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Unread 04-19-2006, 09:22 AM   #1
1997gcherokee
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4.0 tune up

what is needed to tune a 4.ol engine on a 1997 Grand Cherokee.

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Unread 04-19-2006, 09:28 AM   #2
Decipticon
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plugs, wires, cap, rotor, coil.
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Unread 04-19-2006, 09:35 AM   #3
dpierson
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While you are doing that also do an oil change, lube all suspension zirk fittings, check all fluid levels, add bottle of injector cleaner to full tank of gas. You might also consider a new O2 sensor if its been more than two years.
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Traded 8/9/07

[SIZE=1]Black 94 ZJ Laredo 4.0L 42RE/NP231 Command Trac
Sylvania Silverstars, Alpine CD Head Unit, Pioneer 3-Ways in the Doors, Blacked Out Grill, Kolak Exhaust, Clear Corners, Bilstein Shocks, Gas Tank Skid, Rear Hitch, Hitch Wiring, TC Skid, Hellwig RSB, Military FSB, Brembo Front Rotors, OME SS, B&M Supercooler, RE Tie Rod, Limited Power Leather Seats, 30x9.5 Toyo Open Country ATs, Optima Red Top

Next Mods: Upgrade Battery Cables, Sliders, Black Steelies, 3" Lift, Rear Locker, Bumper, HO Alternator, Winch, Driving Lights[/SIZE]
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Unread 04-19-2006, 10:02 AM   #4
MAUSS
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The O2 sensor is a good idea. Most people never think of replacing them and they don't last forever. It will probably help the fuel economy too. The special sockets are something you can usually borrow at Autozone or Advance auto parts.
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Unread 04-19-2006, 10:28 AM   #5
ynotyj
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Don't forget your air filter. It's inexpensive and easy to replace, and should be especially if you drive in a dusty area.
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Unread 04-19-2006, 02:05 PM   #6
doyll
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How many miles are on vehicle and how many on this tuneup? Spark plugs last 60-80k+. Cap and Rotor last at least that so check them for burn and corrosion and replace if needed. Plug wires either work or start developing too much resistance and short out. If engine isn't missing and starts right up, they are probably fine. They can can be ohmed to see if resistence is within limits. O2 sensor will usually throw an error code if it's going bad and can be tested. Coils usually work or die completely or when hot.

Why replace a bunch of parts that probably have nothing wrong with them? Many shops don't have real mechanics, only parts changers. Shops make more money just changing everything instead of only replacing bad parts. That's a big part of why I don't let them work on my stuff.

Just my .02

Good luck!
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1997 ZJ 4.0, 42re, 242, 3.73, tow hooks, reciever hitch, skids, OBA, F>R lift, Rancho 9000s, Addco 1.25", JKS discos, 265/75r MTs on stock wheels, 99+ intake, Banks look-alike header, sliders,

NEED: adjustable upper front control arms, front track bar frame bracket for JKS/RE bar, adjustable rear track bar, Addco rear sway bar, winch
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Unread 04-19-2006, 02:08 PM   #7
dpierson
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The O2 sensor should be replaced every two years regardless of a code or not. They can throw off your mileage even before throwing a code.

Plugs, rotor, and cap are cheap so I'd do those in for sure. Spark plug wires and coil can be spendy but once you buy new ones they shoudl last quite a while.
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Dan

Traded 8/9/07

[SIZE=1]Black 94 ZJ Laredo 4.0L 42RE/NP231 Command Trac
Sylvania Silverstars, Alpine CD Head Unit, Pioneer 3-Ways in the Doors, Blacked Out Grill, Kolak Exhaust, Clear Corners, Bilstein Shocks, Gas Tank Skid, Rear Hitch, Hitch Wiring, TC Skid, Hellwig RSB, Military FSB, Brembo Front Rotors, OME SS, B&M Supercooler, RE Tie Rod, Limited Power Leather Seats, 30x9.5 Toyo Open Country ATs, Optima Red Top

Next Mods: Upgrade Battery Cables, Sliders, Black Steelies, 3" Lift, Rear Locker, Bumper, HO Alternator, Winch, Driving Lights[/SIZE]
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Unread 04-19-2006, 02:16 PM   #8
doyll
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New tires would be nice too. Don't forget a new muffler, it might be getting weak. Oh! how about a new fuel pump? The Cat might be about to plug so might as well put a new one in too. Yeah! I-6 exhaust manilfolds always crack and leak. Put a new one on now too. New shocks.. new ball joints, .. new seats.. Hell just pull the cigarette lighter and put it in a new rig!!

Seriously, how many miles are on vehicle and how many on this tuneup? Spark plugs last 60-80k+. Cap and Rotor last at least that so check them for burn and corrosion and replace if needed. Plug wires either work or start developing too much resistance and short out. If engine isn't missing and starts right up, they are probably fine. They can can be ohmed to see if resistence is within limits. O2 sensor will usually throw an error code if it's going bad and can be tested. Coils usually work or die completely or when hot.

Why replace a bunch of parts that probably have nothing wrong with them? Many shops don't have real mechanics, only parts changers. Shops make more money just changing everything instead of only replacing bad parts. That's a big part of why I don't let them work on my stuff.

