Engine not smooth when cold + strange noise?
05-17-2015, 05:51 AM
#1
Engine not smooth when cold + strange noise?
I'm a bit worried by a recent experience with my car. I started it up, and immediately headed up a hill (about as steep as a beginner ski slope (blue in Europe, green in the US?)). As I gently accelerated, the engine very quickly/briefly pushed less (or not at all?), then suddenly pushed more, slightly jerking the car forward. This happened two or three times. The last time it happened, I was watching the revs and they were at about 4000. I remembered that the engine was cold, backed off, and when the engine was warmer and I next accelerated, it was fine. Perhaps the car is always like this - I almost always let the car warm up a bit before driving and I'm not sure I've ever headed straight up that hill right after leaving the garage. Or perhaps this is something new ...
Perhaps related to this, a more Porsche experienced friend recently told me my car always sounds strage at low revs. So I asked a local specialist to check it out. They told me there's some (rattling?) noise coming from inside one muffler, probably due to rust, but no need to replace it yet if it doesn't bother me. But then when driving the car from their shop to their parking lot, they said "Hmm, maybe there's something else, maybe make anothe appointment and we'll look again, but don't worry, the engine should be fine and you can drive long distances - if anything there's less noise when the engine is warm. Just keep an eye on the temperature and pressure." They also said the noise happens/is worst when crossing 3000 rpm and (or? / especially?) when the oil pressure crosses 4.
One other thing to mention is that very recently, while using the wrong coilover settings over some rough roads, I had an impact that cracked the oil pan. But this almost certainly did not lead to overly low oil while the engine was running (I won't add details here as it's in another thread), and there were no other impacts. Also, I think the impact was born mainly (hopefully entirely) just by the oil pan. The car has an X74 plate installed under the engine to protect it, and the plate was undamaged. The impact was at the point the plate does not cover, the drain hole, where there was an IMS Guardian plug which hit the road. I cannot, however, rule out that the impact might have loosed a wire or fuel line or done something else.
Anyone know of any issues these clues might suggest? Does this sound like any problems anyone has experienced? Should I leave the car sitting till it's looked at again, or go ahead and enjoy driving it?
Thanks for any advice about this!
Perhaps related to this, a more Porsche experienced friend recently told me my car always sounds strage at low revs. So I asked a local specialist to check it out. They told me there's some (rattling?) noise coming from inside one muffler, probably due to rust, but no need to replace it yet if it doesn't bother me. But then when driving the car from their shop to their parking lot, they said "Hmm, maybe there's something else, maybe make anothe appointment and we'll look again, but don't worry, the engine should be fine and you can drive long distances - if anything there's less noise when the engine is warm. Just keep an eye on the temperature and pressure." They also said the noise happens/is worst when crossing 3000 rpm and (or? / especially?) when the oil pressure crosses 4.
One other thing to mention is that very recently, while using the wrong coilover settings over some rough roads, I had an impact that cracked the oil pan. But this almost certainly did not lead to overly low oil while the engine was running (I won't add details here as it's in another thread), and there were no other impacts. Also, I think the impact was born mainly (hopefully entirely) just by the oil pan. The car has an X74 plate installed under the engine to protect it, and the plate was undamaged. The impact was at the point the plate does not cover, the drain hole, where there was an IMS Guardian plug which hit the road. I cannot, however, rule out that the impact might have loosed a wire or fuel line or done something else.
Anyone know of any issues these clues might suggest? Does this sound like any problems anyone has experienced? Should I leave the car sitting till it's looked at again, or go ahead and enjoy driving it?
Thanks for any advice about this!
05-17-2015, 01:41 PM
#2
Race Director
I'm a bit worried by a recent experience with my car. I started it up, and immediately headed up a hill (about as steep as a beginner ski slope (blue in Europe, green in the US?)). As I gently accelerated, the engine very quickly/briefly pushed less (or not at all?), then suddenly pushed more, slightly jerking the car forward. This happened two or three times. The last time it happened, I was watching the revs and they were at about 4000. I remembered that the engine was cold, backed off, and when the engine was warmer and I next accelerated, it was fine. Perhaps the car is always like this - I almost always let the car warm up a bit before driving and I'm not sure I've ever headed straight up that hill right after leaving the garage. Or perhaps this is something new ...
