njmaxseltd

iTrader: (19)

Some people are reporting poor idle after cleaning the throttle body.

You should check your idle speed after you clean your throttle body. Most cars idle speed will increase slightly. The ECU will detect a high idle and try to keep it down. It's possible your getting to much air bypassing the throttle plate and causing your rough idle. Keep in mind things are nice and clean around that plate so more air can get in. To check and adjust your idle speed do the following:

Warm up the car by driving for approx. 5 minuts. Turn off the engine and disconnect the throttle position sensor. Start the engine and observe the idle speed. Most likely it will be high. Using the set screw on the side of the throttle body near the cables, adjust it back down to about 750 RPM's in neutral (park for autos). Make sure you have no accessories on. (Headlights or A/C) Turn off the engine, reconnect the throttle position sensor and start the car to verify correct idle speed. Auto's should idle at 600 in drive and manuals should be about the same in neutral.

Every car I've cleaned the throttle body on had to have it's idle adjusted. Most of them, including mine ran almost 300 RPM's to high. I was idling at almost 1K after the cleaning.

Jimbrowski

Just as the ECU has kept the idle stabilized with the dirty TB, it will keep the idle stable once the TB is cleaned. It just needs some time to adapt. An easier way to check would be to reset the ECU the way you would if you were reading codes with the check engine light.
A often overlooked happening when cleaning the TB is the flooding (fouling) of the spark plugs on that first startup after the cleaning takes place. What I used to do after each cleaning is give the car the old "italian tuneup". Drive the car around town WOT through as many gears as possible (within reason, of course). If the plugs are a little fouled due to all the crap that was just sprayed into the engine, this will clean them out.
If you would like a product that cleans your injectors and combustion chambers well, try Berrymans Total Fuel System cleaner.
There is also a product I used to buy when I was a mechanic inthe early 90's. It was a FoMoCo product called "Top Engine cleaner" or something like that. Could be bought at any Ford Dealer, and was a part of tuneups on Ford Vehicles.
This stuff was in an aerosol can, and you would disconnect the inlet at the TB (hard to do in the VQ since the car will stall with the inlet disconnect behind the MAF, but with a spray wand from a WD-40 can, it can be done) while the car was running. Spray as you run the engine above idle (to keep it running). This stuff was a foam type of product that was flammable. YOu would spray until about 1/2 can was gone, then let the engine speed return to idle. Then continue to spray until the engine stalled. The foam works like oven cleaner inside the combustion chamber, using the heat inside to remove the deposits. Let the car sit for about 20 minutes, then restart. The engine will spew large clouds of smoke for about 20 minutes. Take a long drive, and the engine will clean itself out shortly. I used this stuff on my old Max, every 10-15k, as well as a TB cleaning with Gumout every 5-6k.

njmaxseltd

iTrader: (19)

Jimbrowski, I agree with you on the fact that the ECU should adjust your speed back to normal, however, if you go by the factory service manuals instructions on checking for proper idle speed adjustment you will definately fine it to be off. My cars idle, upon start up, was shooting over 2K RPM's on a warm engine after the cleaning. Then it would drop to normal speed. I knew this wasn't correct. Upon checking the default idle speed I found it to be way off. Several cars I have cleaned have had the exact same condition. A quick 5 minute procedure identified that fact that the default idle speed or throttle plate position was off. To much air was getting in the intake around the throttle plate. This caused high idles in some cars where the ECU had reached it's limit of adjusting the idle speed. Others like mine showed signes of revving upon start up. Then the ECU would adjust it to normal. Once the default setting was correct, all these symptons went away. On cold mornings I had to stomp on my brakes to keep the car from running away from me at a stop sign. After setting the idle speed correctly, this also went away.

Bottom line here is that it's a good idea to check your idle speed after you clean your throttle body. Or even from time to time such as after a tuen up, mods, ect. Nissan has certain default values which should be taken into consideration. The ECU isn't the only thing running your car. There are mechanical adjustments that must be set correctly in order for the ECU to actually perform the best it can.

xHypex

iTrader: (1)

Since this is about idle and TB cleaning I'll ask about my strange experience here. I cleaned my TB and didn't have any idle problems or the like. However after about 3 weeks and a 220 mile trip I got a strange idle. I was at the very end of my trip sitting at a light in neutral (I drive a 5spd) when the idle rose to 1500 then 2000 and dropped to 1200 only to level out at 1500 again. It was almost like something was accelerating my car and then letting off the gas. Could this possibly be related to my TB cleaning
-hype

njmaxseltd

iTrader: (19)

That is a strange one. Have you checked to see if your throttle cables are binding or catching on anything? Have you tightened them up lately? To tight perhaps? It wouldn't hurt to check the default idle setting, but I don't think that is your issue.