Just my .02

Good luck!
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1997 ZJ 4.0, 42re, 242, 3.73, tow hooks, reciever hitch, skids, OBA, F>R lift, Rancho 9000s, Addco 1.25", JKS discos, 265/75r MTs on stock wheels, 99+ intake, Banks look-alike header, sliders,

NEED: adjustable upper front control arms, front track bar frame bracket for JKS/RE bar, adjustable rear track bar, Addco rear sway bar, winch
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Unread 04-21-2006, 10:28 AM   #9
adgjqetuo
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What can be some symptoms of bad O2 sensors?
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04 Jeep grand Cherokee Overland - 23k ~ 71k - Sold
98 Jeep Grand Cherokee Laredo SE - 73k ~ 150k - Sold
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Unread 04-23-2006, 06:46 AM   #10
greasefingers
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High CO emmisions & a sudden decrease in mpg. Early ones are only good for about 60 k miles. They can drift (which will not throw a code) before failing or going out of range. If unsure then just replace it.
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94 Black Laredo 4-Liter with QuadraTrac (42RE trans & NP249 TC) 200,000 + miles purchased new

88 Cherokee 2-door with 5speed manual 139K miles(deceased) purchased new
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Unread 04-23-2006, 08:03 AM   #11
Woody
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Quote:
Originally Posted by doyll
New tires would be nice too. Don't forget a new muffler, it might be getting weak. Oh! how about a new fuel pump? The Cat might be about to plug so might as well put a new one in too. Yeah! I-6 exhaust manilfolds always crack and leak. Put a new one on now too. New shocks.. new ball joints, .. new seats.. Hell just pull the cigarette lighter and put it in a new rig!!

Seriously, how many miles are on vehicle and how many on this tuneup? Spark plugs last 60-80k+. Cap and Rotor last at least that so check them for burn and corrosion and replace if needed. Plug wires either work or start developing too much resistance and short out. If engine isn't missing and starts right up, they are probably fine. They can can be ohmed to see if resistence is within limits. O2 sensor will usually throw an error code if it's going bad and can be tested. Coils usually work or die completely or when hot.

Why replace a bunch of parts that probably have nothing wrong with them? Many shops don't have real mechanics, only parts changers. Shops make more money just changing everything instead of only replacing bad parts. That's a big part of why I don't let them work on my stuff.

Just my .02

Good luck!
Well in comparison;

I change the plugs, wires, cap and rotor every two years. Why? 2 mpg difference that usually develops around that time

I change my O2 sensor about every two years. Why? 3mpg difference that develops within that span of time.

Coil, no I don't change the coil unless it's being a problem child.

Just one of those saves me at least 80 gallons of gas a year, that's over $230 right now. Spend $75 on all those goodies when I do them and they pay for themselves.
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Unread 04-23-2006, 08:47 AM   #12
adgjqetuo
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Are they expensive? How many are there, and are they easy to replace?

Maybe i'll head to autozone today
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04 Jeep grand Cherokee Overland - 23k ~ 71k - Sold
98 Jeep Grand Cherokee Laredo SE - 73k ~ 150k - Sold
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Unread 04-23-2006, 01:02 PM   #13
doyll
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Quote:
Originally Posted by Woody
Well in comparison;

I change the plugs, wires, cap and rotor every two years. Why? 2 mpg difference that usually develops around that time

I change my O2 sensor about every two years. Why? 3mpg difference that develops within that span of time.

Coil, no I don't change the coil unless it's being a problem child.

Just one of those saves me at least 80 gallons of gas a year, that's over $230 right now. Spend $75 on all those goodies when I do them and they pay for themselves.
I understand what you're saying Woody. I suppose you are driving 40-50000 miles in 2 years and probably do need to do a tune-up. As for saving 80 gallon of gas,... no way to prove or disprove it. Maybe you only needed plugs. Maybe you didn't need anything. Maybe you needed everything.

All I'm saying is replace what is bad after checking to see what is bad instead of doing a blind replacement of parts and assuming when mileage gets better it was because all parts were bad. Ohming plug wires and looking at cap/rotor contacts to see if they are bad is a cake walk. I'm saying replace worn or bad parts. If injectors and combustion chamber are clean with good plugs, wires, cap, rotor, etc. and mileage is low, I would replace O2 sensor too.

I put in injecter/combustion chamber cleaner in mine when I bought it because it was showing 16 mpg on computer. Cap and rotor, plugs were good and wires ohmed good. I have no idea how many miles are on them. In the first tank of gas, ( 200 miles) mileage went from 16 to 20 mpg on onboard computer (mostly from injector/chamber cleaner I assume). I got 19.5 - 21mpg highway for the next 22000 miles. I won't talk about city driving because I live in a town that has no speed limit over 25 mph and a population of 4000. Start up, drive a mile or 2 and park. Oh well.. I get about 14 in town. When I was in SoCal I averaged 18-19mpg for all-around driving.

Now I've installed a 99+ intake manifold and Banks look-alike header (stock exhaust header was sounding like a lifter when I'd start engine... $200 for both) and lifted it 3.5" More torque and power now and my highway mileage is 20.5 -22.9 mpg with stock tires on it and 18.5 - 21 mpg with 265/75r16 MTs on it. (mud lugs creat a lot of resistance) Nothing else was changed, but I've only put 3500 miles on with new intake/exhaust.
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1997 ZJ 4.0, 42re, 242, 3.73, tow hooks, reciever hitch, skids, OBA, F>R lift, Rancho 9000s, Addco 1.25", JKS discos, 265/75r MTs on stock wheels, 99+ intake, Banks look-alike header, sliders,

NEED: adjustable upper front control arms, front track bar frame bracket for JKS/RE bar, adjustable rear track bar, Addco rear sway bar, winch
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