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Chevy Blazer GMC Jimmy Maintenance and Repair



  • repairdogrepairdog Posts: 948
    There is a vac hose that runs to the system from the intake - on drivers side under the hood the line from the intake Ts over to the reservior in the fender and down to the heater box - see if its rotted out. Also if its Auto climate control (temps in degrees on the controls) then it has a blend motor thats electric also on the heater box and these fail. Sometimes on all types the temp selector controls get deposits on them so rotate around 10 times and see if they work.
  • jhighlandjhighland Posts: 1
    I had new Michelin tires put on my 2000 Jimmy about a year ago and started noticing what I thought was loud tire noise. After three tire rotations and balancing and two front end alignment the noise was so loud I could barely hear my stereo so they ruled the tires defective and gave me brand new Michelin’s but the noise is still there? It starts at 5mph and increases from there. I put the car in neutral while going 40mph and the noise is still there. Apply a little pressure on the brakes, noise still there. The only time it goes down is when I turn to the left, but not the right. Jacked the back end up and started the engine and put it in gear at 40mph, no noise. Jacked up the front, did not pull the tires off but there appears to be no slack in the bearings

  • msrhoadesmsrhoades Posts: 2
    About two months ago i had a p0300 multiple misfire code so i replaced the plugs, wires,cap,roter and dist. it ran fine intill yesterday morning. it now has a p0304 code #4 cyl. misfire, i checked the plugs and the wires. they are still new. i did replace the cap and rotor again but it didnt fix the problem. the vehicle has a slightly rough idle. im at a loss. any help would be great.
  • Thank you for the quick response!

    I'll act on your advice and check it out, though I have my doubts because the trouble began when I changed the positive battery terminal, like the other guy. I wonder if messing with the battery somehow screws up the blend motor, from some GM design flaw. Either way, I'll be messing with it until it's fixed.

    Thanks again. For the record, I own a 98 Jimmy, 115K easy miles.
  • repairdogrepairdog Posts: 948
    97 is known to have a faultly ignition module in the steering column and many strange symptoms occur.

    Also grabbed this from OBD-codes site, may help.
    "Symptoms may include:
    the engine may be harder to start
    the engine may stumble / stumble, and/or hesitate
    other symptoms may also be present
    Causes a code P0304 may mean that one or more of the following has happened:

    Faulty spark plug or wire
    Faulty coil (pack)
    Faulty oxygen sensor(s)
    Faulty fuel injector
    Burned exhaust valve
    Faulty catalytic converter(s)
    Running out of fuel
    Poor compression
    Defective computer

    If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coil. In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors."
  • repairdogrepairdog Posts: 948
    Yes, you are correct. The air and heat on automatic climate control systems are handled by the body computer and requires a special scanner/code reader. I saw info on this and couldn't remember where - found it after some searching as follows from an MT-2500 post dated 05-30-2006:

    "Here is the low down on the recalibrating.
    But every year is a little different.
    The 98 and 2000 recaibrating does the recailbrating a little different. But you remove the RDO/BATT 15 amp fuse for a minute. Then put it back in and turn ign on.
    On a 2000 the air tempterature valve sensor and mpotor will cycle the air mix door threw full hot and full cold positions. On the 98 pull same fiuse and install and turn key on. Then the electronic actuator should cycle the air mix door threw the hot and cold positions."

    See if that works and post back on results so others can know! Spread the info cause GM won't.
  • thanks repairdog. i have checked most of those but there are a few i have not checked or better yet didnt know to check. i will repost with the problem if i can fix it.
  • pro1600pro1600 Posts: 5
    Freaky thing. 1997 GMC Jimmy SLT 4WD 130K was running fine. Parked for 5 days and then encountered this problem. Starts fine. Idles fine. No warning lights. Put in Drive and get about a hundred feet but won't shift thru the gears (stuck in 2nd?), speedometer not working and the ABS light comes on. Turn the car off. No warning lights and the process repeats.

    Could this be a problem with the speed sensor? If yes, where is it located, what does it look like, and how do I fix it?

