Hello fellow Z enthusiasts.

 

I have a TT auto 91 import....heres my problem with her :confused:

 

I recently blew the auto box and had this replaced with a second hand unit, since this (I mention the above although it could be coincidental) I get erratic tick over in drive and reverse only when stationary!!If I let the car roll then the revs settle down straight away, apply the brake and draw to a halt and the revs fluctuate sometimes to 300rpm and even to stall! I have changed the IAA valve and cleaned up all the contacts too.I have also cleaned up the TPS connectors too.Once under way the car acts perfectly and seems to be working fine,come to a T junction and Im having to put her into neutral to alleviate the wild idling.

Is there any sensor on/in the auto box that may be broke you think? torque converter?

 

Please help, any suggestions gladly recieved!

 

GaiJin

check your afm it sounds like its overfuelling when stationary but receiving more air when moving

Worth a try, but what makes me doubtful-and Im no expert at all- is that Im just allowing the car to slowly move off by removing my foot off the brake and the problem goes,Im not even accelerating at all.The same is true when I run her and allow her to slowly draw to a halt in drive position.As soon as shes stood still I have the problem :headvswal Doh

 

Thx for your speedy reply btw

 

GaiJin

sounds like the gearbox/tc is not disengaging (properly) at low revs ...

could be anything from incorrect TPS voltage to mechanical problem in the gearbox/tc.

 

see if selfdiagnosis of the AT-ECU gives a clue on where to look

Thx Lymon, actually I had the car in for a diagnostis check and a specialist centre locally a few weeks back to see if they could find the fault.The engine seemed to check out sweet but he did say that the autobox pressure readings were all over the place...problem solved I hear you say! I then visited my local Autobox guru and he said that nobody could accurately read autobox pressure readings and that my problem DID lie with the engine (probably the IAA valve) and threw the whole thing into doubt.

 

Thank you for your response and advice mate!

 

GaiJin

Dunno if this is associated with the problem but when revving the engine,the rev counter needle dips for a fraction of a second before the engine revs.Could this be a vacuum problem u think?Could this also be part of the idling problem too?

 

Many thanks

 

GaiJin

Watch the box is not overfilled! I also had mine replaced and the engine will stall when you came to a stop when its cold unless you popped it in neutral. This problem disappears when its warm so I dont bother about it but I can see on the dipstick that the oil is overfilled. Also if i drive enthusiastically as it were the auto dipstick pops up.

 

Maybe I should siphon out the excess!

 

Other possibilities might be air leaks in the small vacuum hoses about the engine - maybe one was nipped or cracked when the engine was tilted back to drop the box.

Thx WillieO, Ill go have a good look around the hoses although I havent initially spotted or heard anything.What you said about the oil overfill is certainly worth a look,I hope that this is indeed the problem...fingers crossed ;)

 

GaiJin

Thx WillieO, Ill go have a good look around the hoses although I havent initially spotted or heard anything.What you said about the oil overfill is certainly worth a look,I hope that this is indeed the problem...fingers crossed ;)

 

GaiJin

Checked the oil level and found that it need .50 ltr to bring it up to the mark.

 

Did an ECU diagnostic...code 55 everything ok, went on to do the left exhaust gas sensor and got the 5 flash ok signal.

I then carried on into the right side diagnostic,revving at 2000rpm as before, and got the 2 flash indication that the ECU was now monitoring the right side ...but got no other code.Could an exhaust gas sensor be giving me these problems as previosly described?

Oh btw....even though I topped up the auto box its not made any difference :(

 

GaiJin

Just a thought - like many other cars this will have a "moving" sensor (from the speedo, or gearbox or whatever) that determines whether the car is stationary or not, and adjusts the idle revs accordingly. If you are coasting the revs will be slightly higher than if stationary. Don't know whether this ties in with your "pulling away everything is ok" statement. In addition, do you get the same problems with the AC running (which also raises the revs) or when you change to engage reverse from neutral, or when the steering is operated at idle?

 

In any case, is your idle actually adjusted correctly (i.e. with the IAC disconnected)? And is the IAC connected correctly - I think this can sometimes be misconnected to the VVT solenoid and vice versa!

