Jump to content

Un-fixable Rough Idle 94 Fs Blazer

BigBlaze

By BigBlaze
in Ask A GM Technician

Recommended Posts

BigBlaze Enthusiast

BigBlaze

Posted
Posted

I am officially at whits end.. My 94 full size blazer has a intermitent rough idle (feels like a dead misfire). The truck has never shut off during one of its episodes... Has never set the SES for this problem(yes the SES light is functioning correctly)... Seems worse on a cold start and once engine is at running temp. Just replaced the engine, but had the same problems with the old engine.

 

List of new parts over the past year: No i'm not a habitual parts changer. most parts got replaced with new engine!

 

plugs, wires, cap, rotor, reman distributor, ignition module(module died three days after replacing dizzy), coolant temp sensor, o2 sensor, IAC, knock sensor, etc...

 

TBI unit has been rebuilt, checked for vacuum leaks, fuel pump checks out, pressure and volume, all sensors in spec..

 

Any ideas?? RUNNING OUT OF HAIR TO PULL OUT!! use to look like this guy------> :sigh: now this-----> :lol:

Nytemare Senior Enthusiast

Nytemare

Posted
Posted
I am officially at whits end.. My 94 full size blazer has a intermitent rough idle (feels like a dead misfire). The truck has never shut off during one of its episodes... Has never set the SES for this problem(yes the SES light is functioning correctly)... Seems worse on a cold start and once engine is at running temp. Just replaced the engine, but had the same problems with the old engine.

 

List of new parts over the past year: No i'm not a habitual parts changer. most parts got replaced with new engine!

 

plugs, wires, cap, rotor, reman distributor, ignition module(module died three days after replacing dizzy), coolant temp sensor, o2 sensor, IAC, knock sensor, etc...

 

TBI unit has been rebuilt, checked for vacuum leaks, fuel pump checks out, pressure and volume, all sensors in spec..

 

Any ideas?? RUNNING OUT OF HAIR TO PULL OUT!! use to look like this guy------> :sigh: now this-----> :lol:

Sounds like you have a ground fault in the engine harness...or body harness or a bag ignition relay. My guess would be to replace the relay that controls your ignition...IGN1 comes to mind...but you need a manual to be sure. Sometimes the relays get worn out and start to fluctuate (the magnetic coil part...not the switches). There should be a butt load of relays in the relay box that have the same part number as your IGN1 relay, you can just swap them. Or they're 12 bucks for a new one....This could be the case with the fuel pump relay too...causing the fuel pump to intermittently shut off and come back on.

BigBlaze Enthusiast

BigBlaze

Posted
  • Author
Posted

I'm fimiliar with the dying relay, had a trans am pull that one on me once.

 

I can't find any ignition relay on the truck, or on alldata... maybe time to check harness wires though.

BigBlaze Enthusiast

BigBlaze

Posted
  • Author
Posted

any more suggestions. i plan on attacking my truck again first thing in the morning... hopefully with a brain full of fresh ideas.

Nytemare Senior Enthusiast

Nytemare

Posted
Posted
any more suggestions. i plan on attacking my truck again first thing in the morning... hopefully with a brain full of fresh ideas.

I cant remember...but doesn't that year truck have a fuse-able link? Usually they cause problems when the heat shields fall off the stock manifolds or when a set of headers are installed. It should be on the firewall on the passenger side, if it has one.

BigBlaze Enthusiast

BigBlaze

Posted
  • Author
Posted

yesterday i decided to go over the ignition with a fine tooth comb, and upon pulling of the dizzy cap... a hold down bolt broke off in the dizzy... had to pull the dizzy to remove the bolt...... guess what....the reluctor wheel was rubbing. replaced the dizzy and it now runs great!!! so much for the reman i put in a year ago.

 

Thanx to all who offered a helping opinion!

Nytemare Senior Enthusiast

Nytemare

Posted
Posted
Do a compression test.

Good idea....I've seen bad things happen due to similar dizzy problems. Rebuilt an engine a while back where a guy got water on the cap and corroded the terminal for #5 cylinder. when I popped the head off and removed the valve, I could remove the valve seat with my fingers and the head was cracked between the two valves. All due to a rough idle. Compression test will tell you a tonne of info.

