Question about small stumble at speed

[friesza]

I have noticed over the last couple of weeks that when I am driving my blazer seems to jerk...or stumble lightly...when cold it will do it from a standstill..when warm at cruising speed...about 1800 rpm and up....on my way home from work tonight I tried running it at different speeds...when gunning it from 45 to 65..it was fine..decent power...but when i cruised at around 2500 to 3000 rpms steadily it did its little herk and jerk....
i just replaced fuel pump, filter, plugs, wires, cap and rotor last July....so I am at a loss for this problem....I do have the dreaded rear leak in the intake gasket...but its not that bad.....
Just getting tired of putting money into this thing....but I like driving it...

Any help appreciated

[old_master]

We need year, make, model and 8th character of the VIN.
Is the Service Engine Soon light on?
If so, what DTC's are in memory?
What brand of parts did you use?

[friesza]

Originally Posted by old_master

We need year, make, model and 8th character of the VIN.
Is the Service Engine Soon light on?
If so, what DTC's are in memory?
What brand of parts did you use?

2000 chevy blazer....i will get the vin tommorrow
light is not on
I used genuine GM fuel pump, autolite plugs I believe, and got the cap rotor and wires from schucks...cannot remember what brand.
I only have 97000 miles on it and have had way too many problems with it....both from hubs replaced twice...heater core replaced...intake rear coolant leak which I need to fix, leaks about a cup a week...oil lines leaked...door pins ..electrical for speakers...and several small things.....

Also over the last year my gas mileage has went down...I used to get between 18 and 20 on the hiway....now 16 to 17.5... sorry to rant

[old_master]

The 4.3L CSFI engine can be very fussy when it comes to secondary ignition parts: plugs, wires, distributor cap, rotor and ignition coil.

Plugs: Cross reference data from one brand to another, MOST of the time is not correct. Heat range and reach are the two most important things when it comes to plugs. There is usually a difference in the angle and design of the taper seat also. The best plugs for your engine are AC Delco 41-993 with a gap of .060

Plug wires: For the most part, unless you get el cheapo's, they will perform reasonably well. When it comes to technical specifications, Autolite Professional series and AC Delco are the best.

Distributor cap and rotor: Somewhere in the design and manufacturing process, the aftermarket companies lose it here. Not sure what it is, but this thread is a good testimonial: http://www.automotiveforums.com/vbul...44#post6100044 Make sure you use silicone dielectric grease on all terminals, inside and out, of the distributor cap.

Fuel pump: AC Delco / Delphi is the ONLY way to go here... good job!

As far as the other issues you've had....
There is only one reason a front hub/bearing assembly fails prematurely, low quality parts.
The cooling system must be flushed and maintained with Dexcool coolant faithfully every 3 years or 50,000 miles. If not, expect problems with intake gaskets leaking, heater core leaking, and radiator leaks. Most of all, NEVER add green ethylene glycol coolant to the system.
Oil lines: The factory lines are junk, no two ways about it, they ALL leak sooner or later. The best fix is to modify them, (do a search in the How-To section). Second best option is use lines made by Dorman, most auto parts stores have, or can get them.
Door hinge pins: Common problem if they are not lubricated at each oil change. It's a moving part, it needs to be lubricated or it'll wear out, same as hood hinges, door and hood latches, steering and suspension parts, etc etc.
From what you have mentioned, the speaker wiring is the only thing that is not considered normal maintenance. Ya can't blame the truck for neglect or improper maintenance on behalf of the technician

Without the SES light on, and no DTC's in memory, it will be tricky diagnosing this problem. I would start with quality ignition parts, a fuel filter, and check fuel pressure and leakdown. Key on, engine off, fuel pump running: pressure must be 60psi to 66psi and must remain above 55psi for 3 to 5 minutes after the fuel pump shuts off. At 97,000 miles, technically all of the oxygen sensors are due for replacement. In a pinch you might get by with replacing just the two upstream sensors.

[friesza]

Originally Posted by old_master

The 4.3L CSFI engine can be very fussy when it comes to secondary ignition parts: plugs, wires, distributor cap, rotor and ignition coil.

