Engine Pinging

[95hardbody]

Hey guys,

I'm somewhat of a lurker here, and have a '95 Hardbody truck with the KA24E engine. Love the engine, plenty of power for all circumstances. Won't take a 240SX by any means, but it's plenty fast for a 4x4 truck.

Anyway, I've noticed that the engine pings, at heavy throttle, in 100 degree heat, using 87 octane. I've checked and verified the timing is 10* BTDC. The correct plug for it is an NGK ZFR5E-11, and I've looked before for a 6E-11, to go one heat range colder. Nobody's heard of that plug, and nobody sells it. I got a set of KJ20CR11s from Autozone (Denso) which are supposed to be as equivalent to a ZFR6E-11 as it gets, and they seem to run good. Pinging only at heavy throttle.

Yesterday, I installed a set of Bosch Platinum 4229s. Just the regular platinum, not +2 or +4. On the drive home from work today (98*F ambient temps), the pinging was pretty heavy...anywhere past 1/4 throttle all the way to WOT. I hated to even drive it home, it was pinging so bad. When I got home, I changed the plugs back to the colder Densos and it's back to pinging only at heavy throttle.

Is no ping at all on days like this just too much to ask? I plan to run a tank of premium next time (going on a road trip this weekend), and I know that'll keep the pinging at bay, but this is a 100% stock motor...it should be good to go on 87, even in temperatures this high, shouldn't it? I've pulled up on the EGR diaphram at idle, and the engine tries to die, so it seems like it's getting good EGR flow.

Any other tips from the experts? I know you guys know at least as much as the KA24E engineers themselves, so I'm hoping someone will have had my experience before, or can suggest a fix.

Thanks in advance,Jason

[gumby]

try running a bottle of injector cleaner through it with the 93 octane.

[im two techno]

check the temp sensor for the ECU id replace it.also check the knock sensor they are somwhat cheap.and use at least 89 fuel

[C-Kwik]

Are you sure it was ping? There would have to be a serious hot spot for detonation to occur at 1/4 throttle. Carbon deposits maybe. Try putting in a tank of premium grade fuel. See if the problem goes away and perhaps that will confirm if it is indeed knock/ping. It should be able to run 87 octane without ping though. But I really just want to confirm if it is knock or not.

[95hardbody]

Are you sure it was ping? There would have to be a serious hot spot for detonation to occur at 1/4 throttle. Carbon deposits maybe. Try putting in a tank of premium grade fuel. See if the problem goes away and perhaps that will confirm if it is indeed knock/ping. It should be able to run 87 octane without ping though. But I really just want to confirm if it is knock or not.

Thanks guys for your responses so far.

It was definitely spark knock. "clink clink clink" I had that once before on an old Oldsmobile, and the solution was to clean the EGR passages in the intake manifold -- the engine wasn't getting enough EGR. That doesn't seem to be the case here. But there was a discernable difference between the Bosch plugs and the Denso plugs, which leads me to believe that maybe the Bosch's were the wrong heat range...although they were the ones that were supposed to go on this engine. Bosch advertises that their center electrodes run cooler than other plugs, but I think that's what was heating up and causing a hot spot. I don't think it was pre-ignition, I think it was spark knock.

I could easily bring it on with the gas pedal. Push it far enough, and it would sound like a popcorn machine. Back off just a bit and the ping goes away. Ease on the gas again and it came back. It's the on-off threashold that differs between the two plugs. With the Bosch plugs, that threashold is pretty shallow (about 1/4 throttle). With the cooler Denso plugs, that threashold is much deeper, about 3/4 throttle.

I don't think this engine has a knock sensor (at least not on the truck). I'd certainly look into that if it had one. I can't find it -- if it does have one. Higher octane gas does solve the problem, as does colder temperatures, no A/C load. It's just under those most severe conditions, when it's 100 outside and I have the A/C on, and when I'm using more than 1/2 or 3/4 throttle (with the Denso plugs). I decided I'm not running those Boschs again...unless I can fix the spark knock. I also think that it's no big deal to run higher octane gas if it's supposed to be in the upper 90s for a short spell. I know the truck is "supposed" to use 87, though, so I'd like to be able to use 87.

I'll run a tank of injector cleaner through it, and use 92 octane this tank. We're going on a road trip with it this weekend, and I feel confident that I won't have any problems with the higher octane fuel. I had this problem before (severe ping, even at 92 octane), and discovered that the timing was set at 18* BTDC. When I set it back to 10*, truck ran great, no ping, even at 87 octane. And that still stands today...except on the hottest of days like we're experiencing this week. Even then, as long as I don't push the truck hard, it's fine.

Any other ideas. Again, I appreciate your comments so far.

Thanks,Jason

[95hardbody]

Does anyone have any further thoughts on this? Thanks,

[Ubernoober]

As miles build up, carbon hot-spots can build up also. Particularly with short runs back and forth to work. The premium fuel + injector cleaner + long trip you are about to do may actually help reduce this problem a bit. The other choice is to try and run some type of top-end cleaner. SeaFoam seems to be popular here.

95 so I am guessing you have a few miles on yer baby. If the drive plus cleaner doesn't change anything, I would definitely check the temp sensor as mentioned earlier and run some cleaner through it. Also, cleaning the MAF may help. It may not be dirty though and you have to be VERY careful about doing this. There are a few threads that discuss this. The idea is that perhaps it is metering you a tad lean. Of course, the O2 sensor is tied to this, but changing that is up to you since now a little fixing has started turning into a major tuneup.

I think you have effectively eliminated the EGR.

[95hardbody]

Thanks -- I might try some top end cleaner. I don't think carbon buildup is a problem, but I guess it could be. My drive to work is about 25 miles each way, at speeds of 40-60 mph. I might go ahead and replace the O2 sensor. There's occassionally a check engine light that comes on, always after a hard acceleration, but only once or twice a week. 30 seconds after it comes on, it's back off again. I don't know how old the O2 sensor is...possibly original (186,000 miles). If a new O2 sensor doesn't fix it, I probably won't go any further. It's not really that big of a deal...it only happens on the hottest of days under the most severe conditions. Even if it's as hot as 90 outside, it runs perfectly fine.

Regarding the Seafoam, how do you guys use that? I've used GM Top Engine cleaner on an older Oldsmobile, and it was easy...I just slowly poured it down the carburetor throat and towards the end of the can, dump it all in and stall it. After 30 minutes, start it up and watch the smoke show. It worked very well. Is Seafoam similar? Do I need to remove the spark plugs and apply it directly to the cylinders, or shoot it down the throttle body throat?

Thanks again,Jason

[Ubernoober]

Just like the GM stuff. Members here say the easiest way is to use the vacuum line from the brake booster.