3rz rough idle and stalling issues..Looking for any advice

Now before I get torn apart by people saying there are already a million threads on this, 1. I already know that 2. I’ve tried using them with no success. All I’m looking for is just any input from other people because at the moment I am stuck on where to look next.

So let me explain the deal, a few weeks back my motor(99’ 3rz-fe auto) started acting strange on my way home in traffic where it started to idle real low and rough and acted like it wanted to stall but I was able to keep it alive in neutral, then after a few days it would just beat me to stalling before I could keep it alive and it is pretty random when it decides to stall, the only common pattern I’ve noticed is that it’s mainly after it’s warm and when I’m slowing down to a stop at say a stop light or behind cars in traffic, so my first thoughts were clean the maf, clean the TB, check vacuum lines and I changed the spark plugs, drove it and nothing changed, so then I keep digging in trying to think of what else is could be and I thought maybe it’d be a clogged fuel filter changed the filter and nothing changed, throughout this I knew there was a chance it could be the IAC but a new one at autozone was $190 so I tried to avoid it but ended up just biting the bullet on one and it bumped my idle up and kind of solved the low idling problem, next was it was still running rough and still stalling so I decided I wanted to pull off the egr valve and clean it/test it, I cleaned the carbon out of it and hooked it up to the vacuum line on another car and it functioned just fine, next i checked the TPS to make sure it was it giving signal and it was reading consistent increase in voltage with the throttle opening but after all of this and it was still having problems so my next idea was to look into ignition I got a new set of ngk wires and I picked up a new coil for cylinders 2 and 3 because I had thought maybe the coil was becoming heat soaked, this didn’t fix my problem either, so after a few days of staring at the engine bay and reading page after page online I took a look at my fuel pressure regulator and pulled off the vacuum line and smelled inside to see if there was any chance of the diaphragm in the regulator being broken and I did smell fuel so I replaced the regulator and I actually ended up going like 2 days with no stalling, but I noticed that when I drove on the freeway at really any speed above like 45 the truck wants to slow down and the only way I can stay up at speed is having my foot in it the entire time along with this trying to speed up the truck has a major hesitation and insane lack of power so after this test drive I got back onto side streets and it ended up stalling again, and today on my way to work the hesitation was really bad and the truck would try to stall on acceleration, so I’m really stuck because I feel like I’m running out of options and I’m tired of throwing money at parts that won’t fix the problem.

Part of this that’s making it difficult is that I have no CEL, no pending codes, can’t check fuel pressure as we don’t have a Schrader valve to check on, so at this point I’m pretty much guessing and I need some other peoples opinions, let me know if anything needs clarification but any help or ideas would be greatly appreciated!

 

Possibility the cat is getting plugged up. Seems like you covered everything else. Dill a 3/16 hole before and after catalytic converter. Use a gauge like this to check the pressure differences. then plug the holes with a self taping screw. Pressures should be even.
You can check fuel pressures with a kit you can rent from autozone.

 

That’s a good possibility, would I have to do it with pressure gauges or could I just pull the cat and visually check it

 

You could pull cat.

 

Well cat was clear and in good shape, so anymore ideas would be appreciated

 

The no codes - no pending codes is going to make this a bitch... I am hoping that the issue just hasn't been continuous enough to set a code/pending. The "problem" has to happen enough times in a "key on period" to exceed the error count for that particular code to set a pending/code. Lets hope that this is the case.

Basics first.

Check battery voltage first, then cables etc... give them the "wiggle test". The PCM/Coils all ground at the same point IIRC. Multiple brown wires on 2 ring terminals.

Does you scan tool have the capability to show fuel trims? If so what are they? Short term is what is happening right now, long term is what is happening over a period of time. Ideally should be +- 5%.

Off the top of my head I am thinking check the brake vacuum booster (maybe a big vacuum leak) and then find the line that comes from the charcoal canister and unplug it and plug the port (maybe pulling raw fuel into the intake from over filling the tank).

next time it starts acting up, unplug the MAF to see how it reacts and see if it sets a code.

 

Shot in the dark, I'm curious to see what the compression numbers are, also if the timing is correct.
Won't cost you much but elbow grease and time.
Also you can rent a compression tester from AutoZone or the like for free, just put a deposit down and get it back when you return it.

 

Compression #’s
Cyl 1: 175
Cyl 2: 160
Cyl 3: 165
Cyl 4: 175
How would I go about checking timing though?

I don’t have a scan tool to check my trims just the ones at autozone that just read codes, the battery is 12+ with the car off, the terminals passed the “wiggle test” but I’m not sure where that ground your talking about is, I’ve pulled the maf while it’s running and it kills the motor and throws a code making me think it’s functioning properly how would I check the vacuum on the brake booster to see if it’s the cause of stalling, like I know if it was bad overall I wouldn’t have assisted braking, but I have noticed that it is becoming a little harder to stop the truck when it’s warm so that has me wondering if it has something to do with it, or if my bigger tires are just making it a bitch

 

My gut feeling says something vacuum related. Mine runs very poorly when I've got a vacuum line unplugged and one of them could have easy been damaged with all the other activity.

Fortunately, checking them is pretty straightforward:
https://www.popularmechanics.com/cars/how-to/a3094/how-to-find-a-vacuum-leak/

 

Sounds like you may have a cracked exhaust manifold. This happen a lot on 3RZ engines.

 

Fuel pressure was good sitting at 45 psi at idle, and I replaced the exhaust manifold about 2 years ago with a steel one from the 01-04 3rz so I know that’s okay I haven’t tried smoking out for a vacuum leak I’ve only tried carb cleaner so maybe I will try that to see if there are any different results

 

Well I think I found the solution to my problem, thank you for the input from anyone who replied and to anyone in the future trying to chase down a gremlin like this check your coolant temp sensor, I found a tsb from the early 2000’s for this sensor and sure enough it was toast, I hope this can help

 

Nice find, especially without a scanner. If yours had live data you would have picked that up right away. Best money you can spend on that truck is a live data scan tool. Less than 100 bucks.