Injectors or Cat or both?
Thread Starter
Joined: Jun 2006
Posts: 7
From:
Injectors or Cat or both?
Hi folks,
Someone out there can save me a whole lot of time and money by answering this:
1997 E420. One day my check engine light started flashing, I lost a lot of power instantly and barely limped it home. The local mechanic pulled all the codes and said I need 4 injectors and an air pump. All 4 injectors on the driver's side cylinder bank were not working.
When I start the car cold, I hear the infamous cat rattle.
Is it possible that the computer shut down the bank b/c the cat is bad? Is it possible that the cat isn't bad and I actually need 4 injectors?
Any advice is appreciated. Thank you!
Someone out there can save me a whole lot of time and money by answering this:
1997 E420. One day my check engine light started flashing, I lost a lot of power instantly and barely limped it home. The local mechanic pulled all the codes and said I need 4 injectors and an air pump. All 4 injectors on the driver's side cylinder bank were not working.
When I start the car cold, I hear the infamous cat rattle.
Is it possible that the computer shut down the bank b/c the cat is bad? Is it possible that the cat isn't bad and I actually need 4 injectors?
Any advice is appreciated. Thank you!
Super Moderator
Joined: Feb 2006
Posts: 889
From:
RE: Injectors or Cat or both?
>When I start the car cold, I hear the infamous cat rattle.
The"rattle" is a sign that the CAT is old and likely needs replacing.
Most manuals will recommendto replace them if they rattle, butyou can continue to use the cat until it stops reducing oxides. A cat failure code will be generatedwhen they are out of limit.One thing you need to look out for is if the cats have melted down and/or become clogged. If this has happened, they must be replaced.
>Is it possible that the computer shut down the bank b/c the cat is bad? If the cat is no longer reducing oxides, and is ie "used up", a code will be generated and stored stating this. The car should still run, but the check engine light will stay on, and it will not pass emmissions. If the cat has become clogged it certainly will shut the engine off, but I don't believe a code is generated for "clogged" cats. Some do-it-yourselfers will let the car cool down, remove the section of pipes with the cats, and test them by blowing air through them with a garden leaf blower, (the kind you plug-in and blow leaves off the driveway). Plenty of air should pass right through with little resistance. If the air backs-up, or is significantly blocked, obviously the cats are clogged.
>Is it possible that the cat isn't bad and I actually need 4 injectors?
Its possible. The injectors can be bench tested. There are elaborate tests at facilities, and some hobbyists will simply test them with an air compressor, some soapy water, and a 9 volt battery.If all the injectors on that banktest to be bad, its possible that that bank ran very hot, since overheating will ruin an injector by melting the little filter inside preventing all flow. A clogged cat could cause this side to run hot, soyou need to test the parts to find out. If your mechanic has already determined this, it is likely the problem. Blue
The"rattle" is a sign that the CAT is old and likely needs replacing.
Most manuals will recommendto replace them if they rattle, butyou can continue to use the cat until it stops reducing oxides. A cat failure code will be generatedwhen they are out of limit.One thing you need to look out for is if the cats have melted down and/or become clogged. If this has happened, they must be replaced.
>Is it possible that the computer shut down the bank b/c the cat is bad? If the cat is no longer reducing oxides, and is ie "used up", a code will be generated and stored stating this. The car should still run, but the check engine light will stay on, and it will not pass emmissions. If the cat has become clogged it certainly will shut the engine off, but I don't believe a code is generated for "clogged" cats. Some do-it-yourselfers will let the car cool down, remove the section of pipes with the cats, and test them by blowing air through them with a garden leaf blower, (the kind you plug-in and blow leaves off the driveway). Plenty of air should pass right through with little resistance. If the air backs-up, or is significantly blocked, obviously the cats are clogged.
>Is it possible that the cat isn't bad and I actually need 4 injectors?
Its possible. The injectors can be bench tested. There are elaborate tests at facilities, and some hobbyists will simply test them with an air compressor, some soapy water, and a 9 volt battery.If all the injectors on that banktest to be bad, its possible that that bank ran very hot, since overheating will ruin an injector by melting the little filter inside preventing all flow. A clogged cat could cause this side to run hot, soyou need to test the parts to find out. If your mechanic has already determined this, it is likely the problem. Blue
Senior Member
Joined: Dec 2004
Posts: 2,410
From:
RE: Injectors or Cat or both?