Plugs: Cross reference data from one brand to another, MOST of the time is not correct. Heat range and reach are the two most important things when it comes to plugs. There is usually a difference in the angle and design of the taper seat also. The best plugs for your engine are AC Delco 41-993 with a gap of .060

Plug wires: For the most part, unless you get el cheapo's, they will perform reasonably well. When it comes to technical specifications, Autolite Professional series and AC Delco are the best.

Distributor cap and rotor: Somewhere in the design and manufacturing process, the aftermarket companies lose it here. Not sure what it is, but this thread is a good testimonial: http://www.automotiveforums.com/vbul...44#post6100044 Make sure you use silicone dielectric grease on all terminals, inside and out, of the distributor cap.

Fuel pump: AC Delco / Delphi is the ONLY way to go here... good job!

As far as the other issues you've had....
There is only one reason a front hub/bearing assembly fails prematurely, low quality parts.
The cooling system must be flushed and maintained with Dexcool coolant faithfully every 3 years or 50,000 miles. If not, expect problems with intake gaskets leaking, heater core leaking, and radiator leaks. Most of all, NEVER add green ethylene glycol coolant to the system.
Oil lines: The factory lines are junk, no two ways about it, they ALL leak sooner or later. The best fix is to modify them, (do a search in the How-To section). Second best option is use lines made by Dorman, most auto parts stores have, or can get them.
Door hinge pins: Common problem if they are not lubricated at each oil change. It's a moving part, it needs to be lubricated or it'll wear out, same as hood hinges, door and hood latches, steering and suspension parts, etc etc.
From what you have mentioned, the speaker wiring is the only thing that is not considered normal maintenance. Ya can't blame the truck for neglect or improper maintenance on behalf of the technician

Without the SES light on, and no DTC's in memory, it will be tricky diagnosing this problem. I would start with quality ignition parts, a fuel filter, and check fuel pressure and leakdown. Key on, engine off, fuel pump running: pressure must be 60psi to 66psi and must remain above 55psi for 3 to 5 minutes after the fuel pump shuts off. At 97,000 miles, technically all of the oxygen sensors are due for replacement. In a pinch you might get by with replacing just the two upstream sensors.

Well the hubs were directly from Chevrolet....the first 2 were under warranty...the second time I forked out of pocket...trust me I take good care of my vehicles....oil lines were under warranty too and havent leaked since...and the coolant was actually done at 50000...the heater core went out soon after...and just recently did the intake start leaking.....
Now having problems finding any Ac Delco parts around here...everyone says 4 to 5 days wait...plus a shipping fee...if I am going to pay a shipping fee then I will order them myself....sheesh...both Napa and Schucks are trying to sell me either BW or accell brand parts....I remember when I was younger you had to ask for something other the Ac Delco parts if you wanted aftermarket.
I hope this works.....

[Rick Norwood]

Originally Posted by friesza

Well the hubs were directly from Chevrolet....the first 2 were under warranty...the second time I forked out of pocket...trust me I take good care of my vehicles....oil lines were under warranty too and havent leaked since...and the coolant was actually done at 50000...the heater core went out soon after...and just recently did the intake start leaking.....
Now having problems finding any Ac Delco parts around here...everyone says 4 to 5 days wait...plus a shipping fee...if I am going to pay a shipping fee then I will order them myself....sheesh...both Napa and Schucks are trying to sell me either BW or accell brand parts....I remember when I was younger you had to ask for something other the Ac Delco parts if you wanted aftermarket.
I hope this works.....

Like Old Master says, AC-Delco is the only way to go. I will NOT EVER BUY ANYTHING ELSE. I learned my lesson, the hard way. Pay the shipping cost, but stick to yer guns!

[Rick Norwood]

Originally Posted by old_master

The cooling system must be flushed and maintained with Dexcool coolant faithfully every 3 years or 50,000 miles. If not, expect problems with intake gaskets leaking, heater core leaking, and radiator leaks. Most of all, NEVER add green ethylene glycol coolant to the system.

O.K. Not to crap on this thread, but one very simple question. When you go to buy antifreeze (non Dexcool) and you see the bottles on the shelf made by the same company that makes Dexcool, that claim their (non-Dexcool) antifreeze is safe for all makes and models and can be mixed with any color of coolant, WTF?

[old_master]

http://www.ricksfreeautorepairadvice...-wrong-coolant

For a couple of bucks difference in price, is it worth the risk?