Possible Symptoms Of Faulty Throttle Position Sensor

[DRIFTBOY]

Could you please tell me your experience of symptoms of a faulty TPS?

I have a running issue with my car and I'm trying to eliminate parts before I waste any more cash!

Thanks,

Martin.

[FlappySocks]

What engine? I had a bad TPS on a Megasquirt setup. Jerky & loss of power. It was imediatly obvious what was happening when I looked at the logs.

With a strandard M20, it will just cause idle issues.

[DRIFTBOY]

Sorry, I forgot that!

It's an M30 turbo on MS 3.57 with M50 TPS.

It is very jerky, but only sometimes.
Tonight though, it was almost undriveable.
It seemed happier at 4000rpm in second gear than at 2800ish rpm in third, and it cuts out whilst driving along, kangarooing down the road!

Thanks!

[FlappySocks]

Yep, sounds like a TPS. Get the one from RS Electronics. But before you do, log some data. Drive around with smooth movements to the accelerator. If it doesn't look smooth on the log, there is your answer.

[DRIFTBOY]

Thanks for that!

Unfortunately I'm a complete numpty with laptops and MS, so logging data is not in my reportoir!

I'll just try to get another TPS and try that!

If I get one from RS Electronics (I've heard of them before with regards to TPSs) will the map have to be altered?

Your advice is much apreciated!

[FlappySocks]

This is what you want. They are really good quality, and cheap. You will have to make a bracket up out of scrap metal



http://uk.rs-online.com/web/search/sear ... &x=21&y=15

No you dont need to remap anything. The only thing you have to to re-recalibrate the TPS, which takes 10 seconds. But it does involve you getting your laptop out. The same would apply to any TPS, even an M50 one.

[DRIFTBOY]

Wow, that is cheap!

That's a really great help flappy!

Making a bracket is not a problem, I'm still scared of the laptop though!

I'll cross that bridge when the TPS turns up!

[zaust]

I am trying to solve the same problem on mine. But I have now started to check the injector connections as the tps is fine !!! Might be worth a look.

[DRIFTBOY]

Thanks Marc.

I have checked all of the connectors in the engine bay, I would have thought that injectors would cause a misfire on the affected cylinders..?

Mine is all or nothing, it either goes or it don't!

I need to get the MS program on my laptop, and I think I need Winzip on there first to do that (I only have a zipped copy), maybe then I can diagnose it for certain.

[FlappySocks]

When I had a bad M50 TPS, the problem only occurred when the engine warmed up, and was most noticeable when accelerating around roundabouts. I wont buy TPS's of ebay again.

[Ant]

Martin, you can test the TPS you have with a multimeter, outer two pins 5K ohms total.

any combination of 1-2 or 2-3 should add up to that total.

TBH, having just ready your email, I'd be triple checking the CPS as it was always an issue on Toby Unnas install. Rubs away on the back of the W-Pump pulley so can be a coont to spot.

All else fails, gimme a call @ the yard

[DRIFTBOY]

When I had a bad M50 TPS, the problem only occurred when the engine warmed up, and was most noticeable when accelerating around roundabouts.

Now you say that, I didn't have the problem first thing this morning or until a few miles after leaving work!
And it was certainly bad under acceleration, I gave severall people a jump tonight with the banging from the exhaust!

Ant - many thanks for that advice, I'm going to go and take the TPS off and check it in a mo, and check the CPS lead again (that was a thought I had but I didn't see anything last time).

I looked at my email after sending it, sorry if it came across as an abusive rant, it certainly wasn't meant to be, and I was a bit drunk and still furious with my car at the time!

Thanks guys!

[DRIFTBOY]

CPS lead is fine, and I've routed it past the inside of the bottom hose, so it's miles away from the water pump pulley, and the sensor is the correct distance from the trigger wheel (although I suppose I still can't rule out CPS related just yet).


The TPS at the outer pins reads 3.65 ohms, 1-2 3.8 ohms and 2-3 1.87 ohms.


RS Electronics are about to receive an order!

[DRIFTBOY]

This turned up today;

(My M50 one on the right).



Superb service from RS Electronics!

The mounting lugs are the same distance apart as the M50 TPS, so no new bracket needed!

I wired it in and now the engine will turn over but won't fire, or even hint at firing.

Normally when it's cranking the rev counter needle will flick around, but it's now not moving at all.

So, could the TPS not being reconfigured to the MS cause this, or is it more likely to be a fault with the ignition side of things?

Thanks!

[FlappySocks]

Even if you haven't calibrated it yet, I would have expected something to happen. Sure you wired it in right?

I know you dont like computers, but in Megatune/Turning/Realtime Display it will show you what your accelerator peddle is doing.

[DRIFTBOY]

Wow, thanks for the speedy reply!

I have come to terms with the fact that I am going to have to learn how to get my laptop communicating with the MS, I feel I might get rather frustrated tomorrow!

