Discussion
I'm looking for some help with regards to EFI and exhaust systems.
I put the GTS in for her MOT the other day and all was well until the emissions test. Everything is fine apart from the CO reading. It's averaging about 1.2 rather than the limit of 0.2! The oxygen sensors appeared to but okay but flicked down to .96 for a split second which would also have been a fail. The mechanic reckoned it was the Cats playing up so I booked her in for a retest and did some asking around.
After phoning Roger at Monkfish, I ordered new O2 sensors and fitted them. I noticed that the previous owner had obviously changed them at some stage as they were cheap universal types that had been spliced into the old connectors. At the retest the level had actually gone up to 1.6 on the CO but the O2 sensors were now reading steady within limits but also now I get a powertrain light when the revs are held steady at 2000-2500 rpm for a minute or so and as soon as a heavier load (throttle) is applied or the engine is allowed to idle the light goes out. During normal sedate driving it will come on whilst cruising on the motorway for a few minutes then go out then come on again after another 20 mins or so and go out etc etc. When driven hard the light does not come on.
The fault code just indicates rich exhaust and nothing further. There are no other codes. I've checked all the vacuum hoses to find splits etc but found none and the seal around the inlet manifold seems to be okay. The MAF and IAT sensors are functioning.
Why would the reading on the CO have gone up further after the O2 sensor change?
The car is getting new Cats tomorrow (custom Magnaflow high flows). Will this solve the problem do you think? (For emissions anyway)
Could the rich exhaust be ignition? I've just changed leads and plugs (10mm spiral core leads and NGK iridium plugs). I've checked and double checked every lead.
Could it be the Dizzy cap and rotor? (It's a VT 1 GTS with the 5.7 Harrop stroker)
Any help or ideas would be great. Is there something I've missed?
I put the GTS in for her MOT the other day and all was well until the emissions test. Everything is fine apart from the CO reading. It's averaging about 1.2 rather than the limit of 0.2! The oxygen sensors appeared to but okay but flicked down to .96 for a split second which would also have been a fail. The mechanic reckoned it was the Cats playing up so I booked her in for a retest and did some asking around.
After phoning Roger at Monkfish, I ordered new O2 sensors and fitted them. I noticed that the previous owner had obviously changed them at some stage as they were cheap universal types that had been spliced into the old connectors. At the retest the level had actually gone up to 1.6 on the CO but the O2 sensors were now reading steady within limits but also now I get a powertrain light when the revs are held steady at 2000-2500 rpm for a minute or so and as soon as a heavier load (throttle) is applied or the engine is allowed to idle the light goes out. During normal sedate driving it will come on whilst cruising on the motorway for a few minutes then go out then come on again after another 20 mins or so and go out etc etc. When driven hard the light does not come on.
The fault code just indicates rich exhaust and nothing further. There are no other codes. I've checked all the vacuum hoses to find splits etc but found none and the seal around the inlet manifold seems to be okay. The MAF and IAT sensors are functioning.
Why would the reading on the CO have gone up further after the O2 sensor change?
The car is getting new Cats tomorrow (custom Magnaflow high flows). Will this solve the problem do you think? (For emissions anyway)
Could the rich exhaust be ignition? I've just changed leads and plugs (10mm spiral core leads and NGK iridium plugs). I've checked and double checked every lead.
Could it be the Dizzy cap and rotor? (It's a VT 1 GTS with the 5.7 Harrop stroker)
Any help or ideas would be great. Is there something I've missed?
I am no expert but it still sounds like a faulty O2 sensor if the light comes on. Had nightmare problems when fitting 'sports cats' to one of my cars with sensors, then went catless and still problems albiet lesser than with the cats, then Monkfish moved the position of the sensors and problem solved. Rather than muck about as I did (for 3 months 
) I would suggest you ask Roger at Monkfish to sort it for you. Best of luck.
) I would suggest you ask Roger at Monkfish to sort it for you. Best of luck. Edited by Paul-C on Monday 19th February 13:11
Check for exhaust leaks etc too. It will make the o2 think its lean and dump in fuel.
You could pop a wideband on there to check whats happening and do some logging as well.
See what your fuel trims are. They will indicate if the car thinks it needs to put more fuel in or not.
If it has aftermarket headers the o2 sensors might not be getting hot enough to switch properly, apparently they get lazy and dont work well. Eventually if you are too rich the cats will die....
You could pop a wideband on there to check whats happening and do some logging as well.
See what your fuel trims are. They will indicate if the car thinks it needs to put more fuel in or not.
If it has aftermarket headers the o2 sensors might not be getting hot enough to switch properly, apparently they get lazy and dont work well. Eventually if you are too rich the cats will die....
woody vt said:
Thanks for the input. I'll see what happens after the new cats are fitted. I do have headers so maybe...
Not entirely sure about the O2 sensors as they are new and the fault code doesn't implicate them directly. It's just a "Rich exhaust". Still a possibility yet I guess.
