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Gary
Gary, Chevy Technician
Category: Chevy
Satisfied Customers: 16888
Experience:  15 years GM master tech
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I have a 1994 Chevy 2500 Suburban 4WD with a 7.4. I did a

Customer Question

I have a 1994 Chevy 2500 Suburban 4WD with a 7.4. I did a full tune-up(plugs, cap, rotor, wires, distributor, everything runs well with the dist advance wire disconnected, timing is set at 4 BTDC and runs ok, as soon as you restart with the advance wire rehooked it sits and has a rough idle and shakes and has an intermittent miss while driving. Everything is correct. Spark gap, timing, wires, firing order. What am I missing? ECM? EGR valve which is electronic?
Bob D
Submitted: 1 year ago.
Category: Chevy
Expert:  Gary replied 1 year ago.

I am sorry your having this problem

was it doing this before the tune up and complete distributor was changed ?

Customer: replied 1 year ago.
Started acting up. Assumed plugs were the issue. Pulled them out, were at .040 to .050 gap and looked tan but you could see they were in for awhile.
Expert:  Gary replied 1 year ago.

if you unplug the EGR valve will it still do this ?

Customer: replied 1 year ago.
C
Expert:  Gary replied 1 year ago.

see it it still does this with it unplugged

Customer: replied 1 year ago.
Still the same just logged a code
Expert:  Gary replied 1 year ago.

this is a complete new distributor or a rebuilt one ?

and if you leave that timing connector wire unplugged it will not miss or idle rough ?

Customer: replied 1 year ago.
New
Idles good. Slight intermittent miss nothing defined
When advance wire hooked timing is at 34 degrees at idle
Expert:  Gary replied 1 year ago.

this should not be a knock sensor issue pulling the timing like that as that would retard the timing

if with the timing light before you plug in the timing connector the timing mark is not jumping and is nice and solid at 4 degree's then the only thing left is the computer itself pulling that timing advanced when it should not be

Customer: replied 1 year ago.
Since you state this it does jump around in advance mode. Not when it is disconnected though
Expert:  Gary replied 1 year ago.

i was saying if the timing connector is unplugged and it does not jump around the odds of a timing chain issue are ruled out is what i was getting at

since it advances like this just when plugged in the only thing left to do this is the computer itself

Customer: replied 1 year ago.
Thank you
Expert:  Gary replied 1 year ago.

anytime

dont forget to rate us here at Justanswer as i do not get credit for my work until you rate us here

Customer: replied 1 year ago.
I will when I replace it!
Expert:  Gary replied 1 year ago.

sure thing

you can always get me back through this post any time for any follow up