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Latest Articles

  • Posts

    • Atlas
      Wow I'm in a pickle. (Broke down truck) and a story.

      By Atlas · Posted

      Blazer is all put back together. Another hard-won battle. The 4.3 is not easy to work on in such an archaic and narrow chassis originally designed for an inline 4.   My baffle issue is solved. I returned to the OG junkyard but was ready for a fight. The Blazer I had picked from was stacked on another vehicle so I had no idea how the heck I was going to get myself to working height to pull the front end apart. I had seen an S10 pickup on the ground so I was hoping the part would be the same, AND, I couldn't remember if the S10 still had a front end or not. But I didn't need to worry because it turned out to be my lucky day. The yard had just taken in a '98 Blazer, sitting right up front, on the ground, with room to work around it, and the front end hadn't been hit. The baffle and all the clips were factory perfect. I also scored another good handful of odds/ends and the whole shebang only cost me $20.   Got everything back together and it fired right off, sounds good, runs good. I've got a little coolant drip from a lower water pump bolt (D'OH!!). I did the right thing and snugged it down a little bit, and of course that didn't fix it. Yet again, I will have to soak everything in coolant to drain it down to the water pump, remove the bolt, and attempt to re-seal it. Nothing is easy on this truck. Nothing. But now all the radiator plastics are correct, snug, and fully functional. No more rubbing on the cooling fan. It runs, drives (took it for a 30 mile drive last night), no Check Engine lights, EGR is working, no vacuum leaks. We're getting closer...   The replacement wiper motor arrived yesterday. The tailgate was already disassembled and waiting, so I threw that in. It works! Sort of. Two new issues on the list. While the motor is strong enough and the gears aren't stripped, the wiper is hanging up on the bottom of the rear glass. This is the old style where the lower half folds down like a truck tailgate, and the glass swings up, and they meet in the middle when closed. The glass isn't sitting flush with the tailgate, now that I look at it. No rubber bumpers that I can see for adjusting, so I'll have to look at the hinge adjustment to see if I can correct it. Also, the washer/squirter just dumps fluid underneath the truck. The lines actually run inside on the floor so I'm guessing the tailgate is soaked at the rear trim and the line is disconnected. There's also a drain there....probably for this reason.   The leaky water pump bolt was really disappointing. JUST STOP LEAKING...OMG!!   Replacing the window motor and a rear door speaker are still to do, and then everything will work. I want this to feel like a "good" vehicle worthy of dropping $600 for new tires before I do. That means no leaking first. I hurt, and I'm kind of cranky, so I'll probably take a day of rest and do the water pump again tomorrow.
    • KARNUT
      Slate Electric Truck

      By KARNUT · Posted

      Just saw on Jay Leno the new Scout. That’s the way it should be done.
    • Atlas
      Slate Electric Truck

      By Atlas · Posted

      EV's have their nuances too. Best to operate the current type of lithium batteries between 20-80% charge. No real need to charge until you hit around 20%. Occasionally charge to 100% when needed. Longer term storage, battery should be 50-60%. At least those are the guidelines for our iX. We've been exceptionally good to the battery in that car...easy to do when you can charge at home like we can.   EV's lack so many of the rituals and so much of the visceral feeling ICE vehicles provide, which is why I think they're hard to accept for a lot of gearheads. They're fun in different ways, though.
    • diyer2
      Winter Returned

      By diyer2 · Posted

      We have got a lot of rain lately, we needed it. Storms/lightning took out a floor fan. Dirt roads badly rutted from run off.   Power here is sketchy, whole house surge protector in the service panel and all electronics plugged into surge protectors. My biggest concern is my stereo, I've been an audio nut for years. $25 k in equipment. Stereo is on it's own special surge protector.
    • Donstar
      Navigating senior years.

      By Donstar · Posted

      Happy Birthday!  I also turned 72 this year.  In some groups I consider myself to be a young senior and in others I realize I have serious years behind me!  In June I spent a week in the hospital due to a blood clot following knee replacement surgery.  The hospital Doctor assigned to my care specialized in Geriatric medicine!  He is a great Doctor but the fact I required this type of specialized care  made me feel old!  Aging comes with new challenges but I sure appreciate getting older!  It most definitely beats the alternative!!

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...