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Throttle Pot Sender, how, what to look for when it is failing?


Steve-B

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Hi, I've got a 2001 VHPD in our SV and I think the Throttle Pot / sensor on the throttle bodies is failing but I need someone to verify please. The car has always (Even with Caterham return spring) kangaroo'd a bit, but now...

 

Symptoms

1) can't settle in any low-speed gears at all w/o kangarooing, have to drop a gear to slow the frequency of it down

2) pootling along let's say @ 30Mph in 2nd, the engine is almost constantly "jumping", which is like really annoying in traffic

3) it doesn't completely seem RPM related, will do in 1st, 2nd and 3rd up to about 40Mph - past that it seems to settle in (mostly)

4) If moving along at a fair old clip in 5th, if you floor it there is a definite "sluggish period" then wahey it fast-forwards you.

 

There's no oil pressure or oil level issues, the engine temp is fine.

 

I had thought it was bad/old plugs so put new ones on about a month ago, but the Penn7's blat it got so bad in village today I came back early.

 

🤔 Does this sound line it is the Throttle Pot, and should I replace it 🤔

 

Edited by - steve-b on 21 Jul 2013 10:04:22

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Steve

How old is the tps ?

If it was me I would change it as a matter of course .

Mine seems to show ,as a stutter when the last one failed,it may also be worth checking the wiring as sometimes they can chaff or break *eek*

 

I'm doing mine next week *thumbup*

 

HTH

 

 

Edited by - markiebabes on 21 Jul 2013 18:20:55

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It does sound like the TPS, FWIW when mine failed I happen to have the TPS reading setup on the dash, when I pressed the throttle it would go from about 2% up to 100% instantly in the first few millimeters of pedal travel. You can imagine what the engine was doing with 100% fuel, not a lot of air and not very many revs 😳

 

Of course it was fine if you drove everywhere at WOT but that's not entirely practical 😬

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Steve

have a look on eBay 😬 *thumbup*

I found them for £25ish instead of £50ish from others *eek*

 

Relatively easy to change with laptop conected up,you just need to know what the base setting is .45v from memory if its out it won't start or run *thumbup*

 

Have a look on here for TPS setting instructions *thumbup*

 

Otherwise give John Bio a shout *wink*

 

 

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I swapped out my TPS to try and fix my hesitation / misfire problems, but it didn't change anything on my '96 1.8K.

 

After advice on here it was sorted by directly wiring my TPS to the ECU and giving it a separate earth.

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  • 4 weeks later...

Hi Mark,

 

Sorry for slow reply, I've been travelling for work. Which one on the page are you referring to? They seem to run from £15 to £90 and I don't want to get the wrong one. As an aside, do you think All Parts in High Wycombe would have them???

 

Quoting markiebabes: 
Steve

My link has expired but try here 😬 *thumbup* mine was a Freelander one *wink* Make sure it's the one with the half moon spindle *thumbup*

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If you have a scrapyard nearby, I'd go there and get one - cost me £2 the last time I went. In fact, I'd get several on the chance that one might be duff.

 

The readings I got from a known good TPS were as follows (with the multimeter on the 20k resistance scale):

 

Closed

pins 1-2 4.29

pins 1-3 4.44

pins 2-3 0.3

 

Open

pins 1-2 0.17

pins 1-3 4.44

pins 2-3 4.6

 

Hope that helps,

 

Adam

 

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  • 3 weeks later...

Hi guys,

 

New TPS installed, 85-90% of the kangarooing problem is still there after a blat out to Penn7's and a few stops yesterday. I'm totally baffled now what to do -- it's the most annoying thing I've run into in a very long time. There MUST be something else wrong, but I'm durned if I can figure it out so I'm availing myself to POBC for ideas!

 

When I installed the new TPS, I did the usual turn on the ignition, but not start, 5 full-pedal to floor pushes/releases, turn off ignition, immobilise the car which is the calibration procedure. Then I disabled the immobiliser, started the car, blipped throttle some as it was warming up, and it seemed slightly better.

 

Driving out of my house/village it seemed marginally better, but once in start/stop traffic it was back again. Where Penn7's meet is a long 30Mph zone before the pub, so even that stretch was miserable to find a throttle position that didn't kangaroo.

 

After leaving Penn7's it seemed worse, or it's just my imagination. Dropped in to see Son, came away, just has bad as before.

 

I'm seriously open to ideas, this is not a TADTS but I'm really stumped what next to look at replacing….

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Long shot this mate, but might be worth a look. Years ago and in 2 separate K engined cars I had plug lead problems that gave symptoms just like you describe, both were at about 10 years old. It appears that carbon based plug leads can deteriorate with age. As old ones heat up it results in a reduced spark presumably as resistance increases. I think it would be worth changing these if they have not been done already. Include the dist cap and arm but swap those as a pair at a different time so you can tell if it was the leads.

Cheers

Ian

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Hi Ian, interesting thought, and very easy for me to pop into Hugh Wycombe and collect at AllParts.

 

I can almost see sense in the suggestion, already have installed new plugs (correctly gapped)....

 

--------------

 

Should this not solve it is there any thought of the crank sensor on the bell housing, or is that used just at start?

 

 

 

Edited by - Steve-B on 1 Sep 2013 18:21:25

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Crank sensors are funny beasts and they do fail in odd ways. Recently seen a Merc 55 that would run for about 5 mins and then stop for no apparent reason. That turned out to be the crank sensor. Once warm it gave spurious readings. I would take it simple items first and see how you get on.

I am assuming fueling is ok and water temperature sensor ok as far as you know.

 

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Hi Ian,

 

Water temp/pressure and oil temp/pressure are both great and in normal ranges. Fuel pressure seems OK, it's definitely drinking Optimax just fine thanks :)

 

I'm going to try John's suggestion first, then do the dizzy/leads route second. If both of those fail, then the crank-sensor's the next to be replaced.

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  • 3 weeks later...

*wavey* Hi John,

 

I think you're on the right track, I spent yesterday afternoon with a mate moving all the loom around. In doing so I could see where 2 years ago when I put the engine back in that there were places where the loom & HT lead were "on top/very near" each other.

 

Moved, cable tied down took it out for a spin. HUGE improvement over where it was with a new TPS, but a small amount of hesitation left. Will get new plug leads this week + fuel filter and see how we go.

 

 

 

Quoting BIO: 
Just make sure that the cable from the crank sensor does not run close to the HT cable from the coil pack, and then check the balance of the throttle bodies .

 

John

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