1997 2.4 rough idle/rich/black smoke

Hello everyone.
So I recently bought a 97 Tacoma 2.4 5spd rwd that was not running and sitting on a farm for years.
I bought it as a project truck that I can restore. I finally got it running and driving but I have some issues.

1. rough idle on start up and warmed up
2. light black smoke out the tailpipe @ idle. If I rev it up, black smoke comes out like it’s a diesel
3. strong fuel smell, so I know it’s running rich
4. when driving, truck stutters and has poor acceleration. I also hear it backfire sometimes on acceleration

So far I have replaced

1. Fuel pump (denso)
2. Fuel filter (o Reilly’s)
3. Fuel injectors (eBay but credible source)
4. Fuel pressure regulator (standard motor product)
5. Egr Valve (standard motor product)
6. Upstream & Downstream O2 Sensors (denso)
7. Spark plugs (ngk iridium I believe I can’t remember but I got the ones the manual says to get) I did notice the old plugs weren’t that bad but were completely black on the tips
8. I cleaned my maf sensor twice since I’ve owned it. It does appear to be the original denso
9. I’ve cleaned throttle body, iac valve, replaced air filter. Inside my throttle body was very black as well
10. Changed engine temp sensors

I replaced all vacuum lines regarding egr, some others I didn’t but not really sure if they are bad or not. I haven’t tested any vacuum leaks not really sure how to do so. Here’s the kicker, my engine light is on but when I plug my actron cp9185 scan tool it can’t connect to the vehicle so I don’t know what codes I’m throwing. I’m not much of a mechanic, I do what I can and continue to learn as I go. I have relied a lot of my troubleshooting based on the internet but now I’m seeing the $$$ add up and I’m hoping to pinpoint my issues now with the majority of the stuff I replaced already lol. My next suspicion is the cat converter. It appears to be original but I don’t hear any rattling or anything when the truck is running or when I push on it. I’ve read online that bad cats can cause black smoke and rough running car so that’s why I was leaning towards that.
What are your thoughts?

 

You really need to look at codes and sensor data before continuing to throw parts, have you checked pin 16 of the DLC for power and pins 4 & 5 for ground?

 

Hey Dm93, thanks for the reply.
I will check those connectors today. The DLC has power, it powers up my scan tool but it just won’t establish a connection to the vehicle. I did order an auto link scan tool that came in today that I’m gonna try out. Will report back later. Thanks.

 

Have you checked the entire intake tract for critters? They and their houses can seriously limit the airflow.

After that I would be suspicious of the MAF, good thing to look at with the computer.

 

I’ve replaced the intake boot that connects to the throttle body (old one ripped apart when taking off intake system) but the other boot closer to the air filter is still original and could probably get replaced. As far as I can see and feel, there’s no rips or cracks that’s letting air escape. I may need to triple check today when I get a hand on the truck.
As far as the maf, I’ve used the crc mass air flow sensor cleaner to spray on the resistors and the metal prongs the resistors are connected too. Is there a part of the maf that is inside that tube it sits on that I need to clean as well? I only unscrewed the two philips heads on top to get the sensor out and cleaned that piece.

 

I have the same problem with my 95.5 2.7L not connecting to the scanner. I've seen others say the same thing. These early OBDII 4 cyls seem prone to this problem.

I have no experience with the the 2.4. But, it seems you are running rich under all circumstances. I know you said you got the injectors from a reliable source, but there are some really good fakes out there and numerous TW members have reported getting bad one.

You might try unhooking the injectors one at a time and see if the amount of unburned fuel (black smoke) lessens out the tailpipe.

 

Have you found a resolution to connecting a scanner to your truck? I’ve read that some scanners aren’t canbus ready and I’m unsure if my actron scanner is canbus or not, I use it for semi trucks. That’s why I got a auto link scanner that does say it is canbus, about to find out in a second if it works.
The injectors I got were based on another forum member here that said they work with his truck, same motor. I can try that and/or swap back the originals and see what happens. Thanks for the input!

 

The new scanner doesn’t connect to vehicle either. Checking the pins on the DLC of truck, there’s 4 wires I tested the ohms of pin 5 and it reads 0.02ish. I tested voltage of pin 16 and it’s reading 12.56 with red prong of multimeter on pin 16 and black prong on pin 4 or 5. So I believe pin 5 has proper ground.. unless I am missing something.

 

This is what came out the tailpipe from cold start this morning. It appears to be water mixed with the carbon in the exhaust system.

one thing I forgot to mention is that the truck has 377k miles. A lot, if not, all the parts on this truck were original besides plugs, wires, coils, distributor cap.

 

No resolution, but I haven't really tried. Since mine is 95 and ODBII wasn't required to meet gov't regs until 1996, I always thought maybe the scanners were looking for something not there in the 95 version of the signals or a slight variation in pinout or something.

I once read on here where someone said the O'Reilly's scanners have had some success connecting. Also, others have said dealership scanners sometimes connect when store bought ones won't.

