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Chevy Blazer GMC Jimmy Maintenance and Repair



  • repairdogrepairdog Posts: 948
    You don't have a MAF - you got the older model with the map - any codes on - SES or check engine light on? Did you repkace the cap/rotor too I hope. The older CPI injection can leak under the intake and may require replacement (search above and many posts) but you should be smelling a heavier gas small than normal - look on the dip stick too and smell that for gas. Check fuel pressure cause low will cause bed idle or be related to the CPI.

    Believe the older model have a heater control valve in the line in the engine compartment that may be frozen on allowing hot coolant to always circulate (nwer models do not have this - always flows).
  • repairdogrepairdog Posts: 948
    Check the fuel pressure - requires 60 psi cold start and 54psi to run. Possible that the cleaning damaged the regulator or injector poppets - cheap design with mostly plastic parts. As for the cranking - have to ask but how is the battery and alternator - get them tested at the local auto shop its free and a failing battery/alt can cause many problems on Blazers with a lower voltage. Don't assume fuel only. In hot climates I only get 3 years from a 3 year full warranty battery so been there often. Alts average about 60-80k as norm on Blazers too.
  • jnkraabjnkraab Posts: 2
    the battery is 6 months old and alt is 1 year old, battery cables were replaced 2 summers ago...this morning the truck started better on 2 cranks to go but still seems harder to start then there any way to know if its the regulator or poppets? or should i replace both?...also the poppets, are they the injectors or part of them and can i buy these parts seperate and are they hard to replace?

  • repairdogrepairdog Posts: 948
    Check the fuel pressure first if thats the orginal fuel pump. The CSFI system has 6 separate injectors each a plastic tube with a small poppet or injector on the end that clip into the intake under that plastic upper intake cover - these are fed by the central assembly or spider that has the regulator and the electronics that distributes the fuel - the fuel rail is bolted into this (see the 2 metal lines from the rear of the engine) and this has a test port to check the pressure. Each piece is not cheap but if this turns out to be bad GM now has a new replacement system called MFI that bolts right in and replaces the whole mess as one piece (redesign). Search the internet on this and you'll find the system - not allowed to get other links on this forum and the article is in pdf so can't paste it.
  • kennedbkennedb Posts: 3
    Original Post: (2382)
    Vehicle stopped running while moving down highway. Attempted to restart and will not. Battery just replaced. When attempting to start the engine vibrates/shimmys like crazy. Thought it was the timing chain...checked it and it looks good.

    Update: Installed new fuel filter still won't start.

