Is the pic below showing the animal we want.
Thanks for your kind offer, Richard, but I live in Wales.
Are those Gunson testers any good.
I have read that Oxygen sensors will perform the same tricks as a MAP sensor.
Thanks for your help
Greg
Not Yet Fixed
Moderator: RichardW
<font color="blue"><font size="2"><font face="Comic Sans MS">Hi Guys,
Found this on How Stuff Works:
Here are some fast and reliable diagnostic procedures which you can use to check out most oxygen sensors. A great time to do this is when you are performing a tune-up.
The following symptoms will help tip you off to a failed oxygen sensor:
<font color="blue"><b>Surging and/or hesitation</b></font id="blue">
Decline in fuel economy
Unacceptable exhaust emissions
Premature failure of the catalytic converter
You will need the following equipment:
A handheld volt meter (digital VOM)
A propane enrichment device
An oxygen sensor socket
The manufacturer's vehicle specific test instructions.
It should take less than 10 minutes to perform a diagnostic check on most vehicles.
1. Verify the basic engine parameters, per the manufacturer's specifications for the following: timing, integrity of the electrical system (supply voltage), fuel delivery mixture performance and internal mechanical considerations.
2. Treat the rich mixture performance as follows:
a. Disconnect the sensor lead to the control unit.
b. Run the engine at 2500 rpm.
c. Artificially enrich the fuel mixture by directing propane into the intake until the engine speed drops by 200 rpm. Or, if you're working on a vehicle with electronic fuel injection, you can remove and plug the vacuum line to the fuel pressure regulator.
d. If the voltmeter rapidly reads .9 volts, then the oxygen sensor is correctly sensing a rich mixture. But, if the voltmeter responds sluggishly, or if it stays below .8 volts, then the sensor should be replaced.
3. Test the lean mixture performance as follows:
a. Induce a small vacuum leak.
b. If the voltmeter rapidly drops to .2 volts or below in less than a second, then the oxygen sensor is correctly measuring the lean mixture. But, if the voltmeter responds sluggishly, or if it stays above .2 volts, then the sensor should be replaced.
4. Test dynamic performance as follows:
a. Reconnect the sensor lead.
b. Set the mixture to specification.
c. Run the engine at 1500 rpm.
d. The sensor output should fluctuate around .5 volts. If it doesn't, replace the sensor.
Diagnosis
When performing diagnostic work on your customer's vehicle to determine the cause of a driveability problem or perhaps the reason for failing an emissions test, take the opportunity to check the operation of the oxygen sensor for proper functioning.
Recalling that an oxygen sensor will influence the air fuel mixture preparation only when it has reached proper operating temperature (at least 350oC), it is essential to first ensure that the engine and sensor are warm enough to allow operation in a "closed loop" condition. It may take as long as 2 1/2 minutes after cold start for proper exhaust temperature to be reached (somewhat shorter for heated-type oxygen sensors).
To check the performance of the oxygen sensor, run the vehicle engine at about 2000 rpm (or at normal cruise when working with a dynamometer) to ensure that the sensor remains hot throughout the test procedure. Do not remove or disconnect the sensor lead in order to test it as this will eliminate the "closed loop" signal to the electronic control unit and result in a non-cycling voltage condition. Using a correct electrical impedance test device as found with a laboratory type oscilloscope, connect your test leads so as to read voltage from the signal wire to the electronic control unit. With vehicles that use a heated oxygen sensor (three or four wire), it may be necessary to bridge the connector leads and tap into the signal wire with an appropriate test probe at the connector plug in order to obtain the signal. The oscilloscope will allow you to read the electrical response pattern of the oxygen sensor to changing exhaust gas oxygen content as a measure of its performance.
Before proceeding, be sure that you are using the correct measurement scale for your specific equipment as specified by the test equipment manufacturer. (Invariably, this will be a low voltage scale.)
