Rough idle when cold

[Westell]

I have a 1995 chevy blazer with 72k just changed spider injection 2 months ago perfect fuel pressure holds over 50psi for 5 minutes. Blazer idles a little rough when started fine when not idling goes away as it warms up. Tuned up about 4 years ago (not ac delco parts tho?). Could this be a tune up issue or something else. Also no codes no lights.

[MT-2500]

Originally Posted by Westell

I have a 1995 chevy blazer with 72k just changed spider injection 2 months ago perfect fuel pressure holds over 50psi for 5 minutes. Blazer idles a little rough when started fine when not idling goes away as it warms up. Tuned up about 4 years ago (not ac delco parts tho?). Could this be a tune up issue or something else. Also no codes no lights.

What are the perfect fuel pressure readings?
What brand of plugs in it?
I would go over the tune up end and with AC delco parts.
Check for any cylinder miss

And check the computer sensor readings and for codes.
Any check engine lights?
Old style or new flat top dist cap?

[Westell]

no codes no engine lights. Key on fuel pump prime 62psi running stays between 56-60psi. After prime will stay over 50psi for 5 minutes. Like i said runs great warm. It has the flat top dist. plugs and wires i believe are all auto-zone Bosch i would assume. I would guess its a miss but its very slight. blazer still gets 14 15 mpg in city lots of hills and lights. It seems like a weedwacker when there cold rough until the plug gets hot pretty much just like that.

[MT-2500]

Originally Posted by Westell

no codes no engine lights. Key on fuel pump prime 62psi running stays between 56-60psi. After prime will stay over 50psi for 5 minutes. Like i said runs great warm. It has the flat top dist. plugs and wires i believe are all auto-zone Bosch i would assume. I would guess its a miss but its very slight. blazer still gets 14 15 mpg in city lots of hills and lights. It seems like a weedwacker when there cold rough until the plug gets hot pretty much just like that.

Any check engine lights or stored codes.
Make sure you have good ac delco plugs.
Might want to check camshaft retard setting.
And get a scanner read out of sensors and any engine misfires.

[Westell]

I will scan in the morning when it runs rough and see what it gets. I am going to change the plugs and wires i know neither is ac delco. Camshaft retard i have no idea how to check that? Its storing no codes no ses light abs lights comes on every so often no clue why. Cleaned egr about a year ago. But i will see what the sensors are doing and reading.

[MT-2500]

Originally Posted by Westell

I will scan in the morning when it runs rough and see what it gets. I am going to change the plugs and wires i know neither is ac delco. Camshaft retard i have no idea how to check that? Its storing no codes no ses light abs lights comes on every so often no clue why. Cleaned egr about a year ago. But i will see what the sensors are doing and reading.

Camshaft retard is like what setting the timing used to be.
But needs a capable engine scanner to check and set it.
When you scan it watch for stored codes and past and present codes any misfires AND IF SCANNER READS OUT CAMSHAFT RETARD POST BACK READING..
If abs light is coming on at times it will also be needed to be scanned with a ABS capable scanner before turning ign off to get to the problem.
POST BACK ANY ABS CODES.
A lot of abs problems with wheel speed sensors and sensor wiring.
Take a look at wiring and plug-in's.

[Westell]

Alright scan shows no stored codes none. Live data shows no misfires everything shows good. Only thing that i could see that seemed odd is ignition advance was jumping from -10 through -25 at idle? and would jump to about -30 with throttle but other than that everything shows up clean. Is ign adv camshaft retard and is what im reading bad or no. Seems to be rough when warm now as well. Abs is showing right side front speed sensor open circuit. If ign adv is bad what can i do to fix this?

[MT-2500]

Originally Posted by Westell

Alright scan shows no stored codes none. Live data shows no misfires everything shows good. Only thing that i could see that seemed odd is ignition advance was jumping from -10 through -25 at idle? and would jump to about -30 with throttle but other than that everything shows up clean. Is ign adv camshaft retard and is what im reading bad or no. Seems to be rough when warm now as well. Abs is showing right side front speed sensor open circuit. If ign adv is bad what can i do to fix this?

Timing is preset by the crankshaft sensor and is controlled by the VCM and is not adjustable.

Camshaft retard setting is where the dist rotor is pointing to the spark plug terminal in dist cap.

To set it it needs a read out with a engine capable scanner.
Should read out as close to - or + 0 degrees as toy can get it by turning dist.

On ign advance/timing it should not be jumping all over the place.
Check it with a load on the engine and see if it holds steady.

[Westell]

Ok with load driving it will hold around -35 when pedal is released it will go to -0 and hold for around 10 seconds and start jumping again. start driving again -35 full throttle half quarter pretty much any and its right in the ballpark of -35. Could i be getting a false reading. I have spoke to others check dist make sure its not off its right on, old master suggested chain may have jumped a tooth but everything is right. Wires look pretty aged everything is around 3 years old. I did change pump and spider recently could this have fouled the plugs i was burning a bunch of fuel about 90 miles on 19 gallons. I have no trouble starting it at all starts right up and runs doesn't ever stall just seems like a slight miss that's easier to notice when first started. Has slight pinging when cold sounds like spark knock.