Throttle position sensor on 1998 2.5 v6 Auto Petrol

[sp2cpss]

Hello Forum folk,

I am hoping you can help me with diagnosing a problem on my 1998 2.5 V6 Auto petrol Bongo. My Bongo is behaving a little sluggish and the revs varying, they drop even lower when reversing. Also it seems that the problems only really start happening when the vehicle has been running for 5 minutes. I will put my foot down a little on the accelerator to increase power a little, say when exiting a roundabout, not to kick down but just to speed up and nothing happens so I press a little more and the next second the revs jump to 3000 and its off like a shot. After doing much reading on the web about possible reasons why a little I decided to lift the seats and have a look myself.

First thing looked at was the plugs, I removed all 6 and replaced with new. They seemed to be black although not fluffy stuff so perhaps it is running a little rich, I reckon it has been drinking a bit more than usual lately too so might fit. However changing the plugs has made no obvious difference. I inspected the leads too and they look in reasonable shape, no splits etc.

I checked the air filter and this was in good shape too.

I have also took up the slack in the throttle cable (not to piano wire standard mind)

I read about the diagnostic port and connected up an LED and made necessary loop to look at the engine codes, there were quite a few and some could have been old so I cleared them out and am now left with the following, 11, 12, 15 and 11 again it seems.

The throttle position sensor shows up in the diagnostics (12) so have made various measurements to see if it is perhaps that and this where I really need some help.

Ian kindly sent a few pages from a workshop manual and although slightly different to my setup it did help me make the necessary measurements. So with the connector to the TPS disconnected then I have the following voltages on the four connector pins:

~0v on pin number 4 (black/blue)
12v on pin number 3 (Brown)
5.13v on pin number 2 (orange/blue)
5v on pin number 1 (white/black)

so then reconnecting to the TPS and switching the ignition on with throttle closed, measurements on what I think is TCM according to wiring diagram at least on via

0v on TCM port 2M (other end of pin 3) (Brown)
0.622v on TCM port 2T (other end of pin 2) (orange/blue) (start of the 'sweep')
5v on TCM port 2A (other end of pin 1) (white/black)

with Throttle open then:

12.22v on TCM port 2M (other end of pin 3) (Brown)
3.791v on TCM port 2T (other end of pin 2) (orange/blue) (end of the 'sweep')
5v on TCM port 2A (other end of pin 1) (white/black)

The 'sweep' when opening the throttle looks smooth but does the range (0.622v to 3.791v) look limited ? Maybe I should be achieving 0.5v to 4.5v but no amount of TPS manipulation sees a higher voltage than 3.9v.

This is my first forum post and attempt to look at faults on my bongo so any help appreciated, certainly learning lots.

cheers,

[sp2cpss]

Had another look this evening and I also notice a 'buzzing' sound when slightly opening the throttle which then fades away when further opening the throttle.

Can be heard easily with just ignition on; if I disconnect the TPS connector then noise is completely gone.

Any thoughts ?

[sp2cpss]

Any thoughts on the TPS sweep of 0.622v to 3.79v and the buzzing sound ?

Thanks,

[g8dhe]

In the past there has been a report of the TPS having a dodgy track on the variable resistor such that it would jump around as the wiper crossed over the damaged section. The manual certainly states that the voltage range should be wider and its not unknown for variable resistors to develop corrosion/damage under the connecting rivet between the tag and the carbon track which could result in the sort of readings your getting.
I can only suggest that disconnecting it and measuring the resistance itself as the wiper is turned might give you some clearer answers or possibly opening it up to see if you can see the track itself and what state it is in might help.

[Bongolia]

First let me say I have very limited experience on Bongos specifically.
It sounds very much like the TPS. What mileage is shown on odometer? If the vehicle has been used for a lot of town driving it is possible that the leading part of the track has worn.
I know there is a lot of debate about voltages Vs resistance but the way we check these is by resistance.
Engine off.
Disconnect the plug from the pot and connect an ohmmeter between the wiper and the ground pin or the volts pin it doesn't really matter slowly open the throttle and you should see the resistance change , it doesn't matter what the readings are as long as they increase (or decrease) without any sudden drop off. If the sweep is OK then I would accept that its OK and look elsewhere.

Is the butterfly clean and moving freely? Again not sure on Bongo but if there is a black grey ring around the periphery of the butterfly do not mistakenly remove this just clean any muck with carb cleaner and check it is free to move and not sticking.

