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Discussion Starter · #1 ·
Hello all, new to the forum and hope you all can guide me to a solution. I have a 98 Amigo 3.2 4x4 manual transmission. Engine runs perfect but I burn a quart of oil every 150 miles (that number is correct). I have tried Marvel oil up top, in the oil, use Rotella, used Motor Medic before the oil change. I have put about 600 miles on the truck since I have owned it and I doubt I am going to be able to clean the carbon out of the oil passages on the pistons. By the way I learned all this great stuff from the folks on this forum, thank you!

Is there certain model year 3.2 or 3.5 I can drop in my truck that will not have the same oil issue and that will use my factory harness without me having to cut it up and make changes?
Thanks for your help.
 

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98-99 3.2L and 3.5L engines use a mechanical throttle control system, starting in 00 an electronic throttle control system was added ("drive by wire"), to accommodate this mod the intake manifold, throttle body and the Powertrain Control Module (PCM) were changed. Also starting in 00 an Ion Sensing Ignition System replaced the existing system, this required replacing the Ignition Coils, adding a new ignition module and removing the Camshaft Position Sensor.

The Trooper 3.5L is essentially a stroked Rodeo 3.2L, sitting side by they look identical, the difference is pistons with a shorter compression height and a 70mm longer stoke crank. The Trooper 3.5L engines typically burn more oil because the 3.5L pistons do not have enough oil return holes. If you want a replacement for your 98 3.2L a Trooper 3.5 probably is not a good choice. A 03 Axiom 3.5L engine supposedly has pistons with more holes, solving the oil burning problem.

A 00-04 Rodeo 3.2L can be retrofitted back to the 98-99 configuration by swapping the Intake/Throttle Body, Ignition Coils, engine wiring harness etc. Rodeo/Amigo/Passport/Rodeo Sport 3.2L all use the same V6 3.2L

There is also a 04 Rodeo and 04 Axiom 3.5L Gasoline Direct Injection (GDI) available, this engine cannot retrofitted to operate in your truck.
 

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Before you yank that perfectly-running engine (except for the oil burning), you might try a few more things that won't cost too much and can't hurt.

Gumout Regane Hi-Miles carbon-cleaner has a higher load of PEA than Chevron Techron cleaner. PEA is a very powerful carbon solvent. I'd run a double-dose of the cleaner in at least 2 tanks of gas and then see if the oil consumption has improved any.

Regane is cheap at Walmart, and the Hi-Miles stuff has a bit of top-end lube:


Something else to try if Regane doesn't help, is a 2-stroke-outboard carbon-cleaner. These are specifically formulated to remove piston ring deposits on 2-stroke outboard motors, which by nature are prone to getting deposits. I've been repairing outboard motors as a "hobby" for over 50 years and I can tell you they do work!

Mercury Power Tune is readily available and inexpensive, that's what I'd use. OMC used to have a very effective "Engine Tuner" product, but Bombardier backed out of the outboard business and that's the end of that. There's still New Old Stock (NOS) around if you look for it.


The way to use this stuff is, with a warmed engine, find a vaccum port or a spot in the intake tube, between the MAF and the throttle body, where you can spray it in while the engine is idling. Spray until you've got this horrendous white cloud coming out the tailpipe, then turn off the engine.

Pull the spark plugs, and spray the remainer of the can (equally distributed) into all cylinders. Let sit overnight.

Before you reinstall plugs and crank away, might be a good idea to turn over the engine a few times to expell any excess liquid. Don't want to hydro-lock the engine, do we! Perhaps pull the fuel pump relay(s) so no fuel is spraying while you're doing that.

Reinstall spark plugs and fire 'er up. She's gonna smoke like there was no tomorrow, you'll kill any mosquitoes in the neighborhood! Take the rig out and run the engine hard, at least until there's no more smoke.

One of our members had a 3.2 that was also burning a lot of oil, as I recall it was in an older Rodeo. He used the Gumout Regane and said it helped.

If those 2 treatments don't do the trick, likely nothing will except a teardown. But you'll have only spent about $35 or so trying.

Hope that helps, let us know how things turn out...........ed
 

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Discussion Starter · #4 ·
98-99 3.2L and 3.5L engines use a mechanical throttle control system, starting in 00 an electronic throttle control system was added ("drive by wire"), to accommodate this mod the intake manifold, throttle body and the Powertrain Control Module (PCM) were changed. Also starting in 00 an Ion Sensing Ignition System replaced the existing system, this required replacing the Ignition Coils, adding a new ignition module and removing the Camshaft Position Sensor.

The Trooper 3.5L is essentially a stroked Rodeo 3.2L, sitting side by they look identical, the difference is pistons with a shorter compression height and a 70mm longer stoke crank. The Trooper 3.5L engines typically burn more oil because the 3.5L pistons do not have enough oil return holes. If you want a replacement for your 98 3.2L a Trooper 3.5 probably is not a good choice. A 03 Axiom 3.5L engine supposedly has pistons with more holes, solving the oil burning problem.

