87 ranger 2.9 idling REALLY high.

[Primosboy]

So I just bought this 87 that was parked and sat for two years. Changed out old gas and fuel filter and ran sea foam through it. Would only run when you pump the gas and even then ran crappy. I changed out the map and fires right up now. Idles smoothly but at 3k rpms. After it warms up it goes down to about 2100. Rev the engine and it takes a good 5 seconds to get back down to 2100. I've taken apart and cleaned throttle body, fuel rail and injectors, vacuum lines.. Changed iac and pcv.. Cannot hear any hissing of open vacuum.. I've sprayed starter fluid around all areas air could be sneaking in.. Another detail may not be related but the rpm gauge will cut out intermittently. Drops to zero and then after few seconds back on. Any ideas?

 

[PetroleumJunkie412]

Report back with the following:

Remove ECT sensor. Check resistance at room temp, after an hour in the freezer, and after soaking sensor end in boiling water for a few mins.

Check resistance of IAT sensor.

Key to run, engine off. Look up how to backprobe wires, then test voltage of tps sensor at closed and WOT.

Remove iac, take and post photo of what the inside looks like

 

[Snoranger]

Remove ECT sensor. Check resistance at room temp, after an hour in the freezer, and after soaking sensor end in boiling water for a few mins.

I would NEVER go through that much trouble for a $15 part.

 

[franklin2]

I would NEVER go through that much trouble for a $15 part.

Where do you buy your sensors? My local stores want over $30 for that sensor.

 

[Snoranger]

Where do you buy your sensors? My local stores want over $30 for that sensor.

You can get the cheap one for $10 from rock auto.

 

[franklin2]

Once you get it warmed up and the upper heater hose is hot, we can assume you are in the neighborhood of 190-200 degrees F coolant temp. My book says the ECT sensor should read 2000-2800 ohms if you wanted to unplug the wiring and take a resistance reading. On the air charge temp sensor, I am trying to guess what temp it would be. If we assume around 100 degrees, that sensor would read around 16,000 ohms.

 

[Primosboy]

I found it. was the rearmost plenum gasket. Broke in half. Put some duct tape over the seam until I get gaskets and rpms dropped right down to 800.

 

[PetroleumJunkie412]

That'll do er.

 

[Dirtman]

 

[bobbywalter]

Hmmm....I thought I saw a post in here.

 

[bobbywalter]

Where deeed my powst ghow.