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Chevy S10 - GMC S15 and Sonoma Engine and Underhood Problems



  • i have a 98 s10 2.2 and i hav a code coming up #0303 it is cylinder 3 miss fire (small) and i am wondering if this is common and what causes it
  • toneygtoneyg Posts: 19
    Let me give you some advice on this problem from experience. this sounds like from what you are describing, that your catyletic converter is stopped up. two things you can do is(a) have it replaced at about $150.00 or(b) remove it yourself. just take a sawzall with a metal cutting blade and cut it out. Then go to your local parts store and get you some exhaust pipe,clamps and 2 couplings. then tie your exhaust system back together. you will have to do this yourself, because a shop will not do this, but they will weld it for you . this will cost you about $25.00 to $30.00. this should solve your problem, also it will give you a little more power and performance,not to mention it will improve your gas milage. and it won't hurt your motor,because it is not computer controlled.Let me know if this solves the problem. thanks for the e-mail
  • toneygtoneyg Posts: 19
    This problem your are describing is coming from a computer malfunction. You need to replace the computer from under the passenger side dash panel. They are only $75.00 to $125.00 depending on where you get it from and the parts store will change out the control chip from your old one to the new one for you at no charge.(Autozone does this)
  • Thank you. You may have something there. I had my Converter replaced under warranty about 6 months ago. It was rattling really bad. I thinking that it may have broken off and might have stopped up my muffler. I will go have it checked.
  • Hello. I have a 1996 Sonoma 2 wheel drive, 4 cylinder pick up. Recently replaced radiator, thermostat and it's still runs hot only when I'm at a red light or idling - goes up to 210, then driving temp gauge goes back down to normal once I start moving again. This happens about 15 minutes after I start driving vehicle. Also, when I turn off engine, I can hear a bubbling sound, like it's boiling water, but, the overflow doesn't get hot. Other than this, the truck drives great. Any advice out there?
  • jpfjpf Posts: 496
    That era 4 cylinder engine (2.2 liter overhead valve engine) had a head gasket problem. I had a 95 Corsica with the same engine that need 2 head gaskets within 90 thousand miles. This could be your problem. Good luck.
  • you need to see if the cooling fan is coming on at a stop. there not needed much when moveing
  • A couple of weeks ago, I through a check engine light, it read that it was overheating. It has a new radiator in it and it had leaked a gallon of antifreeze put more in it and it leaked a half gallon, looked everywhere for a leak, couldn't find anything. Then we though it was an intake gasket and put pressure on it and nothing. It never heats over 210 and now, it seems to be only moving up one mark. What could be the problem? Does anyone else have this problem?
  • Not sure if the Buick 3.8 will be the best bet. For an easy engine swap that should definately boost some HP while delivering the necessary torque, consider the 3.4L engine used in the early nineties Camaro. Forgo the FI intake, and swap in an Edelbrock 60 degree V6 four barrel intake, or similar. I have considered this option for my '83 S15 2WD, but haven't raised the funds yet for the engine.
  • msgtwlmsgtwl Posts: 1
    It has a 2.2L without the converter. Recently I started having problems with it missing when the engine is cold. Any idea where to start? Could it be a coil pack? I'm going to hook it up to a friends scanner tonight.
  • have you seen any antifreez or was the radiator just low? if so you may have had a air pocket. after the air worked its way out the antifreez went down.thats my guess since you just put a radiator in. the way to stop the air pocket is to pour the antifreez slow. add a little at a time. and make sure it gets to operateing temp .as the thermostat opens the cooling well go down. hope that helps
  • toneygtoneyg Posts: 19
    luckily, I have experienced this same problem. as luck would have it, After I replaced the radiator,hoses, thermostat, heater core, freeze plugs,fan clutch and electric fan also. It turned out that the radiator cap was faulty. Replaced it with a new one and it solved my problem. Try this, and check your thermostatic fan clutch,or electric fan and relay, which ever you have on your truck. E-mail me back, if this solves your problem. Happy to be of assistance,thanks for asking.
  • Hello. I am no genius when it comes to diagnosing problems with my truck. I have noticed in the past that smoke was coming out of the front of my 2000 s-10 2.2 rwd, I finished a transmission fluid change and was letting the truck idle while I checked for leaks and noticed that the smoke was coming out of a section around where the oil pan connects into the engine. There is also a piece of exhaust coming from the engine that crosses over that area. I have noticed some liquid buildup on the exhaust pipe crossing over. Could this be an oil seal leak and the oil hitting the hot exhaust is causing the smoke? Could this be an exhaust leak? Any tips would be appreciated. Truck has 110K on original engine/trans. Original exhaust.
  • toneygtoneyg Posts: 19
    One of two things could be the problem.(A). You have a rear main seal leak. Which is a little costly. Meaning,the oil pan and exhaust system has to be removed, and the crank shaft has to be removed to replace these seals. Or (B). It's your oil pan gasket, which also requires the removal of the exhaust system and the pan. You also have to raise the engine to do this. This would be the least expensive of the two. This needs to be repaired ASAP before the problem gets worse.
  • Thanks for the's much appreciated!
  • Buy aftermarket cooler lines and have them installed. Dont remove the lines. that is very dangerous not to mention a hack job
  • I just bought a 99 GMC Sonoma 4.3L V-6. Experienced check light coming on/off over several weeks,hesitation during start up and while driving and fuel mileage is in the toilet (15-16mpg on average). Code came up P0300 "random multiple missfire". I changed plugs, wires, cap, rotor, fuel filter and dumped several cans of chemtool injector cleaner over 3-4 tanks. Dealer finds no problems and code light is off now, hesitation at idle is intermittent, seems to still be there slightly at normal driving speeds and fuel economy still in the toilet. Can't tell if it's ignition, tranny lag or something else. I'm pretty sure this model should be getting at least 20mpg on average. Anyone have any ideas?
  • I have a 99 Sonoma, same problem, replaced plugs, wires, cap, rotor, injectors cleaned, still have problem...16-17mpg at 82,000 miles. Any luck finding your problem?
  • 99 GMC Sonoma 4.3L V-6

