|
|
Post by 77shaker on Nov 21, 2015 4:53:02 GMT 1
I just signed up here hoping to get some help with this since other forums are more vehicle specific help and not actual mechanic help. I am having some trouble with this p0420 code (Catalyst System Below Threshold). I am almost ready to do a whole motor swap to a carbed motor here if this doesn't get fixed. Vehicle is a 1999 Chevy S10 4.3 VIN W. Exhaust setup is stock manifolds to a resonator delete, Magnaflow cat into a Pypes Muffler. I had a cheap Thunderbolt cat on last year to replace the stock cat which went bad. That Thunderbolt cat went bad in about 6,000 miles. The Magnflow cat is now the third cat this truck has had at 16x,xxx Miles. Something not right there. I figured putting a name brand good cat on would help but the code is still there. When the magnaflow cat went in a few thousand miles ago i replaced the sensor in the cat. The code popped up and i erased to see if it would come back on. It did. It's been on for quite a while and i'm tired and very annoyed at how the truck drives. I get very very spotty power decreases. Bad MPG and odd idle sometimes. A tractor trailer can pull harder than this truck can right now. I just replaced the o2 sensor with an AC Delco yesterday and have about 50 or so miles on the truck since then and light is still on. Same code. Now for the parameter reading i am getting steady rich/lean reading for the pre cat sensor. the post cat sensor which is brand new now is reading the same as the other sensor which is very slow rich/lean very sporadically. Sometimes a big jump and sometimes a small jump. Isn't this sensor supposed to be a steady reading and not a rich/lean jump? If it is then this sensor would be saying the cat is bad but the cat is brand new! I am so lost with what is wrong and i figured i will try and get more input on this before i start replacing thing after thing. I am going to drop the cat and inspect it but i peeked in there and everything is there. Nothing loose. I'm lost on this. I hate computerized cars unless it's new car. Please any help appreciated. My inspection is in February and i want to get this fixed before snow and freezing weather. Here is the truck.  |
|
|
|
Post by Noberator on Nov 21, 2015 9:11:43 GMT 1
Hello and Welcome to the Forum.  This is a UK based Forum so not familiar with your truck and set up.  A scope should show the oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady if it isn't it's pointing towards the rear Cat is faulty or blocked hence down on performance. Is there any damaged to or leaking exhaust manifold, catalytic converter,muffler, exhaust pipe?  I'm not familiar with the Thunderbolt Cat so is it an aftermarket one or whether it's Manufacture approved (OEM unit.) Aftermarket ones in my experience don't last long. |
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Nov 21, 2015 15:18:23 GMT 1
LOL, he has already stated it runs bad !!
|
|
|
|
Post by 77shaker on Nov 21, 2015 15:37:59 GMT 1
I had no idea this was uk based lol.
Its a chevy 4.3 v6 motor. If thst helps any.
The thunderbolt is long gone and it was aftermarket.
It has a magnaflow one on there now which is basically brand new.
I guess the thing to do is just pull the cat off and look.
The piping is new out of the intermediate pipe and back.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Nov 21, 2015 19:32:49 GMT 1
Take the lambda sensor out of the front pipe before the cat, stick a pressure gauge in and run engine, rev intermittently to max rev and immediately let it back to idle, observe the amount of pressure increase. Put sensor back in and remove rear sensor and repeat the test, compare the readings observed and let us know the results  |
|
|
|
Post by mayfly on Nov 22, 2015 14:56:57 GMT 1
Again not familiar with your truck but if you've replaced 3 cats and it's running bad then you have an underlying problem that needs sorting first. What are emission readings like ?
|
|
|
|
Post by Rhubarb on Nov 22, 2015 15:51:42 GMT 1
Its running rich!
Get someone to diagnose it, and stop throwing parts and money at it!