Not entirely sure about the O2 sensors as they are new and the fault code doesn't implicate them directly. It's just a "Rich exhaust". Still a possibility yet I guess.
woody what reader are you using? I have an ODBII reader but get no joy with it
Stigmundfreud said:
woody vt said:
Thanks for the input. I'll see what happens after the new cats are fitted. I do have headers so maybe...
Not entirely sure about the O2 sensors as they are new and the fault code doesn't implicate them directly. It's just a "Rich exhaust". Still a possibility yet I guess.
Not entirely sure about the O2 sensors as they are new and the fault code doesn't implicate them directly. It's just a "Rich exhaust". Still a possibility yet I guess.
woody what reader are you using? I have an ODBII reader but get no joy with it
I just have to short out two of the pins on the port and use the powertrain light to read any faults with a combination of flashes (a bit like morse code). The VT2 gen 3 cars can do this also and I would think the Monaro would be the same. I can email you instructions on which pin etc etc from my book if you wish as well as all the Gen 3 codes and meanings. I have the 5.0 ones and the V6 ones too should anybody else need them.
Thanks for the offer Bob but the port setup is ever so slightly different for the older cars. EFI live can read and log everything for me as you say but I need a slightly different connector from Aus (next on my shopping list now!).
We will definitely meet soon though I promise! Everytime I think I can get to one of the meets, HRH either sends me somewhere or puts me on a rubbish duty
We will definitely meet soon though I promise! Everytime I think I can get to one of the meets, HRH either sends me somewhere or puts me on a rubbish duty
meant to let you know and forgot, we had a great run out round Loch Lomond on Sunday, bigwheel, myself and a bunch of Vectra C owners. Fabulous weather, quiet roads, decent grub and some entertaining driving on the way home out via Stirling - Glen Ogle even better than the run up to the Rest and be Thankful. We're hoping to meet up again this Sunday at the Scottish Motorsport show at Lanark market. Looks like a good day out - chance to get a ride in a car driven with a certain Colin McRae apparently........www.scottishmotorsportshow.co.uk
As for that connector - take it ringram doesnt have any in stock?
As for that connector - take it ringram doesnt have any in stock?
woody vt said:
After phoning Roger at Monkfish, I ordered new O2 sensors and fitted them. I noticed that the previous owner had obviously changed them at some stage as they were cheap universal types that had been spliced into the old connectors.
Been thinking about your problem when I suddenly wondered.........when you say 'spliced into the old connectors' was the original wiring altered / cut in any way? If so this is the problem, it cannot be cut / spliced / soldered etc, the wiring has to be replaced. Checked with Roger at Monkfish to make sure I was right BTW.
If it isnt this, and the O2 sensors are not faulty, it will be their position for sure.
I've already got me coat on if not
Thanks Paul. I didn't explain very clearly but I meant the connectors had been cut from the original sensors and soldered onto the universals to enable fitment. The main loom on the car is unmolested. I'm waiting for an obd1 connector to arrive from Aus so I can see exactly whats happening. I wondered if the Engine coolant temp sensor might have an effect as I noticed that when cruising on the motorway, my temp gauge indicates between 79 and 81 degrees C which seems a little low. I have recently found the rich indication is limited to the left side of the engine, so maybe a bad O2 sensor loom??? Fault diagnosis also points towards fuel pressure regulators, possible leaky injectors and all manner of other things. I really need to get a proper diagnostics machine on there before I go and do too much.
Where should the sensors be repositioned if that is indeed the problem?
The new cats are on now too incidently and I had the Wortec middle boxes removed.
What a growl!
Where should the sensors be repositioned if that is indeed the problem?
The new cats are on now too incidently and I had the Wortec middle boxes removed.
What a growl!woody vt said:
Thanks Paul. I didn't explain very clearly but I meant the connectors had been cut from the original sensors and soldered onto the universals to enable fitment. The main loom on the car is unmolested. I'm waiting for an obd1 connector to arrive from Aus so I can see exactly whats happening. I wondered if the Engine coolant temp sensor might have an effect as I noticed that when cruising on the motorway, my temp gauge indicates between 79 and 81 degrees C which seems a little low. I have recently found the rich indication is limited to the left side of the engine, so maybe a bad O2 sensor loom??? Fault diagnosis also points towards fuel pressure regulators, possible leaky injectors and all manner of other things. I really need to get a proper diagnostics machine on there before I go and do too much.
Where should the sensors be repositioned if that is indeed the problem?
The new cats are on now too incidently and I had the Wortec middle boxes removed. What a growl!
Where should the sensors be repositioned if that is indeed the problem?
The new cats are on now too incidently and I had the Wortec middle boxes removed.
What a growl!Please let me know what you find with the diagnostics machine, I hate problems like this! Roger moved the sensors further away from the original cats position (which had been removed) which cured mine, he will be able to guide you. I wasn't there when it was done sorry.
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