Could it be the catalytic converter ?

Hi guys,


I would much appreciate your opinion on this matter: my 325i (114k) has good performance in the 1st gear (i.e., starting from stopped position). The 2nd and 3rd gear is poor however (acceleration is very sluggish, takes quite some time to pick up speed). Acceleration in the 4th gear is again pretty strong. My gut feeling tells me the tranny is nearly busted (have replaced the torque converter recently with no much improvement).

The reason the thread title is dealing with the cat is that sometimes I was able to smell something funny coming out of exhaust (I confess that at the beginning I was overfilling the engine with oil so that might explain the smell ). My exhaust is also quite noisy and when I took the whole exhaust out while changing the torque converter, I could hear something that appear to be "coarse dust" inside the cat. The muffler exit looks clean (no soot).

No CEL light but recently the average consumption went up and now I am at 21.4mpg for combined driving (have not reset it for like at least a month). But I guess that could also be linked to the AC running almost all the time ...

Another weird thing is that my car seems to have moods. Sometimes its performance feels much better than other times but I am yet to figure out what triggers those mood swings. I've changed the injectors recently therefore it's not that.

So what do you think ? Can my cat be on the way out ? Can an almost failed cat give poor performance on 2nd and 3rd gear ? I feel that that would be very unlikely but knowing how much a new tranny costs , I thought I'd ask anyway.

Thank you.

Search for 'Stomp Test' and report back with any codes.

Hi Jonesin,

Did the stomp test. The result was 1444 - no fault codes stored/found.

how'd you see particulate from the cat when you dropped the exhaust??

also, a bad (as in clogged) cat does not 'get better', or 'act up' only in a particular gear.

if you suspect a restriction in the exhaust, then it would be consistent through the range, not just in 1 gear or 2.

you could get a backpressure test done, as well as a cat effficiency test, but they'll cost you some money better well spent checking the simpler things like fuel pressure, top engine cleaning (a sort of fuel injection service) with seafoam, and cleaning the iac and throttle plate.

as for smelling something, what does it smell like?? old socks, newspaper, polo ralph lauren?? rotten eggs is an indication of a cat that is overworking, and if you are not thrashing it about then you may have something else going on there.

also, what fuel are you using??


why did you replace the tq converter??




df

Buy a temp laser and check temp before and after the cat, after a ten min drive, after cat should be about 10% hotter then before cat. To check back pressure, find an old o2 sensor and drill it out. Buy a brass fitting so you can attach an vacuum line to it. Weld or soder or screw it to the o2 sensor and install it before cat. Your going to want to check pressure on the car when it's hot. If my memory serves me right I think normal spec on any car should be bellow 2.5 psi at 2k RPM anything more is a clogged cat. But if it was clogged you would know it even in park by trying to rev it up, plus you would get a random miss fire code. Hope the info helps.

Hi drivinfaster,

Originally Posted by drivinfaster

how'd you see particulate from the cat when you dropped the exhaust??

I dropped both the cat and the muffler and separated them. When I shook the cat, I could hear something as coarse dust rattling inside.

Originally Posted by drivinfaster

as for smelling something, what does it smell like?? old socks, newspaper, polo ralph lauren??

No need to be sarcastic ... that would only drive people away from this site .

Originally Posted by drivinfaster

rotten eggs is an indication of a cat that is overworking, and if you are not thrashing it about then you may have something else going on there.

My first impression was that it smelled of something being burnt ... But believe me it was a kind of smell I can hardly describe. For some unknown reason the smell seems to have disappeared recently.

When I did the last oil change I've put 9 - 9 1/2 qts of oil in the car (Bentley says 7 won't make the same mistake again) because judging by the dip stick 7qt just didn't seem to be enough. That smell was strong at the time. But now, 2500 miles later and with no oil top up at all, the smell is gone as far as I can tell (that is, before I could have smelled it a yard distance from the car - today I can't, even close to the car). So I wonder if overfilling with oil didn't have anything to do with it.

Originally Posted by drivinfaster

also, what fuel are you using??

