Engine won't rev and hunts

[ANDTWENTY]

so I took it off cleaned it (just a hazing of oil) checked vacuum lines were clear reattached and set the TPS as per the Haynes manual. I then adjusted the rod so that the TPS would still click and it was resting on the idle screw and the drum was also on the rest. Started it up and it now hunts on idle as well as throttle open.

[Laird Scooby]

Originally Posted by ANDTWENTY

Just checked timing, I have been taking the longer mark as 0° is this correct?


If so then I lined up the crank pulley with that one if you look square on at the plate which is slightly off set.


I then looked at the cam which is marked with white pen and also appears to be out slightly. Could this be the issue or am I referencing it to the wrong marks, guessing these white marks aren't original marks?

The timing mark you have arrowed in your first pic is actually 20 deg BTDC, the next long mark is 10 deg BTDC and the short mark, right at the very end where the pointer housing goes back at an angle is in fact the TDC position.

Like Kay says, it looks like it's correct but to be doubly sure, recheck by moving the crankshaft onto the 0deg mark. I don't know how to do the "drawing on pictures" thing like you've done with the arrow so can't do it.

A better way of adjusting the throttle butterfly to its correct position is to get the engine warm and then locate the red/white wire terminated in a 2-pin multiplug near the coolant expansion tank. Make a jumper wire and connect this to the red/white wire and the other end to battery -ve - the idle speed will drop. Now adjust the throttle stop screw so the engine idles at 600rpm, lock the locknut on the throttle stop screw at this position and if you wish, use paint (or Tipp-Ex) to seal it as Kay suggests.
Now, remove your jumper wire and the engine speed should climb then stabilise at about 700rpm (if memory serves on the B230F) and that is the idle speed sorted.

Now to adjust the TPS with the ignition off. As you look at the TPS, work out which way the throttle spindle turns as you view it when the throttle is opened. If it's anti-clockwise, loosen the two screws securing the TPS and turn as far as it will go clockwise. Now turn it back slowly until you hear the microswitch click. Nip the screws up just enough to hold it, set your multimeter up on continuity and connect the probes to the earth and the idle microswitch wires on the TPS - it should buzz to indicate continuity, open the throttle gently and as you open it, the buzzing should stop.
Release the throttle so it goes back to idle position and it should buzz again. If all is well, tighten the TPS screws properly and if you wish, blob some Tipp-Ex/paint on to seal them.

Now, swap your meter probes into the full throttle microswitch and the earth on the TPS, still on conituity and get in the car and floor the throttle - you should hear the buzz from your meter to indicate that not only are you getting full throttle but the ECU will recognise it too.

I find this method preferable to Kays method overall as it takes wear on the components into account, especially on the base idle speed setting. Kays method is perfectly valid on new/near-new components but let's not forget your car is nearly 30 years old now and will have at least some wear on it!

Looking at the pic of the back of your alternator, i can see the witness mark on the spade terminal for the diesel rev counter where you initially connected the field/warning light wire. If you look you will also see that terminal is marked with a "W" which if my memory of learning German is correct, stands for "Wende" or in English, "turn" as in turns of the engine. I'm sure Kay will put me right if i'm wrong!

This would have caused a fluctuating voltage on the warning lights and a certain amount of self-excitement for the alternator so it might have putout 14V but not at full current.

Re your ABS warning light, if you clear the fault using the code reader, it should stay off now if there isn't a problem.

[Laird Scooby]

Originally Posted by ANDTWENTY

so I took it off cleaned it (just a hazing of oil) checked vacuum lines were clear reattached and set the TPS as per the Haynes manual. I then adjusted the rod so that the TPS would still click and it was resting on the idle screw and the drum was also on the rest. Started it up and it now hunts on idle as well as throttle open.

Read my post above, follow that! I'm not surprised it hunts on idle as well now, i suspect you've got the throttle butterfly way too large for the idle fuel map as dictated by the idle microswitch in the TPS so in effect, you've introduced a huge air leak.