Perhaps related to this, a more Porsche experienced friend recently told me my car always sounds strage at low revs. So I asked a local specialist to check it out. They told me there's some (rattling?) noise coming from inside one muffler, probably due to rust, but no need to replace it yet if it doesn't bother me. But then when driving the car from their shop to their parking lot, they said "Hmm, maybe there's something else, maybe make anothe appointment and we'll look again, but don't worry, the engine should be fine and you can drive long distances - if anything there's less noise when the engine is warm. Just keep an eye on the temperature and pressure." They also said the noise happens/is worst when crossing 3000 rpm and (or? / especially?) when the oil pressure crosses 4.
One other thing to mention is that very recently, while using the wrong coilover settings over some rough roads, I had an impact that cracked the oil pan. But this almost certainly did not lead to overly low oil while the engine was running (I won't add details here as it's in another thread), and there were no other impacts. Also, I think the impact was born mainly (hopefully entirely) just by the oil pan. The car has an X74 plate installed under the engine to protect it, and the plate was undamaged. The impact was at the point the plate does not cover, the drain hole, where there was an IMS Guardian plug which hit the road. I cannot, however, rule out that the impact might have loosed a wire or fuel line or done something else.
Anyone know of any issues these clues might suggest? Does this sound like any problems anyone has experienced? Should I leave the car sitting till it's looked at again, or go ahead and enjoy driving it?
Thanks for any advice about this!
Perhaps related to this, a more Porsche experienced friend recently told me my car always sounds strage at low revs. So I asked a local specialist to check it out. They told me there's some (rattling?) noise coming from inside one muffler, probably due to rust, but no need to replace it yet if it doesn't bother me. But then when driving the car from their shop to their parking lot, they said "Hmm, maybe there's something else, maybe make anothe appointment and we'll look again, but don't worry, the engine should be fine and you can drive long distances - if anything there's less noise when the engine is warm. Just keep an eye on the temperature and pressure." They also said the noise happens/is worst when crossing 3000 rpm and (or? / especially?) when the oil pressure crosses 4.
One other thing to mention is that very recently, while using the wrong coilover settings over some rough roads, I had an impact that cracked the oil pan. But this almost certainly did not lead to overly low oil while the engine was running (I won't add details here as it's in another thread), and there were no other impacts. Also, I think the impact was born mainly (hopefully entirely) just by the oil pan. The car has an X74 plate installed under the engine to protect it, and the plate was undamaged. The impact was at the point the plate does not cover, the drain hole, where there was an IMS Guardian plug which hit the road. I cannot, however, rule out that the impact might have loosed a wire or fuel line or done something else.
Anyone know of any issues these clues might suggest? Does this sound like any problems anyone has experienced? Should I leave the car sitting till it's looked at again, or go ahead and enjoy driving it?
Thanks for any advice about this!
The noise you mention is probably not from "rust" in a muffler.
It could be from a loose/broken exhaust hanger, or possibly from a loose heat shield, or even from a loose converter "brick". If the latter these can create a sound that ranges from a dull non-rythmetic knocking noise when cold to a buzzing noise when hot.
The stumble in fact could be from the loose brick shifting position and interfering with exhaust flow. Because the engine is cold if cold enough the engine controller might not be in closed loop mode yet and it might not register a problem, thus no check engine light and no code. The brick resumes a more optimum position after a short time and then the DME will find nothing to complain about.
You need to have this looked into. However, I would be a little leery of using the local specialist...
05-17-2015, 02:30 PM
#3
"Should I leave the car sitting till it's looked at again, or go ahead and enjoy driving it?"
Don't drive it, get it checked. You will not have peace of mind till then.
Don't drive it, get it checked. You will not have peace of mind till then.
05-17-2015, 06:50 PM
#6
Agressive acceleration up a rather steep slope on cold tires? Was perhaps what you experienced some brief wheel spin?
The noise you mention is probably not from "rust" in a muffler.
It could be from a loose/broken exhaust hanger, or possibly from a loose heat shield, or even from a loose converter "brick". If the latter these can create a sound that ranges from a dull non-rythmetic knocking noise when cold to a buzzing noise when hot.
The stumble in fact could be from the loose brick shifting position and interfering with exhaust flow. Because the engine is cold if cold enough the engine controller might not be in closed loop mode yet and it might not register a problem, thus no check engine light and no code. The brick resumes a more optimum position after a short time and then the DME will find nothing to complain about.
You need to have this looked into. However, I would be a little leery of using the local specialist...
The noise you mention is probably not from "rust" in a muffler.
It could be from a loose/broken exhaust hanger, or possibly from a loose heat shield, or even from a loose converter "brick". If the latter these can create a sound that ranges from a dull non-rythmetic knocking noise when cold to a buzzing noise when hot.
