Posted: 11/14/2009 8:40:51 AM EDT
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I own a 1999 S-10 4x4 with the 4.3 V6. It is equipped with the manual transmission. Usually when I shift up to the next gear and load the engine, I hear some detonation. It will also do it when under moderate acceleration as well. It does it really bad if I run 87 octane in it. When I use 89 octane, It seems to not do it as often but, still present.
I did the plugs and wires about 4 years ago and the mileage at that time was 90,000. It's not sitting at 126,000. I'm concerned that someday I might explode the engine from this problem. |
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detonation is caused by,
Octane too low Lean mixture Ignition timing advanced Lugging and over fueling cooling system not working fuel rating shouldnt be the problem (our ZR2 runs just fine on 87). Lean mixture could come from a plugged fuel filter or injectors being plugged (check fuel presure at the engine that will tell you if the filter is plugged, pull the injectors and get a spray pattern test done, injector cleaner might help but i would pull them and do it right also look for vacuum leaks). Timing i dont know if there is still a distributor on the 99 but if so check the timing (on the later 4.3Ls the distributor is locked into place but but it could be a tooth off, so check it, this should throw a code though). Lugging is a gimme, just dont do it, try running the engine at higher rpms. If the cooling system isnt working you should notice it running hot. Look at that stuff and you should find the problem. Other things i would look at would be spark plugs, make sure they are tight and the proper part number. A plug that is loose will let air in making the mixture lean, and a plug that is not the right part number could be holding too much heat making the fuel ignite before the plug fires... |
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Quoted:
Check over your PCV system too. Oil lowers octane, so if you are sucking in a little oil it could cause problems during the high load situations you speak of. I do use about 3/4 to 1 full quart of oil between changes. And thats every 3 months or 3,000 miles. Maybe the rings are getting bad. |
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No seafoam please.... Get someone with a decent scanner and check the EGR, then Knock Sensor, then the CRT. The rings are not bad with that kind of oil usage. Also check for vacuum leaks at the HVAC line that runs under the brake booster. Listen to this guy... |
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No seafoam please.... Get someone with a decent scanner and check the EGR, then Knock Sensor, then the CRT. The rings are not bad with that kind of oil usage. Also check for vacuum leaks at the HVAC line that runs under the brake booster. CRT? Detonation has went away. I recently had to put a new thermostat in it. I do need to keep an eye on my oil levels to see if the engine running too cold would cause opil consumption. |
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No seafoam please.... Get someone with a decent scanner and check the EGR, then Knock Sensor, then the CRT. The rings are not bad with that kind of oil usage. Also check for vacuum leaks at the HVAC line that runs under the brake booster. CRT? Detonation has went away. I recently had to put a new thermostat in it. I do need to keep an eye on my oil levels to see if the engine running too cold would cause opil consumption. CRT = Cam Retard Timing this can but is uncommon to cause det. This is the measure of diffrence between the cam and crank signals and helps the computer advance and retard timing but mostly is a refrence for misfires and should set a P0XXX code (I can look up what code exactly in the morning). Was the truck overheating before changing the t-stat? If not cold temps should not cause det. as it is caused mostly by high combustion temps. Also it could of been bad gas.... How long was this going on reason being is that for about the last 6-8 months I've gotten quite a bit of shit gas from different stations around town. I noticed this while tuning a few customers cars and one of my own. It popped up as excessive knock retard on a few pulls then would go away. ETA: If you have any future problems with you S-10 feel free to PM me as by mistake I've become quite familiar with these POS trucks by mistake... 
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| You need to have it scanned for defaults as soon as possible. 4.3 V6's are known for this and are notorious for spinning #2 or # 3 main brg. About 40 percent of the engines that come in, the blocks are not rebuildable. I have done 40 or 50 of them to date. They are not a bad engine. |
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I'll guess the EGR system is not functional. Clogged or broken.
