Rough idle + intermittent stalling
 

1995 2wd Tacoma
2RZ-FE
Manual Transmission
200K miles
Second owner, dealer maintained until I got it about a year ago.

I've been chasing a rough idle and intermittent stalling problem. It generally restarts, although it takes some extended cranking at times. No codes on the scanner and no CEL.

Truck was running fine until a few months ago when it stalled the first time and I could not get it restarted and towed it home. At that time I replaced the following:
Spark plugs (Toyota)
Wires (NGK)
Distributor cap/Rotor (Toyota)
Fuel Filter (Toyota)
Battery (Duralast Gold)
Air Filter (Generic Oreilly)

It ran all right. Drove it a couple hundred miles. Then had a difficult time getting it started (warm) and then stalled at a stop light and could not get it started. Towed it home. At that time I replaced the following:
PCV valve and gasket (Toyota)
Most vacuum hoses
Fuel Pressure Regulator (Toyota) - Some fuel in the vacuum line
Added a fuel pressure gauge (LCE)
Oil/Filter change (Toyota)
Fuel injectors (Five O Motorsports) - Were at low end of resistance
Injector cups (Toyota)
Cleaned throttle body
Fuel pump (Denso) - Resistance was too high
Valve cover and spark plug gasket (Toyota) - Leaking
Smoke tested the intake, no leaks

Drove it on several short trips. All was fine. Drove to work and stalled about 10 minutes into the trip at idle. Restarted and drove ok another 20 minutes in traffic. Drove home and stalled 10 minutes into trip at idle. Restarted and drove ok. Did the following:
Cleaned IAC
Tested as per FSM-all ok
Smoke tested the intake, no leaks

It now seems to be running worse. It starts with a couple of cranks, idles rough, then will eventually die after a few minutes.

Any advice? Tips? Things I should check next? Thanks so much!


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Engine bay when I got it.

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Replacing fuel pump.

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Replacing valve cover gasket.

Valve adjustment???

Yes, I thought about that. I've adjusted a 22R. That's pretty straightforward. Never messed with the shims, so was hoping for something else before I went there.

Poor idle that gets even worse on warm-up is sometimes a symptom of tight valves.
Don't delay checking, or an upper end job could be in your future

My '79 is the daily driver until this gets sorted out. I will hopefully have some time this weekend to dig deeper, check valve clearances and sensors.

Did not have a lot of time today to work on the truck. However, I did check the charcoal canister as outlined in the FSM. It failed the test. Blew air through the tank pipe and no air came from the other pipes. Plugged canister?

Not sure if this is my only problem. But seems to be a problem. I know you can delete the whole egr system. Anybody reroute the hoses and just delete the canister? The part is discontinued, so a used ebay part seems like the option.


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A few updates and a question.

I cleaned the charcoal canister (I think?). I back flushed it with 43psi as per the FSM. I can hear the check valve opening and closing. Very little if any air comes out the ports when I test. Probably not my issue.

I tested the oxygen sensors. The front (bank 1) sensor resistance was double the specification. I replaced it with an oem denso unit. Truck started and seemed to run fine. I drove it around the neighborhood and back roads for about 25 minutes. Starting, stopping, hills and idling. No issues.

Started it today on second or third crank. Drove 10 minutes to the store and it stalled in the parking lot. Restarted just fine. Came out of the store and had a hard time getting it to start. Many cranks. Finally started and drove home 10 minutes just fine.

Does anyone know the correct g/s for the mass air flow sensor at idle? I am reading 3.09 g/s. I could not find the specification in the manual.


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I am getting:
11.28 g/s at 2500 rpm

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Video of the MAF voltage reading between signal wire and ground at idle. FSM says normal voltage is 1.0-1.5.

Still chasing this problem. Just wanted to update with what I have tried. I found a crack in the exhaust manifold between cylinders 2 and 3. Seems pretty common. I replaced the cast manifold with a welded tube style from a 2001+ truck. It fit perfectly.

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I measured and adjusted the valves. All were within range except the rear intake valve on cylinder 4 was right on the edge of spec. A tight 0.006". Closest to the firewall. Not the easiest place to work but managed to get the shim out and picked up a thicker one from the dealer. Got if all put back together this evening and it started right up and seemed much quieter. Unfortunately the rough idle/miss started after about five minutes. It didn't stall and seemed better than before. But something is still going on. Any suggestions on what to look at next?

The MAF g/s seems normal, I would start to suspect the ECT(coolant temp sensor), I assume TPS should read 0% at idle but some code readers start it off at 8-10% RAW data.

Yes, the ECT was one thing I was thinking about last night. Will locate and test that next. Thanks!

ECT replaced with oem sensor. Idle is better, no stalling after idling for 15 minutes. Still occasionally has an erratic rpm. It hangs around 700-710, but will occasionally drop down to 650-660, stumble and recover.

I was looking at the throttle body and noticed the set screw is not contacting anything. Would this effect the TPS not reading 0%?

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that is normal i think?..its for catching the throttle when you come off the skinny pedal, i wouldn't mess with that adjustment usually. What is your fuel trims LT/ST, and maybe check the MAF again.

Went for a short drive yesterday, returned home and let truck idle in the driveway for a few minutes. All seemed ok. Went out today and could not get it started. It would turnover, start, then immediately stall. I cranked on it for awhile and couldn't get it to run and gave up. The investigation continues.

Been reviewing your case and from what I can suggest, I would do both dry and wet compression testing. I was gonna say maybe the IAC is gummed up but you cleaned it. TPS seems ok numbers wise. You'd have accel issues if TPS is wearing out. You already took care of the fuel side with good quality replacements. I was gonna say injectors but even though aftermarket, the problem existed before those were changed.

The engine itself being 200k but who knows how well it was maintained gets me thinking about its condition. Do you have blue smoke coming out when first started or during those drives? Maybe have someone follow you or get a camera pointed to the tail pipe while you drive through various engine loads.
Does the oil dipstick have a fuel smell? I'm wondering about those piston rings...

Stalling out if fuel, air, spark have been looked at and taken care of can only mean a compression issue as a possible culprit. Of course, it doesn't hurt to recheck everything.