The stumble in fact could be from the loose brick shifting position and interfering with exhaust flow. Because the engine is cold if cold enough the engine controller might not be in closed loop mode yet and it might not register a problem, thus no check engine light and no code. The brick resumes a more optimum position after a short time and then the DME will find nothing to complain about.
You need to have this looked into. However, I would be a little leery of using the local specialist...
First, I'm pretty sure it wasn't wheel spin, as I actually was accelerating gently, the car didn't shimmy the way it does when hard acceleration induces wheelspin, and the tires were almost certainly up to operating temperature as they're winter tires (good new ones), and it was fairly warm (65 degrees?) and quite sunny.
Second, maybe it's helpful to clarify something about the noise. I don't hear anything that I would call knocking (I certainly can't pick out individual knocks). I may have heard buzzing. I haven't heard anything unusual as I go over bumps, if that tells us anything. Every sound I hear from the engine (or anywhere else, other than tires and wind) changes with engine speed and throttle opening. I can't say more than that because I don't hear anything that doesn't sound the way I've come to expect the car to sound. Though since my friend told me he thinks it sounds strange, I've sometimes found the low rev sound (somewhere between 2 and 3000 I guess) to be a bit annoying when I have the windows open.
Third, is there nothing inside the muffler that could come loose, for instance due to rust?
Last edited by rs10; 05-17-2015 at 07:11 PM.
05-18-2015, 03:59 AM
#7
Race Director
Thanks! Many interesting points. A couple follow-up notes/questions.
First, I'm pretty sure it wasn't wheel spin, as I actually was accelerating gently, the car didn't shimmy the way it does when hard acceleration induces wheelspin, and the tires were almost certainly up to operating temperature as they're winter tires (good new ones), and it was fairly warm (65 degrees?) and quite sunny.
Second, maybe it's helpful to clarify something about the noise. I don't hear anything that I would call knocking (I certainly can't pick out individual knocks). I may have heard buzzing. I haven't heard anything unusual as I go over bumps, if that tells us anything. Every sound I hear from the engine (or anywhere else, other than tires and wind) changes with engine speed and throttle opening. I can't say more than that because I don't hear anything that doesn't sound the way I've come to expect the car to sound. Though since my friend told me he thinks it sounds strange, I've sometimes found the low rev sound (somewhere between 2 and 3000 I guess) to be a bit annoying when I have the windows open.
Third, is there nothing inside the muffler that could come loose, for instance due to rust?
First, I'm pretty sure it wasn't wheel spin, as I actually was accelerating gently, the car didn't shimmy the way it does when hard acceleration induces wheelspin, and the tires were almost certainly up to operating temperature as they're winter tires (good new ones), and it was fairly warm (65 degrees?) and quite sunny.
Second, maybe it's helpful to clarify something about the noise. I don't hear anything that I would call knocking (I certainly can't pick out individual knocks). I may have heard buzzing. I haven't heard anything unusual as I go over bumps, if that tells us anything. Every sound I hear from the engine (or anywhere else, other than tires and wind) changes with engine speed and throttle opening. I can't say more than that because I don't hear anything that doesn't sound the way I've come to expect the car to sound. Though since my friend told me he thinks it sounds strange, I've sometimes found the low rev sound (somewhere between 2 and 3000 I guess) to be a bit annoying when I have the windows open.
Third, is there nothing inside the muffler that could come loose, for instance due to rust?
The only time I have had a comment on any of my cars and the engine noise was last year when a co-worker commented on how noisy my Boxster was. I knew it was making noise but had grown used to it I guess. His comment prompted me to have the noise addressed and I ended up having the tech replace both exhaust manifolds with used ones I bought. One of the original ones had a loose converter brick and the thing was knocking about when cold and buzzing something fierce when warmed up.
Nice and quiet now, though. Nice and quiet.
If the exhaust system is plain old steel sure something could rust out. I've never rusted an exhaust system out on any car. 'course, some models came with stainless exhaust. But the Boxster's exhaust system, well, save for the "new" (used) converters, is all original and has nearly 300K miles on it. And it wasn't rust that did in the converter.
A busted hanger or bracket can cause the thing to be noisy. But I dare say the more common problem is a converter coming loose.
Unfortunately this loose converter is probably the more expensive problem to address if the car is out of the fed. emission warranty.
Regardless the tech will ID where the noise is coming from if he hears anything out of the ordinary.
