Post Reply 
 
Thread Rating:
  • 1 Votes - 5 Average
  • 1
  • 2
  • 3
  • 4
  • 5
1991 Chevy k1500 Weird Weird
11-21-2012, 12:20 AM (This post was last modified: 11-21-2012 12:21 AM by voltagexdt.)
Post: #1
1991 Chevy k1500 Weird Weird
Ok first the stats..

1991 Chevy K1500 350 TBI
Reg Cab
Dual Optima Batteries.
This is an audio truck.. (will relate in a second)

The basic issue..
When im driving the truck seems like its stuttering slightly..
When i go uphill it really begins to stutter..

Now when I turn the bass up in the truck, the truck will buck and backfire.

Any ideas at all?

Heres my list of what i have done since i have owned it.

Truck Maintenance




Code:
___2010_____

July
     Replaced Clutch
     Pressure Plate
     Slave Cylinder
     Throw-Out Bearing

___2011________

May 1st
     Changed plugs
     Changed air filter
     Changed distributor cap
     Changed rotor

May 5th
     Replaced radiator
     Fixed power steering leak
     Installed tailgate hindges (truck mount side)

May 10th
     Replaced rear bumper
     Installed Custom Headliner


May 10th
     Replaced oxygen sensor

May 13 2011
     Replaced throttle body gasket
     Cleaned throttle body
     Replaced coolant temp sensor
     Replaced engine temp sensor

May 14th 2011
     Re-wired plow solenoid

May 15 2011
     Timed truck

May 17
     Installed Alarm
     Installed Power Locks
     Installed Clutch safety switch
     Installed Tach

May 20
     Fixed Floor Boards
     Installed Throttle position switch
    

May 21
     Re-attached ebrake cable

May 22
     Installed pvc valve
     Installed ignition coil

May 23
     Installed M.A.P. Sensor
     Cleaned EGR Valve (old)

June 3rd
     Installed hitch
     Installed Headlight Dimmer (junk yard part)
     Installed window weather strips (junk yard parts)

June 4th
     Installed EGR Solenoid
     Installed EGR Valve

June 8th
     Replaced all Vacuum Lines


June 10th
     Installed Optilux Model 1900 Driving Lights

June 17
     Installed KN drop in filter

June 18
     Installed Monroe Rear Shocks


June 23
     Installed NEW drive shaft
     Installed 2 new universal joints
     Installed front drive shaft seal
     Fixed spare tire cable end ( tire holder )


June 26
     Installed fog lights


July 2 2010
     Installed new front shocks
     Installed new front rotors
     Installed new front brake pads
     Installed new front calipers

July 3rd
     Installed Air Horns


July 8th
     Installed New Steering Wheel
     Installed WINK Rear View Mirror

July 11th
     Installed New FlowMaster ™ super 44 Muffler
     Mounted and balanced used M/S Tires


July 14th
     Installed Nerf Bars


August 5th
     Installed Rear View Camera System


September 11
     Installed new clutch master cylinder
     Installed new clutch slave cylinder


9/22/11 11:21 PM
   Sound deaden floor with fat mat


9/26/11 12:44 AM
     Installed sub and amp system

11/01/11 12:49 AM
     Installed new power steering cap

12/1/11 12:50 PM
     Install StreetGlow Blue Neon

12/8/11 2:33 PM
     Installed Spal power window kit and switches
     Installed Optima Yellow Top battery (3 year warranty)


12/23/11 12:21 AM
   Installed new 105 amp alternator
   Installed second battery system

____________2012_____________

01/05/2012
Installed Underspring Spring Helpers


02/07/12
     Installed new reverse fog lights.


02/10/12
     Installed Bushwacker Fender Flares


02/17/2012
      Installed 3" lift in rear with new blocks, and new U-Bolts
      Adjusted Front Torsion bars to raise truck up


3/31/2012
     Installed used tires and rims
33 x 12.5 x 15

4/6/2012
     Installed Cobra CB
     Installed Firestik 2 Antenna


5/8/2012
     Installed Throttle Body Spacer
     Installed new seat cover.

