Bad Idling - again!
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Senior User
Joined: Jul 2004
Posts: 103
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From: Miami
Bad Idling - again!
Out of touch without power for past 10 days in Miami, thanks to Hurricane Wilma.
Over the past few weeks I've posted on a couple of threads about my idling woes on my 93 4.0 with 156k miles. Engine runs fine once above about 1800 rpm, but idling remains rough. In fact have to put it in N when at a stop. Over the last 3 weeks, I've done:
New OEM plug wires
New MAF
New IAC
Cleaned throttle body and passage to IAC
New O2 sensor
New PCV valve at valve cover AND where hose meets air intake hose.
Did the Seafoam carbon buster method
Checked all vacuum hoses
I've run the codes and nothing shows up.
Only thing I didn't do was replace the spark plugs, as I did that last year about 10K miles ago. Could it be the Seafoam treatment has ruined the plugs?
If I need to replace again, which type? Last time I used Champion 13 RS14YC6.
Thanks!
Over the past few weeks I've posted on a couple of threads about my idling woes on my 93 4.0 with 156k miles. Engine runs fine once above about 1800 rpm, but idling remains rough. In fact have to put it in N when at a stop. Over the last 3 weeks, I've done:
New OEM plug wires
New MAF
New IAC
Cleaned throttle body and passage to IAC
New O2 sensor
New PCV valve at valve cover AND where hose meets air intake hose.
Did the Seafoam carbon buster method
Checked all vacuum hoses
I've run the codes and nothing shows up.
Only thing I didn't do was replace the spark plugs, as I did that last year about 10K miles ago. Could it be the Seafoam treatment has ruined the plugs?
If I need to replace again, which type? Last time I used Champion 13 RS14YC6.
Thanks!
Post Fiend
Joined: Apr 2005
Posts: 5,720
Likes: 5
From: Washington state
use a spray can of FI, TB or O2 sensor safe carb cleaner, spray around intake manifold base and plenum base, 4L's often vacuum leak like a sieve in these locations, rpm increase=leak found. solution=tighten bolts and respray to test for broken or missing gasket section.
also spray around MAF tube, TB and all vacuum hoses for leaks, cracked hose or cracked vacuum tree not easy to see.
is IAC actuating?, pull wire from IAC while idling, rpm decrease=PCM command reaching IAC.
also may be sticking EGR valve or other failure in EGR system.
i've used full can of Seafoam on several engines, no problemos
use Autolite or Motorcraft plugs only as per their replacement book. plugs usually show up as a high rpm, high load problem
check idle fuel pressure at fuel rail test point, >30psi and steady
also spray around MAF tube, TB and all vacuum hoses for leaks, cracked hose or cracked vacuum tree not easy to see.
is IAC actuating?, pull wire from IAC while idling, rpm decrease=PCM command reaching IAC.
also may be sticking EGR valve or other failure in EGR system.
i've used full can of Seafoam on several engines, no problemos
use Autolite or Motorcraft plugs only as per their replacement book. plugs usually show up as a high rpm, high load problem
check idle fuel pressure at fuel rail test point, >30psi and steady
Last edited by 96_4wdr; Nov 2, 2005 at 09:38 PM.
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