Trottle Body/Injector cleaning necessary? - Page 2 - Toyota RAV4 Forums
4.3 Mechanical Intakes, Exhaust, Tune-ups, 4x4 system, Suspension, Brakes, etc.

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#11 (permalink) Old 02-17-2013, 12:45 PM
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^^^what bigbird and Shep said^^^

The throttle plates in my ex-wifes car were sticky and would kind of "snap" open directly off idle. There was a slight buildup just as bigbird described, so I used a can of CRC MAF cleaner and the problem was solved for $6. Beautiful.

As far as injector cleaning, most gasoline sold in developed countries has enough detergent already in it to make this unnecessary. I do put in a bottle of Regane or Techron before each oil change, but that may be just my OCD.

For the record, my ex-wife's '03 Mercury Marauder (I still service it for her) has over 165,000 miles and has never had any injector or fuel-related issue using my routine.

It's actually my sister's, but I'm the family wrench.
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#12 (permalink) Old 02-17-2013, 03:15 PM
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To add to RF Overlord's post, the gasoline spray from the port mounted fuel injectors cleans the back side of the intake valves. That's a good thing. The next generation of gasoline automotive engines will have DI (direct injection), which will spray gasoline directly into the combustion chamber. No longer will the bottom of the intake port and the back side of the intake valves be cleaned of carbon buildup. That's a bad thing. This is the big bug-a-boo right now with DI engines. Some auto makers have good control on their DI engines of the carbon buildup, by using high swirl technology, multiple spark plug firings, staggered fuel spray, etc. Other auto makers, like Hyundai, don't do enough research, rush their technology to market, and leave the consumer to deal with carbon buildup on their DI engines by having to have the shop do carbon cleaning through various methods. Of course that's not a warranty issue but a maintenance issue. You know who pays for maintenance issues on a new vehicle. That's probably the main reason I just bought a '13 new style RAV, which for now still uses older technology port fuel injection. DI itself isn't a bad technology. You gain power and economy at the same time by allowing higher compression ratios running regular grade gasoline. It is a more costly technology that the automakers must embrace in order to meet the ever increasing gov't demand for more efficient motor vehicles. Likely next year, Toyota will be going to DI on their 4 cyl engines, just as Honda has started to do. Will Toyota have the carbon problem of DI engines solved right away? Only time will tell.
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#13 (permalink) Old 02-17-2013, 05:23 PM
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Originally Posted by bigbird1 View Post
Carbon can accumulate on the bottom of the throttle plate and inside the throttle body below the plate from blowby vapors emanating from the crankcase. The PCV system takes crankcase vapors and recirculates them back into the intake system for elimination.
I understand PCV (Positive Crankcase Ventilation). Its done using intake manifold vacuum which occurs downstream of the TB. All four stroke engines have some reversion (backwards flow) thru the intake so that's the only way I can see any buildup getting back to the TB. And I have seen sticking throttle plates on cars with a zillion miles. But it's usually due to wear not buildup. A quarter turn on the do-not-adjust throttle stop screw fixes it.

Buildup can be and is an issue on diesel engines like my F-250s. Since they have no manifold vacuum the blowby is fed in before the throttle plate. One popular mod is converting to the old road draft tube.

Fred
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#14 (permalink) Old 02-17-2013, 05:38 PM
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Originally Posted by bigbird1 View Post
To add to RF Overlord's post, the gasoline spray from the port mounted fuel injectors cleans the back side of the intake valves. That's a good thing. The next generation of gasoline automotive engines will have DI (direct injection), which will spray gasoline directly into the combustion chamber. .... Will Toyota have the carbon problem of DI engines solved right away? Only time will tell.
Excellent explanation! I'd heard about long term carbon issues on DI engines but didn't know why. The carbon on the valves comes from oil getting past the intake stem seals. The gasoline from port injection helps keep buildup down. Carburetted engines wouldn't do as well as evidenced by the hundreds of Fiat 128 valves I've dug the caked on carbon off of. Funny they never ran any different with nice shiny valves.