Only grade 89 or higher as written on the fuel tank cap. Exxon, Shell and Costco when the price goes through the roof .

Originally Posted by drivinfaster

why did you replace the tq converter??

Because it was slipping and was advised that it would be much cheaper to change that and see if it gets better than the whole transmission.

Regarding performance, the best I can describe is this: I am stopped at the traffic light on "pole position". When lights turn green, I take off and leave everyone behind. Then tranny switches into 2nd ..., acceleration deeps and next everyone else passes me by ...

Thanks very much for your input and advices Pat7762. Appreciated !

Originally Posted by bmw4te

Hi drivinfaster,


hi
I dropped both the cat and the muffler and separated them. When I shook the cat, I could hear something as coarse dust rattling inside.

then if it is rattling and spilling out debris, then yes. your cat has deteriorated. you will need a new one...

No need to be sarcastic ... that would only drive people away from this site .

if i had a dollar for every time i heard that...

My first impression was that it smelled of something being burnt ... But believe me it was a kind of smell I can hardly describe. For some unknown reason the smell seems to have disappeared recently.

could have been a plastic bag maybe. i've pulled a lot of those off exhausts in the past. they eventually burn off, but will smell rather funky until then.

When I did the last oil change I've put 9 - 9 1/2 qts of oil in the car (Bentley says 7 won't make the same mistake again) because judging by the dip stick 7qt just didn't seem to be enough. That smell was strong at the time. But now, 2500 miles later and with no oil top up at all, the smell is gone as far as I can tell (that is, before I could have smelled it a yard distance from the car - today I can't, even close to the car). So I wonder if overfilling with oil didn't have anything to do with it.

or you could also have a leak...

Only grade 89 or higher as written on the fuel tank cap. Exxon, Shell and Costco when the price goes through the roof .

good. can't tell you how many times we've attempted to assist people only for them to turn around and confess they were using less than required fuel grade...


Because it was slipping and was advised that it would be much cheaper to change that and see if it gets better than the whole transmission.

slipping is not the first thing i think of as a symptom of a failing tq converter. they usually shutter, and most times fail to maintain lock up (which could be caused by so many other things that should be checked *prior* to replacing one). having been in the business for many years, i found that only about 20% of the tq converters i saw replaced were necessary, but since it was 'factory warranty' they were replaced wholesale...

fluid level and condition should be 1st, then engine performance should be verified as proper, things like the tps, brake switch, coolant sensor, tcc solenoid should also all be checked as well before replacement.

Regarding performance, the best I can describe is this: I am stopped at the traffic light on "pole position". When lights turn green, I take off and leave everyone behind. Then tranny switches into 2nd ..., acceleration deeps and next everyone else passes me by ...

again, it appears that you have a failing cat, and that should be replaced. however, it has been my experience that cats do not fail, then unfail, then fail again based upon engine speed and load. however, since it does in fact appear that by your description that you have a bad one, i would look into getting one and replace it, or, hollow that one oout and see if this driveability issue is still present.

also, things like plugs, coils, dirty injectors, and such should also be checked. fuel filter and fuel pressure as well.


as far as the shop telling you to replace the tq converter, were they a trans shop?? it has also been my experience that 99% of the guys out there spinning wrenched don't know a thing about auto transmissions (or else they'd have their a2 cert ) except how to replace them.


oh yeah, and as for my *sarcasm*, don't worry. it's not contageous.



df

Hi Drivinfaster,

I apologize for this late reply but was very busy recently.

First, thank you so much for all the details and explanations provided which are excellent teaching material and I am truly grateful for that.

Now about the CAT. Expensive piece of kit !! Pelican has it for $800 (OEM). I've found some other shops online that sell compatible units for $500. Any advice ?

By the way, my exhaust smells nothing like the exhaust from a new car. Will that further confirm that my CAT is dying ?

Furthermore my muffler must be punctured somewhere as my exhaust is loud. It only slightly growls when stationary and idling but the noise gets far more "vocal" when I give her gas. I also feel slight continuous vibrations in the gas pedal when accelerating, especially at low speeds.

