Well...since I moved down to the hot sticky southeastern part of North Carolina (Fayetteville), my truck starts to spark knock at half throttle or more after a long time out on the road (like 15-20 mins). I'm running 89 octane in it, but really should be running 87, since that's what it's designed to run on. What are some things to check?
My first step is checking the timing. It may be advanced, I don't know. I have a light, so I'll check that out. Plugs are new. Wires and cap/rotor, condition unknown. The truck runs fine otherwise, and even has lots of power for a 4-cylinder, so I wonder if the timing isn't advanced already on it. If so, I suspect that retarding it a few degrees would take care of the spark knocking, no?
Sounds like combustion chamber deposits or clogged injectors. Both should be taken care of by a proper injector cleaning. I recall a setup sold by Napa that replaced the fuel inlet with a aerosol bottle and a regulator. You just hooked it up, started the car and let the car run til the bottle was empty. This took care of injectors, intake valves and combustion chamber deposits. Not sure if they sell it anymore. It cost about the same as you normally pay for the same service at a garage, about 100 bucks. If you did it yourself, the next time you just needed the aerosol bottle which was about 10 bucks. Aaron
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Aaron Ford
95 2WD Nissan PU E
2002 Oldsmobile Intrigue GX
"The hard part about playing chicken is knowing when to flinch" Scott Glenn in The Hunt for Red October
Jadcock – So what do you think of NC? That is where my in-laws live and also where I met my lovely wife. We’ll be up there this summer, so please make sure the weather is nice for us
About your problem, my truck started doing the exact thing that you are describing about 4-5 months ago. The problem was corroded contacts on the cap and rotor. Quick change and the truck ran like a champ with 87 octane. If you let it go for too long, your truck might start to miss. Might want to change the wires too for good measure – HTH
Thanks
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Current Wheels: 86 SVO 1E, 89 Nissan D21 VG30E, 50 Fleetline Cpe
Past Wheels: 94 Vette LT1, 01 Vette Z06, 87 Vette L98, 80 Vette L48
Thanks for all the replies so far. Mileage is 175k miles. Past history mostly unknown. I bought the truck last November. Except for this spark knock when it's real hot out, the truck really runs like new. It has a lot of power for a 4-cylinder. It doesn't outrun Camaros or anything, but it easily keeps up with traffic. I do use that gas pedal, though, and if I have to be easy on it (1/4 throttle) to keep it from knocking, it DOESN'T keep up with traffic very well.
Good tip on the combustion chamber deposits. I have prior experience with GM Top Engine Cleaner -- that stuff really works. It isn't without risk, though, and I don't know the condition of the head gaskets on this Nissan. That Top Engine Cleaner puts a lot of pressure on the head gaskets I think, and I don't want to try it yet, not if I don't have to. I'll get a cap and rotor and maybe a set of wires -- and I'll check the timing.
By the way (CarGuy), North Carolina is great... We live in Fayetteville and I work at the Ft. Bragg Army Installation as a civilian contractor (in their Environmental Compliance office). Ft. Bragg is about 200,000 acres spanning five different counties -- and there's a lot of artillery training going on here all the time. You can hear it a lot at the house...they call it "Bragg Thunder". I hear, though, that this isn't anything compared to when the Marines come to train in March and October -- they bring out the BIG GUNS. Ft. Bragg is also home to the 82nd Airborne, the Army's elite group of paratroopers. They have jump schedules publicized and you can go watch them. We're excited to do that. They have a jump scheduled next Saturday...we're gonna take the Nissan out there and get out in the dirt and get dirty and watch some paratroopers.
Now that you said that... I fully agree with the investigation of the combustion chamber deposits. I have seen many vehicles where this is a major problem... and the engine pings like hell no matter how far you retard the timing.
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Originally posted by jadcock Mileage is 175k miles.
How do you recommend I do that? Aaronford suggested a kit from a retail store...would/should that do it safely without risk to damaging anything else? I've never used the kits, so I don't know how effective they'd be.
I've also heard of doing stuff like pouring ATF down the throttle and/or carb cleaner spray. I'd like to use something intended for the purpose (unlike ATF), but also something that won't cost a lot of money to buy in a kit format. I know I know...wanting to have my cake and eat it too...
I bought a new cap and rotor for it. It's a good thing I did -- the old parts were nasty! The contacts on the cap were so burned/worn, they were white and flaking off! The engine runs really good now, and a little smoother than before, but the ping is still there under moderate-to-heavy throttle.
Hey, I have never used anything but the Napa kit and that was several years ago. I have heard that Amsoil Power Foam works to clean comb chamb deposits, but I have never used it. I have also heard that water sprayed in a heavy mist into the intake in a hot engine while it is running will also do it but I'm not so sure about this one. Based on the cleanness of a cylinder after a head gasket leak, I believe it would work. I do not, however, believe that it is terribly safe. I would try the GM Upper Comb Chamb Cleaner or the Power Foam or have it done professionally, if it were me. Aaron
PS Curry, can I borrow your BS meter? Aaron
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Aaron Ford
95 2WD Nissan PU E
2002 Oldsmobile Intrigue GX
"The hard part about playing chicken is knowing when to flinch" Scott Glenn in The Hunt for Red October
Originally posted by jadcock The engine runs really good now, and a little smoother than before, but the ping is still there under moderate-to-heavy throttle.