    Obviously your PCM is detecting misfires but cannot isolate a perticular problem. On your model it is usally a dirty or bad connection at the crank sensor, or an intermittant problem with fuel pressure.

    Here is an explanation. The PCM interprets irractic changes in the pulses coming from the crank sensor as misfires. Basically, your vehicle skips a beat due to any number of reasons and the PCM sees it as random misfires. Check the plug to the crank sensor and see if it is oily or dirty. I would also invest in a fuel pressure guage and verify there isn't any drops in fuel pressure. You have a engine that needs at least 55-60 psi fuel pressure at all times, or the fuel injectors will not spray fuel. GM has a poppet inside the injectors that prevent opening unless there is sufficient pressure, even though they are being told to open by the PCM. Good luck.
  • toneygtoneyg Posts: 19
    What is the odometer reading. From past experience, I've found that 2 things can contribute to this kind of problems. 1 is the catyletic converter clogging up and the egr valve also. The other is you air filters and PCV valves sticking. So my advice would be to have these items checked
  • I have a 2002 gmc sonoma with a 2.2 with 90k miles on it whenever my truck starts the rpm is kinda jumping around and whenever I go foward it hestates to shift to second gear but after that the truck runs good any ideas?

  • p0303 does indicate that the PCM sees a misfire on #3.

    The most common problem is ignition arcing because of no dialectric greese on the sparkplug boot. Bad spark plug, fualty injector for #3, engine compression problem on #3, ect. You got to do some troubleshooting and hope its one of the easy problems. If your due for a tune up, do one and see.
  • tomf8tomf8 Posts: 6
    i have 99 s10 2.2ltr. eng the engine does not come up temp. and also no heat at heater in cab. i have changed thermostate 2 times and will not come up temp, runs about 130degrees. thanks for your help.
  • If you have an electric fan for the radiator, I would suspect that it is coming on to early and too long, probably a bad temp sensor for the fan, or if you have AC the radiator fan switch for that.