I'll leave the discussion about the tranny (and maybe fuel pump) for tomorrow.

Question: could this growling sound also come from a faulty cat ?

Not likely for that sound to come from the cat. There is a little good news however, you can use an aftermarket, such as a Magnaflow ($491.52 from http://rockauto.com) opposed to an OEM. Far cheaper. THough with other aftermarket brands, I personally would check back here to confirm others have used a brand successfully before going cheaper than that.

Originally Posted by jonesin

There is a little good news however, you can use an aftermarket, such as a Magnaflow ($491.52 from http://rockauto.com) opposed to an OEM. Far cheaper.

Thank you very much for the tip Jonesin !!! Will buy a cat + muffler from there.

Now with that out of the way, I would like to get back to performance + (maybe ?) tranny issue.

I've recently noticed that every time I begin accelerating, mostly on hard acceleration, I hear clicking noises. Can't really tell where they're coming from though. Could they have anything to do with transmission ?

Originally Posted by drivinfaster

[...]having been in the business for many years, i found that only about 20% of the tq converters i saw replaced were necessary[...]

You're right about that. Changing the TQC did not fix the problem. The only good outcome was that I learned a lot by taking the tranny out and replacing the real seal

Originally Posted by drivinfaster

[...]things like the tps, brake switch, coolant sensor, tcc solenoid should also all be checked as well before replacement.[...]

Have changed the tranny filter and fluid 4 times by now in the past one and a half year I owned the car. I had a small leak by the gear selector seal, which I've fixed so I am planning to do a fluid "top up" soon just in case ...

If I accelerate hard in the first gear, shifting to the second is jerky and rough. Could that be a symptom of a slightly low fluid ? On the other end, a gradual acceleration will produce smooth gear shifting.

TPS = new one installed a few months ago. However I have not changed/tested the throttle valve switch (PN 13631703562) that sits on top of the throttle housing. That one being $80 I hesitated to do it blindly ... But if you think it's worth doing ... I will.

Brake switch = you mean the brake light switch ? Yes, changed that one already. But can that have an impact on performance ?

Coolant sensor = there are two and both were changed.

Tcc solenoid = appears to be two on my tranny (PN 24337537062 and 24337537063). They seem to be enclosed by the larger tranny sump. Haven't touched those but are they replaceable/DIY-able ? $50 each at ECS tunning. If DIY "doable", I will replace them as they are not that much.

Originally Posted by drivinfaster

[...]also, things like plugs, coils, dirty injectors, and such should also be checked. fuel filter and fuel pressure as well.

- Plugs: new NGK a few months ago
- coils: new from ECS Tuning a few months ago
- dirty injectors: all new (rmfd) from Pelican Parts a few months ago
- fuel filter: changed last summer
- fuel pressure regulator: changed 2 months ago. Because I overfilled with oil , most likely oil got into the vacuum hose linking the regulator to intake manifold. Is that a problem ?

To check the fuel pressure I guess I will have to take it to my indy shop, right ? Strange that if I level the gas pedal, the car gets a sudden "bust" - that's the acceleration I would like to have but without really flooring it. I mean, the response to depressing the gas pedal is not linear - more like all or nothing. Is that normal ? Or is something wrong with fuel pump ?

Thank you very much for your help.

Bump !

Don't know why you bumped. The ball is in your court. Last you posted you were going to take it to your indy mechanic. Until you do that, there's not much we can suggest that hasn't been covered.

Hi hornhospital,

Originally Posted by hornhospital

Last you posted you were going to take it to your indy mechanic.

I did not say that. What I said was:

Originally Posted by bmw4te

To check the fuel pressure I guess I will have to take it to my indy shop, right ?

So it was a question: do I have to take the car to an indy shop for that test ?

But the reason I bumped was because I've asked quite a few questions. Here they are again (more details on my previous post):

1) What's the story with the clicking noise I am hearing while accelerating ? Tranny, differential, U-joint ?

2) How can I test the throttle valve switch ? Do I need to change that part ?

3) Brake switch = same as the brake light switch ?