I haven't even managed to get Megatune on to my laptop yet!

I'm not sure I did wire it in right, I kind of assumed (possibly very wrongly!) that the wires are in the same order as the M50 one..?

I'm starting to think that I might be barking up the wrong tree here, or that there is more than one fault to deal with perhaps.

[FlappySocks]

You will know in an instant if you wired it right if you can get your laptop working.

Maybe Ant is right, and it's a CPS problem. No spark without a working CPS. The laptop will help diagnose that too. Also, check to see if the fuel pump remains running when you crank the engine. if the fuel pump stops after a few seconds, it's not getting a signal from the CPS.

[DRIFTBOY]

Yeah, I'm going to make an effort tomorrow to get my laptop chatting with the MS, even though I hate computers and they hate me back!

I have a spare CPS, so I might try that too if I have no joy with the TPS, even though the lead runs nowhere near the water pump pulley and doesn't appear to be damaged.

That's handy to know about the fuel pump, I didn't know that.

Thanks again!

[carannc]

I have recently downloaded tunerstudio software for MS, its really simple to set up and will detect your MS simplyfing it alot. I would also look at the front toothed pulley to ensure the rubber has not given way and scuppered all your timing. Look for any shiny teeth on the pulley as it may be rubbing on the CPS.

[DRIFTBOY]

Cheers carannc, trigger wheel / pulley are fine.

Well I've been outside in the glorious sunshine today for some more tinkering.
I've not yet got the laptop thing sorted but...

... I put the M50 TPS back on, changed the CPS and it started!

However, I believe this was purely coincedence, as it soon stopped again.

Then it started again, and I noticed that when it was idling that if I tapped the TPS just lightly (not whacking it!) the engine almost stalled.
So I re-wired in the RS Electronics TPS and it passed my highly scientific 'tap test'!

So, I ran the car round the block and....

... it stopped again!

When I got it back home again I noticed something else, if I gently tapped the MS unit with a finger whilst it was idling the engine almost cut out again.

So, could it be that I had a faulty TPS AND a bad connection in the MS..?

I'm going to have a play with the laptop now!

[blingsta]

Cheers carannc, trigger wheel / pulley are fine.

Well I've been outside in the glorious sunshine today for some more tinkering.
I've not yet got the laptop thing sorted but...

... I put the M50 TPS back on, changed the CPS and it started!

However, I believe this was purely coincedence, as it soon stopped again.

Then it started again, and I noticed that when it was idling that if I tapped the TPS just lightly (not whacking it!) the engine almost stalled.
So I re-wired in the RS Electronics TPS and it passed my highly scientific 'tap test'!

So, I ran the car round the block and....

... it stopped again!

When I got it back home again I noticed something else, if I gently tapped the MS unit with a finger whilst it was idling the engine almost cut out again.

So, could it be that I had a faulty TPS AND a bad connection in the MS..?

I'm going to have a play with the laptop now!

im sure i mentioned in another thread that the problem could be inside !.. poss a coil driver? i take it you didnt open up the m/s ?

[DRIFTBOY]

I haven't touched the MS, I'm too scared!

I was thinking possibly coil driver too, it's in a non-starting mood again at the moment and has no spark at the plugs.

[DRIFTBOY]

Well after confirming today that it's safe (or rather safe-ish with my ham-fisted way with electrical stuff) to fiddle with the MS I decided to have a good look at it.



And I can't find anything wrong, nothing smells burned and the wiring connections all look good to me.

Anyone want to buy an E30 turbo?

[FlappySocks]

Tell me you put a laptop on this first before pulling it apart?!

Is the CPU firmly plugged in? Send it to me if you like. So long as you cover return postage, I have a test rig I can put it on.

[fowler]

thats the warrenty void then Lol !!!
should of taken it to Ant !!! me thinks

[FlappySocks]

Looks like one of my early DIY kits. Too late to test now, but a common mistake was to not drill the holes for the drivers cleanly. Stray bits of metal would break though the insulation and short the drivers. Running a large drill bit over the holes to coutersink them solves that problem.

[DRIFTBOY]

Thanks for your time and help guys.

No I didn't get a laptop on it, and even if I did I'd probably still be clueless as to what I was looking at!

Yes the warranty is probably void, if there was one!?

And it'll be difficult to arrange taking this to Ant as I can't drive my car, even with the MS unit built up!

I'm confident the unit ws built to a high standard (I didn't do it!), but it just seemed strange that if I lightly tapped the unit with a finger when the engine was idling the rev counter briefly dropped to zero and it almost stalled.

Trouble is, testing for an intermittent fault with multimeters etc. is very trickey!

[winx]

Anyone want to buy an E30 turbo?

Yup

[DRIFTBOY]

Anyone want to buy a whole heap of trouble?

Nope!