    Thanks in advance!
  • I found the problem to the clicking in the front axle. It turns out the vac. actuator under the battery tray was being engaged for some reason. It was causeing the cable to the diff. to be pulled in 2HI. I disconnected the cable from the actuator and there is no more clicking. Would the vac. switch be the cause of all this trouble? I can't find any vac. diagrams in a repair manual. Any help with this would be greatly appreciated
  • repairdogrepairdog Posts: 948
    If vac is applied to the actuator then the coupler should be engaged - if you simply pulled the vac line to it from the intake it should have uncoupled. Look on the firewall and you should have a small solenoid that controls the vac down to the actuator - when 4Hi on the output side should have no vac and when 4wd on Hi/Lo/Auto (if you have 4 button) the vac should be on to the actuator. Also if not the small $15 solenoid then on to removing battery power for 30 minutes and see if the TCCM (4wd computer) resets.
  • repairdogrepairdog Posts: 948
    To be sure need an ABS scanner to read the code (s).
    Each front wheel hub has a speed sensor and then one in the transfer case for the rears. The front sensors sense as square cogs/gears go by - you can unbolt the 2 sensor torx head bolts and see the cogs and check if all there and also see if the sensor wire is intact and a connector about 2' up on the frame (for replacing the sensor that comes with the wire pigtail). The no speedo seems to point more toward electrical and 97 is known for a faulty ignition module in the steering column (not the key/tumbler) and many posts on it and it causes many strange problems - most power goes thru it or is activated thru it.
  • Thanks again, Repairdog. I appreciate your time.

    Nothing changed, unfortunately. I tried the RDO/BATT fuse a few times, and then I moved on to other fuses in hopes that something would reset or cycle. I've tried everything but the ECM fuses, which I'll pull and replace tonight.

    The monkeying did confirm that the A/C works, apparently, because it blows cold air until the engine warms up. Then it becomes a blast furnace inside.

    Does anyone know where the blend motor is buried in the heater box? I see that there's a "cut here for service" knockout on top of the heater box, under the hood. I thought maybe I could rig the blend door with a coathanger or something--anything to avoid tearing the whole vehicle apart while it's 100 degrees outside, not to mention the cost.
  • repairdogrepairdog Posts: 948
    Pull the glove box open (bend the piece in to get it to drop all the way down) and you will see it on the top of the box - inside the cab - believ you can remove the 2 screws that hold it on and the other in rear is not a screw but a small bump to position it - as I've read on this but not done this one myself. Info online if you look for blazer heater blend motor. It has a plastic drive gear that may strip.
  • I'll take another look behind the glove box. When I looked the first time, I saw only the two vacuum actuators for the vents, and they work.
  • efk4755efk4755 Posts: 4
    The air conditioner in my 1998 Blazer all of a sudden stopped working at the beginning of the season. I checked the freon and it was where it was supposed to be. Suddenly it started working again. Now it's developed a mind of it's own. It will blow cold air for a while and suddenly stop and start blowing hot air. Then after a period of time it will start to blow cool air again. Anyone have any ideas?
  • repairdogrepairdog Posts: 948
    Could be the pressure switch, a loose connector (internal the pins can make/break contact) on the pressure switch or right behind the compressor, incorrect 134 level, belt slipping, comp clutch problems, etc. Also if auto climate control an electric blend motor that controls a door to keep the temp at the selected temp - you would have actual temp degrees marked on the control. Possible controls probems also. A vac line from underhood drivers side so check that the line from the intake to the reservior is intact and not rotted out 5/32" small and 7/32" larger.
    I check the main things then off to the AC shop which has the correct gauges and tools. Most compressors go around 80-100k if that long - some do better but not in hot climates.
  • I have a 2000 Blazer 4 wheel drive with 126,000 miles. When I go into reverse and apply the brake, the front end would shimmy and shake. It would almost be a grinding feeling. It does not have a problem going forward and braking forward. It drives in reverse normally. It only comes up while braking in reverse. I know it is not the brakes because I just changed them along with the rotors on both sides. I took the tire off and inspect them. It seems to be in good working order. Can somebody tell what is wrong? :confuse:
  • repairdogrepairdog Posts: 948
    Worn parts. Grease ALL the fittings on the front end first (upper & lower ball joints, tie rods, idler arm both ends, and all links between - like 10 total). Did you grease the slide pins on the calipers? Have the front lower ball joints been checked or replaced? Check hubs, tie rods, idler arm. Did you do the rears as well - they may have problems too and feel like its in front - yes hard to tell with the rear discs and those calipers are crappy single piston plastic type that I replace with rebuilts each rear brake job - they bind in the bore after being pushed back in and also check the rear bolts on the brackets - no one pulls them out correctly and greases them then they rust/freeze and usually lock the caliper in one place and eat the inside of the rotor.
  • flryiteflryite Posts: 2
    Just wanted to thank covah23 and repairdog. The noise in the right front tire when turning left in my 99 Blazer 4WD was indeed the bearing (hub). I bought the part from an ebay supplier, new for about $110 with shipping, and paid the guys at my Firestone dealer to install it. (labor was $127).

    Thanks again.
  • pro1600pro1600 Posts: 5
    Repairdog - I'm taking your advice to replace the ignition module first. I searched all posts & the web, but couldn't find instructions or pics on the replacement process. I have the column exposed but I can't figure out which component is the ignition module. I bought a new module from Autozone, but I don't see anything like it anywhere around the steering column or under dash area. On my vehicle, there is a large black rectange box with a wire loom just below the key tumbler, but I can't figure out how to remove it. Here's a link that shows a pic of the ignition module that I got from Autozone. Is this the right component for my 1997 GMC S-15 Jimmy 4wd 4.3L? kieID=1V7010TXT1V701318U&clientid=discountautoparts
  • I just had the EXACT same proble with my '98 GMC Jimmy, and all it was was a relay that needed to be replaced. This was found out AFTER some control switch in the dash had been replaced (didn't fix it) and on the third time back to the repair shop. After replacing the relay my air has been working fine ever since.
  • repairdogrepairdog Posts: 948
    Thats the one in the dist that controls the spark timing - you need the the ignition switch which is really a module but misnamed - sorry. rttype=410&ptset=A
    There was a post recently on replacing but heres some more info: Access panels are 7mm and T25 torx and the top steering wheel cover E6 series Torx fasteners but std 1/4 drive 3/32socket works.
  • pro1600pro1600 Posts: 5
    Thanks for the pic. Almost there, but I can't get to the top torx fastener because the top steering wheel cover is in the way. The top steering wheel cover is loose, but I can't remove it because it's molded behind the key switch cap. Does the plastic key switch cap come off the ignition switch? If yes, how? Does it just pry off?
  • pro1600pro1600 Posts: 5
    More info that might help diagnose my problem. I just noticed the trip meter & odometer are not working. Does this indicate that it's a mechanical problem instead of an electrical problem? There's a plastic nosecone on the front passenger side of the transfer case that has a wire loom and a cable attachment. Could this be the unit that senses the speed and sends signals? Should I focus on this instead of the ignition switch module?
  • covah23covah23 Posts: 14
    Glad it all turned out ok. Love the sound of "Nothing" don't you? :)
  • pro1600pro1600 Posts: 5
    Mystery solved. There was a broken vacuum line that runs from under the battery tray in the front right corner (couldn't see what it attached to) back to the transmission. It was pure luck that I found it.

    I was having trouble replacing the ignition module. Everything was removed except a stubborn wire connector above the key switch. Is there a special locking connector? I took a break and was scoping out the transmission speed sensor when I noticed the broken vacuum line by the exhaust headers. I spliced in a new piece of vacuum line, reconnected the original ignition switch module and took it for a test drive. Speedo is working, shifts fine and no ABS light. In fact, it had been running sluggish before and now it seems peppier...but maybe I'm just happy that it's running again. ;)

    Now I just need to reassemble the steering column & lower dash!
  • repairdogrepairdog Posts: 948
    That vac line to under the battery tray is the front axle coupler actuator. Also see if the feed end from the intake is rotted and over to the reservior in the drivers side fender. Is 4wd working OK - probably wasn't before.

    Found this on the white connector:
    "For the small white connector from the top of the metal, key tumbler, rotate the switch towards the passenger seat to remove. This gets the small wires out of the way so you can get to the upper left fastener. Uses reverse Torx fasteners E series to hold the switch in."
  • repairdogrepairdog Posts: 948
    Did not see this post, sorry - if everyone would post in the main section I try and read it daily.
    Sealed 1 piece hubs are most likely the reason - jack the front end up and spin them - if you hear or feel any grating/grinding thats it. 4wd need to jack up under the
    lower control arm so the CV axle will rotate so be careful and it requires a good floorjack.
  • jpmccrjpmccr Posts: 31
    2001, Chevy Blazer - Ok, got the power issue resolved. Now the front end is shimmying (sp?) or shuddering - take your pick. Just did a front brake job. Once I got the old brakes off I checked the rotors and they were real smooth. No grooves at all. However once I got them all put back together and drove it, the front end shudders. Question: just because the rotors were smooth could they be warped enough to cause this? Didn't feel this with the old pads. I am thinking they need to be turned. Curious . . .
  • repairdogrepairdog Posts: 948
    Did it start with your brake job? Is it only when you stop? How many miles. 4wd?
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