[ANDTWENTY]

Originally Posted by Laird Scooby

The timing mark you have arrowed in your first pic is actually 20 deg BTDC, the next long mark is 10 deg BTDC and the short mark, right at the very end where the pointer housing goes back at an angle is in fact the TDC position.

Like Kay says, it looks like it's correct but to be doubly sure, recheck by moving the crankshaft onto the 0deg mark. I don't know how to do the "drawing on pictures" thing like you've done with the arrow so can't do it.

A better way of adjusting the throttle butterfly to its correct position is to get the engine warm and then locate the red/white wire terminated in a 2-pin multiplug near the coolant expansion tank. Make a jumper wire and connect this to the red/white wire and the other end to battery -ve - the idle speed will drop. Now adjust the throttle stop screw so the engine idles at 600rpm, lock the locknut on the throttle stop screw at this position and if you wish, use paint (or Tipp-Ex) to seal it as Kay suggests.
Now, remove your jumper wire and the engine speed should climb then stabilise at about 700rpm (if memory serves on the B230F) and that is the idle speed sorted.

Now to adjust the TPS with the ignition off. As you look at the TPS, work out which way the throttle spindle turns as you view it when the throttle is opened. If it's anti-clockwise, loosen the two screws securing the TPS and turn as far as it will go clockwise. Now turn it back slowly until you hear the microswitch click. Nip the screws up just enough to hold it, set your multimeter up on continuity and connect the probes to the earth and the idle microswitch wires on the TPS - it should buzz to indicate continuity, open the throttle gently and as you open it, the buzzing should stop.
Release the throttle so it goes back to idle position and it should buzz again. If all is well, tighten the TPS screws properly and if you wish, blob some Tipp-Ex/paint on to seal them.

Now, swap your meter probes into the full throttle microswitch and the earth on the TPS, still on conituity and get in the car and floor the throttle - you should hear the buzz from your meter to indicate that not only are you getting full throttle but the ECU will recognise it too.

I find this method preferable to Kays method overall as it takes wear on the components into account, especially on the base idle speed setting. Kays method is perfectly valid on new/near-new components but let's not forget your car is nearly 30 years old now and will have at least some wear on it!

Looking at the pic of the back of your alternator, i can see the witness mark on the spade terminal for the diesel rev counter where you initially connected the field/warning light wire. If you look you will also see that terminal is marked with a "W" which if my memory of learning German is correct, stands for "Wende" or in English, "turn" as in turns of the engine. I'm sure Kay will put me right if i'm wrong!

This would have caused a fluctuating voltage on the warning lights and a certain amount of self-excitement for the alternator so it might have putout 14V but not at full current.

Re your ABS warning light, if you clear the fault using the code reader, it should stay off now if there isn't a problem.

Just re checked the timing, i missed the 0° which is marked on the lower cover, with this lined up the top one lines up perfectly.

The only 2 pin connector I can find has a yellow and red wire that goes down and through the wheel well, guessing it's for an abs sensor, is this the right one?


Or is this the one?


Even undoing the screw so that it no longer touches the butterfly lever the idle doesn't drop below 1100 ish, however clamping off the air hose to the idle air valve does drop the idle down to the point it might stall, could the idle valve be letting too much air past preventing me from lowing the idle? and the fault code for it also seems to back this up as being faulty.

just checked the idle valve by disconnecting it, which made no difference to the car running. checked the voltage and it was 13 something, so battery voltage. I then went into the car and turned on heater fan, lights etc and the idle lowered and stayed lower.

there is also now a lambda light on so ill check codes, code came back as TPS has no idle signal/faulty signal, this may be because I had it loosened to get it to idle smoothly

The idle air control valve works when connected to 12 volts but when disconnected the shutter inside overshoots and leaves an air gap

[Laird Scooby]

Originally Posted by ANDTWENTY

Just re checked the timing, i missed the 0° which is marked on the lower cover, with this lined up the top one lines up perfectly.

