1. Checking the Throttle Body (Plate and TPS) Adjustment

Connect an accurate tachometer then warm up the engine.  Let it idle in Park with a/c off.  Pinch off the hose between the air intake and the IAC valve (don’t damage the hose with something sharp!)  Idle speed should drop below 500 rpm, or the engine may stop: both are normal.  If idle speed does not drop, adjust as below.  First remove the hose clip.

2. Adjusting the Idle Speed

On the side of your throttle body, there is an adjustment screw.  Loosen the lock nut.  Start the engine and turn the adjustment screw until idle is 480-520 rpm.  Switch off the engine and tighten the lock nut while holding the adjustment screw so it doesn't turn.

3. Checking the TPS Adjustment.

Check the gap between the adjustment screw and the throttle lever with a feeler gauge.  Insert a .45mm feeler gauge.  There should be no click from the TPS when the throttle is closed. Then insert a .15mm feeler gauge.  There should be a click from the TPS when the throttle is closed.  If these are incorrect, then adjust as below.

4. Adjusting the TPS.

Loosen the TPS adjustment screws.  First turn the TPS clockwise (away from the electrical connector) until it stops.  While keeping your finger on the throttle disk so it won't move,  turn the TPS counter-clockwise (toward the connector) until you hear or feel a "click".   Continue turning until it stops, then tighten the screws.  Go back to step 3 above to check the adjustment.

[Response 2:] I used expensive injector cleaner with marginal success - so I did an injector overhaul. There are some shops that do a "complete flush" without removing the injectors using some technique, but I decided to do it myself. Removing injectors was straightforward - just keep things clean. I took the injectors to a shop and they did a pressure flush ($15). There are other home ways to do this like using bicycle pump with pure injector cleaner - but after a few attempts I decided not to try. They were badly crudded but after a bit of flushing, were good as new. After 220 K km, the shop said they were just fine. I also replaced the 2 rubber o-rings. One around the injector (fat doughnut type) and one around the injector holder (skinny ring type). The o-ring around the injector holder was brittle - so the new rings sealed a big vacuum leak. Use silicon lubricant to ease the o-ring replacement. All this took a couple of hours. Made a big difference at idle.

[Tip from Ed O'Briant] My experience with a rough idle still present after a tune up and TB, IAC cleaning, etc., on higher mileage cars has been this (assuming no vacuum leaks, etc.):  dirty, clogged, sticky, leaky, and otherwise compromised fuel injector operation. If you haven't done it, pull the fuel rail and the injectors. Either bench clean them yourself or send them off to the proper folks.  Chemicals in the fuel tank don't cut it! They may help somewhat but in no way replace pulling those bad boys!  On our '90 745T with 115K miles, I found that all four of the injectors had LOUSY spray patterns-streaming fuel instead of atomizing it. Also, two of the injectors were leaking-when power alone was applied to the leakers, without compressed air, the injectors just dripped cleaner when they should, of course, be tight. Leaking injectors cause a very lumpy idle! Hard, brittle, cracked injector o-rings are also antithetical to smooth engine operation.
After cleaning, none of the injectors leaked and they atomized the cleaner so well that the vapor hung in the air for a minute or more. Idle is now incredibly smooth. Smoother and faster acceleration/deceleration, no hesitation, as well. A testament to this is my wife's attempting to start the car TWICE since the injector cleaning, which is not normally a problem, except the car was already running!
Remember this if nothing else: There is NO such a thing as a clean, optimally performing fuel injector on a high(er) mileage engine, despite whatever the injector manufacturers/oil refinery folks may say about modern injectors and fuel blends, making injectors all but impervious to getting crudded up. It just ain't true.

The fuel rail is the thing that holds the injectors in place and provides fuel pressure, unbolt it. The metal rings which go from the injector body to the fuel rail just act as snap rings. They are pushed on from the side and lock the fuel rail to the injector. Most likely, the rail will have to be separated from the injectors before you try removing them. They just push into place with finger pressure (into the rail and manifold), but can become stuck with age, grunge and dried rubber. Carefully, wiggle pry or pull the injector out of its hole in the intake manifold (one at a time please).

