Idle surge/pulse and noise identification

[ErockSteady]

Hello everyone.

I recently bought my father's 98 EB with the SOHC, and was really happy with it until I started doing all the research on the timing chain issues. It's only got 86k miles, and is in super shape, but I'm not sure if it has timing chain rattle or not. It definitely has some type of noise. Timing chain(s)? Fuel injectors? Vacuum leak? Something else?

Also, I'm having a real problem with a surging idle. It only happens in park and neutral when warm. It's a very consistent surge from about 600-800 RPM, every 1-2 seconds. It only happens when NOT under a load. As soon as it's in gear, or the A/C is on, it goes away. I've cleaned the IAC, but that has not helped. I unplugged the MAF while running, and after an initial RPM drop, it continued to surge. Could it be the intake gaskets? I would think if it were the intake gaskets I would see more problems when in gear, driving, idling at a stoplight, etc. This seems to be a low, warm, unloaded idle problem only.

Here is a youtube link of a few seconds of it running. Please note that the rattle/clicking/pinging noise seems a LOT louder and higher pitched in this video than it does in person. I think it must be my phone's microphone. I was actually surprised to hear how bad it sounded on the video. It almost makes the surge hard to hear (you might need to put headphones on to hear the surge). In person, the rattle is much harder to hear, but the surge is VERY noticeable.

http://www.youtube.com/watch?v=xOuYyxmcrbo&

Thoughts? Thanks!!

 

[Mebob2001]

TPS is responding/working properly? not a voltage drop on the low refrence or something like that? i have had 2 friends with thos EB truck and they have bin nothing but elec issue's...

 

[ErockSteady]

TPS is responding/working properly? not a voltage drop on the low refrence or something like that?

Good idea. I'm not sure. I just found the thread about testing the TPS, I'll have to get a voltmeter and test it out.

Could a bad IAC do this? I had a Crown Vic with the 5.0, and it did the exact same surge at warm idle. Cleaning the IAC cleared it up on the Vic. I tried cleaning my Explorer's, but it didn't help.

 

[swshawaii]

CEL or trouble codes checked? These engines are notorious for lean codes and vacuum leaks. (p0171/174)
Carefully test with unlit propane around the intake. If you've ruled out the IAC and MAF sensor, start there.

 

[ErockSteady]

CEL or trouble codes checked? These engines are notorious for lean codes and vacuum leaks. (p0171/174)
Carefully test with unlit propane around the intake. If you've ruled out the IAC and MAF sensor, start there.

I will take it in to O'Reilly's and get the codes checked and go from there. Thanks guys!

 

[Jasonx521]

It is most likely a vacuum leak. The SOHC has issues with the oring gaskets leaking that are between the upper and lower intake and lower intake and heads.

Using propane around these two areas should produce a change in the idle.

Have a shop with a smoke machine find the leaks if the propane doesn't find the leak.

 

[ErockSteady]

It is most likely a vacuum leak. The SOHC has issues with the oring gaskets leaking that are between the upper and lower intake and lower intake and heads.

This is an option I've been thinking of as well. I've read mikeh's excellent write up here and 2000StreetRod's here about installing the 00M12 kit.

Should I go with the kit over just buying some Fel-Pro gaskets separately? I would guess it would be great to change out the chain tensioner and galley plug to while I'm in there, but how are the quality of the gaskets in the kit, does anyone know? Will I just be dealing with shrinking and leaking gaskets again down the road?

 

[ErockSteady]

Getting back to my original post with the linked YT video, how likely is it that it's a vacuum leak (i.e. intake manifold gaskets)? I would almost think that old/bad intake gaskets would produce more random idling troubles. This is very consistent, only under no load, and only when warm. About 100 RPM surge every second, but audibly very noticeable.

Has anyone had this exact problem that was solved by the 00M12 kit install?

I do, however, have the occasional tell-tale high RPM surge/stutter/stumble on very cold mornings, so this would point to the intake gaskets, no?

 

[1992fordgreen]

Sounds a lot like TPS, or o2 sensors bank 1 and 2. Replace them all they probably all need it anyway.

 

[ErockSteady]

Yes, I think maybe a key point is that the idle is super smooth when in gear (foot on brake) or when AC/defrost is on. As soon as the motor is unloaded, it surges. Loaded, no surge. It's funny listening to it with the defrost on...it clicks on, smooths out, clicks off, starts pulsing. I would think a vacuum leak would not change like this.

 

[ErockSteady]

Update:
http://www.explorerforum.com/forums/showpost.php?p=3267228&postcount=25