Evenin all,

 

My car has a history of idling high (2000rpm) and I thought I had cured it with a replacement idle valve but the problem has returned, only this time it seems to be intermittent and sometimes has a bit of hunting. I have just got in after carrying out an ecu diagnostic check (got a code 55, happy days) and also checked the o2 sensors. From my understanding the left o2 sensor is constantly lean (engine light is always off) but the right is fine (engine light blinks). Could this be the cause of the high idle? Are the connectors for the o2 sensor reachable (if so where are they?) or do they go straight to the ecu?

 

Any help much appreciated because this problem is really beginning to get to me :smash:.

 

ps I have cleaned all connectors (maf, TPS, idle valve etc, and fitted a series 2 PTU) and throttle bodies.

 

cheers :duffer:

 

Alex

Evenin all,

 

My car has a history of idling high (2000rpm) and I thought I had cured it with a replacement idle valve but the problem has returned, only this time it seems to be intermittent and sometimes has a bit of hunting. I have just got in after carrying out an ecu diagnostic check (got a code 55, happy days) and also checked the o2 sensors. From my understanding the left o2 sensor is constantly lean (engine light is always off) but the right is fine (engine light blinks). Could this be the cause of the high idle? Are the connectors for the o2 sensor reachable (if so where are they?) or do they go straight to the ecu?

 

Any help much appreciated because this problem is really beginning to get to me :smash:.

 

ps I have cleaned all connectors (maf, TPS, idle valve etc, and fitted a series 2 PTU) and throttle bodies.

 

cheers :duffer:

 

Alex

 

Alex,

 

A faulty O2 sensor could well influence the idle of the car as it is sending incorrect information to the ECU (which in turn has control over the idle valve). Couple of things for you to check first -

 

(1) base idle: disconnect the yellow connector on the idle control valve and see what the rpm's do. Idealy they should sit at 850~950rpm for a TT. If not, get a screw driver and adjust the idle to that level and reattach the yellow connector.

(2) TPS: cleaning the connector is good but won't help if the TPS is set incorrectly. Easiest way to check the voltage is to connect a ConZult or Blatz diagnostic kit to the car. Failing that, do a search for "TPS voltage setting" on this forum and a writeup will come up showing which terminals to check using a multimeter. Although the range of operation is more important to the TPS, the voltage (at idle) should be around 0.40~.042V. If you haven't got a multimeter, then loosen the two bolts holding the TPS to the side of the throttle body (don't remove them) and slowly turn the TPS until you find that the rps increases. Now turn the TPS back SLIGHTLY to the point just before the rpm's increase and secure the TPS. Now you must turn off the engine, disconnect the black connector of the TPS and turn the engine on (but don't start it). This will clear the values stored in the ECU. Reconnect the TPS and start the car to ensure it still idles at 850~950 rpm.

(3) Boost leaks: boost leaks can affect idle as well. Go around the engine bay using a stethoscope (if you have one otherwise stick a piece of vacuum tubing in your ear and go around the engine with the other end but DONT connect it to anything as it is likely to cause damage to your ear). It could be a hearline tear in a pipe or perhaps a clip has come off somewhere.

 

As for the O2 sensors: have a look in the FAQ section of this forum and look for the "engine by numbers" thread. There you'll find a picture with all the connecors labelled. Basically, the O2 sensors have a connector each at the to of the engine at near the fire wall. You'll find three identical looking connectors - one is for the knock sensor (and has 2 wires), the others are for the O2 sensors and have 3 wires (black, red, white).

 

If you need to replace the sensors then I've got a brand new pair in stock at about half the price that Nissan charges (£120/pair from me vs £110 each from Nissan). I would suggest you replace the pair (if necessary) to avoid having the other one go in the future.

 

Hope the above is of some use to you.

 

Regards,

 

Dan

Hi Alex,

 

As far as I am aware, the light on the ECU/engine light should flash on and off 5 times or more within 10 seconds at 2K revs for both sensors if they are functioning correctly. If one of yours isn't flashing at all, it certainly ain't gonna help!

 

Have a look at EF & EC-47 onwards in the service manual if you haven't already. It shows you exactly how to get it into diag mode 2 and what should be happening when you check your O2 sensors.

 

Hope this helps!

I know it sounds obvious, but have you got a really good connection on the temp sensor? Mine was clean but still ticked over too high intermittently, because the fan would blow the old brittle connector apart slightly. Since clamping the connector tight (a 4 tie wrap knot) it's been idling perfectly again. I know it's obvious but thought it might help.

Dan: cheers for all the info. I will set the idle and TPS correctly anyway but i have an NA so need not worry about the boost leak. Kinda hope cleaning the o2 connectors will help because the problem is intermittent but I will contact you if i need a pair.

 

Splitfyr3: checked the pages you suggested fairly certain i've done the diag correctly. Unfortunately points to a left o2 sensor constantly lean :(

 

Trevz: interesting point. The yellow conector on the temp sensor has broken so I can't use the metal clip to keep it in place. Think I'll use your idea and see what happens.

 

Cheers guys, I have a few things to check/do now that will hopefully cure it. Bloody car has been running perfectly today tho :D

 

Alex

but i have an NA so need not worry about the boost leak.

 

 

Boost leaks are not exclusive to TT's - every car has vacuum hoses and pipes all over the place. Perhaps better terminology would be a "vacuum" leak. ;)

 

HTH

 

Dan

Think you can buy them nissan yellow plugs new from somewhere maybe nissan ,and solder on to old wires and re loom up with black insulation tape .Saves cable tieing .

Think you can buy them nissan yellow plugs new from somewhere maybe nissan ,and solder on to old wires and re loom up with black insulation tape .Saves cable tieing .

 

Yeah I'm sure I've seen them somewhere but that would then expose my terrible soldering skills lol!

 

Chcked the TPS today (voltage was spot on already) and set the base idle although it didn't need adjusting much. Fairly certain that there is a loose connection somewhere because the car has been fine for the last 2 days. Think all I can do is wait for it to go wrong again and then try fiddling with it.

 

Thanks for the help guys.

 

Alex

Fairly certain that there is a loose connection somewhere because the car has been fine for the last 2 days.

 

I think that kind of points to the ECU water temp sender contact (the yellow one on the water pipes). If you need a new one I usually stock them (although I've been cleaned out this week). New stock should be arriving in the next 10 days. £22 for the new sender and £20 for the connector and wiring harness (you'll still need to solder or crip on the wires). Check out http://www.smithys-place.co.uk/oem.php for more info. The image is for illustration purposes only but the blue connector now replaces the yellow one.

 

Regards,

 

Dan

I think that kind of points to the ECU water temp sender contact (the yellow one on the water pipes). If you need a new one I usually stock them (although I've been cleaned out this week). New stock should be arriving in the next 10 days. £22 for the new sender and £20 for the connector and wiring harness (you'll still need to solder or crip on the wires). Check out http://www.smithys-place.co.uk/oem.php for more info. The image is for illustration purposes only but the blue connector now replaces the yellow one.

 

Regards,

 

Dan

 

I have changed the sensor but the wiring harness conector is damaged so the metal clip is useless and it could just have been coming apart. I have just used the ty-wrap method suggested by Trevz to see what happens but it does look a tad messy so wll be something I will attend to in the future.

 

Cheers

 

Alex