| Do you own a 4x4Toyota Pickup or 4Runner with a 22RE or 3.0L V6? Does the idle go up-down-up-down-up-down-up-down when you step on the brake pedal? Does it happen ONLY when you step on the brake pedal, and ONLY at idle? Perhaps it happens only if applying the brakes with the air conditioning on? I'm not talking about a vacuum leak that will cause your engine to stall if the brake pedal is pressed or won't allow your engine to run at all without lots of gas. Note: this is not an actual brake problem or failure of the brakes. It's an engine idle fluctuation problem that I first encountered myself on several 22RE engines (and later discovered it can also occur on the 3.0L V6). The most common cause for this problem is when the idle speed is set too high. There is a cut-off point built into the ECU (engine computer) in which it will basically stop the injectors from pumping fuel into the engine when you step on the brakes. The theory is that if you are stepping on the brakes, then you are not stepping on the gas (and the injectors can shut off). The injectors turn back on again once the engine reaches a minimum RPM threshold so the engine does not actually shut off. Normally, you would never notice this behavior, that is, unless something is wrong.... Now, you can try lowering your idle speed back down to factory settings which should be printed on the Emissions sticker on the underside of the hood. If the sticker is missing, you can roughly shoot for about 800RPM's. If you've tried adjusting the idle speed set screw and it doesn't seem to be doing anything anymore, then something ELSE is causing the idle speed to be too high. This is where the fun can begin. TMore Information on the Symptoms: First, let's review the actual symptoms of the problem in more detail. At idle speed only, after the engine is fully warmed up, when you step on the brakes (no matter how hard), the RPM's suddenly start fluctuating up and down and up and down and up and down etc.... by a few hundred RPM's. Each cycle is about 2-3 seconds from up to down to up again. The RPM's drop quickly but take a little bit longer to come back up. It may appear that the lowest RPM is actual idle speed (what the RPM's suddenly dropped to), and the highest speed seems to be a bit above normal idle speed. If you take your foot off the brake, the problem goes away instantly and RPM's return to normal. Put your foot on the brake again and the problem returns. I've noticed in my experience that sometimes the problem only happens a few cycles then goes away. And in other cases the problem happens every time and the entire time the brake pedal is pressed. As another symptom, be it quirky, try shifting your truck into 4WD high. Don't worry about locking your hubs. Just pull the stick straight back into 4WD high. Does the problem go away? It should have gone away if your vehicle has the same problem. Put the stick back in 2WD and the problem ought to come back (assuming your vehicle's case was not an intermittent issue) Try one thing more. This is assuming you are parked safely somewhere and do not intend to drive the truck around while doing this next test. Put the stick back in 2WD if it isn't, and remove the fuse for the brake lights (NOT the fuse for the tail lights). Your brake lights will not light up at this point, but try stepping on the brakes again. Did the problem go away again? Ok, put the fuse back in so you don't forget to do it later! One last test you can do is pull the brake light bulbs themselves. Basically anything that will keep the circuit broken for the brake lights will "fix" the idle/brake problem. If you tried taking the bulbs themselves out and the problem goes away, then it is further evidence of the same problem (the idle speed being too high). If you pulled the bulbs out, make sure to put them back in! What causes the Idle Fluctuation: There appears to be a fuel injector cut-off system that kicks in while applying the brakes. The theory is that if you are applying the brakes, the injectors don't need to be pumping gas so they shut off temporarily until the RPM's drop down to normal (you don't normally accelerate while stepping on the brakes to slow down, right?). Under normal circumstances, if you apply the brakes and the RPM's are already below the threshold, then the injectors do not cut out. If you are cruising down the freeway at 70mph and need to slow down to a stop, and the RPM's are at 3000RPM's, the injectors will shut off once you apply the brakes, and they will stay off until the RPM's get to the threshold that turns them back on again (approximately 1000 RPM's). So if your engine idle speed is set too high from the start, then applying the brakes can make the injectors cut out while simply sitting at a stop light causing the RPM's to suddenly drop to the threshold only to have them turn back on, and off, and on, and off, etc... I believe the injector cut-off thresh hold is around 1300 RPM's, but don't hold me to that. It seems to have varied a little from vehicle to vehicle, at least in my experience. It has always seemed to be between 1000 and 1500 RPM's. What does the A/C have to do with this? Well, when the A/C system is on, the engine idle speed is kicked up a little bit to compensate for the extra load of the compressor pump. If the bizzare idle only occurs when the A/C is on, then you can either turn down the main idle speed (if the idle speed is too high overall) or turn down the A/C idle speed (which is typically a little dial in the dash behind the glove box). Again, check your owner's manual, under-hood