Members satannica Posted March 4, 2011 Members Share Posted March 4, 2011 I've no idea about this one. Car is an auto-tranny Mercedes A-Class on 110k. It just had the front disks/pads replaced and the braking operation seems fine - just mentioning in case it's important. Problem is complete lack of usable accelleration. If tap the gas in neutral to try and rev, it's very hesitant, or may not rev up at all. The rev counter does dip below the normal 900rpm idle speed. On driving, if I have the gas pedal half way down, it will gain speed slowly but surely. Here's the big thing. If I gas all the way down to try and accelerate, there's nothing, in fact it dies. Also, straight after a strange noise comes from what I think is the front right tyre. It sounds kinda like grindy scrapey sound, as if the disk was jarring on the pad. I kinda thought that the disk was just warping a little being new, maybe the missus hadn't let them bed in properly (it's her car). But the sound doesn't disappear until I tap the brake and then it's gone. I could believe it may be a brake issue as they've only just been done a few days ago and have about 400 miles on them. It was driving fine before that. But the hesitating revs and poor acceleration is throwing me off the scent a bit. Link to comment Share on other sites More sharing options...
Members Murdoch Posted March 4, 2011 Members Share Posted March 4, 2011 How long since the spark plugs have been replaced? Link to comment Share on other sites More sharing options...
Members satannica Posted March 4, 2011 Author Members Share Posted March 4, 2011 12 months and by the last invoice 10,800 miles ago... I was initially thinking coil pack as I was always chasing the one in my rat bastard Ford Mondeo. But what's happening in this car is much worse than what the Mondeo was when the coil pack went bad. You reckon it's a spark out? Link to comment Share on other sites More sharing options...
Members Murdoch Posted March 4, 2011 Members Share Posted March 4, 2011 Sounds like it to me. It seems like, when you stomp your accelerator, there isn't enough to spark to instantly ignite the gasoline when it enters the chamber, essentially temporarily flooding your car until the remaining spark can ignite it. Link to comment Share on other sites More sharing options...
Members pioneerprogress Posted March 4, 2011 Members Share Posted March 4, 2011 Mercedes you say? Easy fix... Craigslist mod. Link to comment Share on other sites More sharing options...
Members satannica Posted March 4, 2011 Author Members Share Posted March 4, 2011 Aye, it does sound reasonable. I'll pull them in the morning and see if that improves things. Cheers sah! Link to comment Share on other sites More sharing options...
Members wrathchild1 Posted March 4, 2011 Members Share Posted March 4, 2011 asking for car advice in the amp forum. I bet half of the people on he cant drive. but theyll tell you whats wrong with it anyways.. Link to comment Share on other sites More sharing options...
Members TurboRotary13b Posted March 4, 2011 Members Share Posted March 4, 2011 Man you could have quite a few problems. Is it making a louder noise when you accelerate? Does the noise seem to increase or decrease with RPM or Speed? Do you smell anything strange? Link to comment Share on other sites More sharing options...
Members Rampage Posted March 4, 2011 Members Share Posted March 4, 2011 asking for car advice in the amp forum. I bet half of the people on he cant drive. but theyll tell you whats wrong with it anyways.. So it's pretty much the same thing you get when asking about an amp on here, only you get serious advice? Link to comment Share on other sites More sharing options...
Members satannica Posted March 4, 2011 Author Members Share Posted March 4, 2011 Man you could have quite a few problems. Is it making a louder noise when you accelerate? Does the noise seem to increase or decrease with RPM or Speed? Do you smell anything strange? Er actually I thought I smelled bringing from the brake after it was driving for a while with the noise. I can't see any scoring on the disk, but I definitely smelled something not too nice. I think the longer you leave it go on, it does get louder. Link to comment Share on other sites More sharing options...
Members wrathchild1 Posted March 4, 2011 Members Share Posted March 4, 2011 So it's pretty much the same thing you get when asking about an amp on here, only you get serious advice? its always the tubes. Link to comment Share on other sites More sharing options...
Members bdubbs Posted March 4, 2011 Members Share Posted March 4, 2011 I am leaning towards ignition issues as well. Link to comment Share on other sites More sharing options...
Members OverDriven Posted March 4, 2011 Members Share Posted March 4, 2011 It could be ignition coil, it could be mass air flow sensor, it could be catalytic converter (plugged up), it could be oxygen sensor, among other things. Are you getting a check engine light? Link to comment Share on other sites More sharing options...
Members satannica Posted March 4, 2011 Author Members Share Posted March 4, 2011 No check light at all, so not totally sure it's the MAF. But at 110k, I guess the mileage is right? Link to comment Share on other sites More sharing options...
Members OverDriven Posted March 4, 2011 Members Share Posted March 4, 2011 No check light at all, so not totally sure it's the MAF. But at 110k, I guess the mileage is right? I'm not entirely sure on those cars, but my very first guess would be the catalytic converter anyways. Being at the shop and up on the rack could have knocked the core loose if it was already about to go. The core will block exhaust gasses from exiting and you get the exact symptoms your describe. It also smells because the cat gets red hot when this happens. Keep the door open, put the car in neutral and hit the gas hard. See if you hear hissing like pressure buildup from the exhaust. BTW you also usually get no check engine light when its the cat. Link to comment Share on other sites More sharing options...