 

Like I was saying - just thoughts.....

You sure the auto box needed topping up? These dipsticks are hard to read with hot clean new fluid. But I think it needs to be read hot with the engine running.

 

I feel sure the stalling I have when cold stopping is caused by torque converter drag or clutch drag rather than an electrical or fuel issue. I am also sure that the fluid in mine is too high but maybe this is not connected with the stalling when cold. I just keep knocking it to neutral when I pull up when its cold.

 

As for your o2 sensors check each connector for green oxide. One of mine wasnt reading but after cleaning the pins on the connector on the NHS battery side one it came back to life. Even when it wasnt right it didnt cause rough idling, I had what seemed like a misfire or judder under load that turned out to be connected to the old box being about to die.

You sure the auto box needed topping up? These dipsticks are hard to read with hot clean new fluid. But I think it needs to be read hot with the engine running.

 

I feel sure the stalling I have when cold stopping is caused by torque converter drag or clutch drag rather than an electrical or fuel issue. I am also sure that the fluid in mine is too high but maybe this is not connected with the stalling when cold. I just keep knocking it to neutral when I pull up when its cold.

 

As for your o2 sensors check each connector for green oxide. One of mine wasnt reading but after cleaning the pins on the connector on the NHS battery side one it came back to life. Even when it wasnt right it didnt cause rough idling, I had what seemed like a misfire or judder under load that turned out to be connected to the old box being about to die.

 

Thanks for the help guys,I havent had the aircon on or indeed tried it with aircon on but will do so. When I blew the old box the garage that replaced the box for me I suspect used the old torque converter :rolleyes: .

On the dipstick, theres a mark for hot on one side and cold on the other and dipped it 4 or 5 times to be certain of the reading-as you say with clean fluid its hard to tell!

Can you tell me the location of the sensors Willie?

 

Thanks for your help I really appreciate it.

 

GaiJin

Just a thought - like many other cars this will have a "moving" sensor (from the speedo, or gearbox or whatever) that determines whether the car is stationary or not, and adjusts the idle revs accordingly. If you are coasting the revs will be slightly higher than if stationary. Don't know whether this ties in with your "pulling away everything is ok" statement. In addition, do you get the same problems with the AC running (which also raises the revs) or when you change to engage reverse from neutral, or when the steering is operated at idle?

 

In any case, is your idle actually adjusted correctly (i.e. with the IAC disconnected)? And is the IAC connected correctly - I think this can sometimes be misconnected to the VVT solenoid and vice versa!

 

Like I was saying - just thoughts.....

 

 

Stuart, by IAC you mean Idle Air Connector on the IAAC valve right? The answer is no I didnt :headvswal and am unsure of the correct procedure if you can help mate.I can say however that before I had exactly the same problem before I changed the valve and had the vehicle through a complete diagnostic check the result of which was that the engine was running and set up perfectly. I do find your theory of the motion sensor interesting,Ill look into that!

By 'when pulling away everything ok' statement I clumsily meant that once moving the revs rose and fell with acceleration/deceleration/gearchange seemingly perfectly.

As mentioned before, when I have the car in neutral or park and rev it (warm) the engine halts for a split second before it revs-sometimes momentarily down to 300 rpm is the root of my problem or maybe Ive two problems with the car at the same time aarRRGGGgghh!!

Many thanks for your assistance my friend.

 

GaiJin

Can you tell me the location of the sensors Willie?

 

 

The O2 sensors themselves are in the erxhausts right after the turbos on the downpipes. They have a length of cable up to the connectors. The connectors are white plastic with 3 wires in and out. These wires are red white and black iirc.

 

The nearside connector is towards the rear top plenum battery side. The offside one is down the side of the plenum about midway I think. Once you spot the battery side one you can find the other side one easily. You can carefully disconnect them and check the connections inside. All connections on these cars are brittle with heat and age and maybe some green oxide on the actual connections.

