I think this has been coming on for awhile. In the last few weeks, I thought I was feeling a slight loss of power, then everything went back to normal. I figured the air conditioning was kicking in because it's been hot here the last month and I've been using the A/C.

Today, I was driving down the road, the car lost power and did not regain it as before. I looked out the rear view mirror and saw black smoke coming from the tailpipe so I pulled over. The check engine light did not come on and the lamp is good. When I popped the hood, I was hit with a blast of heat and the engine seems pretty warm although the dash temperature gauge didn't indicate anything out of the ordinary. I restarted and again I saw black smoke, not a huge amount, but it was there. I noticed the engine was idling high; about 1200 RPM then slowly returning to normal. I turned it off and let the engine cool while I did some shopping.

I limped the Rodeo home and I did not want to burn out the catalytic converter so I turned off the engine and coasted a lot.

I checked the fuel pressure regulator vacuum hose for fuel and did not find any. The check engine light has not come on at any time. I haven't jumped the diagnostic connector to read codes but I doubt there are any since the check engine light did not come on.

A friend who owns a newer Toyota said his engine was blowing black smoke and the exhaust manifold was glowing until he replaced the oxygen sensor. I didn't think the O2 sensor had that much of an effect on the air / fuel mixture. Hmmm.

I searched this forum and found 2 other Rodeos that had a similar problem, but there were no followups by the owners that indicated what the trouble was. :(

Any ideas?

Thanks,
Dale

When the problem is fixed, I will post the solution.

I dunno....could be the oxygen sensor....could also be leaking fuel injectors maybe?

Thanks for the reply.

I just jumped the 3 pin diagnostic connector.....No codes.

It could be the oxygen sensor, but wouldn't that set a code? I don't know for sure.

It could also be leaking injectors, I hope not. The car has been running pretty well until now. It has a new fuel filter.

The way the Rodeo has lost power is almost like a clogged catalytic converter, but that wouldn't explain the black smoke and the way the problem comes and goes.

I may be off to the dealer.

:(

Dale

Now that I've looked in the service manual a bit, I see that I should be getting a code 45- Rich HO2S signal indication. With that much black smoke, the computer should have set code 45. Since it didn't, I'm thinking there is a problem with the oxygen sensor or it's wiring.

I've never replaced the O2 sensor and the car has 132K on it. With the (lack of) maintenance I've seen on this Rodeo, it could be original. Check / Replace interval is 60K miles.

Dale

I went ahead and ordered an oxygen sensor a few minutes ago, It needs one anyway and I think its a good place to start. One symptom of a bad O2 sensor is engine surging and poor fuel economy, which I've always had in the Rodeo. From what I've read, when they fail, they go "lean" and the computer richens up the air / fuel mixture. I bought the part online for $66.87 with free shipping compared to the same part for $95.99 + tax at Schucks. It's a Bosch with OEM connections and I should get it early next week.

Curious to know how you make out...

Will do. I'm kinda flying blind on this problem.

More-

I've cold started the Rodeo and have found there is no black smoke until the engine warms up and goes closed loop.

I did hook up a vacuum gauge to the intake manifold and have found the reading is the same (17.5 in/hg) as it has always been. The needle is steady.

Disconnected the MAP sensor and found it's vacuum port is not clogged and the vacuum line is clear. I hooked up a hose to the sensor and found that sucking on the line did have an affect on the engine. Good. Disconnecting it's electrical connector set the check engine light. More good.

I removed the O2 sensor fuse and revved the engine, more black smoke. It did not light the check engine lamp. Now that I look at the wiring diagram, the fuse is for the heater portion of the O2 sensor. So, no useful information here.

Reset the ECM, no smoke while cold and smoking resumed when the engine warms up. Lots of black watery crud is coming from the tailpipe.

I wish I had a 1996 or newer Rodeo, I could use a OBD II scan tool to check all of the sensor readings and this repair would be much easier.

Thats all for now.

Dale

The problem is now fixed.

Before installing the new O2 sensor, I removed the electrical connector and started the car. To my surprise, I did not get a check engine light but I did get plenty of black smoke as usual.

