Mot Fail S16

[welshpug 1,657]

MAP sensor is nowhere near the throttle body on this engine, its inside the ecu and has a length of vacuum pipe going to the ports on the front of the manifold between the runners.

[Jemehan 3 1 Cars]

I had seen that pipe. that is connected however is a little tight. Need to get a longer bit of piping really.

[pugpete1108 62 1 Cars]

I stand corrected

[Jemehan 3 1 Cars]

Well... Filled the car up today, she runs much better with less hesitation. I am going to change fuel filter asap. Thinking of getting the car code read too to see if that pulls anything up. Wat do you guys recon? Also, car still not getting full power until roughly 3k revvs, any ideas?

[Jemehan 3 1 Cars]

Turns out there is no less hesitation. which sucks. Also no Diag plug either so cannot go that way. I did however see an alan key bolt next to the air intake, wondering if anyone could identify?

 

 

Dont know if this is a mixture adjuster? Anyone any ideas why the car is bogging too as previously mentioned. the ACAV diaphrams move when the throttle is used so i assume they are working?

[Miles 331 1 Cars]

You cannot adjust the mixture on these engine's, mind you should have a Diag plug as it plugs onto the ECU cover which was there even on ODB 306's, Mind that blue plug should not be on the ATS

[Jemehan 3 1 Cars]

Do you know what colour plug should be on there? So there is a plug on the ECU for code reading?

[welshpug 1,657]

grey as pet IAT sensor's body colour, blue plug is the coolant sender/switch for the gauges, which is the blue one...

[Jemehan 3 1 Cars]

I had a look, there is a grey one underneath the hosing that is a 3pin plug, it looks like it goes into the thermostat housing. The blue one, well you can see where that goes, and the blue is a 2 pin. nothing else will reach that spot either...Im just trying to work out why the car is rich and why its now hesitating.

 

Do you know of any documents that explain how the ACAV system works? maybe if I learn more about it i will know if something is wrong. Something is up with her car apart from fuelling. put my foot down, theres a long pause before any power and sometimes it bogs and there is no acceleration at all

[Josh_Quant 27]

should be a green 2 pin plug for diagnostic.

[welshpug 1,657]

dont forget that the ecu coolant temp ill be green too.

[pug_ham 244 3 Cars]

Do you know of any documents that explain how the ACAV system works?

 

I have a copy of the Zx Haynes owners workshop manual which has a description of how the ACAV system works but its over a few pages so not ideal for scanning but basically it uses a solenoid to alter the inlet tract length between long & short starting at approx 1800rpm using butterfly valve inside the intake.

 

The section you need is here in pdf format (right click save target as).

 

g

[Jemehan 3 1 Cars]

Thanks Graham, what a fasinating read. The good news is the ACAV works fine! I was speaking to a local mechanic last night too and decided to pop down on my lunch hour. We jiged and poked around and he disconnected some of the sensors. (ATS, Crank Sensor and that yellow one in my picture above) Disconnecting these, one at a time, none of them made a change to performance. I now need to get a volt meter on them to see if they are sending signals out at all. The mechanic thinks the reason the car is running with issues is not mechanical, but he said he thinks one or more of the sensors have failed. Anyone heard of this previously or which is most likely to go?

[pug_ham 244 3 Cars]

Yellow on in your picture is likely to be the throttle body heater which isn't needed & could even be left unplugged imo.

 

It could be your TPS (throttle position switch) is dying or one of the plugs is wrongly connected on the throttle body, iirc you can run with the tps unplugged & the symptoms are similar to this.

 

Drives ok but is really hesitant when you ask more of it too fast.

 

g

[Vili 18]

Turns out there is no less hesitation. which sucks. Also no Diag plug either so cannot go that way. I did however see an alan key bolt next to the air intake, wondering if anyone could identify?

 

 

Dont know if this is a mixture adjuster? Anyone any ideas why the car is bogging too as previously mentioned. the ACAV diaphrams move when the throttle is used so i assume they are working?

The blue plug is connected wrong. It should be connected to thermostat housing. There should be gray plug connected to that connector. You have connected engine coolant temp to inlet manifold temp (and probably vice versa).

[Vili 18]

About the diagnostic plug, there should be green plug near the ecu. There's roughly 20 cm wire from the ecu connector to the green plug.

[Jemehan 3 1 Cars]

There is a Grey plug just below this that looks like it goes into the thermostat housing, however this one i found was a 3 pin plug and the blue one is a 2 pin. I will have another look to see if i can see a grey 2 pin further down. It would be good if thats all thats causing me this issue. Ill let you all know how i get on. Still need to get a voltmeter to test this. Was going to see the Hobbit tongiht, but it may be another evening of poking and reading.

[Jemehan 3 1 Cars]

About the diagnostic plug, there should be green plug near the ecu. There's roughly 20 cm wire from the ecu connector to the green plug.

The ECU is to the bottom rear of the battery and hard to get at, i will have another look see if i can see it down there, thanks for letting me know.

[pug_ham 244 3 Cars]

The blue plug is connected wrong. It should be connected to thermostat housing. There should be gray plug connected to that connector. You have connected engine coolant temp to inlet manifold temp (and probably vice versa).

 

Agreed, or at least the blue plug is connected to in the wrong place, that is the ATS which should have a grey two pin plug connected.

 

Still doesn't explain the unused grey three pin plug the OP mentioned in an earlier post, usually they are colour coded to the sensor or component they fit & most are keyed so they can't be wrongly connected & looking at the Haynes manual section I linked to above, the TPS usually has a black three pin plug & the only grey three pin around the throttle body is for the ISAV(Idle speed auxiliary air valve).

 

g

[Jemehan 3 1 Cars]

The Grey 3 pin is in an aqward place behind some water pipes. It does plug into a grey socket so i did not think this odd. I will have another inspection and see if i can see where else it should go. The ISAV is plugged in correctly and seems to work fine, she does idle lovely!

Going to take it to the MOT station at lunch to get the emmissions re-tested if they have a minute!

[pug_ham 244 3 Cars]

The Grey 3 pin is in an aqward place behind some water pipes. It does plug into a grey socket so i did not think this odd.

If its plugged in then it isn't spare! I thought you meant not connected to anything & just hanging loose.

 

It's very likely the knock sensor if its well hidden & on the front of the block.

 

g

[Jemehan 3 1 Cars]

There are a couple wires around the bay that are just loose, but they dont look like they can go anywhere. and the car has been like it has for some time, I will be surprised if somethings is plugged in wrong, but anything to make it run better. Ive taken it to go in for an MOT so thats where it is now, dropped to 3 cylinders when i got there, starting to wonder if it is a coil pak!

[welshpug 1,657]

I will be surprised if somethings is plugged in wrong

 

 

I would not, given the only two you pictured were incorrect.

[Jemehan 3 1 Cars]

 

 

I would not, given the only two you pictured were incorrect.

I will take the battery out so i can see the whole of that side, look where the other plugs go. Just need to see if it fails MOT again and what on.

[Jemehan 3 1 Cars]

So i have looked for other loose wires around the housing and throttle body and i have come across a black 2 pin wire, however when i put my multimeter on it, it wasnt giving out any signal. Where as the blue one was. Also, the blue one has been patched into the loom here and I dontthink it was originally a blue wire there. Any one got any ideas. Im starting to think maybe the wiring is ok? and it is a damaged/dying coil .

 

sorry to bring this up again, but its bogging is bugging me and can be dangerous if it happens when i pull out of a junction.