Thread: Idle Problem

I'd be doing the rounds with a can or carby cleaner looking for vacum leaks before i touched the MAF.........

Originally Posted by Lucus

I'd be doing the rounds with a can or carby cleaner looking for vacum leaks before i touched the MAF.........

Done that a few times on mine. When I first bought it I even had the plenum top off and found one of the velocity stacks had come loose and was rattling around. Quick dab of araldite fixed that right up.

Boxer, it should only have one adjustment, a hex head bolt that sets a DC output voltage from the sensor that sets the idle carbon monoxide level (or mixture setting).

Use a voltmeter between red and black wire and blue and red wire check the voltage with the ignition on (you'll need to probe the connector somehow - I managed with trailing some wire out of the connections, but you don't want to damage the connector pins), but the engine not running and make a note in case you need to reset it. The screw allows you to set the carbon monoxide base line with these voltages. The setting of the DC voltage has no effect on the overall voltages produced by the air flow meter output for any given air flow so should only affect idle. I can't see a big problem with playing with this and it should be easy to go back to your previous setting.

Turn the adjustment screw clockwise to richen the mixture, and anticlockwise to lean the mixture. Although it will go from 0 volts to over 3.5 volts you should be aiming for something between 1V and 1.5V.

This unit has 4 connections:

Red/black is Ground
Blue/Green is the Air flow signal- should be .2-.7 volts (no air flow). Tick over on the 3.9 is about 1.7 volts
Brown Orange is +12v
Blue/red is the CO trim value.

To be clear - this will only make any difference to cars without Lambda (O2) sensors.

Thanks Ben. I'm gonna head to a makes shop to stick it on the gas analyser, will also check the fuel pressure. I'm being lazy again by saying this, but any idea what the base and vac pressures should be?

On top of that, I've had 2 specialists tell me that my MAF might be shagged and I'd be up for about $600. If that's the case, then I'm gonna jam a Microtech on it. At least then I can tune it myself.

Don't have the figures here with me, but will post later if no one else has beaten me to it.

A new MAF is expensive but you could try reconditioned ones, second hand ones and reproduction ones. Check Flea-bay. Any of the 5AM or 3AM meters should work. This one should be ok, he'll ship from the US: http://cgi.ebay.com/ebaymotors/93-19...spagenameZWD2V

To test the air flow sensors output, connect a voltmeter between the red black wire and blue green wire (sensor output). Remove the air filter and blow into the mouth of the air flow meter (into hole that runs around the edge of the air intake). At tick over the voltage is around 1.7 volts. This should jump when you blow!

Re the IACV adjustment post back a bit.

I should point out that the one I fitted is identical in appearance to the OEM Geguine Parts valve except it's plated finish & not black.

I pulled the piston out yesterday to find the pintle adjustment is different but both posts are correct ^ ^ ^.

My replacement valve is an A/Mkt one. "Standard IAC-030" which is labelled for Land Rover as well as Holden Camira JB Made in the USA, & from memory 50% of the LR price & came from "Automotive Service Solutions" Ph1300 30 40

http://www.efi.com.au/pagePartsnavSensors.php


I originally went searching for GM 25527077 or AC - Delco 217-437 & this seems to be the same one including a better price than LR Genuine Parts.

Seems like my mixtures are looking good now and from what you mentioned in the other thread Ben, it does make sense, yet the car does seem to be running leaner across the board. Yet, I might still try playing a trick on the computer to see if I can get it even leaner. Based on what this says.

Throttle Position Sensor

The Throttle Position Sensor is mounted on the side of the plenum chamber inlet neck and is directly coupled to the throttle valve shaft. The potentiometer is a resistive device supplied with a voltage from the ECU. Movement of the throttle pedal causes the throttle valve to open, thus rotating the wiper arm within the potentiometer which in turn varies the resistance in proportion to the valve position. The ECU lengthens the injector open time when it detects a change in output voltage (rising) from the potentiometer. In addition, the ECU will weaken the mixture when it detects the potentiometer output voltage is decreasing under deceleration and will shorten the length of time the injectors are open. When the throttle is fully open, the ECU will detect the corresponding throttle potentiometer voltage and will apply full load enrichment. This is a fixed percentage and is independent of temperature. Full load enrichment is also achieved by adjusting the length of the injector open time. When the throttle is closed, overrun fuel cut off or idle speed control may be facilitated dependant on other inputs to the ECU. The throttle position sensor is designed to be self-adaptive. (At least in theory, adjustment is neither possible nor necessary. This is one small advantage of the 14CUX system over the 14CU system.)

To troubleshoot the Throttle Position Sensor, first disconnect system power and then disconnect the EFI Cable Harness from the ECU. Using an Ohmmeter, verify that resistance between terminals 3 and 25 is between 4000 and 6000 Ohms. Next, reconnect the EFI Cable Harness to the ECU, and turn the ignition key switch "on". Take voltmeter readings from pin 20 to ground. With the sensor in the throttle-closed position, you should read 0.085 to 0.545 volts. With the sensor in the throttle-open position, you should read 4.2 to 4.9 volts. In between these extremes, turning the throttle position sensor should produce a smooth sweep of voltage readings.

The Throttle Position Sensor on our example system is marked "215SA", "84925A", "Lucas", "Made in UK", and "2499". It has a 3-lead pigtail on it that's about 6" long, and the 3-pin connector on the end of the pigtail is marked "Rists". The three cables to the pigtail are color coded "yellow", "red" and "green" respectively.

I technically should be able to ever so slightly back off the TPS and therefore reduce the injector open times. I guess it all just depends on making sure the TPS is within spec as per above.

Boxer, it does say that adjustment of the TPS is not possible??

However, I've got a spare TPS if you need it. I'm sure we can come to some agreement!