4/15/2012
     Installed new front sway bar mounts

5/30/2012
       Tinted windows

6/8/2012
        Installed Kenwood KVT-614

6/22/2012
Installed New Blue Bed Webb

6/23/2012
  Installed JVC KW-AV60BT

6/27/2012
     Installed cut-through sub box and 2 12" Memphis Audio 12s.


7/9/2012
            Installed new radiator cap

8/1/2012
           Installed front receiver hitch

8/15/2012
           Installed 3 slightly used Firestone tires

9/1/2012
          Installed used transmission
         Installed new clutch
         Installed new clutch master and slave cylinders
         Installed new front drive shaft
         Installed used oil filter holder

10/01/2012
          Installed new smittybilt xrc3 front winch

10/19/2012
          Installed new headlight assembly (projector)
          Installed HID lights High and low


10/26/2012
       Installed HID foglights

11/13/2012
       Installed NOCO IGD140HP Grey 140 Amp High-Performance Battery Isolator

11/16/2012
       Installed new O2 Sensor

Nov 19, 2012
     Installed new Bosch platinum 4 plugs
     Installed new 8mm spark plug wires

Nov 20, 2012
     Installed new fuel filter
     Installed new ignition control module
      Installed junkyard ECM

Also inspected cap and rotor and they are great.
Also checked timing..
As well checked wire harness just to make sure and tested all fuses.
Find all posts by this user
Quote this message in a reply
11-21-2012, 11:30 AM (This post was last modified: 11-21-2012 11:33 AM by Rupe.)
Post: #2
RE: 1991 Chevy k1500 Weird Weird
What, no Audio-mat / Dyna-mat behind the door panels and head liner? Wink

All kidding aside, let's go back to basics. If it seems worse when the electrical system is working hard (high draw condition) then you should be hunting for an electrical problem. Just by the age of the vehicle I'd go after poor grounds first. Since this seems to be a bit of a show truck you can use your imagination to make things "sanitary" by adding ground straps between the body and the engine and then between the body and the frame, paying special attention to the factory ground for the fuel pump, which breaks out of the harness along the frame rail near the tank. (usually a self taping screw) While we are on the topic that new HO alternator normally grounds to the aluminum mounting bracket, which at that age probably has it's own ground issues. I'd add a ground strap between the alt and the engine block to be sure. Now that grounds are covered take a look at fuel pump pressure just to be sure the pump itself is not on the way out.

Another hint might be watching the tach. If the tach jumps at the same time that would point to a primary ignition issue. IOW, not the high volatge but the 12 volt side of things. OTOH, that may be solved with added ground straps... OR... may be related to voltage drop due to high draw through the ignition switch. If you have not done so already, you should add accessory relays for most of those extra goodies instead of drawing power straight from the ignition switch.

Last but not least, personally I am not a fan of aftermarket ignition parts, especially when it comes to dist caps for GM. They quite often burn through then arc under load. The other thing is the plug wires don't always seat well when mixing brands with the other parts. They may feel tight but a poor connection will also lead to early break down of the plastic insulation and poor running.

Keep us posted on your progress. Would love to hear this be resolved before I leave on vacation Monday night.

As a side note, I am fabricating new body / cab mounts for a 93 Chevy PU at the moment. Just did the frame ears and radiator support last night. Rust NEVER sleeps!
Find all posts by this user
Quote this message in a reply
11-21-2012, 07:08 PM
Post: #3
RE: 1991 Chevy k1500 Weird Weird
already did all new grounds.. however didnt check fuel pump..

also added ignition control module.. no help
and msd ignition coil.. no help

fuel seems good as i can see the spray good from the tbi.

one last thing.. when im hitting the bass.. i still dont drop below 12.8

Tach is digital... engine does drop..
Find all posts by this user
Quote this message in a reply
11-22-2012, 12:14 AM
Post: #4
RE: 1991 Chevy k1500 Weird Weird
Hard to say based on watching a dash gauge for voltage drop but there could be some transient spikes. The other thing is you may have more than single problem. IOW, weak fuel pressure (old pump?) and voltage drop from a poor frame ground. The pump amp draw typically goes up as the pump gets weak with time. A new pump will be maybe 3-4 amps but an older one may show up to 10 amps so a bad ground can play tricks that you can't find by watching the injector spray. Those pumps crap out around 120 - 140k miles so changing it could be cheap insurance if you are close. Add in something else rattling around with the heavy bass and who knows? What I would do is hunt down the problem WITHOUT the stereo thumping and go from there.

