Chasing Ghosts

I just dealt with a plugged intake manifold (egr ports), and it sounds the exact same. I knew it was engine related because I could cruise around 40mph very smooth with the engine off then I'd accelerate slighty, hit 44 (or whatever) when the engine kicks on I could feel the shutter.

It's the Intake MANIFOLD that you want to ask about and you probably want to ask about the EGR ports specifically.

A dead giveaway would be if spark plug #4 comes out blacker than the rest. I think cylinder 1 and 2 EGR ports get clogged first and it sends a bad mix to cylinder #4 thus causing the shutter.

You also want to ask about the EGR "cooler" and get that cleaned or replaced if it hasn't been.

 

I know the EGR cooler is harder to get out, but that's possibly even more important to clean. Those tiny little passages really clog up. Such a shame to take all that stuff apart and have access to the cooler but not take it out and clean it.

The shudder ("shutter" is a camera part or little door to cover your window on your house) is likely coming from coolant in the combustion chamber, which comes from a blown head gasket. Cleaning the EGR system only helps in preventing a blown gasket; it won't unblow the gasket.

There are tests for finding exhaust gas in the engine coolant. Ot you can take out the spark plugs and inspect the inside of the cylinders. A blown head gasket letting coolant into the cylinder will make that cylinder look like it's been steam cleaned ... because it has been steam cleaned.

 

If you don’t DIY the Exhaust Gas Recirculation cleaning, you’re depending on pros who often have only a sketchy understanding of the system, miss portions of the system. Too, and this is a sand-pounder: they’ll replace expensive components that simply need cleaning.

as mentioned above, could be both the intake manifold (has EGR passages) and the EGR “cooler” (colloquial name for the component first inline at connection to the exhaust manifold) have been missed.

With your miles and symptoms it sounds like head gasket failure as commenced. This is a debacle for Toyota, and they maintain a head-in-the-sand stance, mores the shame.

more info in my signature: links to EGR cleaning and head gasket repair. The latter should be your priority now, then the former (to avoid a repeat).

or just sell and move on.

 

I will dissent from the catastrophists suggesting a failed head gasket. That would seem more likely to me if there were a shudder on startup, after the car had been sitting.

You seem to be describing some engine roughness that comes on when the engine is under moderate load, but not present at idle or at heavy load. That pretty much corresponds to when EGR is active (it is not used at idle, and it tapers out at heavy load, but is most used at moderate load).

Engine roughness in that pattern is virtually a smoking gun for the four small EGR passages in the intake manifold being clogged differently. That causes the four cylinders to get four different mixtures of fuel, air, and EGR, but only at the moderate loads where EGR is used. When EGR is inactive, the mixtures are the same and the engine runs smoothly. So the engine roughens under the exact conditions when EGR is brought in.

Notice that this pattern does not implicate upstream EGR components like the cooler. That can be clogged, but when it is, it affects flow to all four cylinders equally.

So I would be inclined to take the intake manifold off and look at those four small passages, and get them very clean. This is quite an easy job compared to knucklebusters like the EGR cooler, probably as quick as 20 minutes or so for someone who's done it before (plus cleaning time).

I wouldn't waste too much time on bush-league 'solutions' like unplugging the EGR. You might think of it as a diagnostic aid (if the roughening stops happening when EGR is unplugged, then you can feel more confident it's something to do with EGR), but not as a fix beyond that.

Even as a diagnostic aid, it's a little complicated. Unplugging the valve is detected by the ECM (you'll get an immediate check-engine light and P0403 code), and the ECM then runs the engine differently (altered ignition timing and so on) to protect it from the lack of EGR control. So anything you notice about the engine running differently with the valve unplugged isn't only because you've taken EGR out of the picture; it's also because of the ECM running the engine differently in response.

Some people, instead, cut off the flow some other way that the ECM can't immediately detect. (It will eventually catch on, and light the check-engine light with a P0401 code, but that won't happen right away). That way, at least, you are checking only the effect of taking EGR out of the picture. But the downside is that the ECM isn't taking those actions to protect the engine from damage (for as long as it takes to catch on and set the P0401; after that point, it is).

 

Yeah there are small diameter EGR passages, one per cylinder, in the intake manifold. They're about 1/4" ID, and they clog up with carbon. Some sort of skinny pipe cleaner brush, and some sprays of brake cleaner will clear them out. You may need to start with coat hanger wire or similar.

The intake also tends to be inundated with oil from the PCV (Positive Crankcase Ventilation) circuit, via hose that comes in around 3 o'clock on the round below the throttle body. A lot of people follow up intake manifold cleaning with an Oil Catch Can install, on the hose between PCV valve and intake manifold. More info in my signature as well.

All that said, with your miles, head gasket failure "may" be happening. Is the coolant level in engine reservoir stable? The failures with 3rd gen are typically on the wall between cylinder one (closest to passenger end of engine, aka the engine's "front") and cylinder two, and lead to coolant leakage into the cylinder, typically cyl one first.

Leak-down test: pressurizing the cylinder when at top-dead-centre of compression stroke, with a special gauge set, watching the gauges, and looking/listening for signs of air leakage, and noting where it occurs. A boroscope inspection of the cylinders is good for this too: a cylinder with leaking coolant will tend to look cleaner than the others, and you may see tear drops of coolant leaking down the cylinder wall. This is something competent mechanics are familiar with, worth "contracting out".

 

They most likely have to be manually cleaned. I'd bet money that alone will solve your issue. I'd seriously consider DIY, but I understand that doesn't work for a lot of people. The EGR cooler (yes right behind the EGR) is important and also more efficient if you do it while doing the intake, but it's also probably not specifically your problem and also a lot harder to DIY than just the intake manifold, essentially it could wait but it may soon become an issue.

If you have a mechanic do the work, I'd consider purchasing a new EGR cooler to have them replace it and ask for the dirty one back. Then in 40-50k miles you can clean the old one and repeat the process minus the parts cost. I suspect a lot of mechanics would decline cleaning it and would also charge for the extra time obviously.

 

Pretty much no way to clean the EGR passages except directly. Because they carry exhaust, even if you run something like Seafoam through the engine, by the time it gets to the EGR passages, it isn't Seafoam, it's exhaust.

 

How’s the engine coolant level in the reservoir, stable?

 

It sounds like you're pretty well eliminated the head gasket. But it would not have thrown a code by itself; but if it caused misfires, that would throw a code.

Anyway, I like @ChapmanF's explanation:

I like to lay the manifold down so the intake port openings face up. Then stick a hose into the hole that connects to the EGR pipe with the end of the hose pointing up. There's a hose on the IM that has a 90º bend that fits well in there. I then use most of a can of carb cleaner to fill up those EGR passages and let it soak for a half hour or so, scrub with a small bottle brush, and then use a pressure washer.

 

His explanations usually are the most logical.

 

There's a simple equation:

plus

Equals:

Blown, or just about to blow, head gasket

This bugs me too, no tests done, but head gasket looks good?: