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Chevy S10 - GMC S15 and Sonoma Engine and Underhood Problems



  • I've been avoiding that diagnoses for sometime now though addressing everything else still was the right thing to do. I've thought about just pulling it and replacing it with a hi performance distributor just in case the pick up coil in there was going/failed all together. I guess I'll try inspecting it and if needed see where the white rabbit leads. Thanks for your advice I'll post back after round 8. Yikes!
  • Well I guess maybe that technical bulletin was rightl. It was the injector harness. Opened the the intake and there was a lot of fuel down in the wells. Changed out the harness and will road test it today. I'll post back later this evening to let everyone know how it went.
  • Well I took off the intake and fuel was everywhere. I swapped out my injector harness and that seems to have done the trick. Gas mileage is up to 18.5mpg in the city from 15mpg. I have a bit more tweaking to do to get the mileage back up in the low 20's where I think it should be but so far so good. Thanks for all of your help and advice.

  • I have been working on this truck and cant seem to find out whats wrong.the truck has less than 70k on it.
    codes came up... idle air controle valve and random missfire.
    It idles very rough with a strong smell of gas also very sluggish at low rpm.cuts out at higher rpm when just reving.I replaced coils,plugs,fuel fliter,fuel injector on #2 cyl.IACV,wires,air fliter, checked fuel reg,checked all hoses,replaced battery term. checked timming still same problem.When I changed the oil it had some gas in it.Im thinking either cat or comp...........please any suggestions.
  • "The Elusive Misfire" This truck is killin me. First had a cylinder 2 misfire constantly. In all have replaced plugs, wires, coils, crank sensor, #1,and 2 injectors, checked for vacume leaks, checked compression static and running, all within specs. Has cold air intake and exhaust. Have no cat on it. 150,000 miles. Only thing I have not done yet is check fuel pressure and regulator. Which I am going to do soon. Basicly had a misfire on cylinder #2 and changed plugs and wires and coils and crank sensor. Lost even more miles/tank of gas. Down to about 230 or so. Used to be around 360 or so. Seems like every time I work on this truck it gets worse. Changed injectors 1 and 2, problem swiched to random misfire instead of steady #2 and intermitten cylinder 1 misfire. Have checked egr and even blocked it off to see if that would eliminate the problem which it did not. Also when the truck is cold the misfire is not present untill about 2 to 3 min's of run time then has a steady mis at idle and all through driving speeds. Holding steady at about 1500 to 2000 rpm mis is obvious. So far everything I have checked comes up nominal. But like I said every time I work on this truck it sure seems to get worse. Obviously the exhaust smells rich! No codes either. If when I check fuel pressure and it happens to come up nominal, really going to be stumped. Any advice would be appreicated. Thanx
  • Also forgot to mention, have changed fuel filter and it was definatly restricted. Havent checked timing. Does have a bit of a chatter once the oil warms up, read in here somewhere about the timing chain tensioner going bad on these trucks. Possibly out of time. The truck used to give a lean sneeze once in a while when you would stomp on the throttle but that has long passed. Doesnt have near the power it used to. Eventho it misses it doesnt seem to show under a load like an arcing plug wire would. The mis also seems to change once in a while. Rare but every once in a great while it will run pretty good.
  • 1.I have a 97 S10 V6 manual and when i shift into a higher gear i hear a churp or squeak sound. I have no idea what it is and have had problems with my tranny b4 (so is it just another one?)
    2. I am also loosing coolant without any spots showing up one the driveway. what could it be?
  • Hi,

    I have a hose on my 91 chevy s10 with the 4.3L TBI enging that broke.

    It is connected to the rear of the intake manifold, it has a funny looking device that goes from hose to tubing. But the piece that broke is a threaded piece that threads into the manifold. I can get the piece out but what the heck do I order so that I get the piece that threads into the intake manifold. It is broken so no way to use it like it is. It corroded and just snapped.

    The hose has to be a heater hose and I see a hose called a Dorman / Heater Hose Assembly. Will this have the threaded piece, it is a special order so I can't go and look at one. Is this what I need?

    I do not see it listed anywhere in my Chiltons manual. Sure hope someone can help me!!!


  • I agree...rule out fuel preasure but after normal checks also test it on the road as well to see what it's doing at driving speeds. I stretched mine through the back of the hood and strapped it to the drivers wiper.Mine was within specs but at the low end showing signs of needing replacement soon but it still wasn't my problem. If it's within specs you may want to consider swapping out the injector harness. Check the 8th digit on your VIN to see what kind of injection system you have. X should be a CSEFI, W should be a MFI or similar acronym.

    Problem I found with my 99 4.3..same code...same symptoms...same replacements....was the CSEFI harness and regulator are one component located under the intake. Had no way to really test the regulator so decided to swap it all out. My mpg went from 15-20. Also, I first had a vacum leak test with a "smoke machine" done just to re-verify my garage tactics where not off. No leaks so I went with the harness swap.

    I posted a technical bulletin from GMC only released in Cali on another site stating that it was determined that the CSEFI units where faulty from the get go.You may have to go back to early Jan 08 postings to see it on this site but it should still be there for more info. Not saying this is your problem...just what worked for me.

    I still have a small exhaust leak, haven't gotten to the cold air and cat back duel exhaust yet but I'm sure I can get it up 2-4 mpg afterwards. Also, if the above doesn't work, timing belt and distributor pick up may be faulty or reaching end of service life. I doubt it but it's just somthing to think about. Hope this helps.
  • You may want to go to Not an immediate fix but can call their technical support line, order a parts manual for your make and They make all of the OEM parts you can/can't get at the dealership.

    I've used them and their manuals since the early 80's to diagnose/order unkown parts. Their manuals have "exploded" views of most any component for your vehicle giving you a shot at finding out what the OEM called it.
  • gonogogonogo Posts: 879
    Pull the vacuum hose off the regulator, if you see fuel or smell fuel replace. Rich mixture would show up more hot.
  • The LMC catalog was a good idea but did not show anything with the intake manifold. About the only parts they did not show.

    Anyway it looks like the fitting is a dorman heater hose quick connect. The only problem is that everything I look at says it is not used on this model. But I found a picture and my truck has it.

  • Just pulled my truck in my shop, hooked up Genisis scanner and found code P0172 fuel trim rich. Fuel pressure regulator? Still have misfire moving around. started on #4 at an idle then went to #2&3. Hmmmm
  • Ok pulled off FPR (fuel pressure regulator). Could not get the diaphram to open so replaced it and it did make a difference with the misfire, BUT it still has a random misfire. Just not as bad as it was with the old FPR. Going to check timing when I get to my shop at home will post info on that tomarrow. Still trying to figure this one out.
  • gonogogonogo Posts: 879
    The only way I know to check timing on a 2.2 is with a scanner, nothing to adjust, all electronic.
  • Ya I figured that out when I got home and started looking at it. By the way the FPR did not make a bit of difference. It was just warming up which it doesnt misfire untill it runs for a couple minutes. So going to check fuel pressure tonight and see if when I apply vacume to my regulator the pressure drops 3-10 psi. If it doesnt then must be in my return line. If it does then there has to be something electrical causing this.">
  • Ok fuel pressure is right on. About 43 KOEO and about 38 KOER. Drops like it is supposed to when vacume is applied to the regulator.
  • gonogogonogo Posts: 879
    I see in your first post you changed plugs, did you use factory platinum. These new electronic ignitions work best with proper resistance in the system.
  • I have a 1996 sonoma with a 4.3 and it is automatic. It keeps setting a P0300 random misfire along with certain cylinder misfires as well. It is also setting a code for the crank sensor low voltage. When under load it starts dropping rpms and stuttering really bad. I have had it to several shops now and no one has been able to figure it out. When the problem occurs , I can floor the throttle and the hesitation goes away. Along with the fluctuating rpms the engine pings when under load. Any help would be greatly appreciated, I am getting tired of just replacing parts and expensive shop bills. Thanks
  • From what you have posted;
    I would first suspect a problem with the crank sensor, or the circutry for the crank sensor. This sensor is used by the PCM to determine cylinder firing. It needs to be checked with a graphing meter like a snap on vantage. If there are any unusual vibrations, it will effect the sensor. If the repair shops you have been taking it too, cant figure it out, try one that is qualified.
  • 1993 2.5 stick service engine soon light comes on when not accelerating for 10 sec.

    Code is 25, ATI/high air. Is there a trouble shooting check list for this problem?
  • toneygtoneyg Posts: 19
    this piticular problem is caused by a faulty ECM. these trucks are notorious for this problem especially the 4.3 engines in the S-10 and S15 in both the trucks,blazers and jimmy's. change this out ant it will most likely solve your problem.
  • bustedbusted Posts: 1
    have a 97 s-10 blazer 4.3, drove truck into 2.5-3ft. of water and stalled. Now it runs rough, sometimes doesn't want to start, without starting fluid. The truck can't get out of its own way. New plugs and wires, temp outside has hardly been above freezing. Does anyone have any suggestion of where to start? After the truck drowned we drained transmission and rear end and added new fluids. Jacked truck up to drain water from exhaust. I know cap and rotor probably need replaced. O2 sensors? CAT? Mass air flow got wet?>? any suggestions of where to begin, to keep from freezing while guessing would be great!!!

    Another problem I have that started even before the water is that on occasion(every 2 months) You will get in the truck to start it and no power anywhere, the key gets locked in the ignition in the on position. Disconnecting the battery for roughly 12hours seems to do the trick. Upon reconnecting the truck acts like nothing happened. What the hell?
  • wondering how hard this tasks is hwo time consuming and if someone who does not mess with trucks day in day out could get it. I have never torn apart a FIE but use to work on Carb Engines. Should i get help with this tasks or tackle it myself????
  • I have 97 4.3l my truck does the same thing with the switch I have no idea what cuases it but i did reliaze that it seems my battery cables will not tight securly and when my truck was doing the switch thing if i move the cables where the battery treminals are then it would free up the key and start.
  • I have a 2002 Sonoma with almost 92,000 miles on it. I just had it tuned up maybe 6 months ago but since Im away at college its hardly been driven. Ever since I got it it feels very sluggish, probably because its a 4 banger but still. I have to have at least a mile or two to pass a car once I get past 50mph. 4th gear just seems to peg out around 4.5 - 5 thousand RPM. I was thinking about a cold air intake or an exhaust but I feel like im trying to make a race horse out of a donkey. Any suggestions?

    P.S. I want to know if there is a way to adjust the position of my gas pedal, its a couple inches lower than my brake and clutch, I just want them to macth up for easier down shifting.
  • I am getting ready to swap out a leaky radiator on my 4.3 2000 S-10. I was just wondering if anyone had any tricks to make it easier to remove the quick connect fittings for the transmission and engine oil coolers.
  • Had the same P0300 Code everyone else did a few months back, swapped, ignition, plugs, wires, coil, crank position sensor, checked fuel preasure, vacum leaks, and finally the fuel injector harness fixed the problem...for now at least.

    Question, truck still seems to hesitate during acceleration a bit but smooths out under hard acceleration. Second, now I have a really bad fuel odor coming through the cab even with windows up and when I get out. Any thoughts out there?

    I don't think I'll ever by a GM product least this make and model as we put men on the moon.... and they can't give us a better product than this?


    I think I'm turning Japanese!
  • i have that same problem.if u figure it out please let me no thanks!!
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