low RPM problem - automatic

[JS2004]

Im about to go out there with a paperclip and try to fathom out the diagnostic port error codes method but wanted to quickly check here too.

 

Car - jspec n/a automatic

 

Background:

 

Car had frontal impact and went in to be fixed. Damage was to front bumper, crash bar, slam panel / front panel. The radiator support also took a little hit.

 

Just go it back, new bonnet, bumper, front panels, radiator support all fitted. Bodyshop said they had to do something with radiator so they took it out, its since been refilled with coolant and left overnight etc to check for no air pockets. (I was told the old coolant looked like gravy). The Air Con has also been emptied and I chose not to have this refilled at this time.

 

Issue:

 

Was moving out of bodyshop, noticed the RPM counter dropped a bit.

 

In neutral RPM settles around 750 which is what it always used to do. I put it in drive with foot on break and rpm slowly drops to roughly 400/500 mark. You can feel the car "juddering" a bit.

 

When driving normally its fine, but when i have to come to a stop the issue returns - tested in L 2 and D - same issue - as well as in reverse. Only way to stop the juddering is to stick it into neutral when stopped. It judders when moving with foot off break and not on accellerator also.

 

Im not too good when it comes to engines - but from the searches ive done it seems it could be linked to the throttle position sensor

 

 

As mentioned above im about to go out there with a paperclip and see if I can get this diagnostics port to work. I know the battery has been out because the clock has reset.

 

Anyone experienced this type of issue in the past and would have a few tips for me to try?

 

Cheers guys

 

Been out to check the diagnostic port.

 

Connected the E1 and TE1 as suggested in the diagnostics port thread - but the orange engine warning light just continually flashes - which as far as I can tell means that the ECU is not recording a problem.

 

What is interesting though is that the OD OFF light is flashing continually. It stops and stays constant once I turn OD off via the shift stick, but comes back on once I put OD back on. As far as I am aware I have not had any delimiter fitted and the car is still recording in KPH which is what similar OD flashing threads suggest.

 

In neutral / Park its hitting around 750 revs and slowly drops to 700ish. Drive / Neutral / 1 / 2 all drop the revs to around 500ish, and the car is noticably juddering and shaking, almost as if its on the verge of stalling itself.

 

I have also noticed two "connectors" which dont seem to be connected to anything near the front of the car, going to add pictures incase anyone can identify those.

 

Would appreciate any help.

 

Further edit - Could this be caused by the idle control valve? There is also a possibility it is a coolant temp sensor?

 

I have attached two pics showing what looks like a connector of some sort but I cannot seem to identify what it is.. Im hoping its something that should be plugged in which will fix this problem.. but thats probably wishful thinking on my part.

 

Cheers

Edited October 30, 2009 by JS2004 (see edit history)

[JS2004]

Been out trying to sort it not making any difference.

 

Would spark plugs be a culprit here? Apparently it needs new plugs, or at least thats what the guys that the bodyshop took it to when they were checking the coolant didnt have any air pockets.

 

Im contemplating taking it to a garage but I want to have a good idea of whats wrong with it first so I dont end up paying for stuff I dont need that doesnt fix the problem.

 

I also cant seem to find there the idle control valve is on an N/A via searches - as it looks like cleaning that out is worth a try. I seem to have learned where it is on a TT engine though..

 

Any ideas more than welcome

[Ian C]

Won't be plugs. Might be the idle control valve, you can find it bolted on the back of the intake plenum, between plenum and engine - it's mostly a stepper motor and a big black hose. Six pin connector on it.

 

It also might be your throttle position sensor isn't adjusted right and it's never engaging the "closed" switch, so the ECU doesn't go into "idle" mode and compensate for being in gear. You'll also find on the overrun that the exhaust might pop somewhat as another function of the throttle closed switch is to cut the injectors if the revs are above about 2000rpm. If that doesn't happen, unburnt fuel ignites in the exhaust (and emissions go up and economy down but you'd be hard pushed to spot that).

 

The TPS is adjustable. Loosen the screws and while it's idling, try rotating it to each extreme, see if one of them changes the engine revs significantly.

 

-Ian

[JS2004]

Thankyou Ian,

 

I will give that a try tomorrow - once I find the TPS

 

Unfortunately I managed to leave the supra manual that I had on CD format at the bodyshop so ill retrieve that tomorrow to help me find where the various parts are.

 

I have found the throttle cable, which is on the top near the back of the engine (towards windscreen) so would probably start looking around there first.

 

The way it feels when driving is that its not putting itself "out of gear" when I have come to a stop.

 

Just to check, changing the TPS wouldnt mask a bigger problem would it? It just seems weird, the impact to the front didnt hit anything major except the panels and rad support. It did have coolant replaced though - and this was not happening prior to the bump.

 

I appreciate your help

[devan]

I had this on my 94 NA Manual.

 

I dont know if this was the problem, but it hasnt done it since.

 

The perious owner had wired up a speedo converter and a de-limiter. However, when i test drove the car to see if it was actually de-limited, it wasn't. I took the speedo cluster out, and found that the wire which goes to the ECU from the de-limiter box had not been connected. So i simply connected this to the ECU. And at the same time, noticed that my car no longer idles low.

 

Worth a look to see if yours is wired up right maybe. But i cant really see how this would affect the revs tbh.

[JS2004]

Had it in a garage today for a quick check, they couldnt find the problem.

 

One of the guys suggested it is maybe a loose hose fitting causing a vacuum issue. When it gets fixed ill post up what it actually is incase others come across this problem.