Man, now I'm puzzled Did you ever get to check the timing on the truck? I remembered when I changed the cap and rotor, I did backed down the timing JUST A HAIR (a mechanic advanced it during the winter, bc he said it would help out ) Anyway, my old parts were just like yours - they were so burnt I couldnt believe it ran at all I sure hope it isn't carbon deposits - that could be a headache - but if the truck has been well maintained and has always had 87 octane ran in it - it would seem unlikely that deposits would be built up - IMHO
Well, that was gonna be my next question -- how to get to the friggin timing mark on the truck! I can't see it anywhere. I hooked up the light and started looking around at something to point it at, and realized I couldn't find the timing indicator! Do I need to take anything off to see it good? There's a single screw at about the 11:00 position on the dist mount...and the Haynes manual said to loosen that and rotate the distributor to adjust the timing. If I can't find the timing mark, I might go ahead and rotate it just a hair and keep trying it. I'll be able to tell if I get it...
In the mean time, I bought a thing of Chevron Techron concentrate and dumped it in with my fillup today. We'll see if a tank or two of that will help any. Else, I'll go with the GM Top Engine Cleaner I guess.
Hold the phone... The timing mark is a shiny steel pin next to the crank pulley. You should see three marks on the pulley. The crank pulley is graduated in (I believe) 2 degree increments. The distributor hold down bolt is where adjustment is made. Notice that the hole in the distib flange is slotted? Look for the pin on the front of the engine above the crank pulley on the alternator side. You need to research this before tearing in to it or you may make something worse. If anyone knows the timing marks indicate, I would love to know. I am guessing 0, 2, and 4 degrees BTDC. When timing most computer controlled cars, there normally is a wire that either needs disconnected, connected, or grounded to disable computer spark advance. Kinda like pulling the vac line on the old HEI's. BTW, does the ping subside with higher octane fuel?
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Aaron Ford
95 2WD Nissan PU E
2002 Oldsmobile Intrigue GX
"The hard part about playing chicken is knowing when to flinch" Scott Glenn in The Hunt for Red October
Aaron, thanks, I finally did find it. I was surfing through the Haynes manual at breakfast this morning and found a diagram of the KA24E timing pin. It shows the marks on the pulley as:
-5 0 5 10 15 20
My underhood decal lists the timing spec as 10 degrees BTDC. The Haynes manual doesn't list anything to disconnect or plug. There are no vacuum lines going to my distributor that I can see. I do have one question. There's a small adjustment screw that sits in the slotted hole and then there's also a larger screw that seems to be the "mounting" screw. Do I need to loosen both before I adjust the timing? The Haynes manual shows clockwise is advance and counterclockwise is retard.
I'm not going to play with the timing yet -- just trying to understand everything in advance before I jump into it. I first noticed the ping when I was back in Virginia -- the weather got hot one day and the truck would ping at moderate throttle. This was on 87 octane gasoline. I then put in some 89, but it still pings. I just put in some Chev. Techron cleaner, along with a fresh fill of 89 octane (from a Shell station). I'm going to wait a week before I do anything else mechanical (like changing the timing) to see if this detergent will work. It said it may require another dose of the cleaner...who knows. I'll find out soon enough I guess. Until then, it runs fine at lower throttle apps...we just don't get where we're going as quickly.
BTW, this is all in 95 degree heat with the A/C on. The engine fan stays locked on much of the time -- especially in traffic. These are really the most extreme operating conditions, I know. But...it should work regardless. I could turn the A/C off to see if it'll fix it, but I want to minimize all the variables -- and be as consistent as possible until I figure out what's going on.
Too bad the KA24E doesn't have a knock sensor like the V6 does....
Originally posted by jadcock I then put in some 89, but it still pings.
That doesn't sound good. If you truck was running fine before - then the current timing shouldn't be too far off or just fine. Huh - what could it be? I think even 89 octane would take away pinging if you carbon deposit build up. It would just create a worse case of deposits tho.
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Originally posted by jadcock Too bad the KA24E doesn't have a knock sensor like the V6 does....
Does my truck has a knock sensor? What year did this start?
but I only know how my truck runs. With 87 it pings under heavy acceleration.
Did you ever get to check the timing on the truck? I remembered when I changed the cap and rotor, I did backed down the timing JUST A HAIR (a mechanic advanced it during the winter, bc he said it would help out 
) Anyway, my old parts were just like yours - they were so burnt I couldnt believe it ran at all 
I sure hope it isn't carbon deposits - that could be a headache - but if the truck has been well maintained and has always had 87 octane ran in it - it would seem unlikely that deposits would be built up - IMHO
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