I am still trying to track down a lean fuel condition and I have checked
and/or replaced almost everything. Again * the vehicle is a 95 Jimmy W
series Vortec 4x4 (OBD2 switchover year).

When I scan the data stream, I get a +25% on long term fuel trim. Here¹s
what I¹ve done to eliminate the problem:

1. replaced the fuel pressure regulator and nut kit on the CPI unit
2. plugs/wires/cap/rotor
3. replaced all old looking vac hoses and tested them for leaks after (all
good)
4. new fuel pump and filter
5. egr, IAT, MAP clean and gasket replace (TPS adjusted * checked ok)
6. O2 sensor replaced and tested


The only other thing I can think of is that the clmate control switch has a
leak (read:hiss) in it and needs to be replaced. Would a leak at this
switch cause the lean fuel condition? I had a bad coil before also so I may
try replacing that also (I have one kicking around already so why not..)

There is a slight hesitation off the line but it¹s bareley noticable. Every
once in awhile I get a random misfire code also. With all the lights off in
the shop, I cannot see any arcing of the wires, cap, etc. Does this sound
like it could also be the ignition module? As far as I know it times the
spark/advance??

Thanks again! I appeciate all your help here guys!
Andrew.

is it possible to have vac leak in climate control cause lean fuel condition?Do you have the proper fuel pressure for this engine? Look at the baro reading on the scanner does it coincide with your area, this can cause a lean condition that escapes diagnosis. I'd doubt if a leak in the hvac controls could skew your mixtrue with such small lines, how is the idle vacuum by the way?
"AWN" <anixon1 (AT) cogeco (DOT) ca> wrote

I am still trying to track down a lean fuel condition and I have checked and/or replaced almost everything. Again - the vehicle is a 95 Jimmy W series Vortec 4x4 (OBD2 switchover year).

When I scan the data stream, I get a +25% on long term fuel trim. Here's what I've done to eliminate the problem:


1.. replaced the fuel pressure regulator and nut kit on the CPI unit
2.. plugs/wires/cap/rotor
3.. replaced all old looking vac hoses and tested them for leaks after (all good)
4.. new fuel pump and filter
5.. egr, IAT, MAP clean and gasket replace (TPS adjusted - checked ok)
6.. O2 sensor replaced and tested


The only other thing I can think of is that the clmate control switch has a leak (read:hiss) in it and needs to be replaced. Would a leak at this switch cause the lean fuel condition? I had a bad coil before also so I may try replacing that also (I have one kicking around already so why not..)

There is a slight hesitation off the line but it's bareley noticable. Every once in awhile I get a random misfire code also. With all the lights off in the shop, I cannot see any arcing of the wires, cap, etc. Does this sound like it could also be the ignition module? As far as I know it times the spark/advance??

Thanks again! I appeciate all your help here guys!
Andrew.

On May 12, 9:03 am, AWN <anix... (AT) cogeco (DOT) ca> wrote:
Sound like you could use a diagnostic smoke machine... they are
perfect for finding any and all leaks. Check out www.ntshoptools.com
for the best deal in smoke machines.

Gene