Which cat rattles? The pre-cat adjacent to the manifold or the one adjacent to the gearbox. Listen with a bit of hose. WARNING: Watch you don't burn yourself or get too close to the pulley belt
Running with a disintegrating pre-cat is bad news and can wreck the engine but usually it is the gearbox cat that rattles (horizontal installation) This cat does not send a signal to the ECU since the O2 sensor(s) are situated either side of the precat. i.e. No sensor after the second cat. Need to do as blue Silver suggests to ensure cats are not blocked which could cause overheating. When cats have been rattling for a long time the monolith (cat block) disintegrates down to a size where potentially it can block the outlet from the can IF the holes in the cat block are NOT ALIGNED with the direction of exhaust flow. Hence blocked exhaust.
All four injectors on one bank failed at once? Possible (overheated as BlueSilver suggests) but unlikely. Possible wiring/connector issue?
Did the car knowingly overheat at some point?
What codes did the garage find? Sure you can trust the garage? Second opinion MIGHT save you some money.
The air injection pump supplies air (O2) to warm up the cats more quickly on cold start etc. These do fail but LACK OF O2 (pump not running) is in conflict with overheating. Maybe the pump has been running to long which overheated the cats and also lead to the pump wearing out. Possible but not the usual failure mode. Usual failure is lack of aux pump running= lack of O2.
Does the car idle OK? If so this suggest the injectors can't be too bad since the amount of fuel is controlled by the duration of the ON pulse.
If the engine runs rough at idle which cylinders are misfiring? (OBD codes will help).
If you swap over the (faulty?) injectors you will be able to demonstrate that the misfire moves with the injectors BEFORE buying new ones.
What causes the car to go into Limp Home/ Acceleration?
If you drive very carefully with MINIMUM acceleration can you get the car to avoid going into LH?
Limp Home occurs when the engine has detected severe misfire and reduces power by applying preset criteria to the fuelling ECU which impacts gearchange and vehicle speed/engine revs etc. Whole idea is to get you home with minimum inconvenience whilst limiting harmful emmission to the absolute minimum. Misfire is the trigger. As a driver you get the impression...You just made it home!
Misfire can be caused by 1001 things. The usual culprit is the MAF if the car has a full Service History. Diagnostic codes will assist here.
Good luck,
Stuart
Running with a disintegrating pre-cat is bad news and can wreck the engine but usually it is the gearbox cat that rattles (horizontal installation) This cat does not send a signal to the ECU since the O2 sensor(s) are situated either side of the precat. i.e. No sensor after the second cat. Need to do as blue Silver suggests to ensure cats are not blocked which could cause overheating. When cats have been rattling for a long time the monolith (cat block) disintegrates down to a size where potentially it can block the outlet from the can IF the holes in the cat block are NOT ALIGNED with the direction of exhaust flow. Hence blocked exhaust.
All four injectors on one bank failed at once? Possible (overheated as BlueSilver suggests) but unlikely. Possible wiring/connector issue?
Did the car knowingly overheat at some point?
What codes did the garage find? Sure you can trust the garage? Second opinion MIGHT save you some money.
The air injection pump supplies air (O2) to warm up the cats more quickly on cold start etc. These do fail but LACK OF O2 (pump not running) is in conflict with overheating. Maybe the pump has been running to long which overheated the cats and also lead to the pump wearing out. Possible but not the usual failure mode. Usual failure is lack of aux pump running= lack of O2.
Does the car idle OK? If so this suggest the injectors can't be too bad since the amount of fuel is controlled by the duration of the ON pulse.
If the engine runs rough at idle which cylinders are misfiring? (OBD codes will help).
If you swap over the (faulty?) injectors you will be able to demonstrate that the misfire moves with the injectors BEFORE buying new ones.
What causes the car to go into Limp Home/ Acceleration?
If you drive very carefully with MINIMUM acceleration can you get the car to avoid going into LH?
Limp Home occurs when the engine has detected severe misfire and reduces power by applying preset criteria to the fuelling ECU which impacts gearchange and vehicle speed/engine revs etc. Whole idea is to get you home with minimum inconvenience whilst limiting harmful emmission to the absolute minimum. Misfire is the trigger. As a driver you get the impression...You just made it home!
Misfire can be caused by 1001 things. The usual culprit is the MAF if the car has a full Service History. Diagnostic codes will assist here.
Good luck,
Stuart
Thread
Thread Starter
Forum
Replies
Last Post