    Observed another thing when attempting to start: When Key is in On Position Gas guage shows full and when attempting to start (turning engine over) the gas gauge shows empty.
    Is this the on-board computer giving a hint or code as to what's wrong?
  • pgurganuspgurganus Posts: 12
    i have a 2000 blazer.when i give it gas slowley it accerates fine till about half way of the pedal then it will lack on power and sputter. when i punch it it just sputters and dont want to go. today my wife and i went out in it and barley made it home it was like it had no power at all changed 2months ago cap roter wires pulgs fuel fliter ran injector cleaner in it still same service engine light is on.if that helps.also took out all 3 o2 synsors and tried it same thing. can some one please help me
  • auto9999auto9999 Posts: 86
    I would doubt a clogged exhaust system
  • repairdogrepairdog Posts: 948
    Just saw some info on the defrost problem - if the controls have lost vacuum they default to defrost so look under your hood on the drivers side and see if the vac hose 5/32" is rotted/broken. It feeds off the intake to a T and to a reservior in the fender and I have had to replace all these lines on my newer models also. You can get your hand to the reservior hose with a few trys, really. That plastic line that Ts off should go to the heater controls so if the lines under the hood don't solve it you will have to get to the back of the heater conrols and make sure the line is plugged in. Let us know if that works.
  • repairdogrepairdog Posts: 948
    Check the fuel pressure at the rail test port. Key on engine off should be 60psi. When you turn the key on (not try to start can you hear the pump running?
  • repairdogrepairdog Posts: 948
    Fuel filter change (under inside frame rail under drivers seat area). Is the air filter clean. Clean the MAF sensor above the filter with spray MAF cleaner or brake (not carb cleaner and be careful don't break a wire on them). Then fuel pressure test as posted many times above. Then I would get it to a shop and put it on an analyzer/scope and look at the ignition circuit/firing pattern and rule that all out first - yes bad plugs/cap/rotor/wires - can happen. Or a sensor failing but should get a code then. Report the fix for others or can feed you more to look at.
  • pgurganuspgurganus Posts: 12
    new fuel filte , plugs are a week old, wires cap, roter are less than 3 months old new air filter. when i got the plugs changed they put it on a analizer and no misfires,all firing is good and she starts right up,only on accleration it acts up. funny thing is its not getting a far as the 02's took them out and same thing and didnt even get a service engine light when i took them out.the place i took it to told me maybe a bad computer but i dont think so i think he wanted me to spend money if u know what i
  • pgurganuspgurganus Posts: 12
    auto9999 did u say u would doubt or wouldnt doubt a cloged exhaust like maybe a clogged cat
  • lbp47lbp47 Posts: 2
    Did you find a solution to this problem? I have the same problem and am looking also. Any help would be appreciated. Thanks
  • pgurganuspgurganus Posts: 12
    i think i found the problem,i unpluged the 2 synsors on the air in take from the filter 2 the carb and no more problems so i am going to assume that was the MAF? CORRECT? now my service engine light is on so i am going to go get those 2 synsors can someone tell me what these 2 are. 1 of them is a box like deal the outher is a verry small one that goes inside the breather tube. she is running better but not quite like she should but no more sputtering and she will go
  • kennedbkennedb Posts: 3
    Have not checked the pressure at the rail test port. When key on (not trying to start) I hear nothing...don't hear the pump running.
  • repairdogrepairdog Posts: 948
    Small one is the intake air temp that is high resistance when cold so a high voltage (5.0) to the PCM and it drops as it warms. The honeycomb with the small resistor is the MAF or mass airflow sensor. I would suspect the MAF but clean it before you replace it and try it out (use MAF spray or brake but not carb cleaner). A new MAF is $150 or so and some sites have trobleshooting tests info on them like autozone.
  • repairdogrepairdog Posts: 948
    Only runs hard till pressure up and may be less noise after a few seconds - but look at the fuse box under the hood for the "ECM B" fuse for fuse pump/ECM/oil pressure power and see if its good, then replace the "F/PUMP" relay and see if it works. If its the pump in the tank its drop the tank and $300 for a pump (dealer is $450) plus labor.
  • pgurganuspgurganus Posts: 12
    yeah i brought it to autozone and the guy put the diagnostic test on it said that the maf is not bad so i showed him what i was talking about and pluged it in and got him to ride with me in the parking lot we got in i floored it and all it did was sputter then i got out and unpluged it floored it and lit up the tires.he didnt have anything to say then.lmao ..... so i changed more problems. thanks 4 all of your help with this problem. i have changed the MAF instead of cleaning it because i didnt need to pay 4 it lol.... thanks again 4 you all's help...............oooooooyeahhhhh back on the road again :) :)
  • repairdogrepairdog Posts: 948
    If you are still working on this one here's some info I came across that may be your problem on starting and shutting off:

    "The ECM operates the fuel pump relay for three seconds or so when the key is turned to run. Then, as long as the ECM is receiving a signal from the crank sensor that the engine is cranking over, it will continue to operate the fuel pump relay.

    There is another system to power the fuel pump directly, once the engine starts, and that is an oil pressure switch. As long as there is at least 4 PSI of oil pressure, that switch will send power to the fuel pump, weather the ECM operates the relay or not."