4) Tcc solenoid = should I change them ? Which one or both ? Can I do it by myself ?

Originally Posted by bmw4te

Hi hornhospital,



I did not say that. What I said was:



So it was a question: do I have to take the car to an indy shop for that test ?
no, but you will need to get a fuel pressure tester

But the reason I bumped was because I've asked quite a few questions. Here they are again (more details on my previous post):

1) What's the story with the clicking noise I am hearing while accelerating ? Tranny, differential, U-joint ?
read the sticky about the noises your car makes. it's at the top of the forum.

2) How can I test the throttle valve switch ? Do I need to change that part ?
you need at least a dvom to check rest voltage, then (depending on the sample rate of the dvom) slowly sweep the throttle to wide open throttle. the best tool is a power graphing meter or oscilloscope (pricey), or an oe scan tool (even more pricey)

3) Brake switch = same as
the brake light switch ?
i do believe so

4) Tcc solenoid = should I change them ? Which one or both ? Can I do it by myself
the tcc solenoid is only 1. the rest of the solenoids are shift circuit solenoids. you will need to know which one is which, but i do not believe that these are your problem. if so, you would most likely have a check engine light somewhere.

i hope this answers your questions.


now, as to what you *should* do?? i suggest read up on the stickeies at the top of the forum, learn from them.

watch 'how to' videos on the subjects that you asked about. even if it is not bmw specific, there are proceedures that are similar in things like checking fuel pressure, throttle position sensors, and such. learn from them.

watch them several times.

get a bentley manual.

and until you have enough confidence in your skills, i suggest you look into maybe take some evening courses at the local vo-tech center. it'll give you some experience and some understanding on general automotive repairs.






df

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Not to spark a debate, but how would anyone know if you have any mechanical knowledge? If someone takes time out of their day to answer your question and you come up with some attitude for no reason, don't expect to get much help from then on. Don't like the response, just ignore it.

<... content removed as it did not have relevance to the subject discussed ... >

Just a quick point to note: many of us give quite similar advice that df have to you. It was not in any way intended asa slight. Instead of abbreviating it it could have continued to say "if you have already attained a solid comfort level with basic (or higher) DIY-ing, then great! Were here to help with questions."

But I know for certain that had I been the one to have written what df did then I would have considered my codicil above to be an implied premise and not bothered to state it either.

Df (though short) is y far and away one of the most knowledgeable people on this (our many other) forum (s).

Thank you Jonesin for your reply. Appreciate it. Always a pleasure to talk to you.

It seems that sometimes same sentence read by two people leads to two completely different meanings.

Based on the feedback received it appears that people think I was very upset that drivinfaster questioned my skills. But in reality what tripped me was what I have perceived as a dismissal. I felt I was told: "what you should do is learn at least something about cars then maybe come back here and ask questions again. But until then, don't bother." That how it sounded to me, perhaps different meaning to others.

Maybe he did not mean that at all but alas, that's the message that transpired to me last night. Which I guess explains my reply.

Well, I'm over it now and in fact reading on the sticky he mentioned although so far that deals with sounds from the rear only. My acceleration triggered click-grinding sound (bad bearing ?) seems to rather come from the front or middle section but it's darn hard to pinpoint it exactly .

Take care.

while i do not intend to offend anyone when i post replies, i also am not psychic and can gain understanding on exactly what 'skill level' one posesses.

i have worked with guys that were a whiz at ac, but couldn't find their wayout of a paper bag with an engine performance diag. similarly, guys that were a fast suspension tech, or good at engine swaps that couldn't figure out basic electrical issues.

the fact that you posted that you were able to r&r a tq converter (after going to a repair shop for advice), and subsequent questions regarding additional concerns led me to believe that you were what i would consider mechanicaly inclined, but not an automotive technician.

now before you get bent (again), please understand that i made the recommendations not to be insulting, but rather to help you gain understanding so that you could do the repairs with confidence.

and for the record, i would have made these suggestions to *any* member, not just you.


however, if you still wish me to not post in your threads then i will oblige.



df

edit: check your guibo, and center support bearing, as well as mounts irt the noise upon acceleration.