A properly functioning oxygen sensor will exhibit a rapidly fluctuating voltage signal alternating between approximately .2 and .8 volts in response to varying residual oxygen content in the exhaust stream. Look to your scope's time reference line for a desired lean-to-rich and rich-to-lean time of less than 300 milliseconds. A response time greater than 300ms. means that the sensor should be replaced. It is important to recall that these values are valid only when checking a sensor operating in "closed loop" in a hot exhaust stream (350o-8OOoC). Sensor age degree of contamination, mixture setting, and exhaust temperature all have an effect on response time.
Without this rapid electrical response to changing exhaust composition, the control unit cannot accurately correct the fuel mixture. A sluggish sensor is either contaminated or beyond its intended service life and must be replaced. Additionally, check vehicle manufacturers' service recommendations and suggest replacement of the oxygen sensor at specified intervals. </font id="Comic Sans MS"></font id="size2"></font id="blue">
Found this on How Stuff Works:
Here are some fast and reliable diagnostic procedures which you can use to check out most oxygen sensors. A great time to do this is when you are performing a tune-up.
The following symptoms will help tip you off to a failed oxygen sensor:
<font color="blue"><b>Surging and/or hesitation</b></font id="blue">
Decline in fuel economy
Unacceptable exhaust emissions
Premature failure of the catalytic converter
You will need the following equipment:
A handheld volt meter (digital VOM)
A propane enrichment device
An oxygen sensor socket
The manufacturer's vehicle specific test instructions.
It should take less than 10 minutes to perform a diagnostic check on most vehicles.
1. Verify the basic engine parameters, per the manufacturer's specifications for the following: timing, integrity of the electrical system (supply voltage), fuel delivery mixture performance and internal mechanical considerations.
2. Treat the rich mixture performance as follows:
a. Disconnect the sensor lead to the control unit.
b. Run the engine at 2500 rpm.
c. Artificially enrich the fuel mixture by directing propane into the intake until the engine speed drops by 200 rpm. Or, if you're working on a vehicle with electronic fuel injection, you can remove and plug the vacuum line to the fuel pressure regulator.
d. If the voltmeter rapidly reads .9 volts, then the oxygen sensor is correctly sensing a rich mixture. But, if the voltmeter responds sluggishly, or if it stays below .8 volts, then the sensor should be replaced.
3. Test the lean mixture performance as follows:
a. Induce a small vacuum leak.
b. If the voltmeter rapidly drops to .2 volts or below in less than a second, then the oxygen sensor is correctly measuring the lean mixture. But, if the voltmeter responds sluggishly, or if it stays above .2 volts, then the sensor should be replaced.
4. Test dynamic performance as follows:
a. Reconnect the sensor lead.
b. Set the mixture to specification.
c. Run the engine at 1500 rpm.
d. The sensor output should fluctuate around .5 volts. If it doesn't, replace the sensor.
Diagnosis
When performing diagnostic work on your customer's vehicle to determine the cause of a driveability problem or perhaps the reason for failing an emissions test, take the opportunity to check the operation of the oxygen sensor for proper functioning.
Recalling that an oxygen sensor will influence the air fuel mixture preparation only when it has reached proper operating temperature (at least 350oC), it is essential to first ensure that the engine and sensor are warm enough to allow operation in a "closed loop" condition. It may take as long as 2 1/2 minutes after cold start for proper exhaust temperature to be reached (somewhat shorter for heated-type oxygen sensors).
To check the performance of the oxygen sensor, run the vehicle engine at about 2000 rpm (or at normal cruise when working with a dynamometer) to ensure that the sensor remains hot throughout the test procedure. Do not remove or disconnect the sensor lead in order to test it as this will eliminate the "closed loop" signal to the electronic control unit and result in a non-cycling voltage condition. Using a correct electrical impedance test device as found with a laboratory type oscilloscope, connect your test leads so as to read voltage from the signal wire to the electronic control unit. With vehicles that use a heated oxygen sensor (three or four wire), it may be necessary to bridge the connector leads and tap into the signal wire with an appropriate test probe at the connector plug in order to obtain the signal. The oscilloscope will allow you to read the electrical response pattern of the oxygen sensor to changing exhaust gas oxygen content as a measure of its performance.