    This all means the crank sensor could be bad or wires/connector bad(front of engine below the timing cover look from underneath) or oil pressure sending unit/wires(located in the back of the engine by the dist) may be bad or when you start this is there oil pressure on the gauge?? No pressure and its doing what it should - shut down. Let us know if you get this one fixed.
  • becky81becky81 Posts: 1
    Please help! I've asked several mechanics where the timing wire is on a '95 Blazer (4.3L). Every time, their answer has been wrong. This is about to drive me crazy! Please help!
  • repairdogrepairdog Posts: 948
    The #1 spark plug wire is the front drivers side one where you connect the timing light to trigger off. This is the one you mean: (pulled from search online)
    "2 versions on 95. If your ECM is under the hood on top of the coolant recovery tank (1st revision ODBII), then no, you cannot time it(ECM handles timing). If your ECM is under the dash then disconnect the brown or tan wire behind the passenger side carpet on the firewall to disconnect the distributor from the ECM, set to 0 degrees TDC, look at the crank pully, you will see 2 grooved marks on it. Use the one on the left to time with. When complete, reconnect the brown or tan wire behind the passenger side carpet".
  • the_jimmythe_jimmy Posts: 1
    How can i tell if the wheel hubs are bad? I have a 1999 Gmc Jimmy, when in 4 wheel drive the front tire wont spin. Like in mud or Snow. But i can feel the engine bog down. i feel the Transfer Case engage, and all the good stuff. But if any one can help me that would be great. :cry:
  • We have a 1999 Chevy S-10 Blazer which we have now replaced the fuel pump 10 times in the last 2 years, we've also replaced the CPS, TPS, Rotor, Cap, Plugs, Wires, Ignition Module, Fuel Pump Relay, Fuel Pressure Regulator & electrical connections on fuel pump. We've also replaced the fuel filter after every pump change. The last pump lasted only 3 days. We have checked for recalls and there are none for the 1999 S-10 Blazer fuel pumps. Does anyone have any further suggestions on what to try next? We are desperate. We appreciate any advise we can get. Thanks!!
  • repairdogrepairdog Posts: 948
    Are you buying the Delco pump or aftermarket and who is putting these in? Is the return line crushed or blocked - by doing a pressure test at the rail the specs are 54-64psi for a new pump and if the line is a problem its goes up to over 70psi. Voltage at the pump correct?
  • repairdogrepairdog Posts: 948
    Hubs contain the wheel bearings and the front CV axles are splinned into them - they grind/grate when failing and are not the problem. Sounds normal to me.
    All power goes thru the transfer case even the rear wheel only or 2HI, The case engages 4LO gear by an encoder motor. For 4HI (and all 4wd modes) an axle coupler on the pass side engages or locks the axle (look under and see the cable and sensor on the front diff). The front diff is open or has no posi unit so only the wheel with the least traction drives - same with rear unless you have the G80 option (look in glove box). If you have the 4th button "Auto" then the trasfer case has a posi type clutch pack unit in it that allows driving on pavement in any condition - it can slip or allow diff front rear wheel speeds. Front drive shaft always turns too for all 98up models for shift on the fly. Try a hard start on a loose dirt road and have someone watch the front tires for spin - one should at least.
  • mstafformstaffor Posts: 4
    I was reading posts on rough idle on GM products. What is a "CPI" unit and how does the "pop valve in the CPI injector work"? I have replaced the IAC, EGR, MAP, throttle position sensor, fuel pressure regular, and 02 sensor as well as the distributer, cap, coil, wires, and Throttle body. I still have a rough idle (not always) and it gets worse the longer it idles (93 GMC p/u with a 5.7 liter, 350 CID engine). Off idle and under a load it runs great! Vacuume at idle is fine. The fuel injectors (2 each) and the enginer computer are all I can think of that are left in the system. It does idle better with the airconditioner on for some reason. No codes. It feels like a lean idle condition from a carburator system (lean roll). If the engine were not a new GM engine (2000 miles on it) and I had not had the problem on my last engine I can think of lots of things that could cause this.

    Any suggestions?
  • bivenserbivenser Posts: 2
    First off I am glad I found this forum. There is a lot of great information here.

    Now to my problem. Long story short, 2000 blazer stalled out and would not restart. Engine really struggled to run at all before it died. Then would not start. Got it home and had it running by putting gas in the intake. Then would start on its own and ideal but dies when in drive and the gas pedal is touched. I changed the fuel filter, checked the fuel pressure, changed the fuel pressure regulator, MAP and TPS. All of this with no service engine light. After all that it popped on. Got a reader and it stated intermittent crankshaft sensor P0339. So I switched the sensor. No luck. I am going to check the voltage into the sensor to check the wiring but other than that I have no idea. Any ideas or advice would be greatly appreciated. Thanks,

  • repairdogrepairdog Posts: 948
    All those are s-10 blazers with 4.3L motors.
    You have the 5.7 with throttle body injectors I believe - correct (looks like a carb or throttle body with the small injectors sitting on top of it with wires feeding it)so would guess its the idle air control valve on the throttle body but been awhile since working on these. AC on ups the rpms thats why it helps. Check the online auto store on this part.
  • repairdogrepairdog Posts: 948
    Unplug the connector to the MAF sensor in the intake above the air filter (larger connector of 2 - other is air temp sensor) and see if it runs better. If so clean or replace the MAF. If this is not it reply and I'll look up the crank sensor relearn procedure that may help.
  • Thank you for your quick reply. Originally we replaced the GM pump with a Delphi which we have now put in 7 of them, then we switched to Carter & have put in 3 of them. Carter is the pump on it currently. The return line is not crushed or blocked, voltage at the pump is correct. We had an ASE certified mechanic who has worked for a GM dealer check it the first few times, then we had a local ASE mechanic change it the last 2 times. PSI is always in the proper range. We have even thought about contacting GM direct and sending the receipts of everything we've replaced to them. If you can be of any further assistance we would greatly appreciate it. Thanks once again.
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