I did not have an O2 sensor socket, so I used a 22mm open end wrench and it came out easily. The exhaust pipe was warm, so that may have helped in removing it. The new sensor already had anti-seize on it, so I screwed it in after cleaning the threads. The hardest part was getting the electrical connector back in place, there is no room to get your hands on it.

Now for the good part of the story.

I started the Rodeo and let it warm up and I got plenty of black smoke when revving it up! I was disappointed to say the least. I sat there and thought about what else could be wrong. It may be time to go to the dealer.

While sitting there, I thought I might try resetting the computer. Easy to do, but I really didn't think it would make any difference. I pulled the fuse and waited 15 minutes. After starting the car, it sounded different and better. I revved it up and saw lots of brown smoke coming from the tailpipe. Hmmm, could this be it?

I threw the dog in the back and went for a spin. I floored the pedal and you could not believe the amount of brown smoke that came from the tailpipe. I did this several times until it cleaned out the buildup from running too rich. Then I went on the highway and did a full throttle run. The off idle hesitation is now gone and the engine purrs.

After returning home, I looked at the inside of the tailpipe and found it was turning a brown / grey color. The pipe has always been sooty black with carbon as long as I've owned it. I think I'm going to pour a bottle of seafoam in the tank and fill it up to check the mileage.

I need to run it some more today and see if the surging problem has gone away as well.


Happy with the Rodeo again (for now),
Dale

I drove the Rodeo around a little today and the surging is still there although not nearly as bad. It won't hold a constant 2000 rpm in neutral. I don't notice the problem while in drive. I think after I replace the valve cover gaskets, spark plug wires and spark plugs this will go away.

Dale

The problem is now fixed.

Before installing the new O2 sensor, I removed the electrical connector and started the car. To my surprise, I did not get a check engine light but I did get plenty of black smoke as usual.

I did not have an O2 sensor socket, so I used a 22mm open end wrench and it came out easily. The exhaust pipe was warm, so that may have helped in removing it. The new sensor already had anti-seize on it, so I screwed it in after cleaning the threads. The hardest part was getting the electrical connector back in place, there is no room to get your hands on it.

Now for the good part of the story.

I started the Rodeo and let it warm up and I got plenty of black smoke when revving it up! I was disappointed to say the least. I sat there and thought about what else could be wrong. It may be time to go to the dealer.

While sitting there, I thought I might try resetting the computer. Easy to do, but I really didn't think it would make any difference. I pulled the fuse and waited 15 minutes. After starting the car, it sounded different and better. I revved it up and saw lots of brown smoke coming from the tailpipe. Hmmm, could this be it?

I threw the dog in the back and went for a spin. I floored the pedal and you could not believe the amount of brown smoke that came from the tailpipe. I did this several times until it cleaned out the buildup from running too rich. Then I went on the highway and did a full throttle run. The off idle hesitation is now gone and the engine purrs.

After returning home, I looked at the inside of the tailpipe and found it was turning a brown / grey color. The pipe has always been sooty black with carbon as long as I've owned it. I think I'm going to pour a bottle of seafoam in the tank and fill it up to check the mileage.

I need to run it some more today and see if the surging problem has gone away as well.


Happy with the Rodeo again (for now),
Dale

I had a 93 that gave me fits with the O2 sensor. It was replaced 18 times. The truck ahd been to 7 different dealers as well as spending a month+ with the Isuzu Tech Rep. During a Check Engine Light spell the smoke would rival anything James Bond ever had and it felt like it was running on 3 cylinders. I had it happen to me in Washington DC and had to drive back to Rochester NY, about 300+ miles. It took 9 hours and used 78 gallons of gas.

I did the plugs, wires, head gaskets, EGR, ALL of it and it only became more sporadic. I could go 2-3000 miles between instances, then it would come back. All I could do was reset the computer and hope for the 50% chance of a fix.

Know that this could be an ongoing issue. Isuzu mechanics I had befriended have told me this is a common problem, especially over 90-100,000 miles, albeit mine was an extreme case.

BTW, if I am not mistaken, there are TWO O2 sensors. One heated and one not. Maybe check the cheaper NON heated one as well.

Best wishes.

souds like you may possibly have a bad cat. convertor take it to an exhaust shop have them check backpressure

I drove the Rodeo around a little today and the surging is still there although not nearly as bad. It won't hold a constant 2000 rpm in neutral. I don't notice the problem while in drive. I think after I replace the valve cover gaskets, spark plug wires and spark plugs this will go away.

