1997 2.4 rough idle/rich/black smoke

Best of luck to ya figuring this out as well!
Are you also having trouble linking a scanner to your truck?
I’m having seriously bad gas mileage. My needle is dropping faster than the temp gauge going up LOL
Yesterday I decided to pull my ecu out and inspect it. My plugs going into the ecu seem to be fine. Gonna clean up the contacts with some electronic cleaner. I opened up the covers of the ecu that’s held on by Phillips screws and the inside looks pretty flawless. Gonna see if I have some time today to put the ecu back in and clean the egt sensor and report back.

 

Yea my OBD is not working right either. I have three different scanners none connect right now. I managed to get one to connect the very first time I tried but it wouldn’t give me any codes. Just said no codes.

as far as the gas mileage. From what I’ve gathered from others here is that when a sensor or something fails or you disconnect the TPS as I was doing to troubleshoot. The ECM going into fail safe or limp mode or something and runs the A/F ratio super rich. Which is why black smoke shoots out the tail pipe and smells of gas badly.

I currently have both the exhaust manifold and intake manifolds disassembled to clean the carbon out of them real good. Also have a new fuel pump, EGR valve and solenoid on order. I also just put a new MAF sensor on but I will not be able to test until I get everything cleaned and new parts delivered and installed. Probably will not be until after Thanksgiving until I get it all done but I will post my results

Oh yea and as far as I know when the ECM fails it’s not the connectors or anything visible I don’t believe. It’s just something in the circuitry on the board or something that causes it to go bad. At least that’s how I understand it anyway. I’m just a newb though trying to act like I know what’s going on

 

Yeah I didn’t have time to mess with the taco today. Good luck with the fuel pump. I went the route of dropping the fuel tank instead of lifting the bed when I did mine. It wasn’t too hard.
I can’t wait for my parts to come in on Wednesday so I can get em installed before Thanksgiving. I’m not really getting my hopes up that it will fix it but ya never know

 

Already have my bed off ready to go!

 

So today I took some time to mess with the taco. I pulled out the egt sensor to inspect it and it was way easier than what I thought. I had to unbolt the egr valve and moved it slightly to give me some room to fit a 14mm open wrench on it. I actually got lucky and it loosened up first try. I have been spraying pb blaster on it the past couple days though so that may have helped too. The egt sensor looked horrible. I cleaned it up and all and reinstalled but truck still running rough and has poor acceleration. Just waiting on my parts to come in on Friday now. Attached are pics of the egt sensor from when I pulled it out and to after I cleaned it with carb/choke cleaner and a rag

 

I drove the truck around the neighborhood and main streets. I noticed it takes really long to get it up to like 40-45mph from a stop. But when I have some speed like turning off the main road to my neighborhood street, I can get it to 40mph no problem and just coast 40-45 pretty easily. With the pedal to the floor the truck doesn’t really respond or anything. Truck still sluggish. It makes me hood it’s got something to do with my throttle position sensor, which I have on the way. Gonna watch some vids/read up on it and report back

 

That thing is a mess! Maybe I need to think about pulling my sensors and cleaning carbon off of them while I have my intake and exhaust off. I pulled my fuel injectors the other night and cleaned them. Then I realized mine don't have the black plastic ring around the bottom of the injectors. Not sure if this is critical or not but here is a pic of the injectors.

 

Yeah and on the inside of the intake manifold there’s a port that you can see when you take the throttle body off. I believe it’s where the egr valve connects to. It was caked in carbon as well so much that I’m pretty sure the port was clogged but I cleaned it up best I could but not completely satisfied with my cleaning. I might have to take out the manifold.
Wow those injectors look great! Mine had rust all on them when I changed them out. I bought the grommet kit from rockauto. And check your motor where the injectors go. I’m willing to bet they are still in there. I had to use an angled pick to get them out.
Here’s a pic

 

So my parts came in! I figured it was a blessing from above to let me get this thing running right before Thanksgiving!
So I thought... lol

I ordered the wrong throttle position sensor. The production date on my taco is 10/1996. the tps has two different types, one that goes up to 96 and one that starts on 97. I figured mine was the 97 one since my truck is a 97 but mines the older style one.

But anywho, I changed out spark plug wires & plugs. I changed out the vacuum switching valve, cleaned the throttle body and changed the gasket. Cranked her up and still running rough haha. I haven’t test driven it yet but I’m pretty sure it’s still lacking power. Even when I rev the throttle up all the way the truck goes into like a rev limiter mode? Again, lack of reading codes has me all over the place. My next approach is getting the right TPS and maybe look into the iac valve. I didn’t really clean it all that good and was never able to separate it from the throttle body. So those are next on the list.

