Hi, I have a 1997 C280 with about 130k on the clock. A new problem has appeared, after the car is driven and hits normal operating temp., anytime you try to take the engine over 3500rpm hesitation and no power. I have replaced spark plugs, coils, mass air flow and set adaptions, fuel filter. There is no check engine light or codes. Before the car warms up runs perfect to 6500rpm or when it shifts? Thanks[/align]

 

How is you catalytic converter? it sounds like it may be clogged.

good luck

 

How can I test that? I think I have good exhaust flow, just passed emissions inspection last month.

 

guys check ur tranny. 130k ? its obvious, when the car is in cold mode or first start up its in open loop. high line pressure shifts hard no matter what then when it operates at normal temp or warmed up its in closed loop means its taking input from your B.O.O brake on off switch /T.P.S. throttle position sensor and PWM pulse width modulators to select gear changes. if your car wont shift thru all the gears warm im sure it wont shift thru all the gears cold either when its cold run it thru the gears manually until it warms up while moving i.e parking lot or somehing and get back to me- hope it explains a little.

 

C230RenntechI understand what you are saying, but would the trans effect engine power in park as well. B/c after the car hits normal operating temp even if I put it in park and try to go over 3500rpm cuts out no power, missing, but holds steady at 3500rpm. It almost acts like a rev-limiter, but when itscold in park it will hit 6500rpms no problem? One more thing, if I drive the car without going over 3500rpm I can drive at highway speeds in overdrive no problem.Thanks for the help I know this is incredibly tough to do, diagnose a car sight unseen. Thanks

 

yes and yes. here you go in park what band is applied ? any forward bands? u have to remember that one is held one is driven and one is drive inside ur tranny at all times except reverse. in park ur in a nuetral state. if u have no power in your car when ur trying to take off but ur okay at highway speeds it very well could be a bad torque converter. see a torque converter uses ur tranny fluid to create torque thru the stator which locks and unlocks depending on the drive condition. in manual modes ie selecting the gear makes u lockup the stator to take off. In cruising speed it is unlocked to alow constant motion u dont neccassarily need torque to go from 50mph to 60 pmh except hills. am i going to fast ? if ur cold and u can take off the line pressure is set oem high so its harder to notice a failure. when its warm all ur sensors kick in and start saying hey this is where i should operate oh crap im slippng what now? the only other idea without hearing the car and seeing it based on ur limited description is an input sensor ie. tps governor (no not mph) its in the tranny and or pending obd satus thats not catching but looping. its saying in real time i see a problem but its not triggering the light yet because it hasnt failed completely. say thanks to mercedes on that it happened to me with my kompressor premature failure do to the iat sensor reading colder which my maf adjusted with only factory parameters ok ill say +/- 3 degrees and caused arich condition which my kompressor kept trying to correct by pushing in more air and staying on longer. so it is electronic if it isnt ur torque converter or stator in ur tranny. but u cannot find it by doing some simple test. brake in drive then right foot the gas while braking slowly to see when the torque converter engages if it is high u have a problem if it is low ur alright but dont one wheelie peely ok? hahaha then u should be closer to an answer n where to find this rev demon ill be aroud let me know ok? hope i helped some..

 

sorry I was too busy for a couple of days to reply. to test for catalytic converter clog is relatively easy. I must also mention that it could also be your muffler that is somehow clogged (it happens every once in a while). in either case the amount of exhaust leaving your car is reduced when car is warmed up.

if converter/muffler is clogged (or partially clogged) I would look for the following:

Over time (as you drive a few tens or hundreds of miles)your 3500rpm would slowly drop and eventially getto the point where it just doesn't have enough juice to move you forward. eventually your top driving speed will also drop,will stall on the side of the road. has rpm/top speed in freewayslowly dropped over the past month?

#1 quick and dirty test (very inexpensive and relatively easy):
when car is warm, I would stick a potato on the exhaust such that it partially covers the output pipe (start with say 10-20% covered, also be careful when you touch sinceyou will have a hot potato and hot tail pipe). then step on the rpm and see if your 3500rpm still holds. incrementally increase covered area until it is fully covered. I would not run the car fully covered up more than 20-30 seconds. just put potato, turn on car, step on gas, observe where rpm drops, then turn off. Then increase covered area on pipe (careful with hot potato), turn on car, step on gas and so on. When fully covered the car should DEFINITELY loose rpm. Next take potato completely off and look once again for your 3500rpm. by now it should have dropped since you have accelerated the clogging process. If it has, chances are very high that something is clogged between the engine and output pipe.

