Idle Problems

[jhcii]

Ok the other day I heard a "pop" and some smoke came out from under the hood when I tried to start my truck (1997 Explorer V8). Ever since then the idle has been messed up. It surges on idle almost like I'm revving the engine between 750 to around 1200 rpm and almost dies on the low end. I've read many, many, many posts here and other sites without much luck. Here's what I have done so far - air filter is new changed before this started - IAC has been changed no difference - MAF has been changed I changed it because when I unplugged it the rpm went up but it idled better but no difference with new plugged in - checked intake for leaks but couldn't find any - checked vacuum hoses and no leaks found. Haven't checked EGR yet. I have searched the entire engine compartment and no source found for the smoke, I figured it might be an exhaust leak as it didn't smell electrical - more like exhaust. I changed the MAF and IAC as both were very dirty and the MAF looked like one of the wires was broke. Any help would be greatly appreciated. I have also disconnected the battery for over 30 minutes to "reset" the computer.

Added info: after computer reset still no difference and I forgot to add that I tested the TPS which is good (voltage varies with throttle movement without any "hiccups")

 

[jhcii]

Ok the other day I heard a "pop" and some smoke came out from under the hood when I tried to start my truck (1997 Explorer V8). Ever since then the idle has been messed up. It surges on idle almost like I'm revving the engine between 750 to around 1200 rpm and almost dies on the low end. I've read many, many, many posts here and other sites without much luck. Here's what I have done so far - air filter is new changed before this started - IAC has been changed no difference - MAF has been changed I changed it because when I unplugged it the rpm went up but it idled better but no difference with new plugged in - checked intake for leaks but couldn't find any - checked vacuum hoses and no leaks found. Haven't checked EGR yet. I have searched the entire engine compartment and no source found for the smoke, I figured it might be an exhaust leak as it didn't smell electrical - more like exhaust. I changed the MAF and IAC as both were very dirty and the MAF looked like one of the wires was broke. Any help would be greatly appreciated. I have also disconnected the battery for over 30 minutes to "reset" the computer.

Added info: after computer reset still no difference and I forgot to add that I tested the TPS which is good (voltage varies with throttle movement without any "hiccups")

A small update - I did test the EGR valve which is good (when a vacuum is applied it does open and almost stall before i release the vacuum. I have also replaced the EGR Solenoid, and have bought a new DPFE to install after my truck cools down. The only thing left after that is the TPS but I've checked that and it appears to work properly (Key On, Engine Off I get voltage that varies with the throttle being opened and it doesn't jump around). When I went to check the EGR those stupid plastic vacuum lines broke so I just got some vacuum line and a tee fitting to fix it and replaced those stupid things as well. Will update after DPFE replacement.

 

[jhcii]

I just found out what the problem was the whole time. The "pop" sound evidently was a "cap" used to plug a port coming off the bottom of the intake riser near the backside on the drivers side. The cap blew off and was sitting on the front of the drivers side valve cover (amazing since it just stayed there the two weeks I drove it). I have no idea what it would be for as nothing is hooked to it (obviously), I only found it while I was looking for the PCV valve so I could check it when I noticed the "shiny nipple" hanging under the intake and saw the cap on the valve cover I put two and two together. Put the cap back on (Pain in the butt as it's tight in there and not made for big hands) and it runs like it used to. If you have the symptom of it "surging" at idle and almost stalling This is where I would check first before replacing the IAC or DPFE. Like I said it's on the drivers side rear of the intake riser (underside) just above the fuel lines. If it isn't capped and has no hose on it then look for the cap on valve cover or try to find one to plug it and it should clear up your problems. I had replaced the MAF, IAC, DPFE, and the EGR Solenoid before I found this little bugger. Hopefully this will help someone out before they shell out $$$ to fix it. Also no codes were thrown and no CEL came on......

A small update - I did test the EGR valve which is good (when a vacuum is applied it does open and almost stall before i release the vacuum. I have also replaced the EGR Solenoid, and have bought a new DPFE to install after my truck cools down. The only thing left after that is the TPS but I've checked that and it appears to work properly (Key On, Engine Off I get voltage that varies with the throttle being opened and it doesn't jump around). When I went to check the EGR those stupid plastic vacuum lines broke so I just got some vacuum line and a tee fitting to fix it and replaced those stupid things as well. Will update after DPFE replacement.

 

[pngeezer]

I just found out what the problem was the whole time. The "pop" sound evidently was a "cap" used to plug a port coming off the bottom of the intake riser near the backside on the drivers side.

This is exactly the same issue my '95 has been having!! I looked for the 'port/cap' that you're reffering to but don't see anything like that. Could you possibly post a photo of the location and this thing so I could check mine?

Thanks so much,

Jim
jimfisherasc@yahoo.com

 

[tmikes]

same thing happen to me with the smoke came out from under the hood and surges on idle. check that cap and it was gone plugged it back up and runs fine now. Thanks for your post helped me out

 

[koda2000]

here's a question for you... when your engine is running, you intake manifold has vacuum. vacuum should hold the plug ON. what caused the "pop" that knocked the plug off? a backfire? what caused the backfire?