Before proceeding, be sure that you are using the correct measurement scale for your specific equipment as specified by the test equipment manufacturer. (Invariably, this will be a low voltage scale.)
A properly functioning oxygen sensor will exhibit a rapidly fluctuating voltage signal alternating between approximately .2 and .8 volts in response to varying residual oxygen content in the exhaust stream. Look to your scope's time reference line for a desired lean-to-rich and rich-to-lean time of less than 300 milliseconds. A response time greater than 300ms. means that the sensor should be replaced. It is important to recall that these values are valid only when checking a sensor operating in "closed loop" in a hot exhaust stream (350o-8OOoC). Sensor age degree of contamination, mixture setting, and exhaust temperature all have an effect on response time.
Without this rapid electrical response to changing exhaust composition, the control unit cannot accurately correct the fuel mixture. A sluggish sensor is either contaminated or beyond its intended service life and must be replaced. Additionally, check vehicle manufacturers' service recommendations and suggest replacement of the oxygen sensor at specified intervals. </font id="Comic Sans MS"></font id="size2"></font id="blue">
-
Richard Gallagher
- Posts: 803
- Joined: 31 Oct 2001, 02:36
- Location: South Bucks
- My Cars:
Greg,
Send me your email address and I will send you the photo I've just taken of the underside of the inlet manifold where the MAP sensor resides. (Which incidentally looks nothing like the oil pressure sensor in your hand!)
The Gunson code reader will not fit your car, professional equipment only I'm afraid.
MAP sensors detect manifold pressure, whereas Oxygen/Lambda sensors test................
Send me your email address and I will send you the photo I've just taken of the underside of the inlet manifold where the MAP sensor resides. (Which incidentally looks nothing like the oil pressure sensor in your hand!)
The Gunson code reader will not fit your car, professional equipment only I'm afraid.
MAP sensors detect manifold pressure, whereas Oxygen/Lambda sensors test................
Hi Richard,
That black hole in pic, has it got a thread in it, also the brass hole, has that got a thread in it.
Where the vaccy pipe goes into manifold, just in from the sealed up pipe----well just inboard of the vaccy pipe is where I unscrewed that oil switch lookalike---has 3 wires attached in a connector. Which puts lookalike right where brass hole is.
I can`t look at it till next weekend now, I use the car everyday, so will let you know what gives.
Thanks for your help,
Greg
That black hole in pic, has it got a thread in it, also the brass hole, has that got a thread in it.
Where the vaccy pipe goes into manifold, just in from the sealed up pipe----well just inboard of the vaccy pipe is where I unscrewed that oil switch lookalike---has 3 wires attached in a connector. Which puts lookalike right where brass hole is.
I can`t look at it till next weekend now, I use the car everyday, so will let you know what gives.
Thanks for your help,
Greg
-
Richard Gallagher
- Posts: 803
- Joined: 31 Oct 2001, 02:36
- Location: South Bucks
- My Cars:
Greg,
if you zoom in on the picture it will give very intricate detail, the black hole is just that, no thread, the brass one does have the thread for the bolt.
The switch you have in your hand looks very much as if its the one which is attached to the engine block underneath the inlet manifold.
Having just looked at my 2.0 16V you can see the MAP sensor from above the manifold if you look from the N/S/F then across the throttle cam to under the arch of the manifold. Its the black plastic thing sticking out at a 45 degree angle with a connector attached.
if you zoom in on the picture it will give very intricate detail, the black hole is just that, no thread, the brass one does have the thread for the bolt.
The switch you have in your hand looks very much as if its the one which is attached to the engine block underneath the inlet manifold.