Hi drivinfaster,

Thank you for your message and clarifications. They were very welcomed and appreciated.

You were right about me only being a mechanical inclined person. Unfortunately the kids, the job and the age could prove to be a serious obstacle for me in getting closer to the status of automotive technician. But I'll keep on learning and hopefully with the help of great people of this forum I will keep/get my bimmer in good shape (and affordable ).

Now it appears that I misread your post and your intentions therefore I am sorry and I apologize for my abrasive reply. Going forward and if it is OK with you, I would like to put that issue to bed. Please disregard my request of not posting on my threads - it was an unfortunate knee-jerk product of late hours and frustration.

Originally Posted by drivinfaster

check your guibo, and center support bearing, as well as mounts irt the noise upon acceleration.

I've changed the guibo recently when I did the TQ. The old one was in very good shape actually but since I had bought a replacement, I changed it anyway (and there is always eBay for the old one ). I have also bought a replacement for the central driveshaft bearing but have not changed the existing one as it looked still in good shape to me (and was in a bit of a hurry to get the car back on the road at the time). Now looking back I think I should have spent the extra hour to change it ... oh well ... Judging by the "alignment marks" I've found on the driveshaft I think the previous owner must have changed them before at some stage. Anyway, changing the cat will give me a good opportunity to work in that area again .

The tranny mounts were changed at the same time.

Maybe I'm wrong but after more digging I begin to suspect the rear CV joints and/or the differential. I do not know enough yet to comment further and still doing some "tests". I have the impression the noise is not audible when the card is cold (i.e., when I start in the morning). But need to confirm that and get back.

There is another detail I would really appreciate to get your input on: after like an hour and a half of driving, the gearshift "housing" gets hot (it won't burn my hand but in some spots it is as hot as the hood). Did some googling and found a thread saying it could be either the driveshaft tunnel firewall or the cat. I personally put back the tunnel firewall when did the TQ so unless they deteriorate over time, that cannot be the cause. Which leaves me with a potentially overheating cat. If that is a correct assumption, how safe is it to drive the car ?

Thank you very much for your time taken to read this.

Take care,
bmw4te

it's not uncommon for the shifter to get warm on long drives. of course exactly how warm 'warm' is, could be an entire topic of debate in and of itself.

i say as long as the metal or other parts are not too hot to touch in order to shift, or rest your hand on then i would not worry.

if the side of the tunnel begins to get hot, though, and you can feel the heat radiating through your jeans to singe the hair on you calf, then, yeah, i'd say that you have a problem. or if you start to smell funky odors, or see smoke. then that might be an indication that something is very wrong somewhere...

friction usually results in heat, and excessive friction results in excessive heat. excessive heat usually results in smoke, steamy hot parts, or things melting, making noises, and just in general all sorts of malfunctioning occurs.

you may wish to check fluid levels, and, when the condition presents, be at the ready to inspect the drivetrain and suspension. (much easier with a drive on lift, but...)

you may wish to do a 'cold' inspection to assess the free play and whatnot of the drivetrain and rear suspension, then, when warm (meaning the condition is presenting) look underneath again and do a comparison to see what appeares to be 'looser'.

other than that it appears that it will be a 'check this' and 'check that' until ou feel confident thatg you have located the culprit. again, the stickies may assist greatly in pointing you in a particular direction.

this is also another reason why i stress to posters to post resolutions and results of their efforts.



df

I think you indicated that you weren't getting any codes. Isn't the ultimate test then for a cat is to go to a mechanic or a testing station with an exhaust gas analyzer? That seems like you could get a definitive answer from the results.

a cat can be tested for o2 retention as well as the ability to reduce co2 and hc. however, the op stated the cat was deteriorating and falling out when he had it apart for a previous repair. so that works as well.

and even when a code is present, as is common on obd2 vehicles, i *always* suggest a confirmation test, unless you wish to spend hundreds on the 'say so' of a mindless machine...

garbage in garbage out works on cars as well, not just pc's.





df