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Nov 22, 2015 16:53:50 GMT 1
Look for things on the engine that can cause it to run rich, things like, engine coolant temperature sensor circuit fault, mass air flow sensor, map sensor etc, but like others have said I also am not familiar with what is fitted to your truck. Not sure if Admin would allow me to direct you to another forum or not that knows about them types of vehicles, maybe he will reply |
|
|
|
Post by chippie on Nov 22, 2015 17:29:51 GMT 1
Look for things on the engine that can cause it to run rich, things like, engine coolant temperature sensor circuit fault, mass air flow sensor, map sensor etc Dirty air filter, start with basics...when was it last serviced? Live data would help..... |
|
|
|
Post by Rhubarb on Nov 22, 2015 17:48:45 GMT 1
Look for things on the engine that can cause it to run rich, things like, engine coolant temperature sensor circuit fault, mass air flow sensor, map sensor etc, but like others have said I also am not familiar with what is fitted to your truck. Not sure if Admin would allow me to direct you to another forum or not that knows about them types of vehicles, maybe he will reply That's fine by me but I don't think it will help him.. It's need a proper looking at and a scan. |
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Nov 22, 2015 18:34:37 GMT 1
Look for things on the engine that can cause it to run rich, things like, engine coolant temperature sensor circuit fault, mass air flow sensor, map sensor etc, but like others have said I also am not familiar with what is fitted to your truck. Not sure if Admin would allow me to direct you to another forum or not that knows about them types of vehicles, maybe he will reply That's fine by me but I don't think it will help him.. It's need a proper looking at and a scan. If that's anything like our place, it will definitely of had a proper looking at, everything changed even that didn't need changing and then it will be sent out still faulty  |
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Nov 25, 2015 20:22:31 GMT 1
77shaker, sorry I forgot to ask, but I must ask because I know its not been to our place, so the only other option is to ask, have it been to Volkswagen VW  |
|
raxx
Tea Maker
Posts: 103
|
Post by raxx on Dec 22, 2015 18:08:12 GMT 1
If and once you get it running right and the emissions are ok there are a couple of cheats available for P0420, I have played with a few to fix P0420 on some Toyota's and over sensitive cat efficiency detection parameters but in my cases there were no running issues and the vehicles in question passed a UK MOT emissions test with flying colours so the cheat just got rid of the P0420 popping up every two weeks on a slightly deteriorated cat...........
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Dec 22, 2015 18:35:38 GMT 1
If and once you get it running right and the emissions are ok there are a couple of cheats available for P0420, I have played with a few to fix P0420 on some Toyota's and over sensitive cat efficiency detection parameters but in my cases there were no running issues and the vehicles in question passed a UK MOT emissions test with flying colours so the cheat just got rid of the P0420 popping up every two weeks on a slightly deteriorated cat........... The problem is there is no manufacturer acurate catalyst monitor strategies published that i have seen , unless some one has them ?? |
|
raxx
Tea Maker
Posts: 103
|
Post by raxx on Dec 22, 2015 19:31:27 GMT 1
If and once you get it running right and the emissions are ok there are a couple of cheats available for P0420, I have played with a few to fix P0420 on some Toyota's and over sensitive cat efficiency detection parameters but in my cases there were no running issues and the vehicles in question passed a UK MOT emissions test with flying colours so the cheat just got rid of the P0420 popping up every two weeks on a slightly deteriorated cat........... The problem is there is no manufacturer acurate catalyst monitor strategies published that i have seen , unless some one has them ?? You're right, it seems to be up to each manufacturer to decide their own parameters and keep it very secret. In the early versions of the T25 Avensis Toyota had two issues; 1- excessive oil burn due to inadequate piston oil return flow and 2- tight cat efficiency detection parameters. So what happened was the oil burn started to degrade the front cat but not enough to fail an emissions test here in the UK (luckily that vehicle had a downstream cat too but after the downstream O2 which helped keep the emissions down) so the system detected poor cat efficiency of the main cat (manivertor) too early and threw the P0420. The software was not updatable in the cable operated throttle versions of the 1ZZ-FE so the fix was new ECU (with new software), new CAT and Toyota wanted mega bucks for it more than the car is worth in most cases so the alternate fix was to cheat the system as long as one is confident the emissions are compliant with our tests. On the fly-by-wire system introduced in 2004 on the T25 the software was updatable so when this problem arose Toyota were updating the SW and changing out the cat still costing around a grand tho. Thats the Toyaota story anyway, I'm sure other manufacturers have similar issues..... |
|