BTW, think back to a time before you had this issue and maybe you can narrow down what you changed about the same time. Perhaps it's as simple as the tach wire chaffing on the firewall? (just an example) Older PCMs can also develop issues with vibration and you have modified the suspension, so more food for thought.
Find all posts by this user
Quote this message in a reply
11-25-2012, 12:00 AM (This post was last modified: 11-25-2012 12:02 AM by voltagexdt.)
Post: #5
RE: 1991 Chevy k1500 Weird Weird
(11-21-2012 11:30 AM)Rupe Wrote:  What, no Audio-mat / Dyna-mat behind the door panels and head liner? Wink

All kidding aside, let's go back to basics. If it seems worse when the electrical system is working hard (high draw condition) then you should be hunting for an electrical problem. Just by the age of the vehicle I'd go after poor grounds first. Since this seems to be a bit of a show truck you can use your imagination to make things "sanitary" by adding ground straps between the body and the engine and then between the body and the frame, paying special attention to the factory ground for the fuel pump, which breaks out of the harness along the frame rail near the tank. (usually a self taping screw)

such a dumb idea you have.. a ground problem no way is it just a simple ground..

i took it to a mechanic and he hunted for a few hours and couldnt find anything...

anyhow i decided to drop the tank... and noticed the um... ground.. um... was um... ya.

I wish i would have listened to you from the get go.

who ever had this truck before me has for some reason gone through and cut various wires and to secure these wires he used wire nuts. been cleaning these up as i find them constantly..

So i cleaned up all the wire nuts used to wire the fuel pump and created a ground.. as the one he had wasnt even hooked up.. how the truck even ran is beyond me.

amazing how such a little thing can cause such havok.

anyhow i wanted to let u know you were spot on.

i didnt even think to look to the rear of the truck for a problem like this.

anyhow alot of stress is off my shoulders and again thank you.
Find all posts by this user
Quote this message in a reply
11-25-2012, 12:10 AM
Post: #6
RE: 1991 Chevy k1500 Weird Weird
As they say, sometimes you can't see the forest for the trees, especially when you are so close. (and so distracted by other possibilities) That's why I like to go back to basics, along with some old fashion experience.

At any rate, thanks for the follow up. It could help someone else the next time they are pulling their hair out.

BTW, now I can leave on vacation with a clear mind!
Find all posts by this user
Quote this message in a reply
11-26-2012, 02:45 PM
Post: #7
RE: 1991 Chevy k1500 Weird Weird
ok bud gotta another one.. truck still stutters ever so slightly going up hill in 5th. not in any other gear but 5th.
Find all posts by this user
Quote this message in a reply
11-26-2012, 10:35 PM
Post: #8
RE: 1991 Chevy k1500 Weird Weird
Have to get up and catch a plane for vacation in 6 hours so try this and see what happens.

Put a double dose of injector cleaner in the tank and drive it for a week. At that point pull a few plugs and see if they are reading lean or rich. (white or dark) If they are stark white then do a fuel pressure test to see if there's enough fuel going in there. Just a few pounds short will make a big difference. You can also check the vac lines to see if any feel too soft. A collapsed line will give screwy vac readings to the ECM and cause it to go lean. Last but not least, make sure all of the plug wires are fully seated at both ends.

Good luck and let us know what happens. Perhaps one of the other moderators can put his 2 cents in if necessary.
Find all posts by this user
Quote this message in a reply
Post Reply 


Forum Jump:


User(s) browsing this thread: 1 Guest(s)