idling issues running out of ideas!

[Darian Key]

I'm really starting to get fed up with my explorer. Its a 97 4.0 ohv with 162k and ever since I got it I've been having idling issues. Ive changed the spark plugs/wires, fuel filter, checked for vacuum leaks, cleaned mass air flow, new iac valve, new throttle positioning sensor, cleaned the throttle body, seafoamed it, etch etc. Now heres the problem. It'll start up fine in the morning then after about 5 minutes of running it'll just drop down and idle like its crammed, if you rev it to about 1500 it runs fine... until you let of the gas then its caming out again. If I rev the CRAP out of it (4000 or so) it'll idle fine for a little while then do it again. After I drive it it idles fine in gear and usually idles OK in park after being driven. Now if I shut it off and start it back up after I drove it it runs like complete shut and only goes away when you drive it. Now heres the real problem that's got me very angry, I got a new throttle positioning sensor and put it on then unplugged the battery for 20 mins to reset the pcm then started it up let it idle to operating temp and drove it. When it was warming up after the pcm being reset it idled perfect then dropped down and ran crappy and it smoothed itself out on its own. Now that I drove it, its shifting hard, shifting way too early, and not downshifting also on top of that at idle it consistently runs choppy and occasionally does the "camed out" idle and won't go away unless its higher than about 1300 rpms. When I say constantly I mean it has not gone away or idled smoothly since the drive. Please give me ideas! Its severely passing me off and I dont have the money to keep doing trial and error. There is one code up and that's for sensor 1 bank 2 sensor saying too lean. I haven't checked since I reset the pcm today though.

 

[Darian Key]

Also forgot to mention when it idling REALLY ruff the exhaust smells really rich

 

[dani9678]

It sounds like the engine temp sensor is faulty or intermittent causing the ECU to think the engine is colder than what it is and enriching the fuel mixture similar to a carbureted engine with the choke stuck on. If the sensor is faulty then the engine will run normal when cold with the extra fuel. What then happens is as the engine is warming up the ECU is not compensating and leaning the fuel mixture. This is when you notice the engine running rough and the rich fuel smell. The engine has two temp sensors I believe. One for the ECU and one for the dash gauge. I don't know off hand which is which but there is a way to test them with a volt meter set to ohms but I don't know the specific reading to look for. Maybe someone else here can tell you what they are.

Matt

 

[Darian Key]

Ive been told that very briefly before but it makes perfect sense. The temp sensor on the dash works like it should though

 

[koda2000]

the dash gauge is controlled by a temp SENDER, he's talking about your temp SENSOR. two different things. the sensor tells the PCM/ECU the coolant temp and the PCM controls how much fuel is send through the fuel injectors.

 

[Darian Key]

Is there any way I can test it with my mulitimeter? Or would it be best just to try a new one

 

[Darian Key]

I let. The pcm reset again and it stalled 3 times while it was getting too operating temp. Once the thermostat opened it ran fine and even after idling for 15+ minutes once it opened not one single hiccup