[sp2cpss]

Thanks both for the advice, I will be taking another look over the weekend, let's see what I find.

[sp2cpss]

Looked at this matter again over the weekend.

I removed the throttle position sensor and measured the resistance sweep between pins 1 and 2 and also 4 and 2 and it was smooth so took the advice and started to look elsewhere.

I had new leads, Diz cap and rotor arm on order anyway so changed these out too but did not cure the problem. The rotor arm was fairly pitted anyway and I suspect the parts may have been originals so the first time changed and likely due.

I moved onto the throttle body which is not located in the most accessible of places on a v6. I managed to remove the air intake and then ease the throttle body off enough leaving it hanging on the top two bolts so I did not have to remove the coolant hoses. Cleaned with carb cleaner although was not particularly dirty.

There was, however, one part that was proper dirty (see part 23-6823) on lush project link. When I removed the air hose to this part then soot fell out the pipe. I removed the part completely and again used card cleaner and this time a cotton bud to clear out leaving it shiny and new looking.
http://lushprojects.com/bongopartsmk2/c ... o=.html#18

It appears to be a small breather valve of sorts.

Put it all back together now and it runs beautifully. I think this was the problem but of course changing the parts I did and cleaning the TB has no doubt helped.

Its worth mentioning that you can just about reach this 23-6823 part from driver side without removing all centre console etc.

I will clear the codes and run for a week and see what shows up now that things are clean.

Cheers.

[Simon Jones]

The rotor arm was fairly pitted anyway and I suspect the parts may have been originals so the first time changed and likely due.

Be careful! The original part (made by Denso) has a special coating on it which looks like it's pitted but its meant to be like that. If you do the old trick of trying to clean it up using a fine abrasive paper it will make the gap larger. You can just about see the textured finish on the end of the arm in second photo:

[teenmal]

Looked at this matter again over the weekend.

I removed the throttle position sensor and measured the resistance sweep between pins 1 and 2 and also 4 and 2 and it was smooth so took the advice and started to look elsewhere.

I had new leads, Diz cap and rotor arm on order anyway so changed these out too but did not cure the problem. The rotor arm was fairly pitted anyway and I suspect the parts may have been originals so the first time changed and likely due.

I moved onto the throttle body which is not located in the most accessible of places on a v6. I managed to remove the air intake and then ease the throttle body off enough leaving it hanging on the top two bolts so I did not have to remove the coolant hoses. Cleaned with carb cleaner although was not particularly dirty.

There was, however, one part that was proper dirty (see part 23-6823) on lush project link. When I removed the air hose to this part then soot fell out the pipe. I removed the part completely and again used card cleaner and this time a cotton bud to clear out leaving it shiny and new looking.
http://lushprojects.com/bongopartsmk2/c ... o=.html#18

It appears to be a small breather valve of sorts.

Put it all back together now and it runs beautifully. I think this was the problem but of course changing the parts I did and cleaning the TB has no doubt helped.

Its worth mentioning that you can just about reach this 23-6823 part from driver side without removing all centre console etc.

I will clear the codes and run for a week and see what shows up now that things are clean.



Well done

Cheers.

[sp2cpss]

Ok Simon that's useful to know about the rotor arm. I haven't thrown anything away so I will take another look. The replacement rotor arm I fitted was from George at Bongo Spares and that I noticed had a white covering on the tip which I left alone

There were some metal chards in the old Diz cap too when I removed it and changed.

I used to own a '98 xj8 until a year ago and the timing chain tensioners were made of that brown plastic you show in your rotor photo's and they used to split, jag eventually changed them out for metal. I mention it as the rotor arm I fitted from George was black plastic as opposed to that brown plastic.

cheers,

[Bongolia]

Glad you got it sorted. I confess I cannot understand the lushlayouts must spend a bit more time on them.
It looks like a PCV valve, has it any electrical connections?

[sp2cpss]

No electrical connections to this part which is an 'air adjust screw' if you look the translated russian pages:
https://translate.google.de/translate?h ... rev=search

I prefer these pages to lush projects.

cheers

[g8dhe]

There actually the same images! Just ripped from a site that runs the EPC CD data, I've been hunting for years for the actual CD but no luck
https://translate.google.de/translate?h ... rev=search
http://lushprojects.com/bongopartsmk2/c ... mgno=.html

[Bvan]

Hi just wondering if this is fitted to the 2.0 also? Might explain issues with mine. Does anyone have photos if possible please?