Dreaded 4.0 SOHC rattle? Help!

[kevinspann]

If you had a vac leak, I wouldn't think it would hardly idle with the IAC unplugged. But it is a common SOHC issue, so it's worth a shot. Did you pull the battery cable to reset the PCM after you changed it?

 

[ErockSteady]

If you had a vac leak, I wouldn't think it would hardly idle with the IAC unplugged. But it is a common SOHC issue, so it's worth a shot. Did you pull the battery cable to reset the PCM after you changed it?

It did idle with the IAC unplugged, just lower and smoother. When I first replaced it, it seemed to idle better for a few days, then it went back to it's surging tricks.

I did not pull the battery cable. I didn't realize I needed to do that after an IAC change?

Another option is the TPS. Anyone agree with that?

 

[koda2000]

do you have a CEL? Does your CEL light up during bulb check? if so, have you pulled codes? with vacuum leaks you usually have the 2 "lean" codes. vacuum leaks can cause surging at idle. if you have early timing chain related issues, it doesn't explain the idle surging.

if no CEL, before spending money on parts, remove and clean the IAC, MAF sensor and throttle body with the appropriate cleaners. it may not help, but it doesn't cost much and can make a big difference in the idle. also (if you haven't already done so) replace your PCV valve with a new Motorcraft PCV.

if/when you install the M0012 kit with the new upper/lower manifold gaskets/o-rings it may solve you idle problem.

BTW, a good tip is to put grease on the metal gasket of the rear tensioner to hold it in place while tightening it, or it will leak like hell, and be sure to tighten both tensioners to correct torque.

 

[ErockSteady]

do you have a CEL?

No CEL

remove and clean the IAC, MAF sensor and throttle body with the appropriate cleaners. it may not help, but it doesn't cost much and can make a big difference in the idle. also (if you haven't already done so) replace your PCV valve with a new Motorcraft PCV.

I've both cleaned and put a new IAC in, but have not cleaned the MAF or throttle body. When the 00M12 kit goes in, I'll be putting a new PCV in as well.

Thanks for the tips!

 

[ErockSteady]

An update:

This weekend I installed the 00M12 kit, and it pretty much solved all my problems. The o-rings between the upper & lower intakes were hard as nails and brittle. The idle is now smooth as silk, and no more pulsing.

The old chain tensioner that came out was actually a little bit stiffer than the new one, but it also had a couple rough spots felt when pushing it it. It was not smooth. The rattle noise is reduced now by about 90% I'd say, but not totally gone. I'm happy.

The job took WAY longer than necessary, since the ECT sensor stripped in the stupid plastic thermostat housing, so I had to drive into town, buy a whole new housing and ECT sensor and sender, and install that as well. Ridiculous the amount of plastic Ford used on these SOHC motors.

 

[2000StreetRod]

thermostat housing

Thanks for posting the update. Sounds like you made a significant improvement. The thermostat housing failure is a common problem. Ford swapped from threaded sensors to clip in sensors on the 3rd generation but still made the housing out of plastic.

 

[ErockSteady]

Thanks for posting the update. Sounds like you made a significant improvement. The thermostat housing failure is a common problem. Ford swapped from threaded sensors to clip in sensors on the 3rd generation but still made the housing out of plastic.

You bet! And a big THANK YOU to you as well for your 00M12 thread which I read about 50 times before starting my project ;-) It was a huge help...much appreciated!

Unfortunately, the only thermo housing I could find in my area was at a local NAPA, and has the original thread design. I had to get my Ex back on the road though, so I bought it. Hopefully I don't have to touch it for a long time!

 

[4pullingGM]

Sounds like good news, glad it all worked out!