I am still unable to id the cause for my less than clean idle. I
have replaced the fuel lines (feed and return), fuel pressure
regulator, fuel filter, plugs, wires, rotor and cap, air filter,
temp sensor, cranshaft position sensor, alternator, EGR valve and
solenoid, head gasket, had the injectors cleaned professionally, a
valve job on the head, replaced the O2 sensor, cats checked and
clear, and replaced the battery.
What I have not done is replace/check the TPS, remove & clean the
throttle body, or replace the fuel pump.
I’m running out of things to look at. Could it be the TPS and/or a
dirty throttle body and/or the fuel pump causing my rough idle? It
doesn’t really hunt for idle, but is inconsistent. Otherwise, when
I get over 1k rpm’s, it generally runs smooth - except for an
occasional hiccup.–
WCManess - 1991 XJ40/6 Base - Black/Grey
Arlington/Texas, United States
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In reply to a message from wcmaness sent Mon 3 Oct 2005:
Wes,
I would vote for the TB after reading the list of replacements
you’ve fitted.
Something which can exacerbate a rough idle are the motor mounts -
both the two either side of the engine or the tranny / third engine
mount - but they may not be the origin of the problem, just
amplifying it.
Have you re-checked the timing after the head job and re-torqued
the inlet manifold nuts / bolts (assuming you fitted a new gasket)
in case a slight manifold leak has developed?–
The original message included these comments:
I am still unable to id the cause for my less than clean idle. I
I’m running out of things to look at. Could it be the TPS and/or a
dirty throttle body and/or the fuel pump causing my rough idle? It
doesn’t really hunt for idle, but is inconsistent. Otherwise, when
I get over 1k rpm’s, it generally runs smooth - except for an
occasional hiccup.
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In reply to a message from Bryan N sent Mon 3 Oct 2005:
Have not checked anything since the gasket replacement & valve
job. I’ll pull off the TB and see what it’s like in there. After
that, I will see what the timing is like.–
WCManess - 1991 XJ40/6 Base - Black/Grey
Arlington/Texas, United States
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In reply to a message from wcmaness sent Mon 3 Oct 2005:
Original problem? The problem in this thread is my not-so-good
idle. The reasons for all the parts changeouts have been many -
too many to list here. I got this cat from an auto auction, and
there were many problems preventing it from being a daily driver.
Now, after a few grand later, I drive it daily. I’m just trying
makje everything good one step at a time. I have 125k miles at the
present.–
WCManess - 1991 XJ40/6 Base - Black/Grey
Arlington/Texas, United States
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In reply to a message from wcmaness sent Tue 4 Oct 2005:
When my beast was idling roughly (it would wander between 700 and
1000), the first thing my JagMan did was pull the TB and clean it
out, followed by checking the air filter and MAFF.–
The original message included these comments:
Original problem? The problem in this thread is my not-so-good
idle. The reasons for all the parts changeouts have been many -
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In reply to a message from JagFab sent Tue 4 Oct 2005:
you have to look for something mechanical, because if it was any of
the electronic components, being off it would show a code. so is
the rough idle consistent? is it on power? what about gas mileage?
I would double check the cam timing, and also loosen the dist body
pinch bolt, and try to rotate left or right a qtr in or so. if the
dist body is off the rotor arm maybe chasing the segment, or the
other way around. or a vacuum leak. pajtas–
jaguarjoe 54 XK 120 rdstr 1961 MKIX 94 XJ6
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In reply to a message from pajtas sent Tue 4 Oct 2005:
The rough idle is not consistent in that it doesn’t hit the
same ‘‘rough spot’’ in the idle rhythm. Sometimes it’s less rough
than others - regardless of A/C usage. I have not noticed a
problem with gas mileage. It seems very good. Wouldn’t the dist
cap show signs of being off - like marks on the posts? How do I
check the timing - do I need a strobe light? I thought you couldn’t
adjust the timing on these cars.–
WCManess - 1991 XJ40/6 Base - Black/Grey
Arlington/Texas, United States
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In reply to a message from wcmaness sent Tue 4 Oct 2005:
my '93 used to have a rough idle to the point the steering wheel
would vibrate noticeably when the car was stopped and in gear…i
too did all of the usual replacements as you have done but no
help…once I changed out my TPS for other reasons the idle
smoothed out…–
Cliff - '93 XJ40 Sovereign (4.0L)
Lancaster/South Carolina, United States
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