The only 2 pin connector I can find has a yellow and red wire that goes down and through the wheel well, guessing it's for an abs sensor, is this the right one?


Or is this the one?


Even undoing the screw so that it no longer touches the butterfly lever the idle doesn't drop below 1100 ish, however clamping off the air hose to the idle air valve does drop the idle down to the point it might stall, could the idle valve be letting too much air past preventing me from lowing the idle? and the fault code for it also seems to back this up as being faulty.

just checked the idle valve by disconnecting it, which made no difference to the car running. checked the voltage and it was 13 something, so battery voltage. I then went into the car and turned on heater fan, lights etc and the idle lowered and stayed lower.

there is also now a lambda light on so ill check codes, code came back as TPS has no idle signal/faulty signal, this may be because I had it loosened to get it to idle smoothly

The idle air control valve works when connected to 12 volts but when disconnected the shutter inside overshoots and leaves an air gap

Good news on the cam timing, it looked right so was really only a doble-check but double-checks can often reveal something!

The first yellow/red wire is indeed for the O/S/F ABS sensor. The second pic in the blue connector looks much more like it and would appear someone has tied it up out of the way. Try it and see, it's almost certainly the right one if it's the only terminal in a 2-pole connector.

If you've set the idle too low on the base idle speed, it will also hunt at idle as it tries to compensate but the AICV overcompensates then it's a constant battle of bring the speed up, too much, reduce the speed to where it should be when warm, too little, bring it back up again etc. It doesn't come within the limits prescribed in the ECU map that it's looking for so it throws a fault code.

Charging voltage with no load should be 14.0V, 14.4V on a cold voltage regulator. Check your alternator drive belt tension.

It may drop a little if the battery is in a low state of charge but not by much and should come up to 14.0V when revved. You've had a lot of starts so it may be the battery is a bit low by now.

There should be a slight gap in the AICV when "closed", first though you need to get the base idle speed right, using my method, re-adjust the TPS if necessary and take things from there.

By the way, if it's automatic, you may need to check/adjust the kickdown cable after all of this has been completed.

Nice colour by the way, Dark Blue Metallic if i'm not mistaken? Paint code is 603 i think if it is.

[ANDTWENTY]

Originally Posted by Laird Scooby

Good news on the cam timing, it looked right so was really only a doble-check but double-checks can often reveal something!

The first yellow/red wire is indeed for the O/S/F ABS sensor. The second pic in the blue connector looks much more like it and would appear someone has tied it up out of the way. Try it and see, it's almost certainly the right one if it's the only terminal in a 2-pole connector.

If you've set the idle too low on the base idle speed, it will also hunt at idle as it tries to compensate but the AICV overcompensates then it's a constant battle of bring the speed up, too much, reduce the speed to where it should be when warm, too little, bring it back up again etc. It doesn't come within the limits prescribed in the ECU map that it's looking for so it throws a fault code.

Charging voltage with no load should be 14.0V, 14.4V on a cold voltage regulator. Check your alternator drive belt tension.

It may drop a little if the battery is in a low state of charge but not by much and should come up to 14.0V when revved. You've had a lot of starts so it may be the battery is a bit low by now.

There should be a slight gap in the AICV when "closed", first though you need to get the base idle speed right, using my method, re-adjust the TPS if necessary and take things from there.

By the way, if it's automatic, you may need to check/adjust the kickdown cable after all of this has been completed.

Nice colour by the way, Dark Blue Metallic if i'm not mistaken? Paint code is 603 i think if it is.

I have connected that cable to the negative on the battery but it doesn't change anything.

the engine will hunt if the butterfly is opened even slightly and the more I screw it in the worse it gets.

I literally can't seem to get the idle any lower

It's a manual and is dark metallic blue, not sure on the code though.

[ANDTWENTY]

Originally Posted by mocambique-amazone

TPS


TPS


Still TPS


The engine management get the signal:
Foot of accelerator - throttle closed
Result: switch of fuel to save energy ( overrun fuel cut off)

It's really simple, trust me.