Dale

Well, the problem didn't go away after the wires and plugs. The engine surging is driving me crazy and I can't figure it out.

I have an appointment next week at the Isuzu dealer for an engine diagnosis. I will post the results when the problem is solved.

Dale

The Isuzu dealer installed a new idle air controller on my Rodeo today. They said mine was "slow to react". It idles down better and doesn't hesitate when accelerating but the surging problem is there, just as bad as before. $171.60. I think the tech should have read the service order, the problem was written right on it. Surging at 2000 RPM, not an idling problem. When I got my car back, they said everything was fixed and it ran great. It didn't take more than a few seconds to discover they were wrong.

I have another appointment tomorrow and I'm not really looking forward to it. Neither should they.

Dale

I have run into this problem before and the map sensor has fixed it. If the plugs are fouled you need to clean them or replace them.

so o2 senosr is coolant temp sensor or is it different one?? my rodeo having the same probalem from where i see you say, black smoke and blah. my shop say it need new coolant temp sensor. and from where you say about it have no socket, so you use 2mm open end wrench. mine did have the same thing and i use my 22mm open end wrench and man it WONT loose up. and correct me if i am wrong, 02 sensor is under the manifold right or on the head muffler????? help please. also one more thing before you fix them did your motor shake too???


-randall

I have run into this problem before and the map sensor has fixed it. If the plugs are fouled you need to clean them or replace them.

Thanks for the reply, Kltec.

The spark plugs are brand new NGK Iridiums. I have checked the MAP sensor while the engine is running with an analog VOM. The voltage changes were smooth when I revved the engine and within the normal range of 1 to 4.5 volts. While I was at the dealer yesterday, the mechanic said all of my sensors checked out fine. Even so, I will keep the MAP sensor in mind.

Basically, the dealer says the surging (see below for description) in neutral is normal. He said something about the computer on the 1995.5 is slow to adjust to engine changes under no load conditions. Since I don't notice any surgine while driving, I shouldn't worry about it. I told him that the torque converter may be "sucking up" the RPM changes so I don't feel it while driving. I think the dealer is unwilling / unable to diagnose the problem and they wanted me out of the service department. It doesn't seem right to me for the engine to do this.

Is there anyone out there willing to do a quick test on their 1995.5 Rodeo for me? This is what the engine does: While in neutral or park, rev the engine to 2000 RPM and hold the throttle at that position. Do the RPMs hold steady? Or, will the RPMs drop to 1700 - 1800 then back up again. The cycle is like clockwork; up and down, up and down.

The surging is less noticeable while the engine is cold and more pronounced when it is warm.

Dale

so o2 senosr is coolant temp sensor or is it different one?? my rodeo having the same probalem from where i see you say, black smoke and blah. my shop say it need new coolant temp sensor. and from where you say about it have no socket, so you use 2mm open end wrench. mine did have the same thing and i use my 22mm open end wrench and man it WONT loose up. and correct me if i am wrong, 02 sensor is under the manifold right or on the head muffler????? help please. also one more thing before you fix them did your motor shake too???


-randall

What year Rodeo do you have and what engine is installed in it?

The O2 sensor and the coolant temperature sensors are two different parts. The oxygen sensor(s) are installed in the exhaust pipe and the coolant sensor is in the pipe behind the block on the 3.2L V6. Do a search in this forum, there was someone else who needed to change the coolant sensor and I provided a photo of its mounting location. Good luck changing it.

Use a good penetrating spray on the oxygen sensor and let it soak in for a few hours. Warm up the engine, it may help as well. Mine came out easily.

On my Rodeo, a new oxygen sensor fixed the black smoke problem. As I recall, the engine did not shake.

Dale

my motor is 2.6L, and it does shaking right after warm up. i might need to change my 02 sensor, i did not think about that. also other thing when my egr valve start suck in that is when it start shaking and when i take egr valve hose to vaccums off it will run smooth. i install new egr valve and still does the same thing. so any idea what the problem??? also i forgot to mention one more thing as when the black smoke come out of muffler, the black smoke does come out of spark plug too?!?!? i had no idea what wrong! any help will be gratefully.


-randall