89 Mallard RV starting to lurch at standstill.

[kemeisland]

I'm sadly selling my first RV and of course right as I have a buyer, there's a mechanical issue!

After a few days off the road, I fired it up to take it for a drive and noticed in park and in drive with the brake depressed, it lurches ... meaning it revs up like I'm hitting the gas, but then it calms down... so low it threatens to stall. It did stall once, at a stop sign.

The RV is on an 89 Econoline 350 chassis. Does anyone know what could be causing this and what I can do? Oil level is good. Drives great once moving. It's just really rough at stops and seems to idle a bit laboriously. I don't want this to prevent the sale or be a problem to the buyer.

I would really appreciate some help. Thank you!

[j-d]

Good for you! Congratulations and thanks for the update.

[kemeisland]

Got it working! It was the Manifold Absolute Pressure ( MAP ) sensor. Super easy to change, had I known. Everything else I tried was way more difficult than the actual solution 🙂

[ernie1]

On my E350 there were two oxygen sensors that were replaced around the time that I had issues with the idling. Don't remember which came first but when they went bad the engine lacked power and the catalytic converter was super hot because the excess fuel caused the converter to fail. Obviously not your problem but I wonder about the oxygen sensors.

[ernie1]

Kemelsland:
Yes the problem corrected itself immediately. Prior to this repair, two Ford dealers told me that there is no idle adjustment other than to somehow rework the computer setting so the the idle speed would increase. Yes the idle increased but it would also drop and hunt constantly.

[kemeisland]

Does it seem like it could be the MAP Sensor, or the Throttle Position Sensor?

[kemeisland]

Is there something that could be shorting out the Idle Air Control valve? Does it have a fuse somewhere? Or else, how long after replacing that does the issue disappear? I replaced the IAC valve and there was no change.

So far I've replaced half the plugs ( the ones I could reach ) but none of them seemed to be having any issues. I replaced the fuel filter. I checked the distributor cap and rotor, no problems there. There are no vacuum leaks, and the throttle body is not clogged. The air filter is also clean.

ernie1: When you replaced the IAC valve, did the issue go away right away?

What else could be causing the problem? It won't idle at all. I have to keep it in park or neutral and keep revving for the engine to stay running. And it starts to hesitate when coasting once the RPM gets down to a near idle.

[ernie1]

I had the same problem with my 1989 Econoline E350 van and the fix was to replace the idle control valve. An easy fix.

[enblethen]

Vacuum line or vacuum control not functioning properly.

[copeland343]

You might clean throttle body and check the idle control valve