Chasing the 2200 rpm ping (2.7)

My manuals (there is 4) is specific to the 2004 Tacoma so I don't know. Maybe not.

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I used to work for Toyota and would always get 2nd gen owners complaining of a ping. It was always a fuel issue. Never heard of the 1st gens having that issue but now we know! I was going to suggest switching fuels when I read the first post.

 

OK, I got around to checking some things out and I may have found the culprit:

1. EGR valve passed the vac test of causing the engine to stumble when when vacuum is applied (good)
2. EGR VSV passed the vac test when applying 12V.
3. EGR modulator didn't pass the the following test: port Q had no vacuum when revving the engine. I removed the top and cleaned it out and tested it again with the same result. Also, air doesn't pass from port Q to the bottom port.
4. I also checked the EGR vac lines for blockage and all is good.

At this point, it looks like EGR modulator could be faulty and may be the cause of my pinging. But its strange that there are no CEL and also strange that the dealer's live data test drive didn't catch this. Troubleshooting emissions is pretty new to me and I suppose I'm fishing for advice at this point.

 

OK, I messed with it some more before ordering a EGR modulator. Not sure if something has changed, but engine is warm and here are the current conditions:

When I "T" in the vacuum gauge at port Q I get no vacuum when revving. (Should mean EGR modulator is bad I think)
I have vacuum at port Q when hooked directly and when revving engine.
Engine dies when pulling vacuum from top port of EGR. (Should mean EGR valve is working I think)
TB port that goes to VSV has no vacuum when revving. (Not sure if this is normal)

 

Remove the EGR modulator and apply a small amount of vacuum to the big bottom port. If it doesn't hold vacuum, then the rubber diaphragm inside is ruptured. It gets old and brittle. This test isn't in the repair manual, but it's really the only thing that can go wrong with the modulator.

The computer only knows the EGR system is working based on the EGR temperature sensor. The EGR valve may be opening enough while cruising to heat the sensor, but it might not be opening enough while accelerating when you get the pinging, but in these brief time windows the computer won't throw a code.

The ports on the throttle body are near the edge of the throttle plate by design, so the vacuum varies a lot depending on how open the throttle is.

 

Awesome response. Thanks.

The bottom port of the EGR modulator does hold vacuum. However, non of the top ports (Q, P, R) will allow air to pass through.... whether the bottom port is pulling vacuum or not.

 

The top ports close (I'm not sure which ones or which direction) when pressure is applied to the bottom port. Applying vacuum to the bottom port just tests that the diapragm is good.

When installed, the exhaust pressure goes through that bottom port which closes the top ports and allows vacuum to build at the ERG valve which opens it. That drops the pressure at the bottom port of the modulator, etc. The modulator balances the pressure and vacuum to determine how much the EGR valve opens.

Anyway, if the tests from the repair manual that you did indicate the modulator isn't working then something may be wrong with it.

One other thing, check that the metal tube from the EGR valve leading up to the bottom of the modulator is clear and free of soot. If that is blocked then no pressure will reach the bottom of the modulator.

 

Thanks for the explanation. I checked the short tube between the bottom of the EGR mod and the metal tube, but not the tube its self. What's a good way to check the metal tube? Poke something flexible it it(like a zip tie)? I haven't removed the EGR and checked any of its passages either but it passed the vac test.

 

You could use the hand vacuum pump on the EGR valve metal tube to check that it's not completely blocked. Otherwise, use a bent paperclip or metal wire to poke through. If there's soot you can spray some carb or brake cleaner into it to clean it. You'd need to do this with the EGR valve removed.

Don't spray into the vacuum port that leads to the diaphragm. That shouldn't be blocked and you're stumbling idle test showed it's working. That port should hold vacuum if the diaphragm is good.

 

Awesome. I have a hand vacation piump and I'll check the metal tube. This is the first time I've used a hand vac pump and I'm glad to be learning the usefulness of it. It will be Tuesday before I can mess with it again. But I'll post the results.

You have an exceptional understanding of this system and I really appreciate your input.

 

Too much time spent reading car forums, reading repair manuals for fun, and tinkering with Toyotas.

You're doing it right by testing parts before replacing.

 

Interesting read...My 99 2.7 will ping every once in awhile....Hope you get it fixed.

Brian

 

Vacuum pump shows that there isn't any blockage in the tube coming out of the bottom of the EGR valve. I also came across info that specified that the EGR modulator filter should be placed in the unit with the course side up. I recall that the one in my truck was course side down. I thought, ah ha. After checking mine, I discovered that the course side was in fact facing down. I flipped it to the correct way and drove home but unfortunately I could still get some pinging under the right circumstances.

I'm trying..... but about ready to starting replacing one part at a time, starting with the EGR modulator.
A fellow board member expressed concern about the pics of the spark plugs and I have ordered new plugs(Denso K16R-U) since they are so cheap ($8.xx delivered from Rock Auto).

Thanks Brian.

 

I messed with this a bit more and discovered that I only get 5 inHg when I hook the vac gauge to port Q but I get 15 inHg when I hook to the line that goes into port P. So there is a 10 inHg loss through the EGR modulator. This is when revving the hot motor. This may be normal(not sure). But also when I "T" in between port Q and the EGR, I'm supposed to get some vacuum and I don't. I have ordered a new OEM EGR modulator off Ebay for $49.95 delivered.

My new spark plugs should be in this week. I plan to install them this week and do a compression test while I'm at it. I don't expect the plugs to make a difference but just wanted to rule it out since they are only $8.

 

I installed new plugs and did a compression test this evening. Warm engine with all plugs removed gave 185, 180, 185 and 200 psi at 1100 ft. Motor has 296291 miles.

New Denso plugs are gapped at .030". Old Denso gaps are .040-.042" and now have 48k miles on them.

 

A fellow member PM'ed me and suggested that the rounding of #1 and #3 could have something to do with the pinging. He also brought how the EGR dumps into the intake manifold. It seems to me that it dumps mostly into #4 since it mounts over that one.
I' curious to hear thoughts about the rounded plugs too.

 

Research is leading me to believe that the rounded edges on the plugs is likely caused by the pinging(detonation). Maybe the pinging is mostly occurring in #1 and #3. The #4 plug didn't look as wet in person and I didn't check to see if the wetness is oil or fuel.

I see in the dealer history records that at 281K there was a P0402 code and the EGR valve was replaced.

I drove the truck to work this morning with the new plugs gapped to .030 and then pinging certainly seems greatly reduced for some reason. If the EGR modulator doesn't solve the problem(should be here Friday), then my next step will be to remove the intake and clean it and the TB real good.... I guess.

 

EGR modulator isn't the problem.

I'm now diving into pulling the intake to clean in out. It does have a good bit of build up. Funny that it didn't look too bad until I scrapped on it a little. TB looks pretty good because I've cleaned it best I can without removing it.

 

I just pulled and strayed my manifold out this week. I found a YouTube video of a guy that sprayed oven cleaner in there and let it soak then sprayed it out with a pressure washer. I sprayed oven cleaner a couple days ago and let it set. Then sprayed some more today and sprayed out at the car wash. It actually got quite a bit of the build up off the runners

 

EGR valve.