 

Guess we are both out of luck when it comes to reading codes on our trucks lol.
I plann on taking the truck to oreillys to see if their scanner can read it. I’m just trying to trace wires from the DTC port right now to see if there’s anything wrong with the wires.
I unplugged the injectors one by one while engine was running (well just the first two) truck still blows smoke pretty heavily. Only when I had 2 injector plugs out the same time did it blow less but I’d say that’s bc the truck is idling on 2 injectors only?
Not being able to pull codes really makes my troubleshooting difficult.
And it is cold out here this morning. (62 degrees in FL, I am a FL boy so that is cold to me )

 

LOL 62- that's T-shirt weather!

i would inspect ALL the wiring. maybe rodents have chewed through a couple of them.

 

Haha it’s been around the 80s lately but just this past week it started to drop into the 60s at night and early mornings. Just today is it a high of 64. Chilly for me
Originally the truck did have a rat problem. Rat poop all up and down the floorboards
I took apart the dash to inspect all wiring and found nothing chewed through besides some stuff on my dash panel that I have since fixed. I may need to inspect again since I can’t trace the DTC port wires fully.
here’s when I took apart the dash

 

I know I’m kinda all over the place but was checking all my vacuum lines and such and popped open the egr vacuum solenoid and found it damp and super black (I didn’t replace this solenoid, only the egr valve and vacuum lines) can anyone tell me what this would indicate? Should I replace the solenoid?

 

So took the truck to o Reilly’s and auto zone. Neither of their scanners can establish a connection either
Now I noticed that my catalytic converter is in fact rattling at idle
When I get the truck up to 50mph in 5th gear it seems to ride smooth. It mostly jerks in 2nd or 3rd gear with the misfiring.
I am going to take dash apart and see if I can see a break or something in my OBDII port wires. Will check back

 

So took dash apart and traced obdII port wiring there’s no breaks or anything in it. Checked wires on ecu all looks well.

There is a wiring harness above the glove box, not really sure what it’s for but it had three breaks in them that I had reconnected. I never took it seriously awhile back bc the truck still ran but I’m troubleshooting the obdII port now and wondering if it’s somehow related? I have them connected though and still can’t establish connection with my scanner. Unfortunately those three wires were chewed right from the harness so I cheaply connected some prongs into the harness but it is connected.. can’t seem to find the replacement plug for it.

gonna call it a day and try again tomorrow. I think I’m going to get a new cat. The old one really is suspicious now with the rattling and with 377k miles it would be a peace of mind replacement. Thanks for the info everyone.
Attached is a pic of that harness above the glove box

 

Here’s an update on what I got.
I ordered a new walker cat converter from rockauto. When I took the old cat out I noticed both exhuast pipes that the cat connected to were caked in carbon, especially the pipe before the cat. Installed new cat and symptoms remain. Got a new maf sensor but isn’t oem denso but tried it out and it’s still the same.

I think I’m going to look into the vacuum switch valve and/or evaporator canister next. They’re one of the only things left I haven’t replaced! Lol

quick question about the clutch. I read that bad clutches can cause poor acceleration. When I drive the truck I notice that 1st gear pulls good, when I’m in 2nd gear that’s when I feel the hesitation/jerking. I can hear the engine reving, but truck isn’t really moving. I can feel the loss of power. Same goes with 3rd, then 4th starts to smooth out and then into 5th but man pedal to the floor the truck barely can get to 60. Is it possible my clutch is causing this? I haven’t looked into the tranny or anything yet as I been trying to figure out this black smoke but do you guys know if a bad clutch causes bad acceleration?

 

If it was your clutch, it would be be bad in all gears.

 

Hmm gonna have to try to drive it again to see how it really feels in first gear. I say it pull good but maybe its supposed to pull better than what I’m feeling? Lmao

anyways. I’m gonna see if I have time today to mess with the taco. I want to take out the egt sensor and see if that is covered in carbon and giving the computer false readings. I’ll try to clean it up before trying to order a new one. I also just ordered some new stuff related to air/fuel and exhaust/emissions. On the way I have:
Throttle body sensor
Throttle body gasket (old one cracked)
Vacuum Control Valve (one under intake manifold)
Air intake/charge temperature sensor (my truck has it separate from maf sensor, attached to the stock air box) I read this being bad can cause a rich condition bc the computer isn’t getting accurate reading on what temp the air is coming into the intake system
New sparky plugs and wires. My spark plugs were black already from carbon so I’m ordering again. And I never replaced the wires so I ordered those as well.
I know it’s like I’m throwing a bunch of money into the truck blindly, but at the same time I get a little piece of mind knowing that I replaced these parts with what I know are good working parts. Still trying to figure out my obd2 port issue if anyone has suggestions
Parts come in on Wednesday

 

You and I are having the exact same issues buddy! Please keep us updated with any successes you find please! I will do the same so hopefully we can help each other figure this out!