fairladyz47597

I've had my car for about 2 months. It has 36,000 miles on it and I keep hearing, what I believe to be, spark knock when I hit the accelerator. It's kind of that gurgly, sort of rattle noise.

It's not very loud and I usually can't hear it if the A/C is on. It's sort of bothering me though. Any thoughts as to what it could be? I was wondering if the plugs needed changed.

I know that running bad gas in the car could also cause the noise, but I use 93 octane so I am assuming I'm fine there.

Thanks

kostat26

iTrader: (41)

what gas are u running?

fairladyz47597

i use 93 octance and usually buy my gas from BP or QT

kostat26

iTrader: (41)

i asked because u mentioned bad gas so i figured u use something else.
how many miles on the plugs?

fairladyz47597

Thanks for the replies.

I actually do not know how many miles are on the plugs. I guess I could contact the previous owner to see if they ever changed the plugs. I'm guessing, though, that with 36k miles, they never changed them.

kostat26

iTrader: (41)

you should have the plugs checked first. and if its not that and u are actually experiencing real knock u have bigger problem to worry about

fairladyz47597

uh oh....maybe bad lifters?

fairladyz47597

I called my mechanic this morning and I am going to take a ride with him in the car sometime this weekend and try to point out the noise. Hopefully I just need new plugs. The warranty should cover tearing into the engine for deeper issues, I would think.

Q45tech

Don't assume the the number selected by the marketing department for pumps is 100% accurate as the fuel varies by production run, stagnation, and locations [pipe line days from refinery].

Atlanta has been pretty good so far this spring, Summer starts today so who knows what the Summer blends will deliver.

Try BG44K to clean the piston and valve deposits.................any heat inducing mods from a redesigned intake?

fairladyz47597

No. I haven't done any engine mods and the previous owner did not make any modifications either. Once again, I appreciate the posts--very helpful info. I will try the BG44K, although I am always hesitant to put anything into my fuel tank. I plan to go into the mechanic tomorrow afternoon to let them hear the noise. That's a good point about gasoline blends. Do you have any particular brand of gas you prefer over the others?

Q45tech

For the last 215,000 mile [314k total on 1990 Q45 purchased brand new] the bulk of my purchases have been QT 93, in winter QT 89 with some Chevron ocassionally on the road.

However I buy BG44k by the case and use it prior to each 90 day oil change.
Maintaining a 17.5 year old high mileage car requires more frequent of everything.

The newer returnless fuel systems seem better as the injector screens are exposed to less [no] recirculating fuel.

Ziggyrama

iTrader: (15)

Gourgly rattle noise does not sound like knock to me. Knock sounds more like a ping sound. Some people also describe it as marbles in a can. Is that what you're hearing?

It's possible you have something loose under the hood. The engine does buck a bit inside the bay when you step on it. It may be causing a rattle.

BTW, if you are hearing knock, that is very bad. Minor to moderate knock is almost impossible to hear with your ears. Severe knock is audible but by than, some damage may have been done already.

Take a peek at your engine bay and check for any loose things that could be responsible. It won't hurt to inspect things and may save you some money.

350zbra

I have the same issue on mine. Tip in throttle at around 2000 rpm, right? I just took mine back to the dealer a few days ago. I always use 93 and I tried every type of fuel there is. It's an 06 with 8800 on it, by the way. It is a spark knock pinging type noise that reprogramming or relearning the exhaust cams seems to have helped but not eliminated completely. There's a thread on here somewhere about a guy putting a catch can on his cause his plenum was filled with oil and he says that fixed it.

fairladyz47597

well i took it to a mechanic. they described the "ping" (that's the word they used) as pre-ignition firing. they said that there is either carbon build-up on my plugs, or bad fuel that causes extra heat, which ignites the gas above the piston before the spark plug emits the spark. he said the piston doesn't change direction, but, instead moves on a wrist side to side against the piston chamber causing the rattle.

I had him put on some expensive NGK Iridium IX plugs in and he cleaned the induction system. He said it wasn't a valve problem because it happens during acceleration. These fixes didn't correct the problem. The mechanic said I prolly have bad gas in my car and recommended Octane Boost [Turbo 108]. I'm going to put that in the next time I fill up.

I like what someone said above about the loose parts around the engine. I plan to check that next. I think maybe I'll just forget about it after that. The mechanics said it's running great so I guess I'll just ignore it.

Wired 24/7

iTrader: (2)

Here's a possible situation.

Your MAF sensor gets slightly dirty or oily. It is a hotwire type of sensor, so it determines airflow by temperature change.

If there is dirt or oil on the filter, it reduces the sensitiviry of the wire.

The ECU thinks there is less air coming into the motor, so it adds less fuel.

Try cleaning the MAF using a spray cleaner from autozone or something.

Do it when the car is totally cold and let the cleaner dry completely before starting up the car, obviously.

This is just a possible situation but it's a cheap and easy thing to try to fix.

Also, it never hurts to reset your ECU. Unplug the negative battery terminal overnight.

fairladyz47597

thanks for the helpful advice. i am gonna have to buy a book for the z which tells me where the MAF sensor is located. I assume it's housed somewhere in the air intake hose where it connects to the engine.

Ziggyrama

iTrader: (15)

That's good advice by Wired. Never hurts to clean the MAF sensor to eliminate another possibility. Be very careful when cleaning it. MAF sensors are fragile. The sensor is located right behind the air filter box. Pop your hood and follow the intake tube past the air filter box. Right after it, you'll see there's a sensor mounted in the tube. Unclip the wire harness going to it, unscrew the screws and carefully pull the sensor out. Take a look inside it. You should see a tiny little wire in there which is the part that is used to measure air flow. Spray some clean in there several times and allow it to dry completely. I like to douse it with the cleaner to make sure it gets any oil or dirt out of there. You can use MAF cleaner or non-chlorinated brake cleaner for the cleaning purposes. They both will do the job. Once the sensor is dry, put it back in and you're good to go.

If your mechanic is right and you had pre-ignition, I recommend that you do compression test to make sure the engine is indeed healthy. If your pistons are rattling inside the block, you may have a bigger issue than you think. Compression test will reveal if the car has been hurt. The reason why I say that is because pre-ignition can be extremely damaging to the engine. Some people confuse it with detonation which is something very different. A single pre-ignition event can burn a hole in your piston, destroy the rings, etc. Detonation can also be bad but generally your engine can tolerate that more than pre-ignition.

Ask your mechanic why he thinks the engine is OK now. I would not be so sure without doing the compression test. It's easy to do. Maybe he already did do it. Ask him what the readings were for each piston.

SpeedRcr

iTrader: (5)

ngk are half the cost of denso iridiums...6 bucks a plugs is pretty cheap

fairladyz47597

that sucks because i paid 25 dollars per plug for the ngk's. looks like i should've done my homework first. i just heard them say iridiums and i figured they were the iridiums everyone had been telling me about. oh well.

fairladyz47597

thanks for the information. i believe i will go ahead and take it back to the mechanic. first i am going to drive it home for lunch this afternoon and check it out to see if the octane boost helped at all. i just filled up this morning. you've been very helpful. i will take a look and see if i can work with the maf sensor to clean it. dang! i can't believe this crap. if something is wrong with the pistons, will the warranty cover it?