Diesels are by nature Direct Injected but probably don't suffer the build up because there's no vacuum to "pull" the oil past the stem.

Wow, this is my 2,500th post!
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#15 (permalink) Old 02-17-2013, 06:20 PM
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As another aside, when electronic fuel injection first appeared in mass production in N. America in the 80's, it was in the form of throttle body fuel injection. One injector was positioned just above the throttle plate in the top of the throttle body. It would spray a continuous fine mist into the intake manifold. This air/fuel mixture was not very homogeneous, as fuel was continuously being introduced into each intake port even when the intake valves were closed. This wasn't much different than carburation. The good side to throttle body injection was that it kept the throttle plate VERY clean, as fuel with detergent was sprayed right onto the throttle plate.

Last edited by bigbird1; 02-17-2013 at 08:04 PM.
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#16 (permalink) Old 02-18-2013, 12:25 AM
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Originally Posted by bigbird1 View Post
As another aside, when electronic fuel injection first appeared in mass production in N. America in the 80's, it was in the form of throttle body fuel injection. One injector was positioned just above the throttle plate in the top of the throttle body. It would spray a continuous fine mist into the intake manifold. This air/fuel mixture was not very homogeneous, as fuel was continuously being introduced into each intake port even when the intake valves were closed. This wasn't much different than carburation. The good side to throttle body injection was that it kept the throttle plate VERY clean, as fuel with detergent was sprayed right onto the throttle plate.
Ah yes, I had this system on my Mustang with 3.8L V6. There were 2 injectors, one for each bank. As you said, it wasn't much better than a carburetor. Had a time trying to keep those injectors clean. Had to run a bottle of Techron through them every few months.

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#17 (permalink) Old 02-18-2013, 08:45 AM
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As another aside, when electronic fuel injection first appeared in mass production in N. America in the 80's, it was in the form of throttle body fuel injection. One injector was positioned just above the throttle plate in the top of the throttle body.
My first EFI car was a 1971 Saab 99. I had 4 port injectors. I loved it. Would start and run smooth at any temp in any weather.

First saw the single TB injector on a neighbor's Chevy pickup when he couldn't get it started. I said I don't know anything about Chevys but let's take a look. Took the cover off the air cleaner and saw it was flooded. Saw the injector - and the connector on the side of it. Unclipped the plug and had him crank it until it started, Then plugged it back in. Problem solved! He was amazed and asked how I did it. Since he knew nothing about engines I probably just said "magic." Same way my wife says I fix lots of things. Just a touch!
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#18 (permalink) Old 02-25-2013, 03:51 PM
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"Special" of the Month?

My wife brought in her 07 to the dealership for the 90k service last Saturday and they also suggested among other things cleaning the throttle body (and change out spark plugs).

Must be the special of the month.

(Looks like my Saturday has 2 more items on the honey-do-list.)
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#19 (permalink) Old 02-25-2013, 04:46 PM
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The other problem that needs to be solved with DI engines is the oil gets diluted with fuel. I saw an oil analysis on a GM vehicle where the full synthetic oil was completely shot @ 5,000 miles due to fuel dilution.

In the past I used Techron in the tank about twice a year and without fail noticed a smoother idle in less than 100 miles. I've done the same in our RAVS but stopped since I switched over to top tier gasoline. My previous three cars all had a short ram or a cold air intake with a cone filter. On those the throttle body had to be cleaned twice a year. Since I just now turned 14K on the odo I'm not concerned about it yet....all stock except for a drop in high flow air filter.

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#20 (permalink) Old 02-25-2013, 06:13 PM
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The other problem that needs to be solved with DI engines is the oil gets diluted with fuel. I saw an oil analysis on a GM vehicle where the full synthetic oil was completely shot @ 5,000 miles due to fuel dilution.
What's the mechanism that causes fuel dilution? When is the fuel injected?

Fred
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