Another low idle thread with a twist! (I think)

[briwayjones]

I've been having a low idle problem on my 2000 X for a while now that is getting worse. It doesn't matter the temperature or whether the vehicle is warmed up or not. At first when stopping at a stop about half the time the idle would drop to about 400RPM. Now it's getting worse and most of the time the idle will drop all the way down to about 200RPM.

Now here's the twist. It was in the shop twice recently to fix a CEL which I was hoping would fix the idle. The CEL was because of a vacuum leak because of a bad upper intake gasket which is now fixed. So it was vacuum tested and everything and shouldn't have any other vacuum leaks. The IAC and MAF have both been cleaned. I'm pretty sure the plugs and wires are fine there are only about 20,000 miles on them.

So what else could this be?

 

[my98nnj]

Non functioning IACV? That is what controls idle speed.

 

[CmdrPopNFresh]

if you dont have a CEL now id take a better look at that IAC...sounds like its getting stuck.

 

[dmc80]

Sometimes the maf and iac are beyond what cleaning will fix. Replace em one at a time, most likely iac.

 

[briwayjones]

Sometimes the maf and iac are beyond what cleaning will fix. Replace em one at a time, most likely iac.

Oh I forgot to mention that the IAC was replaced a couple years ago. It has gotten dirty so it's possible it could be stuck though. I was hoping that's not it being they're about $80 for the stupid thing. I meant to see if I still have my old one to put on there and see if it acts different.

 

[gtyates]

Have you resolved this issue? My '97 with the OHV engine is doing th exact same thing.

 

[alohamonte]

replacing EGR Control Solenoid fixed my low idle problem

 

[gtyates]

Thanks alohamonte. I do not have a CEL showing, so I do not think it is EGR related. My idle, though not as smooth as I think it should be, is generally o.k. My idle drop usually occurs when braking, especially hard braking. I had new pads, brake fluid flush, and the brake booster replaced (due to vacuum leak) about 2 months ago. I wish I had a CEL to help diagnose this strange idle issue. I have cleaned the IAC in the past day or so, but have not driven it since, so I can't verify if it made any difference yet. IAC was not overly dirty, but the cotton swabs I used with carb cleaner were black after wiping everything down.

 

[alohamonte]

Just something to check out. Mine didn't have a CEL either. I also had the drop in idle during hard braking (engine warmed up). I replaced the two hoses at the EGR Vacuum Pressure Sensor at the same time. At least one of the hoses was completely obstructed (cut the hose in half to inspect).

btw, I replaced the IAC before replacing the solenoid, and it didn't help.

(from Wikipedia) EGR is typically not employed at high loads because it would reduce peak power output. This is because it reduces the intake charge density. EGR is also omitted at idle (low-speed, zero load) because it would cause unstable combustion, resulting in rough idle.

If the Solenoid is bad, the EGR will function at idle.

 

[gijoecam]

You mentioned that the shop replaced the upper intake manifold gaskets... What about the lowers? It's the lower intake manifold gaskets that are most prone to trouble.

-Joe

 

[briwayjones]

The weather has been crummy and I haven't had a chance to mess with it anymore. Plus having two Explorers I can drive one while the other is sick so I haven't been super pressed to fix it.

They replaced just the uppers.