Members JaGi Posted March 4, 2011 Members Share Posted March 4, 2011 Could be many things, from a small sensor to your timing jumping out. Give it a service first, new leads and plugs and see what happens. If you think your coil is gone pull all the plugs still connected to the HT leads and turn it over, you can see the spark. Does the car have onboard diagnostics? Many diagnostics you can do yourself with a multimeter. I would guess at a sensor issue but i am not familiar with the ignition and ecu relay system on your car. Link to comment Share on other sites More sharing options...
Members satannica Posted March 4, 2011 Author Members Share Posted March 4, 2011 I'm not entirely sure on those cars, but my very first guess would be the catalytic converter anyways. Being at the shop and up on the rack could have knocked the core loose if it was already about to go. The core will block exhaust gasses from exiting and you get the exact symptoms your describe. It also smells because the cat gets red hot when this happens. Keep the door open, put the car in neutral and hit the gas hard. See if you hear hissing like pressure buildup from the exhaust.BTW you also usually get no check engine light when its the cat. Just went out to test this. No hestiation at all now, but the car is cold. It seems that this only happens when the car is warm. It had its rear tyres replaced yesterday and brakes done a few days ago, so it's been up and down the ramp a coupla times. The missus reckons the accelaration has been "off" since she got it back after the tyre chage... so all this is kinda adding up... Well, how long in labour are you looking at to replace the cat? My mechanic works on an hourly rate plus part cost. Would you get an OEM part, or would an aftermarket manufacturer part be OK? Link to comment Share on other sites More sharing options...
Members Ovid9 Posted March 4, 2011 Members Share Posted March 4, 2011 Well, how long in labour are you looking at to replace the cat? My mechanic works on an hourly rate plus part cost. Would you get an OEM part, or would an aftermarket manufacturer part be OK? If its got 110k on it, I'd probably go aftermarket. Here in the states anyway, they sell "universal" converters that can be welded in place of the old one, significantly cheaper than replacing a whole pipe. They generally aren't as good, but depending on the setup, it can be a whole lot cheaper both in part cost and labor cost. Dunno if those are an option in the UK or not, but you might look into it. Oh, and find out how good your mechanic is at welding. Link to comment Share on other sites More sharing options...
Members kissmyace Posted March 4, 2011 Members Share Posted March 4, 2011 I was gonna say fuel pump ???? Link to comment Share on other sites More sharing options...
Members Nerine Posted March 4, 2011 Members Share Posted March 4, 2011 Try the Mass Airflow Sensor. Thank me later. My car was experiencing major engine issues, stuttering, getting stuck at x,xxx rpm, accelerating slow and then all of a sudden kicking off etc etc. Definitely worth a look. Link to comment Share on other sites More sharing options...
Members DEADBYDAWN Posted March 5, 2011 Members Share Posted March 5, 2011 If you think the brakes could be sticking have you tried to get the front off the ground to spin the wheel with your hand ? If it spins freely get someone to push the brake and release to see if the calipers may not be releasing after you let off the brake. As far as a break -in period on brakes that is a new one to me- now a clutch sure. If that isn't the issue it could be the TPS (throttle positioning sensor), clogged fuel filter,plugs, O2 sensors, Maf sensor, clogged cats (you will smell a rotten egg/sulfur smell usually) etc. etc. and so on.......... Link to comment Share on other sites More sharing options...
Members Jack Tone Posted March 5, 2011 Members Share Posted March 5, 2011 If you hadn't mentioned the weird accelleration issues, I would have said that your right disc caliper is dragging (not releasing). Does the car pull to one side? It sure sounds like it, bad smells and all. Link to comment Share on other sites More sharing options...
Members Ovid9 Posted March 5, 2011 Members Share Posted March 5, 2011 If you hadn't mentioned the weird accelleration issues, I would have said that your right disc caliper is dragging (not releasing). Does the car pull to one side? It sure sounds like it, bad smells and all. Well, the lovely thing is, it could be multiple issues. The brake issue and acceleration issue are probably totally different. I'd forgotten the grinding noise. Just cause they're new doesn't mean they didn't leave out a spacer or something or your caliper isn't starting to stick. I have such a love/hate relationship with cars. Link to comment Share on other sites More sharing options...
Members Belva Posted March 5, 2011 Members Share Posted March 5, 2011 What year is the car? If it's after '96 a clogged cat will usually set a low cat flow or after cat oxygen sensor code. You say no check engine light? I wouldn't rule out improperly installed or sticky caliper. Take it back where you had the brakes done. Link to comment Share on other sites More sharing options...
Members OverDriven Posted March 5, 2011 Members Share Posted March 5, 2011 What year is the car? If it's after '96 a clogged cat will usually set a low cat flow or after cat oxygen sensor code. You say no check engine light? I wouldn't rule out improperly installed or sticky caliper. Take it back where you had the brakes done. If it is the caliper, make sure you have them replace the rotor on that wheel as well since the one that's on there is going to be warped to {censored} and back due to the heat. Link to comment Share on other sites More sharing options...
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