Use the seals in the kit (Bosch injector kit, import parts house, o-rings) with a small dab of grease, vaseline or lubriplate and install them where the old ones were. There is a plastic cap that protects the injector's tip which can be replaced as well. The old one will be stuck so you may need to gently break it loose with a pair of vise grips, adjusted to just barely crush the cap slightly. Make sure to use a dab of vaseline on the end of the injector before putting the plastic cap back on, or it may split. I used a block of soft wood (pine scrap) with a hole drilled in it so the injector needle wouldn't be damaged when
pushing the tip back on. Don't bugger the end and needle, or you will be buying a new injector ($$$).

Put the injector back in its hole (again, small dab of grease) and go to the next one. Do all of them or you will cause leaks. Put the rail back in place, set the clips, tighten bolts, attach fuel line. Make sure no parts are left over. Check everything again for tightness. Attach battery. Start car. Check for leaks.

Be careful, take your time. Its not hard to do, just think and keep parts in a container as you go.

Test for a rich mixture as follows:

Disconnect the sensor lead to the control unit.
Run the engine at 2500 rpm
Artificially enrich the fuel mixture on electronic fuel injected engines by removing and plugging the vacuum line to the fuel pressure regulator.
If the voltmeter rapidly reads .9 volts, then the oxygen sensor is correctly sensing a rich mixture. But, if the voltmeter responds sluggishly, or if it stays below .9 volts, try running it at 3,000 rpm for a few minutes, then check again. No improvement means you buy a new sensor.

Induce a small vacuum leak
If the voltmeter rapidly drops to .2 volts or below in less than a second, then the oxygen sensor is correctly measuring the lean mixture. But if the voltmeter responds sluggishly, of if it stays above .2 volts, give it the 3,000 rpm treatment and try again.  If no improvement, then the sensor should be replaced.

Reconnect the sensor lead and tap your meter into the signal wire

Set the mixture to specification.
Run the engine at 1500 rpm.
You should see rapidly changing readings that average somewhere around .5 volt as the computer keeps adjusting the blend.  The sensor output should fluctuate around .5 volts. If it doesn't, replace the sensor.  Deciding whether or not response is slow enough to justify replacement requires some judgment. A common rule of thumb for minimum activity is eight trips across the rich/lean line in ten seconds, and sometimes you can find specs for cross-counts.

[Another:] A two line flush system is a must. I was selling and training the CarbonClean unit way before Motorvac hit the street. The Motorvac is a spin off the carbon clean . Any unit that uses the two line flush method is worth having done. The GM top engine cleaner and the Ford factory stuff is great chemical and should be used at a 5 to one mixture rate with the gasoline. We have done tons of reasearch on the chemicals and these passed with flying colors. Keep watching our web site for my article " fuel service of the 90's" will post at : http://www.lindertech.com/

1.  Fuel Injection Relay Test. There are 2 relays inside the fuel injection/pump relay. One of them should turn ON when the ignition is turned on (without turning over the engine), and the other relay (which actually turns the fuel pumps) should come ON when the engine turns over/runs. You can check the 1st relay by putting your fingers on the relay module and turning the ignition on and off repeatedly. You should feel the relay click on every time. If it doesn't, that relay isn't working. And you'll find the car doesn't start if the relay did not come on.

[Tip:] To check for possible fuel pump relay failure go between center of cig lighter plug and fuse 11, should be less than .5 V (<500mV). Excessive resistance creates voltage drops that will exceed these values. The volt drops will be high due to poor contact points in relays or the solder joint problems.  It is best to check these volt drops after it has run for a while as that is when the failures usually occur.

 2. Fuel Pump Diagnostic Tests.  On the 740, the fuse-box + relay box can be pulled out a little to facilitate inserting/removing relay modules. So pull it out as much as the wires will allow. Pull out the fuel injection/pump relay module. Now take a small piece of wire to jumper terminals 30 and 87/2 on the relay board (the terminals are identified on the relay module pins. The 2 terminals are the nearest left and middle right pins on the relay board). This should make the car act like the fuel pump relay is ON.

Now turn the ignition ON (without turning the engine). You should hear a whirring sound right from where you are. That will be the main fuel pump. Now go to the gas tank and unscrew the cap. Put you ear to the hole and you should hear a smaller whirring sound. That will be the in-tank pump. If you hear both noises, the fuel pumps should be OK.

To check the pumps individually, you can pull out the in-tank fuel pump fuse after you do the above test, and repeat the test.  You should not hear any whirring at the tank, but you should be able to hear the main pump.