Having just looked at my 2.0 16V you can see the MAP sensor from above the manifold if you look from the N/S/F then across the throttle cam to under the arch of the manifold. Its the black plastic thing sticking out at a 45 degree angle with a connector attached.
<font color="blue"><font size="2"><font face="Comic Sans MS">Hi Richard,
The oil switch lookalike actually came from that brass hole, thats why I thought it was that elusive MAP sensor.
Citroen actually want £85 for a map sensor, the local main dealer, which is in a network, have never sold one.
Will look at weekend. Always dark for me when I leave and return home.
Roll on summer. What trouble is Stempy having ?
Cheers
Greg</font id="Comic Sans MS"></font id="size2"></font id="blue">
The oil switch lookalike actually came from that brass hole, thats why I thought it was that elusive MAP sensor.
Citroen actually want £85 for a map sensor, the local main dealer, which is in a network, have never sold one.
Will look at weekend. Always dark for me when I leave and return home.
Roll on summer. What trouble is Stempy having ?
Cheers
Greg</font id="Comic Sans MS"></font id="size2"></font id="blue">
-
Richard Gallagher
- Posts: 803
- Joined: 31 Oct 2001, 02:36
- Location: South Bucks
- My Cars:
Greg,
RP numbers, the manifold pic is from 7543, registered on 8.8.98, present car is 7381 registered on 2.4.97.
The fact that you had that oil pressure switch screwed into the manifold is rather strange???
Are the holes on the manifold open or closed off? If not, it may be worth removing the switch , closing off the manifold holes with tape then seeing what happens. Engine ECU's generally take the 'greater' information from the temperature sensor, the other sensors make up the the final 'trimming' if that makes sense.
As Stempy appears to have a different MAP sensor he is returning the one I sent him, so I can offer you that one if it interests you.
RP numbers, the manifold pic is from 7543, registered on 8.8.98, present car is 7381 registered on 2.4.97.
The fact that you had that oil pressure switch screwed into the manifold is rather strange???
Are the holes on the manifold open or closed off? If not, it may be worth removing the switch , closing off the manifold holes with tape then seeing what happens. Engine ECU's generally take the 'greater' information from the temperature sensor, the other sensors make up the the final 'trimming' if that makes sense.
As Stempy appears to have a different MAP sensor he is returning the one I sent him, so I can offer you that one if it interests you.
<font color="blue"><font size="2"><font face="Comic Sans MS">Hi Richard,
I had a quick look at manifold today, and there is a distinct boss into which that sensor is fitted, next to the vaccy hose inlet, in the direction of the timing belt end of engine. The switch is hollow inside screw end. I only likened it to an oil switch. There is only the one connector block with 3 wires in area, and that is hooked up to this sensor (?).
When Stempy returns that MAP thingy, please retain it till weekend, so I can check all this out,once and for all. If you don`t mind.Will post ORGa number later.
Thanks very much,
Greg</font id="Comic Sans MS"></font id="size2"></font id="blue">
I had a quick look at manifold today, and there is a distinct boss into which that sensor is fitted, next to the vaccy hose inlet, in the direction of the timing belt end of engine. The switch is hollow inside screw end. I only likened it to an oil switch. There is only the one connector block with 3 wires in area, and that is hooked up to this sensor (?).
When Stempy returns that MAP thingy, please retain it till weekend, so I can check all this out,once and for all. If you don`t mind.Will post ORGa number later.
Thanks very much,
Greg</font id="Comic Sans MS"></font id="size2"></font id="blue">
<font color="blue"><font size="2"><font face="Comic Sans MS">Hello Richard,
I went to local Cit main dealers today. I asked them to show me a MAP sensor for my engine. I had engine number, chassis number handy, but they found right part by registration number ( same as Volvo ). On my engine, the MAP sensor looks <b>exactly</b> like an oil pressure switch, the fact that it is hollow up through the screwed part, will probably be able to measure any variations in inlet manifold pressure.
There are also no other holes in the chamber where vaccy pipe fits to manifold.
