"Poppy" exhaust sound....
 

Over the past few weeks, my Saturn SL2 has been developing an exhaust
noise.....it's kind of a rattly, poppy kind sound. It only occurs
under load (up hills, accelerating from a stop, and similar).


I'll level with you....I'm OK with a wrench, but I know nothing about
diagnosing cars based on their exhaust sound. I got under it and
looked for an exhaust leak, but there was none I can find, and I'd
think that the sound would occur more often if it was......

My wife was describing the problem to her father (a mechanic) and he
suggested that the the lifters needed adjusting. I can kind of believe
that, but there's no clatter from the engine compartment, like I would
expect. I've noticed no decrease in performance, or mileage. It's also
a sight-unseen kind of a diagnosis, which I never completely trust.

Also, this car has hydraulic lifters, which I know almost nothing
about. I understand the principles behind how they work, but that's
about it. I'm guessing "Lifters need adjustment" for hydraulic lifters
translates into "lifters are sticky" but I just don't know....

hell, that might not even BE the problem.


So, any advice on this issue will be greatly appreciated.

Thanks for your time.

is it pingging under a load try a higher grade of gas advance your
timming ?

did you shake the tailpipe vigorously to see if it's bumping against
anything under load? the usual cure for that is to jam something between
the pipe and body and pry it away. all low tech wrench guy stuff.



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tudysm--

So, by inference, does that mean my timing is off? it's got over 100k
miles on it, so maybe.... I've only had it for 30,000 of those miles,
and I've never had the timing checked, so perhaps that's my
problem......?


William,
Didn't rattle when I shook it, so I guess nothing's loose....

Tokay wrote:
> Over the past few weeks, my Saturn SL2 has been developing an exhaust
> noise.....it's kind of a rattly, poppy kind sound. It only occurs
> under load (up hills, accelerating from a stop, and similar).
>
>
> I'll level with you....I'm OK with a wrench, but I know nothing about
> diagnosing cars based on their exhaust sound. I got under it and
> looked for an exhaust leak, but there was none I can find, and I'd
> think that the sound would occur more often if it was......
>
> My wife was describing the problem to her father (a mechanic) and he
> suggested that the the lifters needed adjusting. I can kind of believe
> that, but there's no clatter from the engine compartment, like I would
> expect. I've noticed no decrease in performance, or mileage. It's also
> a sight-unseen kind of a diagnosis, which I never completely trust.
>
> Also, this car has hydraulic lifters, which I know almost nothing
> about. I understand the principles behind how they work, but that's
> about it. I'm guessing "Lifters need adjustment" for hydraulic lifters
> translates into "lifters are sticky" but I just don't know....
>
> hell, that might not even BE the problem.
>
>
> So, any advice on this issue will be greatly appreciated.
>
> Thanks for your time.

How many miles, and when was the last time it got a tuneup? Spark
breaks down most easily under heavy load.

nate

It's sitting at about 125k, and define "tune up"......

I don't take it in for a whole lot of work, unless it'd be cheaper for
the shop to do it, or I don't have the tools for the job.

I change the spark plugs every 3 oil changes (I'm experimenting to find
which gives best economy) but I tried switching out the spark plugs
from Platinum +4's back to standard plugs when I first noticed the
sound, but that dropped performance significantly, and made my engine
noisier (I have no idea why, doesn't make sense to me that it should
get louder with standard plugs).

I changed the plug wires at the turn of 100k, but I thought they were
good for 50k or more....

I change my oil religiously at 3k (It's just my thing, probably don't
need to be so anal about it), and I use full synthetic, and a midgrade
oil filter (Fram tough duty), the air filter I change less religiously
(every 3 oil changes or whenever I think it's getting bad)

I tried a can of Seafoam (1/3 in the oil, 1/3 in the gas, and 1/3
through the PCV) just to see if I could free things up. Did wonders
for my injectors, even boosted my mileage, but the noise persists.

"Tokay" > writes:

>Over the past few weeks, my Saturn SL2 has been developing an exhaust
>noise.....it's kind of a rattly, poppy kind sound. It only occurs
>under load (up hills, accelerating from a stop, and similar).

Sounds like misfire. I bet one or more of your plugs are shot. Take them out
and have a look. When mine was doing this (occasional pop uphill), about 500
miles later one of the plugs had its insulator touching the electrode and no
spark. My plugs were burning up due to too far advanced timing because I did
not follow the correct procedure to set the timing when I rebuilt my
distributor.

"Tokay" > writes:

>I change the spark plugs every 3 oil changes (I'm experimenting to find
>which gives best economy) but I tried switching out the spark plugs
>from Platinum +4's back to standard plugs when I first noticed the
>sound,

+4's sucked in my car. Standard NGKs were much better and cheaper.

>but that dropped performance significantly, and made my engine
>noisier (I have no idea why, doesn't make sense to me that it should
>get louder with standard plugs).

Tighten them down good? Right heat range and right gap? I agree that standard
plugs should be fine if they are indeed the correct plugs.

>I changed the plug wires at the turn of 100k, but I thought they were
>good for 50k or more....

They can be. Some are much worse. The rubber insulation dries out with age,
cracks, and the wire discharges somewhere where it shouldn't.

>I change my oil religiously at 3k (It's just my thing, probably don't
>need to be so anal about it), and I use full synthetic, and a midgrade
>oil filter (Fram tough duty), the air filter I change less religiously
>(every 3 oil changes or whenever I think it's getting bad)

Sounds like my own maintenance plan. Except I use Pennzoil for no particular
reason.

>for my injectors, even boosted my mileage, but the noise persists.

I can't remember, if you mentioned is the noise accompanied by a noticeable
power loss? If so, it could be ping given that your injectors, plugs and wires
seem to be in good condition. Try premium gas. If that doesn't change it,
check your timing. Timing that has been either retarded or advanced from spec
could cause ping.

Something else that is worth mentioning is that if your EGR is not working
correctly, the motor will want to ping when it is hot. If it pings when cold
then the problem is likely to be somewhere else. You can do a quick visual
examination of the valve by having someone rev the motor and seeing if the
diaphragm moves freely. However, the valve could be working and yet the
exhaust passages or intake manifold passage is clogged with carbon.

> Something else that is worth mentioning is that if your EGR is not working
> correctly, the motor will want to ping when it is hot. If it pings when cold
> then the problem is likely to be somewhere else. You can do a quick visual
> examination of the valve by having someone rev the motor and seeing if the
> diaphragm moves freely. However, the valve could be working and yet the
> exhaust passages or intake manifold passage is clogged with carbon.

You should also be able to reach under the EGR valve and gently push up
on the diaphragm with a finger. (If the engine is running it should
stall.) It should move smoothly. If not it might need cleaning which you
should be able to do yourself. Spraying WD40 on the underside of the valve
can free up the stem but you should be able to take the whole thing off
and clean out the carbon with solvent (eg paint thinner).



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