idle surge

[enjenjo]

1999 Ford E250 5.4 two valve. It surges at idle when warmed up, but does not throw a code. Where do I look first?

[wayne petty]

vacuum leaks in the 90 degree molded rubber elbows near the throttle body..

i normally use several help 46002 to fix them if i don't have the proper ford elbows around..

sometimes hard to hear.. must be felt with the engine running. the hose may have an inward pucker when manifold vacuum is present.

P0171 and P0174s are codes you will find with vacuum leaks...

if you have a scan tool that displays live data stream.. including the crazy cheep ELM327 .. get into live data and graph O2B1S1 and O2B2S1... one at a time usually... with a tablet or laptop  you might be able to view both..  take the RPMs to 2500 with the engine warmed up fully.. let it stabilize there...holding your foot on the throttle TOTALLY Still. so it can get into feedback without any addition or subtraction of fuel from throttle motion inputs..

this is a decent oxygen sensor signal at 2500..



if you back off slowly.. taking 20 seconds to return to idle. this should be the pattern you get..




here is an engine that was misfiring  at 2500...




i expect your oxygen sensor signals go go flat line if you have a vacuum leak.  

if you look at the bank one and bank two.. short term fuel trims.. you will see one go up and one go down depending on the engine speed..  as one side may have a bigger vacuum leak than the other.  first time i saw that on a 5.4 i went WHOA!!! what is that..

sorry for the slightly over size pictures..


you may also want to download this file about how the obd2 system works on the 99 model year with gas engines..

http://www.motorcraftservice.com/vdirs/diagnostics/pdf/obdsm99b.pdf


oh this is the hose assembly...  if you look closely.. you can see the elbows you can replace individually with the dorman or other molded rubber pcv hose elbows..

http://www.ebay.com/itm/Ford-F150-E150-Expedition-5-4-PCV-Hose-Connector-Set-New-OEM-Part-XL3Z-6C324-GA-/251583872375

[Arnold]

vacuum leaks in the 90 degree molded rubber elbows near the throttle body..

i normally use several help 46002 to fix them if i don't have the proper ford elbows around..

sometimes hard to hear.. must be felt with the engine running. the hose may have an inward pucker when manifold vacuum is present.

P0171 and P0174s are codes you will find with vacuum leaks...

if you have a scan tool that displays live data stream.. including the crazy cheep ELM327 .. get into live data and graph O2B1S1 and O2B2S1... one at a time usually... with a tablet or laptop  you might be able to view both..  take the RPMs to 2500 with the engine warmed up fully.. let it stabilize there...holding your foot on the throttle TOTALLY Still. so it can get into feedback without any addition or subtraction of fuel from throttle motion inputs..

this is a decent oxygen sensor signal at 2500..



if you back off slowly.. taking 20 seconds to return to idle. this should be the pattern you get..




here is an engine that was misfiring  at 2500...




i expect your oxygen sensor signals go go flat line if you have a vacuum leak.  

if you look at the bank one and bank two.. short term fuel trims.. you will see one go up and one go down depending on the engine speed..  as one side may have a bigger vacuum leak than the other.  first time i saw that on a 5.4 i went WHOA!!! what is that..

sorry for the slightly over size pictures..


you may also want to download this file about how the obd2 system works on the 99 model year with gas engines..

http://www.motorcraftservice.com/vdirs/diagnostics/pdf/obdsm99b.pdf


oh this is the hose assembly...  if you look closely.. you can see the elbows you can replace individually with the dorman or other molded rubber pcv hose elbows..

http://www.ebay.com/itm/Ford-F150-E150-Expedition-5-4-PCV-Hose-Connector-Set-New-OEM-Part-XL3Z-6C324-GA-/251583872375

  Some great info there Wayne!

  My Focus did that on the 90 elbow..was fine till it warmed up and the hose puckered inward..(where it exposed the split).Gotta be careful with my words here :oops:
  lol..no I could not find it..but when I took it to a garage that does a lot of my work..the owner pointed out to his about 16y/o son right where to look :oops:

[348tripower]

I had the same thing happen on a V10 Ford

[wayne petty]

another failure