So my engine has just detail differences to yours. What I will do is get an inlet manifold gasket/rubber sealing rings and replace them, that way I will know it isn`t air leaks from that direction.
If you still have an oxygen sensor, I will check tomorrow how many wires it has, I would buy that from you. Can you give a price plus postage to CWMBRAN, S.Wales for the OXY sensor.
Thanks for all your help,
Greg
I seem to have a right rare beast here, in more ways than one.</font id="Comic Sans MS"></font id="size2"></font id="blue">
I went to local Cit main dealers today. I asked them to show me a MAP sensor for my engine. I had engine number, chassis number handy, but they found right part by registration number ( same as Volvo ). On my engine, the MAP sensor looks <b>exactly</b> like an oil pressure switch, the fact that it is hollow up through the screwed part, will probably be able to measure any variations in inlet manifold pressure.
There are also no other holes in the chamber where vaccy pipe fits to manifold.
So my engine has just detail differences to yours. What I will do is get an inlet manifold gasket/rubber sealing rings and replace them, that way I will know it isn`t air leaks from that direction.
If you still have an oxygen sensor, I will check tomorrow how many wires it has, I would buy that from you. Can you give a price plus postage to CWMBRAN, S.Wales for the OXY sensor.
Thanks for all your help,
Greg
I seem to have a right rare beast here, in more ways than one.</font id="Comic Sans MS"></font id="size2"></font id="blue">
-
Richard Gallagher
- Posts: 803
- Joined: 31 Oct 2001, 02:36
- Location: South Bucks
- My Cars:
Greg,
I just looked on Citroen-PR net and noticed that the MAP sensor was changed from your 'oil pressure sensor' shape to my 'plastic-thingy' on RP number 7328, ie, between your car and both of mine, so you obviously have the right one, sorry for the duff info.
If you are trying to find inlet manifold leaks then get a length of hose, put one end to your ear then move the other end around all of the relevant components, if a leak is there you will be able to hear it.
I do still have the Lambda/oxygen sensor, if you want it then a fiver + £1 p/p will suffice. You'll have great fun (not) tracing and removing the wiring back from the sensor to the connector at the rear of the engine, ho ho!!
I'll also take a look at cit-pr re part compatability for the oxy sensor.
I just looked on Citroen-PR net and noticed that the MAP sensor was changed from your 'oil pressure sensor' shape to my 'plastic-thingy' on RP number 7328, ie, between your car and both of mine, so you obviously have the right one, sorry for the duff info.
If you are trying to find inlet manifold leaks then get a length of hose, put one end to your ear then move the other end around all of the relevant components, if a leak is there you will be able to hear it.
I do still have the Lambda/oxygen sensor, if you want it then a fiver + £1 p/p will suffice. You'll have great fun (not) tracing and removing the wiring back from the sensor to the connector at the rear of the engine, ho ho!!
I'll also take a look at cit-pr re part compatability for the oxy sensor.
<font color="blue"><font size="2"><font face="Comic Sans MS">Hi Richard,
Ground too wet to count sensor wires, will look Saturday. If same amount as yours, I will be pleased to buy it from you at that price. Will have to look for a map sensor like mine, for a spare. Have you got that link handy for that Citroen RP site, please. Will contact you Sat. Thanks for your help,
Greg
Ps. Was wondering whether to have your MAP sensor, along with the black chamber that it sits in. Will it work in my car. What do you think ?</font id="Comic Sans MS"></font id="size2"></font id="blue">
Ground too wet to count sensor wires, will look Saturday. If same amount as yours, I will be pleased to buy it from you at that price. Will have to look for a map sensor like mine, for a spare. Have you got that link handy for that Citroen RP site, please. Will contact you Sat. Thanks for your help,
Greg
Ps. Was wondering whether to have your MAP sensor, along with the black chamber that it sits in. Will it work in my car. What do you think ?</font id="Comic Sans MS"></font id="size2"></font id="blue">