A 00-04 Rodeo 3.2L can be retrofitted back to the 98-99 configuration by swapping the Intake/Throttle Body, Ignition Coils, engine wiring harness etc. Rodeo/Amigo/Passport/Rodeo Sport 3.2L all use the same V6 3.2L

There is also a 04 Rodeo and 04 Axiom 3.5L Gasoline Direct Injection (GDI) available, this engine cannot retrofitted to operate in your truck.
Thank you Buster28. I will loo for the engines you recommend. Can you tell me if any of the Rodeo years had the piston hole problem fixed for oil drain back? I want to make sure I stay away from the problem ones. I am also going to first try the de-carboning as suggested by another member.
 

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Discussion Starter · #5 ·
Before you yank that perfectly-running engine (except for the oil burning), you might try a few more things that won't cost too much and can't hurt.

Gumout Regane Hi-Miles carbon-cleaner has a higher load of PEA than Chevron Techron cleaner. PEA is a very powerful carbon solvent. I'd run a double-dose of the cleaner in at least 2 tanks of gas and then see if the oil consumption has improved any.

Regane is cheap at Walmart, and the Hi-Miles stuff has a bit of top-end lube:


Something else to try if Regane doesn't help, is a 2-stroke-outboard carbon-cleaner. These are specifically formulated to remove piston ring deposits on 2-stroke outboard motors, which by nature are prone to getting deposits. I've been repairing outboard motors as a "hobby" for over 50 years and I can tell you they do work!

Mercury Power Tune is readily available and inexpensive, that's what I'd use. OMC used to have a very effective "Engine Tuner" product, but Bombardier backed out of the outboard business and that's the end of that. There's still New Old Stock (NOS) around if you look for it.


The way to use this stuff is, with a warmed engine, find a vaccum port or a spot in the intake tube, between the MAF and the throttle body, where you can spray it in while the engine is idling. Spray until you've got this horrendous white cloud coming out the tailpipe, then turn off the engine.

Pull the spark plugs, and spray the remainer of the can (equally distributed) into all cylinders. Let sit overnight.

Before you reinstall plugs and crank away, might be a good idea to turn over the engine a few times to expell any excess liquid. Don't want to hydro-lock the engine, do we! Perhaps pull the fuel pump relay(s) so no fuel is spraying while you're doing that.

Reinstall spark plugs and fire 'er up. She's gonna smoke like there was no tomorrow, you'll kill any mosquitoes in the neighborhood! Take the rig out and run the engine hard, at least until there's no more smoke.

One of our members had a 3.2 that was also burning a lot of oil, as I recall it was in an older Rodeo. He used the Gumout Regane and said it helped.

If those 2 treatments don't do the trick, likely nothing will except a teardown. But you'll have only spent about $35 or so trying.

Hope that helps, let us know how things turn out...........ed
Thank you Ed. I will give it a try since there is nothing to lose. I have tried Marvel in the oil and in the plug holes. I use Rotella with Power DIesel stiction eliminator all with no real change. Hopefully that has started the process and your suggestions will help. I rode a lot of dirt bikes back in the 80's and what you say makes sense.
 

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Thank you Buster28. I will loo for the engines you recommend. Can you tell me if any of the Rodeo years had the piston hole problem fixed for oil drain back? I want to make sure I stay away from the problem ones. I am also going to first try the de-carboning as suggested by another member.
The Trooper 3.5L have the oil burning problem, I owned two Rodeo Sport 01 3.2L and a Rodeo Sport 02 3.2L and none burned oil. One had 141,000 miles on it.
 

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Discussion Starter · #7 ·
The Trooper 3.5L have the oil burning problem, I owned two Rodeo Sport 01 3.2L and a Rodeo Sport 02 3.2L and none burned oil. One had 141,000 miles on it.
Thank you again Buster28. Do you know if the '01 and '02 3.2l you had, had the Isuzu "fix" of more oil drain back holes in the pistons? I would like to find a engine that has that fix to it if Ed's suggestions don't work.
Thanks again,
Bill
 

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Discussion Starter · #8 ·
right now I have the Amigo at a gentlemen's house, he is a line pipe welder in Texas, making me a new transmission crossmember support and boxing the rear part of the frame. The guy that sold me the Amigo said the rust wasn't bad but it has holes through the rear frame in several areas. After the rebuild of it I am going to undercoat the tar out of it.
 

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Thank you again Buster28. Do you know if the '01 and '02 3.2l you had, had the Isuzu "fix" of more oil drain back holes in the pistons? I would like to find a engine that has that fix to it if Ed's suggestions don't work.
Thanks again,
Bill
My Rodeo 3.2L pistons were not modified and I am reasonably sure the 03-04 3.2L are fitted with same design pistons. There are not a lot of complaints in the forum by Rodeo owners about excessive oil burning.

There are 3.5L pistons manufactured with more oil ring groove drain holes, it is my understanding none of these modified pistons were installed in assembly line 98-02 Trooper engines and that only factory replacement engines and 03 Axiom 3.5L were fitted with the new pistons. A few Trooper owners reported in the forum they pulled the pistons and drilled 4 more holes in the oil ring groove to solve the oil burning problem.

A 98-03 3.5L piston is not interchangeable with a 98-04 3.2L piston, same diameter but different compression height.
 
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