    If you have a manual driven fan. I would first want to know if any modifications have been made to the engine, or the AC condensor removed or something. Has an add on transmission cooler been added?

    If your positive that the engine is running cold itself and not a problem with the guage and a heater control valve not letting hot coolant enter the heater core. Please post more info about your vehicle.

    Electric fan or manual? If electric fan, how long until it comes on after start up?
    Automatic or manual transmission?
    Modifications or add ons?
    How are you determining engine temp?
    Factory AC, or after makrket or none?
  • Thanks for the info. Can this problem still exist without a code coming up? I have an Auto Xray 1500 scanner and had the dealer scan it w/o any results as well. All tests on the Emmissions system comes back normal. They ruled out the injectors during the last visit. How common is the faulty fuel preasure issue with this mode? Could this be a vacum, or faulty compression issue? What should the mileage be on this type of truck....roughly? Lot's of experience with the v-8s not so much with the 4.3L. Thanks again for all of your help I'll get to checking these out this weekend just to be sure.
  • Not yet...changed the plugs and found one gapped at .065. Changed them out and the P0300 "random missfire" code went off. Still have the gas issue though the idle stumble seems to be gone. Still seems to be missing at normal speeds but I can't tell as the truck rides so freaking stiff in the first place. So far i've logged 135 miles on a half tank....can't be running right but it pulls hard under a load and feels strong through the gears.
    From what I can tell from other postings is that it can be either plugged cat, bad crank sensor, poor fuel preasure, fouled EGR, vacum leak, or a new truck....i just don't know how common any of these issues are in this model to know where to really start. Guess I have to pick one and start ruling them out one by one. Any ideas?
  • About 82K. The truck was purchased from a 68 year old woman who only drove in the texas hillcountry. Trucks in good shape except for the gas economy. I'm going to check the crank sensor and fuel preasure this weekend to rule them out. Sprayed carb cleaner all around block, intake manifold...side, back to front. No change in rpm or evidence of any leaks there. Will be using some soapy water spray on all the hoses this weekend to rule that out as well.
  • Can this problem still exist without a code coming up? Yes. PCM's are not all knowing. They know only what the sensors send them, and sometimes sensor info is wrong.

    How common is the faulty fuel preasure issue? Rare but I have had fuel pumps briefly and intermitantly loose pressure causing random misfires. I actually had to see the failure while it happened. I even had a fuel pressure regulator fail intermitantly dropping the pressure.

    Could this be a vacum, or faulty compression issue? Not a vacum issue, vacum leaks cause a lean miss and your o2 sensor would have caught that and run the engine ritch. Compression can cause misfires but I doubt that is your problem. Compression problems are rarely intermitant and are usally isolated by cyclinder and can be identified as a specific problem with one or more cyclinders.

    No doubt, you got a tuffy, intermitant stuff always is. You basically have to keep trouble shooting until you find it. An intermitant coil failure or not enough output of kv spark could be it also. All the PCM knows, is that every once in a while the crank sensor is picking up a weird vibration and interpreting it as missfires. Hell, one car I finally found it, it was a loose mounting bolt for the crank sensor.

    Heres a suggestion. Start with one system and eliminate it as the problem. Test it until the po300 comes back and if what ever you were testing checks out ok, move on to the next thing. Clear codes and test something else.
  • You are the mandango! I'll get to checking it out this weekend and let you know how it goes. Thanks again for all your help. Most of my gear head friends either moved out of state or are dead. Yikes!!!
  • tomf8tomf8 Posts: 6
    it does not have a/c temp on guage comes up to just above a 100 just a guess on actual temp. eater problem arose before clold eng. temp. problem. there ave been modifications or changes to has 2.2 enh. auto a/c. it takes a long time to get above 100 degrees(many miles5to10). heater is not controlled by heater control valve per-say . it has hot water a the time it is controlled by doors in heater box in cab.
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