some wires in the wiring harness that go to the fuel injectors and TAD/TAB solenoids (they had been chewed).

I checked for ignition in each cylinder by pulling plug wires at idle, in park-all were firing

I checked voltage of one injector (before the wire test above) and it checked

I checked voltage of harness wire and solenoids for TAD and TAB-all checked ok, and they seemed to be cycling on and off ok, BUT the shuddering miss is less pronounced with TAD and TAB not electrically connected.

Vacuum hoses seem to all be intact and working.

Fuel pump sounds good, but I haven't checked the pressure.

My questions are:

Can this be caused by a faulty EGR, or EVR?

Can this be caused by a faulty O2 sensor?

Just WHAT THE HECK is causing this?

I believe you can determine if the EGR system is causing the problem by just removing the vacuum hose from the EGR valve and plugging it. You may get a check engine light from this , but that can go be easily removed . See if that gets rid of the problem.
Sometimes a load of bad gas will also do this. Have you tried to add some dri-gas to the system (water in the fuel). We usually try the simple and inexpensive things first.

Thanks. I'll check the EGR that way. BC requires 5% renewable fuel in gas (translated: ethanol), so I highly doubt it is water in the gas. Dri-gas is an alcohol, which dissolves water. I may try it in the end, but I'm on the second 110 litre tank of gas with it doing this.

Any other suggestions form anyone, if it ends up not being the EGR?