The EGR uses a small quantity of exhaust gas to dilute the air (oxygen) in the intake manifold. This effectively increases the volume of "air" going through the engine, but reduces "Oxygen" percentage. Thereby lowering combustion temperatures. EGR equipped engines generally run MORE ign timing to compensate. When the EGR clogs, the engines ping, due to too much ign timing. It's worth a look into the EGR system at your trucks age anyway. For the record, I hate EGR and what it does to an engine. |
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Mine was running like crap until I filled it with 93 octane the other day. Smoothed right out. Might just be that there is a lot of shitty gas going around right now. If you or the OP gets a P0300, O2, or catalyst codes with difficulty running lower octane fuels suspect the CSFI poppets I've been through a couple dozen of these. Poppet gets clogged and doesn't atomize the fuel properly causes all kinds of problems for misfires to catalyst failures but they have to get pretty bad to start tripping DTCs. I've done quite a few MPI conversions on the 6's and 8's now and it's well worth it and I did my own truck before the poppet's went and was able to drop my VE tables quite a bit and gained about 2MPG on avg. Yeah the gas lately has been weird lately to say the least. We first noticed it on a 5.3L Chevy turbo application, worked on the tune for a week fueled up on the way to the track and EGTs went through the roof on the runs 3-5 and went to look at the logs and maxed the knock retard. Started checking other logs we've been having problems with and all were to do with knock retard. This gas was bought form different stations from around town is what got me. I can understand one station but damn makes my job a little hard with fuel as a variable now. 
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Mine was running like crap until I filled it with 93 octane the other day. Smoothed right out. Might just be that there is a lot of shitty gas going around right now. If you or the OP gets a P0300, O2, or catalyst codes with difficulty running lower octane fuels suspect the CSFI poppets I've been through a couple dozen of these. Poppet gets clogged and doesn't atomize the fuel properly causes all kinds of problems for misfires to catalyst failures but they have to get pretty bad to start tripping DTCs. I've done quite a few MPI conversions on the 6's and 8's now and it's well worth it and I did my own truck before the poppet's went and was able to drop my VE tables quite a bit and gained about 2MPG on avg. Yeah the gas lately has been weird lately to say the least. We first noticed it on a 5.3L Chevy turbo application, worked on the tune for a week fueled up on the way to the track and EGTs went through the roof on the runs 3-5 and went to look at the logs and maxed the knock retard. Started checking other logs we've been having problems with and all were to do with knock retard. This gas was bought form different stations from around town is what got me. I can understand one station but damn makes my job a little hard with fuel as a variable now. The issue has not happended in over a month now. I'm leaning towards bad gas. Maybe I'll run 89 octane instead of 87. Quoted:
Clogged cat and a misfire. Cat was replaced around 89,000 miles. I did have the dreaded misfire issue around 54,000 miles. Had to go through two cleanings to get them things to work good again. I'm interested in the MPI conversion though.... 
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If you haven't I would still see if you can find a buddy with a good scanner and just check on things. The gas issue should be far and inbetween to say the least but has not been around here lately.
The MPI part numbers are stashed somewhere in the shop I'll dig them out tomorrow for you. GMPartsdirect.com is where I've been getting them form as the kit is cheaper from them than wholesale from the local dealer. While doing the swap is also a good time to take care of (clean out) the EGR passages as it will only cost you the EGR gasket and a few pipe cleaners. |
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I've got two S10 Blazers with 4.3's. A 95 and a 96. The 95 is the "W" engine and the 96 is the "Z" engine.
The 95 turned a rod bearing at about 128,000 miles. It has always had issus with the EGR valve getting plugged up with carbon. Been through a couple cans of the GM foam cleaner you spray down the EGR hole but it does it again anyway. When the EGR is stuck open it runs good going down the highway but misses bad at idle speeds and lights up the SES light. Finally got tired of pulling that little bastard out of there and picking the carbon out of it and put a piece of aluminum from a pop can under it awhile back. No issues so far. The 96 has never had an issue with EGR or spark knock. It has 105,000 on the original engine. Isn't the whole idea of the knock sensors to let the computer know when to retard the timing to stop the spark knock? Maybe sometimes its so bad that won't take care of it. I've had the 95 for years and the 96 for only about 3 years. I'm not impressed by the 4.3's. My 2005 K1500 with the 4.8 V8 gets better gas mileage around town than the 95 Blazer and the truck has a 4.10 rear axle under it. The 96 gets pretty decent gas mileage on the highway, about 25 down here in flat terrain, due to the 3.08 rear end I suppose. Oh, when the rod bearing in the 95 was on the verge of going out I thought I had spark knock on it, too. It would make a clicking/pecking sort of noise on acceleration off a stop sign/stop light in the last few hundred rpm just before it up shifted. It just got worse and worse and finally one day while trouble shooting it (I revved it to 4000 rpm and tried to hold it there it finally went south for good. You know those darn things are different. Not all 4.3's are the same, which I found out when I had a rebuilt 4.3 put in the 95 and it kept blowing exhaust manifold gaskets - differnt exhaust port spacing...I'll never pay a shop to replace an engine for me again. |