1997 Tacoma A Lot of Problems No CEL (SOLVED)

Me neither and I have searched pretty much everywhere about it. If I knew of a few who have had to change one I would swap mine out.... still have high ltft... I’m gonna toss in a Rock Auto Denso 02 sensor first though...I have a Denso in there but believe it to be the universal Denso one...

 

Check egr is functioning correctly

 

no, just the sensors that are tied directly into the engine, they might be sending improper information while not throwing a code but that might not even be possible.

 

It is the old type of scanner though for smog, 2000+ is cheaper to smog because everyone has the new machine (correct me if I'm wrong).

 

I find that if I acelerate a lil harder off a stop light it foes smooth, idk if its something to do with the gas pedal? My ecm was supposed to arrive today but UPS never showed up figuired they gotta deliver it tomorrow, as all the suggestions yes ive done those, I’m no longer gonna throw parts at it im done, if it gets a cel good, if not im comptent with that, hey the truck always turns on and gets me from point A to B

I will seafoam this weekend, just ordered a quiet flow muffler from WALKER oe style should be here Thursday for install, I will update as I can, thx everyone

 

Im curious to see what the ecm does for you. Please do report back

 

Installed today, very little difference still rough idle, Ima just take it to the dealer if they find nothing then ill just live with it

 

I have a similar problem. I have a 2.4 with manual trans @ 192k miles. I would describe mine as idling hard, not necessarily rough. Never feels like it's going to stall. It almost feels off balance but I don't hear any noticeable miss. It accelerates fine, no stumbling, but I can still feel the "imbalance". Plugs and wires are newer and check out fine. Just replaced motor/trans mounts but problem was there before replacing. Harmonic balancer was replaced maybe a year ago because it was toast. I took off all the belts to rule out pulley/accessory issues and problem is still there. Compression is within 10-15 across all 4 cylinders. Valve clearances were just checked and all within spec. Couldn't find any vacuum leaks (doesn't mean there's not one that I missed...). No codes or pending codes. I need to replace the fuel filter but I'd be surprised if that had anything to do with it especially since you replaced yours and still have the problem. I know you said you cleaned them but maybe an injector isn't pulling it's weight? I'm out of ideas and things to check too.

I'm in the same boat, it starts every day and gets me to and from work. Would love to figure out what the issue is though. Good luck to you OP!

 

Thanks for the write up, yeah were in the same boat and dont know where its going........my last resort is Ima seafoam it this weekend, change the oil(its due, i like changing every 3k), put my new muffler coming in the mail and Ima take it to the dealer and after all that, ill just live with it, but ive taken it to 3 reputable machanics and all have been stumped

btw here are some things to check

1. Throttle cable holder check if theres any play from north to south

2, check the fan it could be out of balance/play

3. have someone put it in drive and hold the exhaust at various points to see if it gets better

 

Just throwing this out there since its easy and free to check.

Is your exhaust bouncing around making the truck vibrate, making you think you have a rough idle?
Have you measured the actual idle speed and compared it with the FSM specs?

I had a "rough idle" for the longest time and you know what fixed it? Making sure the exhaust system wasn't bouncing around like a tuning fork.
I also changed the transmission mount and engine mounts, which helped some.

 

I had my engine mounts changed, felt like I got robbed of $200 because it felt the same

Ima have my new exhaust installed by this weekend and gonna tell the guy to really “secure” it

And no I havent compared FSM

I just dont wana keep throwing parts at it

Does the cel go off for “fuel pressure” for stuff like pump or fuel injectors

could it be i need new pump or injectors which is causing bad flow, do these trucks get a cel for that? thx

 

Knock sensor, maybe

 

would that throw a code?

 

If the pressure is low enough the computer has to adjust the fuel trims to get more fuel in (based on feedback from the O2 sensor). If the computer still can't get enough fuel in because of low pressure a CEL code will get thrown for lean mixture. To answer your question, yes and no, it would only throw the code if the pressure was low enough. The computer doesn't directly monitor the fuel pressure.

 

No and they do wear out

 

Clogged cat?

 

Cat was changed 4k miles ago by previous owner, and I had it checked aswell


Ima check knock sensor and tps

 

Did you change the transmission mount as well? That one helped my truck more than the engine mounts.

I think you need to get a scan tool and actually read the RPM at idle. A low idle, rough idle, and truck vibration are all different things.

EDIT: Here's my thread where I was diagnosing my issue. It sounds like you've done most of the same things, but maybe some of this will help.
https://www.tacomaworld.com/threads/2-7l-rough-idle-diagnosing-solved.466233/

 

I know you said you checked the battery and alternator but I came across the thread below and sounds like a new battery fixed his "shaking at startup" issue. Might be worth checking the battery again if its more than a few years old. Maybe the voltage isn't where it should be? I need to check mine when I get home because it's almost 7 years old.

https://www.tacomaworld.com/threads/shaking-at-startup-and-delay.641009/

 

Hmmmmmmmmmmm