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rpmdiag, Tech and Instructor
Category: GM
Satisfied Customers: 7722
Experience:  Since 1975
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Timing advance isn't working on 89 Chevy 7.4L, 170,000. It's

Customer Question

Timing advance isn't working on 89 Chevy 7.4L
JA: Do you know your ignition timing number? How many miles are on the car?
Customer: 170,000. It's set at 4 degrees btdc
JA: What is the model of your '2147481646 GM?
Customer: Pickup
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: Yes. Ignition module
JA: Anything else you think the mechanic should know?
Customer: It has a after market edelbrock intake and the only thing left is the map sensor
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the GM Mechanic about your situation and then connect you two.
Submitted: 1 year ago.
Category: GM
Expert:  rpmdiag replied 1 year ago.

Hi, I’m Ron and I’ll be helping you today.
Before we get started though, Please understand that I don't know
your skill level or tools you have to assist us. Also understand that
I can't see, smell, hear, or touch the vehicle either, so patience is
appreciated. JA is a great Q/A site, but it does NOT replace a
repair shop.
My goal is to make you happy and get a great rating in return for
my time. Sometimes I have to give you bad news that I know you
didn’t want to hear, so please don’t shoot the messenger.

Replace the distributor and you will cover all the bases for vacuum and mechanical advance. Make sure you have manifold vacuum going to the vacuum advance too.

Thanks, Ron

Customer: replied 1 year ago.
It's not vacuum. It's electronic
Expert:  rpmdiag replied 1 year ago.

Ok, so it's the ESC distributor. Check your KNOCK sensor, the one I had was defective and the timing would never advance. I also had one with the wrong module causing the same thing.

Thanks again, and please don't forget to rate me and keep this link in case you need me again later on.