3rz Engine Trouble (surging)

[Skrillah]

Alright guys well as the cold has begun to set in...my 2.7L has been giving me some trouble. It has 144000 miles on it and still pulls strong. However, lately I've noticed that the engine surges... only noticeable when you are driving and when the engine is cold. At idle it is fine and even reving it...its still fine.

I"m not sure what the deal is with it. I run Mobile 1, good air filter, fuel filter, pvc, spark plugs, wires look ok although I haven't replaced them in the 4 years of owning it (25k miles i've put on it). I have replaced the stock manifold because of a crack ...that was with a cheap one from ebay though.The TB look fine and so does the MAF although I went ahead and cleaned them anyways.

So, I'm stuck...I did a TPS check last winter when I first noticed it and it was fine. Its only when the cold months hit do I really start noticing and this year seems to be notably worse than last already so I need to get it diagnosed and fixed.

Could the plug wires or o2 sensor cause these symptoms? I'm also thinking it could be another manifold leak since the surging seems to go away once it warms up...still there but very slight...?


Please help!!

Kyle

[MTL_4runner]

Kyle, I assume your year 4runner has no EGR valve on it. I also looked in the FSM and it seems like it wants to point you towards a fuel problem for surging being an issue while driving which would make sense from what your describing as symptoms. This would include issues with fuel pressure, fuel pressure regulator, fuel filter, water in the tank or the fuel fuel pump itself.

I attached a few photos of a 3RZ for others to reference as well.

[Skrillah]

Thanks Jamie!

Well what I'm confused about is the fact that it only does it in cold temperatures, or at least is more noticeable. Even when the engine itself is cold, like when I pull it out of my heated garage...no stumbling or surging.

Would a fuel problem only act up in the colder temps? It first showed signs of the problem last winter but was not as severe as it is now...it was fine all summer until the cold temps hit.

The fuel filter was replaced by myself about a 8k miles ago but was with a cheapo from Pep Boys.

I hate problems like this...so hard to diagnose. Its not throwing any codes either.

[4x4mike]

A long time ago my wife had an Integra and the winter before we sold it, it would surge like you've described. If the engine was really warm or if it were warm outside it would be fine. We had it checked out and we were told it was the knock sensor. I'm not ure if you're motor has these but just thought I'd throw it out there. We endedup waiting for summer and sold the thing.

[MTL_4runner]

A long time ago my wife had an Integra and the winter before we sold it, it would surge like you've described. If the engine was really warm or if it were warm outside it would be fine. We had it checked out and we were told it was the knock sensor. I'm not ure if you're motor has these but just thought I'd throw it out there. We endedup waiting for summer and sold the thing.


There is a knock sensor on the 3RZ but I believe a bad knock sensor should throw a code though.

[4x4mike]

On the Toyota maybe. The Acura never did.

[corax]

check the Coolant Temp Sensor (CTS or ECT) - it controls cold engine fuel enrichment and would not set a code if it was bad (the Fed mandated ECT sensor monitoring in about 2000 or 2001). you should be able to check it when the engine is cold (setting overnight) with an ohm meter and should be a relatively easy check (the gauge may use a separate sensor , so don't go by, "the gauge works fine"). it should be 1 or 2 wires, more likely 2 wires though.

if 2: touch one ohm meter lead to each terminal of the sensor with the connector off
if 1: touch 1 lead to the sensor terminal and the other lead to ground (bare metal on engine, like the intake) with the connector off

you should be able to pick up a cheap DVOM (digital volt ohm meter) at any radioshack for ~$20 or less

the reading will change based on teh temp of the sensor, but the shop manual will have a little graph showing "if it's at this temp, the reading should be . . ." - your local dealership may let you take a peak at the manual if you ask nicely

[Skrillah]

Jamie,

Are you sure there is a knock sensor for the 3rz? I can't find a replacement for the 3rz...i can for the 5vz...

Keith,

How likely is the coolant temp sensor the culprit? A replacement isn't that expensive although I don't like throwing parts at it....where would I find this on the engine itself to check it? You don't think it'd throw a code?

Thanks guys very much for the help!!! Let me know!

[MTL_4runner]

Jamie,

Are you sure there is a knock sensor for the 3rz? I can't find a replacement for the 3rz...i can for the 5vz...


Yes, I am sure there is one.

http://www.ncttora.com/fsm/2003/Repair_Manual/03tacoma/sf2rzfe3/knosen/insp.pdf

[corax]

Keith,

How likely is the coolant temp sensor the culprit? A replacement isn't that expensive although I don't like throwing parts at it....where would I find this on the engine itself to check it? You don't think it'd throw a code?


It's not likely to throw a code for that year model if the reading is just off, if it was completely crapped out it might. As far as the odds of it being the ECT sensor, that I don't know. I've not really worked with this engine at all and don't know what its common failures are. That said, I would start by testing the ECT as it is one of the few sensors that will change how an engine is fueled from cold start to normal operating temp. Again, it would be a good idea to find the FSM (field service manual, or shop manual) and take a look at teh specs and location. You should be able to find it online, maybe someone else can chime in with a link (I've always bought the paper copy, but they are $$$).

[Skrillah]

I have the shop manual, online version that is. I'll have to sift through that and see what I can find.

Jamie,

Thanks for the info. Getting at that sensor looks like a huge PITA! When I changed my fuel filter, I had to go through the wheel well with like 4 extensions and some swivels to get it out. Talking about busted knuckles. I hate to get in there and change it out and have that not even be the culprit...ugh.

Hmmm...