When I adjusted my tickover I did the following:

 

1. Get the car to operating temperature (doesn't take long!!!)

2. Turn off and then disconnect the IAC connector - this can be a bit fiddly, and if the car has run for a while be prepared for hot hands.......

3. Restart the car and tweek the idle control screw (on the IAC thingy somewhere) to get a good tick-over. I purposely set mine a little higher than the standard 750rpm - about 850 I think is what I set.

4. Reconnec the IAC, and do an ECU reset for good measure. Don't forget to give it time for the ECU to relearn and settle.

 

As an aside, if the problem isn't too major you may be able to get away with a real simple fix that worked for me - I just lashed in some fuel injector cleaner into the petrol - double dose to start, and then normal dose with each refill. This has worked wonders on my 300 - smoother idling, good power delivery, better economy (like it really makes much difference!). I use Redex!

 

I used to get idle problems turning the AC between Econ and Normal, and when engaging reverse. Now everything is totally sweet!

 

Good luck

 

StuartR

 

(and perhaps you may want to consider subscribing ;) )

 

Stuart, by IAC you mean Idle Air Connector on the IAAC valve right? The answer is no I didnt :headvswal and am unsure of the correct procedure if you can help mate.I can say however that before I had exactly the same problem before I changed the valve and had the vehicle through a complete diagnostic check the result of which was that the engine was running and set up perfectly. I do find your theory of the motion sensor interesting,Ill look into that!

By 'when pulling away everything ok' statement I clumsily meant that once moving the revs rose and fell with acceleration/deceleration/gearchange seemingly perfectly.

As mentioned before, when I have the car in neutral or park and rev it (warm) the engine halts for a split second before it revs-sometimes momentarily down to 300 rpm is the root of my problem or maybe Ive two problems with the car at the same time aarRRGGGgghh!!

Many thanks for your assistance my friend.

 

GaiJin

before adjusting idle in any way, make sure that :

 

A. throttle position sensor is registering approx. 0.4V at idle and 4.0+V at wot.

B. the closed throttle switch is "on" at idle and "off" as soon as you touch the throttle.

(if it isn't, disconnect the "seperate" connector on the TPS while the engine is running, wait a few seconds and reconnect it.)

C. preferably ECU selflearn levels have been erased (with a conzult or by disconnecting the battery for a few hours)

 

While adjusting idle, it's best to turn on the lights and set the heater on max blow (ECON mode) or just set the idle to approx. 850rpm. (which is about 100rpm higher then the recommended idle rpm)

 

-Eric

When I adjusted my tickover I did the following:

 

1. Get the car to operating temperature (doesn't take long!!!)

2. Turn off and then disconnect the IAC connector - this can be a bit fiddly, and if the car has run for a while be prepared for hot hands.......

3. Restart the car and tweek the idle control screw (on the IAC thingy somewhere) to get a good tick-over. I purposely set mine a little higher than the standard 750rpm - about 850 I think is what I set.

4. Reconnec the IAC, and do an ECU reset for good measure. Don't forget to give it time for the ECU to relearn and settle.

 

As an aside, if the problem isn't too major you may be able to get away with a real simple fix that worked for me - I just lashed in some fuel injector cleaner into the petrol - double dose to start, and then normal dose with each refill. This has worked wonders on my 300 - smoother idling, good power delivery, better economy (like it really makes much difference!). I use Redex!

 

I used to get idle problems turning the AC between Econ and Normal, and when engaging reverse. Now everything is totally sweet!

 

Good luck

 

StuartR

 

(and perhaps you may want to consider subscribing ;) )

 

Hello Stu, thanks mate...The IAC connector,is that the light blue plug or the yellow one below it? Thx for the assistance mate.

As for subscribing, yer its been remiss of me and its the least I can do for the help Ive had from the forum.

 

GaiJin

Update*

 

I cleaned up the terminals and connector on the engine temp switch today and since that the problem has gone! I will have a good run round in her tomorrow and confirm.It may be just coincidental and the problem may be back tomorrow but I will endevour to post any new findings in an effort to assist some other unfortunate soul digging this thread from the archives!

 

Thx for all the help Ive received :bow:

 

GaiJin