Stalling at idle

Hi All,

Got some problems with the Taco. I've got a P0171, 0401 CEL on, as well as a 420 and a 421. The 420 and 421 emissions codes I've had for over a year, I think probably due to a failing cat. I've replaced the O2 sensors, so they're not to blame.

Sitting in traffic with my foot on the brake (AC on, if that matters), the truck sometimes shudders heavily and the engine dies. This has happened twice now. Both times I cleared the CEL codes, waited a few minutes, and started the engine back up. When I stop and put the truck in neutral, no problems arise. No problems when I'm driving either.

I've cleaned the MAF and air filter, done a cursory check for vacuum line problems, checked the air intake for obstructions, but everything seems normal.

Truck has 188xxx miles, and she's an 02. No other major problems... I've got an annoying squeak sounding like its coming from the rear drums, but thats less important now.

What do you think is goin on? Not getting enough air or fuel it seems.

Thanks in advance,
Danny

 

To start with, you can look up the meaning of the codes here:
http://www.obd-codes.com/trouble_codes/

 

Could be a vacuum leak. Start with Vacuum lines. Mine started showing similar codes and I ended up with a cracked Cylinder Head between 2&3 (exhaust side). Compression check and leak-down is not a bad place to start after the vacuum lines are verified. Power steering lines (2 going to intake) are a possibility. any issues with loss of PS fluid?

 

I had exact same problem at 190,000 miles. Spent money at a mechanic who changed vacuum lines, IAC sensor, plugs, wires, and cleaned MAF sensor.

Truck still ended up dying in rush hour traffic on the freeway at the most inopportune time.

Got towed to another shop and it turned out to be fuel filter.

 

GA, didn't think about PS fluid. I hadn't lost any as of last oil change 2K ago, but I'll check.

Mike, yeah, that's what I'm hoping to avoid. I've read a few threads that seem to point to the fuel filter, so I'll replace it today. Heard that its a bitch to get to, but oh well. Seems like not getting fuel would make sense as far as the symptoms go, and maybe when the engine is working harder more fuel gets pushed through the filter, but at idle there isn't enough fuel getting through. Weird that it seems to behave better when I sit in Neutral though

 

The filter is under the cab and easy to access. At 260,000 I had a fuel pump die and that sucker is inside the fuel tank. Have to drop the tank to access it.

 

Neutral RPMs are higher than on drive. If the filter then knock it out sooner than later.

 

@mikesdoublecab Filter on a 2.7 is under the cab on the 2001+? My 2000 2.7 has it on the drivers side block under the intake manifold. It can be done without removing the IM, but it will be a pain. Not sure about the 2001+ version of the 2.7L.

 

Good point. I'm used to my 01... hmmm

 

OP is this an automatic tranny or manual? If it works better in neutral, I would be thinking vacuum. if manual it may be the fuel filter. It is a royal pain to change without removing the IM. I changed mine, but I had the block pulled so it wasn't a problem. I would personally yank the IM off before attempting to change it, but my hands are on the large size. With a long enough extension, you can remove the two bolts holding it on the block, but getting the 17mm (i think that is the right size) banjo bolts out is going to be the tough part with the IM on.

 

Auto tranny. Will look into vacuum leaks too, and I'm gonna try to replace the fuel filter today

 

All 2.7's are on the block under the intake manifold.

 

Wanted to update in case anybody ends up with a similar problem. I haven't had time to change the fuel filter yet, but I checked the PCV valve yesterday and it was definitely broken. I could see the spring rattling around in there. I think it stayed constantly open, which from my understanding would be like having a vacuum leak at idle. Truck seems to run much better with the new PCV. I also changed the ignition coils, but I don't think that really did much. I've got a new MAF on the way, which I'll put in today.

Change/check your PCV if you've got a problem like mine!

 

Thank You for posting a solution. If you can, add a (solved) to the thread title to let everyone know this is a solution.

 

Sadly, I haven't solved the problem. Truck was running rough again today . It isn't stalling, perhaps because I replaced the PCV, but the engine still runs rough (sometimes). After 30 miles of driving today, the P0171 code popped up again and there goes the engine running rough.

I'm also getting a pretty strong vibration sometimes around 2k rpms. Maybe related?

I'm getting a new MAF in the mail tomorrow, so I'll replace that tomorrow and as soon as I can I'll do the fuel filter too. Any other ideas/suggestions?

 

If the MAF doesn't fix it (my 2.7 was similar and started running rough before I started getting misfire codes), it may be time to compression test. Lean running condition will cause burnt valves.

For vacuum, as may be mentioned above, you can try using carb cleaner or starter spray. spray it lightly around vacuum areas working in small sections. if the motor suddenly revs up, you are close to the vacuum leak. Try checking the PS vacuum lines. I believe that caused my initial motor problems before the refill as the air control valve was broken and pulling PS fluid into my intake/burning it in the cylinders.

 

Here's an update... problem still not solved. Truck still loses power and shuts off mid drive... did it three times today. After waiting about half an hour, the truck will start up again and drive okay. Right after stalling, it doesn't start back up... gotta give it some time. Weird!

So far, I've replaced:
1. Ignition coils and spark plugs
2. MAF
3. Fuel filter
4. PCV valve

Cleaned the throttle body, air filter, that little metal egr sensor, checked for vacuum leaks, nothing looks off. I just did the fuel filter and throttle body cleaning tonight, so we'll see if that helps tomorrow. I took it for a test ride for about 20 minutes around my neighborhood and it ran well, but when I sat with my foot on the brake for a while, the idle dipped to about 500rpm and I got a bit of chugging vibrations. So, I don't know the cause of the low idle, but if it runs fine and doesn't stall, I don't really care about the idle.

Any ideas? It seems like its a heat related issue because it only happens after I've been driving for a little while, and then it needs to cool down in order to start up again.

 

Wow. I agree heat is the issue. Is it the ECM overheating? Time to check the wiring harness for melted spots. how old is the fuel pump? At this stage, it may be injectors, fuel pump, ECM issue, wiring harness issue or vacuum. The IAC may need to be replaced, I don't recall if there are test procedures for it off the top of my head (i'll check my FSM this evening).

Edit: given you say it happens more often with the brakes engaged, try putting it in neutral (in a safe area) to see if it returns to normal or stalls out (do not engage front brakes, use the parking brake). It may be the ECM is not compensating for the increased pull on the motor with the master cylinder pushing pressure on the front/rear brakes. This is just my opinion... you have a head scratcher here.

 

I replaced the fuel filter just last night, so maybe that helped solve the problem.

Yeah, it does seem heat-related. I'm gonna drain the coolant and refill ASAP, but as far as I know, the cooling system is working fine. Engine does always seem super hot when I open the hood after it stalls, but then again I'm in Hawaii so everything is kinda hot.

Where is the ECM? Any way to test it for malfunctions?

I looked into IAC tests and they involve applying 12V across different terminals, which I don't have the ability to do. The fuel pump was replaced by the previous owner, I think ~3yrs ago. I'll run injector cleaner through the gas tank as soon as I fill up again.

Putting the truck in neutral raises the RPMs a little bit, closer to 700. Also gets rid of the vibration that the truck has in drive at idle.

Another issue I'm having is vibration at ~2K RPM while driving. I'm pretty sure my driveshaft is worn, causing that vibration. It doesn't happen when I'm sitting in neutral and rev the engine.

Thanks again everybody for your ongoing help with this puzzle

 

Thanks for this intel y'all. I went through all of the above with my 2000 Tacoma (V6, 3.4L, automatic) and found my PCV hose was bad. You can see the hose collapsing while the engine is running/warming up.