sticker, or repair manual for proper idle speed check and adjustment because it does vary per engine, year, and transmission type. Based on my own experiences and the experiences of dozens and dozens of others, adjusting the idle speed is the most common cause, but high idle speed may just be the symptom of yet another problem somewhere. There are a lot of different things that can affect idle speed, so keep in mind that simply adjusting the idle screw may not fix the problem. Timing, plugs, wires, a dirty throttle body, low coolant, faulty temp sensor, EGR problem, faulty or mis-adjusted TPS, and more can affect idle speed. One of these things (and more) may be affecting idle speed. But like I said earlier, first try adjusting the idle speed set screw, or try adjusting the a/c dial in the dash. Which should you adjust, the main idle screw or the A/C dial? If the problem happens when the A/C is not on (or you do not even have A/C), then adjust the idle set screw on the throttle body. If the problem occurs only when you are running the air conditioning, then start with the adjustment dial in the dash. I haven't had to adjust the A/C idle speed yet on one of my vehicles, but I've talked to plenty of people who have. Regarding the 3.0L V6: I recently fixed a 3.0L V6 Toyota with the same problem as seen on the 22RE engine by bypassing the brake light wire so it doesn't go through the ECU, and this means this problem may not be purely associated with the 22RE. The idle problem has been happening on one of my other 22RE-equipped Toyotas for a couple years now which I haven't fixed yet and it hasn't gotten any worse since it originally started. The problem does not appear to be anything more than an annoyance. The Last Resort: Ok, let's say you've tried everything possible to try and fix the problem and you just cannot figure it out. There is something you can try, but since it involves the brake system, I do not condone or recommend it for anyone and am not responsible should you wish to try this. The "last resort" solution I tried involves bypassing the wire that normally runs from the brake light switch on the brake pedal to the computer and then out to the actual brake lights. Instead of the normal route, I bypassed the computer and ran the wire straight from the pin switch to the brake lights and took the computer out of the equation so it doesn't try to cut the fuel to the injectors. Note that there are two wires on the brake light switch. One is always hot regardless if the engine is running or not, and the other is only hot when the pedal is pressed (and the switch closes and power runs to the brake lights). I am not listing the color of each wire because it is not consistent across all years. This wire is singular up until it gets to the spare tire cross memeber where it splits into two--one for each side of the vehicle. My fix was to cut the wire on the brake light switch that runs to the computer, then cut the wire from the computer that runs to the brake lights. I cut the brake light switch wire right at the switch and re-ran it through the dash to the location where I cut the wire running from the computer to the brake lights. On a V6 truck I just fixed I just cut both wires right by the computer and only had to use a 6" section of spliced wire, and this can probably be done on a 22RE as well. I just didn't do it on a 22RE becuase I didn't know what color wire I was looking for at the time and just started at the brake light switch. Make absolutely sure you are cutting and splicing the right wires! What I originally tried but failed to get working was to just run a new wire from the switch to the computer thinking there was a short in the dash--this did not work. Once the two wires were spliced, I joined them together and left the ends going to the computer and out the computer unhooked (but taped up). I call this the "last resort" fix because there is something affecting idle speed and ultimately causing the RPM's to be too high, and you've spent way too much time/money trying to figure it out. Bypassing the wire WILL work, but long term you will really need to fix the real problem. I don't know about every single thing that an affect idle speed, so there's likely to be more things than what I mentioned previously. Some Things to Ponder: I have no recommendation on what way to try first other than start with the easiest/cheapest (adjust the idle speed, timing). I also do not know the possible side effects of using my last resort method. I have not run into any other problems since I fixed it on any 3 of my vehicles, and they have been running great since at least 2000 when I used the last resort fix on the last vehicle. All other engine and electrical systems have operated normally since I made the fix and the brakes work fine for me. That being said, I cannot be responsible for any results you may have good or bad should you wish to try this last resort. While trying to diagnose this problem, I found out some things the problem IS NOT related to in my situations. I replaced the distrubutor, AFM, EFI computer, alternator, battery, and the brake light switch and none of these fixed it. I used a multimeter on numerous wires including the brake light switch wires, the brake light wire, and the main battery posts (checking for alternator output) checking for voltage spikes or drops and found nothing. Some of these vehicles had recent tune-ups with new spark plugs, wires, cap, and rotor and there was no improvement. |
| Strange Idle/Brake Problem on a Toyota Truck/4Runner 22RE Engine or 3.0L V6 |