Engine surge at low rpm

[PlumCrazy]

I have a 94 2.3, and when i coast in nuetral or push in the clutch long enough to let the rpms drop to what should be an idle it surges from like 1100 rpm to 1600 rpm until i put it back into gear and let off the clutch. It seems to get worse as the motor gets warmed up. At first it might surge 3 times then go to an idle, but as it warms up it does it longer. Never did it until it started getting cold outside, like in the 30's

I was thinking mafs, iac, or maybe a vaccum leak(but i havn't found one)

Any ideas?

 

[bubba cakes]

sounds like inlet air temperature control system malfunction

have you tested the bi-metal sensor inside the air cleaner housing? is the vacuum motor door working? how about the vacuum motor itself? could be the Cold Weather Modulator. you might want to systematically check all the components in the iatc system, since this problem only occurs when it's cold.

 

[PlumCrazy]

I havnt had that whole system for over a year now, I removed the bimetal sensor and capped the vaccum line, also removed the the hose and shield on the exhuast manifold along with the air box and the duct to the core support. I just have a 3" pipe from TB to the mafs with a cone filter behind the head light, similar to the OBD II 3rd gen rangers. The only thing left is the intake temp. sensor (the one with wires, not the bi-metal one). I took evrything off last winter and it never affected anything then.

I got a can of MAF cleaner today, I was thinking maybe it was bit dirty ir something. I havnt tried it yet though.

 

[PlumCrazy]

I made a little progress today. I cleaned the MAF sensor to no avail. I was thinking that maybe the aircharge temp sensor was going bad or maybe where I relocated it on the intake tube was causing it to read wrong. So first I just let hang outside of the tube to see if that made a difference during operation, it didn't make a difference, so I went ahead and replaced it with used one just to see if it made a difference, again no change. I did noticed that it stopped surging when I dropped below about 25 mph, so that got me thinking that maybe where I have the filter behind the headlight is leting the headlight socket funnel air into the intake when I am going fast enough. To see if that was the case I took a piece of cardboard ad covered to hole in the radiator support behind the headlight. It helped, now it stops surging as soon as I drop below 45 mph. My conclusion is that the headlight socket is funneling enough cold air into the intake that it is throwing a sensor off(maybe the MAF). If anyone has a more reasonable explanation I would love to hear it, since mine sounds pretty far fetched, but who knows.