#2 little more involved test, but will for sure tell you if a clog is your problem:
when car is cold (easier to touch things when cold) get under the car and un-bolt themuffler. On your model I am not sure if there is a sensor inside themuffler (you will need to check). then turn on the car, let it warm up andcheck the rpm when warm. if your rpm goes up, thenyou have it. also since you don't have amuffler, the car will make lots of noise. If this does not solve the problem then you will need to go closer to the engine and unbolt the catalytic converter.again here I am not sure if your model has a sensor in the converter (probably not since you are not getting any kind ofengine fault). then turn on car (car will be very loud when turned on) step on gas and check for rpm (for sure here you should be able to go to high rpm. if with the catalytic converter and all of the exhaust system off you still can not go to higher rpm, then this is definitive proof that there is something else going on. but I would be willing to bet 95% this is your problem.

QUICK AND DIRTY SOLUTION:
if your muffler is clogged, I would shake/tap/hit it and see if some of the stuff comes out. this may increase your driving possibility (i.e. if stuck on the side of the road), but you will need to get a muffler. If it is your converter, then inside theconverter is a honey comb shape (brittle material). you can break the brittle material until it is all gone and you have a hollow converter and then bolt it right back on. if clogged, it is the honeycomb that is clogged. This allows you to drive the car for a few days/weeks/months until you get a new converter. if you do this, the car will be a little loud as it drives, but hey, at least you are not stuck to the side of the road.

I know you just passed the emission test, but they do not test for absolute flow. At best they are checking for relative flow. I hope this will answer some of your questions and am curious to know if this is your problem.

good luck.

 

I disagree. if u do that potatoe trick w that cat u are NOT testing fr absolute flow. if u have any leaks in ur exhaust pipe it will find its way out there and give u a false reading. any ase test tells u not to perform a flow test this way due to inconsistancies. If u do lose power its because ur over heating the catalyst inside which is ceramic and this will permaturely create failure. its like stubbing ur toe on purpose before puting steel toe'd shoes on to see what it doesnt feel like. Im not knockin parisjas opinion all advice is great since it gives u diff perspectives but if ur cat was bad u would hear it in sound and smell the ceramic choking and overheating plus at highway speeds u wouldnt have power either-cold or not exhaust flows at the same rate the ceramic doesnt expand the metal does.when cold it would have a harder time not throwing a 02 sensor light because of the carbon reading diff from the pre-cat to the catalyst.thats y their are 2 o2's on 95% of all cars after 1998-some have 4. he may be right who knows but thats not a good test and it doesnt fit ur symptoms im anxious to know now please post soon. thanks

 

I performed a few of these test, first I held my foot on the brake going on the gas rpm went to about 1200-1300 and when I took my foot off pulled a hole-shot, no tire spinning, but good seat pressure. Then I manually shifted cold under 3500rpm shifted fine, then when it was warm under 3500rpm and again shifted fine? ThenI did the potato test (used organic to be politically correct) cut to somewhat fit and it blew out around 2000rpm. After I did that test I went out for another ride and in first gear floored it, went to about 3500rpm started doing its thing and held it to the floor for like 30 seconds, stayed around 3500rpms and I also heard a flop back through the throttle-body? No back-fires through the exhaust and no black smoke, seems like it is running lean? If I hold it to the floof in first gear cold it goes to 6000rpm, I don't wont to go any higher it does have 130k.Any Thoughs on this? Thanks

 

Hi guys,

1-it looks like the quick and dirty items both C230Renntech and I have thougt of didn't do it for you. if the potato blew out at 2000rpm thenthat could by itself be an indication that there is enough pressure, but then again it didn't stay on long enough to know what would happen at 3500rpm.did you just kind of put the potatothere, or was it in there nice and tight? I would probably do it one more time and see if I can take to to 3500rpm.

2-if it was me and my car I would see if there is an easy way to do the test#2. This is more involved, but will for sure tell you if the issue is with converter. C230Renntech is also correct to note that if cat converter is clogged you would loose power at freeway speeds. but I disagree with him regarding burnt ceramic smell.

3-if problem is not cat converter (and we know for sure), then I wonder if distributor is good. the electricals average the time it is in one place and if tip is dirty you would eventually reach a point where duty cycle is too low.

I still would bet it is catalytic converter.

good luck& like C230Renntech I am just as curious to know what the problem is. I wish we were all there and we could see the car.