 

Im still not able to figure out where that plug should be going though (in the attached pics).

 

*edit - I checked the wires as you suggested but nothing there - definately not been delimited.

[Metallikev]

Just a thought, but was the battery removed while they were doing all the work?, i'm no expert by all means but my TT is lumpy for a while after an 'ecu reset' so to speak. Give it a drive about for a bit, might be worth a try.

[JS2004]

Hey Kev,

 

Yeah that crossed my mind, ive been to town and back a few times to try and run it in but the hotter it gets the worse the problem is. I didnt want to go too far just incase it stopped working.

 

Im hoping its a case of it not been put back together correctly. that loose plug is still bugging me though - I think ill get some more pics of it. It must go somewhere..

[JS2004]

Update on this incase anyone has similar problems:

 

The missing plug has been identified as the 2nd horn which means its got nothing to do with this problem unfortunately..

 

The cars in the garage at the moment and the mechanic called this morning to let me know what he has found.

 

He thinks that we have a misfire issue and is in the process of sorting out new plugs / cables etc (not sure which parts we need to sort a misfire out - any part numbers?) From other threads seems to be coil packs?

 

Im still stumped as to how this happened. The bodyshop that fitted the bumper had to take the radiator out etc but I didnt think they would have touched bits to cause a misfire (but then again my knowledge is low and limited on engines).

 

He said once he gets the new bits he will do a compression test and see if its fixed it. So I have my fingers crossed that this is the problem.

 

Fuel consumption has gone up a lot ive noticed, not sure if this is related though.

 

I remember that the bodyshop guy said the mechanic they took it to for the coolant said I needed new spark plugs too, so that could also be related. I know theres a guide here somewhere on which plugs to buy so ill have a look at that =)

 

Apart from the above issue, the mechanic who has it at the moment said the engines in great condition especially considering its age =)

[JS2004]

Had a thought - if its a misfire would that not be giving me an ECU error code when I check the diagnostics?

[madwoody1]

don't think mine had a code when i had a misfire they where new standard copper (i think) plugs, had them replaced again with IRIDIUM ones problem was sorted, from what my mechanic said don't try to change the gap because they are factory set and the tip is so small it can be damaged when the gap is changed and i haven't had a problem since

 

 

the mechanic who has it at the moment said the engines in great condition especially considering its age =)

 

the engines are so strong mines done 138k miles i fitted new stem seals but thats it

Edited November 7, 2009 by madwoody1
updated (see edit history)

[dude]

Dude take it somewhere that knows these cars the bodyshop will be trying anything they can think of to get it running right which may end up costing a lot in the end.

Your coil packs cannot 'go down' while its in a bodyshop and if they were faulty it would not show up on tickover before it showed up under boost.

On an older car just turning upthe tickover would sort this out.

[JS2004]

Thanks for the replies chaps

 

As far as the spark plugs are concerned I think ill be replacing those soon, just so I know they have been done - either platinum or iridium as suggested. (lacking a service history)

 

Ive taken it from the bodyshop and its currently in the hands of a mechanic that is more of a family friend at the moment.

 

Its not a turbo dude just an N/A for now. I know of one place in this area that does deal with Jap cars, so if my current mechanic tells me hes not sure I will take it down there - I took it to him first more as a precautionary measure.

[JS2004]

Just a quick update here should anyone else find themselves in my position.

 

I had the spark plugs changed out for new platinum ones - thread where I attempted this is here : http://www.mkivsupra.net/vbb/showthread.php?t=202418 (I ended up taking it to the garage anyways, as lacked tools, and wanted the break/fuel line to be checked on ramps).

 

At the same time I also replaced the spark plug leads with a set I got from Keron (I was not going to pay £100+ for new ones as I did not know if this was the actual problem, it may actually have just been plugs).

 

Anyways the old plugs were a bit nackered so now it has the nice new plugs in and its running like a dream, better than when I first got it. The difference is noticable (though it may just be me thinking it is given that it no longer near-dies at lights).

 

So for anyone who has low RPM problems on idle as described in this thread, plugs may be an area to think about checking along with the various other possibilities such as vacuum hoses / clogged idle control valve / buggy throttle position sensor etc.

 

Hopefully this helps - thanks again to everyone who contributed

Edited November 17, 2009 by JS2004 (see edit history)

[Abz]

JS, Thanks for regularly updating your thread, this is very helpful.

 

I think I might be having similar problems to you, though on a TT Auto.

I had my car serviced recently & just the other day from driving it from Milton Keynes & waiting for the car to cool down I noticed it revving pretty low (300/400 RPM). I then drove it again tonight & noticed it again while I put it in park.

 

One thing I did notice though was the car is not starting up as strongly if you like (Maybe all cylinders are not firing?) and when you switch the engine off it seems to do it quickly (Sounds pretty odd).

 

Will have another look tomorrow & follow your sugguestions.

[JS2004]

Hey Abz,

 

I hope this lot does help. Whilst finding out info for myself on this there was a lot of info on TT`s in comparison to N/A`s. There was a thread (I think by IanC) about how to refurbish the coil pack connectors that the TT has, as the connectors sometimes dont form as good a connection as they should.

 

When I had my problem in P / N the revs went up slightly and the juddering stopped (settled around 650/700) but as soon as it was in gear at standstill the revs dropped, a deep humming sound was heard and the car started to judder. The juddering got gradually worse until the full car was "pulsing" and the steering wheel was shaking up and down. Was weird!

 

Im not sure what the standard idle values for a TT are - did you get any error codes from the ECU?