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05-18-2015, 03:35 PM
#8
Three Wheelin'
Perhaps related to this, a more Porsche experienced friend recently told me my car always sounds strage at low revs. So I asked a local specialist to check it out. They told me there's some (rattling?) noise coming from inside one muffler, probably due to rust, but no need to replace it yet if it doesn't bother me. But then when driving the car from their shop to their parking lot, they said "Hmm, maybe there's something else, maybe make anothe appointment and we'll look again, but don't worry, the engine should be fine and you can drive long distances - if anything there's less noise when the engine is warm. Just keep an eye on the temperature and pressure." They also said the noise happens/is worst when crossing 3000 rpm and (or? / especially?) when the oil pressure crosses 4.
One of my mufflers done this. Shop said one of the baffles inside got loose.
Sounds terrible but doesn't really harm anything.
05-27-2015, 07:22 PM
#9
An update: The local specialist spent a bit more time with my car and concluded that the exhaust is fine, but either the chain or chain tensioner will eventually need replacing. They say there is no urgency, but if I notice the noise getting worse, then I should stop driving till it's fixed. I'd rather not wait, but they didn't have time this week, so I'm making an appointment.
I forgot to ask them if this could account for the jerky power delivery I experienced once, or the difficulty starting. I will, of course. But any thoughts on this would be greatly appreciated!
I forgot to ask them if this could account for the jerky power delivery I experienced once, or the difficulty starting. I will, of course. But any thoughts on this would be greatly appreciated!
05-27-2015, 07:35 PM
#10
Race Director
Both of my electronic throttle Porsches have done this on 1 or maybe 2 occasions per car. My opinion is that the car's initial surge forward uphill causes your foot/leg to lift slightly off the throttle courtesy of gravity and inertia. You (reflexively/subconsciously) correct by pressing harder on the throttle at the same time the car is slowing due to the lift that just occurred, resulting in depressing the throttle harder than you intend to and causing the car to surge forward again. This cycle repeats several times until you consciously lift off the throttle and interrupt the sequence.
Anyway, that's my theory. This has never happened in any other car I've owned, and it has happened in both manual transmission e-gas Porsches I've owned. I think it's a combination of a twitchy throttle and my mighty legs.
Anyway, that's my theory. This has never happened in any other car I've owned, and it has happened in both manual transmission e-gas Porsches I've owned. I think it's a combination of a twitchy throttle and my mighty legs.
05-28-2015, 12:06 PM
#11
Race Director
An update: The local specialist spent a bit more time with my car and concluded that the exhaust is fine, but either the chain or chain tensioner will eventually need replacing. They say there is no urgency, but if I notice the noise getting worse, then I should stop driving till it's fixed. I'd rather not wait, but they didn't have time this week, so I'm making an appointment.
I forgot to ask them if this could account for the jerky power delivery I experienced once, or the difficulty starting. I will, of course. But any thoughts on this would be greatly appreciated!
I forgot to ask them if this could account for the jerky power delivery I experienced once, or the difficulty starting. I will, of course. But any thoughts on this would be greatly appreciated!
If a chain or chain tensioner is truly on the way out driving the car, running the engine is out of the question, imho. The condition should be addressed *before* the condition turns perhaps into a fatal failure.
If a chain is making noise there's the concern it could break. This can lead to serious internal (and external -- bust case) damage. If a tensioner is going bad this can allow too much chain slack to the point the chain can skip a tooth and this too can lead to serious internal engine damage. Either failure mode could render the engine scrap.
If you believe the diagnosis and I am not in a position to dispute the diagnosis then you should stop driving the car and get it in for repairs as soon as you can.
05-28-2015, 12:20 PM
#12
Three Wheelin'
Doubt it would or could be that far out of adjustment and them telling you it's ok to drive.
Also, and maybe I'm thinking wrong, it wouldn't effect starting too much unless they were way out of adjustment. I'd think starting, at least to get it going, would have more to do with fuel and ignition timing than it would the valves in the wrong spot.
05-28-2015, 04:42 PM
#13
05-28-2015, 07:05 PM
#14
Three Wheelin'
That's what I thought they were? Maybe I'm wrong. (waiting on my friend now, getting some pictures to retouch, so bored)
But with all the different cam profiles out there - which is all valve timing is in a way - something would really really need to be out of spec to prevent enough air and gas getting into the chamber and igniting. Now it may be out of adjustment enough to prevent the engine from running smooth, but I'd think the engine would at least start.
For a fun read check out - http://www.badasscars.com/index.cfm/...=cat/cat13.htm
They do v8's but a lot of the stuff applies to just about any engine.
also this is a fun writeup about dyno's http://www.badasscars.com/index.cfm/...prod/prd64.htm