And again:
-Remove the throttle body
-clean the butterfly
-adjust the gap between butterfly and housing
-glue the screw with paint, never touch this again.( Everyone who is working on this screw should be punished)
-adjust the TPS
-mount the throttle body
-adjust the rod

There will be only one other fault: broken wire between TPS and ECU.

Can't believe this by having a closer look to the engine bay


Good luck, Kay

just read back through the posts and saw this, I have set the TPS a couple of times, it makes a click and it gets 12 volts and gives off a signal, if the signal wire had broken somewhere between the sensor and the ECU will it still say okay on the diagnostic tests. presumable it would cause this issue too as it won't see the throttle being opened?

just checked continuity from the orange signal cable from the connector to the connector by the bulkhead and there is so unless its broken in the car perhaps

[Laird Scooby]

Originally Posted by ANDTWENTY

I have connected that cable to the negative on the battery but it doesn't change anything.

the engine will hunt if the butterfly is opened even slightly and the more I screw it in the worse it gets.

I literally can't seem to get the idle any lower

It's a manual and is dark metallic blue, not sure on the code though.

In that case, you need to look for the correct connector. Should be near/under the coolant expansion tank. I'll try and get a pic of mine later but bear in mind mine is a 1988 760, the exact place might be slightly different.

Originally Posted by ANDTWENTY

just read back through the posts and saw this, I have set the TPS a couple of times, it makes a click and it gets 12 volts and gives off a signal, if the signal wire had broken somewhere between the sensor and the ECU will it still say okay on the diagnostic tests. presumable it would cause this issue too as it won't see the throttle being opened?

just checked continuity from the orange signal cable from the connector to the connector by the bulkhead and there is so unless its broken in the car perhaps

Orange signal cable to/from what?

Have to say, i'm not convinced the TPS idle switch is causing the problem , some monkey had been fiddling with mine before i got it and the idle switch wasn't working at all. It still ran passably well though. It was only other faults showing up that caused me to investigate it and sort it out in fact.

Looking at the pic further up of your MAF, it seems to be an 0 280 212 016 which is shared with several other 940s including a turbo version.

Have a look at this thread, someone else is also after the MAF but it might be worth a try :

https://www.volvoforums.org.uk/showt...48#post2551848

Not sure of any others being broken at the moment but worth remembering it might be the MAF still.

I'll try and get that pic shortly.

[kelvinp]

Originally Posted by Laird Scooby

In that case, you need to look for the correct connector. Should be near/under the coolant expansion tank. I'll try and get a pic of mine later but bear in mind mine is a 1988 760, the exact place might be slightly different.

I've never found that cable no matter how much I've looked for it (1990 740 with LH2.4)

Originally Posted by Laird Scooby

Orange signal cable to/from what?

Have to say, i'm not convinced the TPS idle switch is causing the problem , some monkey had been fiddling with mine before i got it and the idle switch wasn't working at all. It still ran passably well though. It was only other faults showing up that caused me to investigate it and sort it out in fact.

Looking at the pic further up of your MAF, it seems to be an 0 280 212 016 which is shared with several other 940s including a turbo version.

Have a look at this thread, someone else is also after the MAF but it might be worth a try :

https://www.volvoforums.org.uk/showt...48#post2551848

Not sure of any others being broken at the moment but worth remembering it might be the MAF still.

I'll try and get that pic shortly.

Reading through this thread, it sounds similar to what I had with now my 740, it wouldn't idle or rev and this turned out to be the MAF. I'd checked everything else and so forked out an extortionate 99p for a BOSCH one on Ebay and it was good as gold. I found out that I had the diagnostics with the LH2.4 but I remember clearing the codes and because of another fault it didn't log the MAF error code if I remember.

[Laird Scooby]

I wasn't able to get a photo of the connector, i'll have a go tomorrow.