 

Yea the carbon on these motors is pretty bad. I've had all my intake parts soaking in gasoline for a few days now. Mine was also totally clogged up where the EGR bolted up. Once tomorrow is over I'll scrub them all down with a wire brush and reassemble everything. My injectors were in pretty good shape when I removed them but a few did have a little rust on them that I scrubbed off with a metal scrubbie. Good tip on checking inside the fuel rail for those black rings that go around the bottom of the injectors, I'll check for them tomorrow also.

 

If you bought the truck running like that. Maybe check the valve timing. Not sure if ignition timing is adjustable but maybe check that as well. It doesn't explain the excessive fuel but it will cause poor performance.

 

I’m guessing the carbon has a lot to do with the egr system? If I end up keeping the truck for awhile I might actually do an egr delete, I dunno yet. Man you are on a great track cleaning out the intake parts. I really should do the same. And yeah when I took out my injectors I thought it was missing the bottom rubber seal too until I realized it was still in the motor

 

Yeah that’s something my dad suggested to check out but I’ve never done that type of work before. Back in the day he had a 22re Toyota pickup so he’s familiar with these trucks plus he’s a huge grease monkey. Me, I’m just a wannabe grease monkey lol. He mentioned the distributor has adjustable timing and that I should check that? Dunno how any of it works, been trying to tackle the easier things first before I go and mess with timing.

 

Check EVERY fuse if you can't get a scanner to read. I've had trouble with my old Actron nowadays on newer cars but every time i can't get any to make contact I have found a burnt fuse SOMEWHERE. Not just power either, last one was on a Ranger that burned the airbag controller fuse.

 

Good idea, I’ve only ever checked fuses related to what I’m working on like for this scenario the efi fuse but haven’t checked all other fuses

 

I would hold off on throwing parts at the evap system or getting a new cat. All the evap equipment you should test then replace as necessary. It's basically vacuum hoses and solenoids. The cat wouldn't cause your rich condition - it's just government EPA shtuff.

I agree with the other poster - check ALL your fuses. Hopefully you can restore communication. Speaking of which, when you have the KEY ON, ENGINE OFF does the check engine light come on? That shows communication - if it's off there is a comm problem. It might not be that way for earlier OBD2 compliant vehicles but that's a general rule of thumb.

For your rich condition check out your fuel pressure regulator. Pull the vacuum hoses and see if any fuel comes out. If you have a ruptured diaphragm in the regulator it will suck the fuel into the intake. At idle you should be able to feel vacuum when you pull the vacuum hose. Also check that vacuum hose's integrity.

Besides having various vacuum leaks you could also have an exhaust leak. If you don't have access to a smoke machine you can make one. An alternate way to test your exhaust for leaks is to do what some dudes did on youtube with leaf blowers or other things to pressurize the exhaust then spray a soap water solution and check for bubbles and go that route. You'd only need to look before the 02 sensors for an exhaust leak.

There's quite a few videos online with homeade smoke machines. I can tell you how I made mine if you want - works well - totally ghetto but I'm not trying to impress anyone ;-) You would need an air compressor or some other air supply at low pressure though.

 

Actually - here you go: Old popcorn tin with a smaller bread tin I got at the dollar store. Install a few air fittings (barbed fittings would've been more appropriate but you use what you got) and you're good to go. Source of smoke is a lit charcoal briquette in the bread tin with a little baby oil (dollar store variety) poured in. Hook up your compressor as low as it will go and connect to your brake booster hose. Remove the air tube from the throttle body and cover it with a plastic bag and a rubber band to keep the smoke from escaping.

 

Yes with the key on, the check engine light is on. I replaced the fuel pressure regulator already as well as the vacuum hose for it. When I pull the vacuum hose off of it with the truck running I don’t feel any change in idle and don’t feel any vacuum on the hoses? Is this a bad sign?
Hmm I’m gonna have to watch some videos on the smoke machine thing bc I’m not following how it works. Sorry it’s all new to me lol but thank you I’m gonna give it a shot

 

Ok, I understand the concept of the smoke machine now. I think my dads garage has a smoke/fog machine like the one you can buy around Halloween for decoration. I can try to use that and watch for any vacuum/exhaust leaks. One thing I always wondered was my charcoal canister or what’s called vapor canister and it’s function. How do I test this canister? I have the older style round one. Idk if it relates to my issues or not. Here’s a pic of my canister

 

Good on you for cleaning the parts. I would NEVER use gasoline as a solvent. It has a low flash point, and you may end up burning down your garage! Buy a parts cleaner or solvent from the parts store.
Please be safe!