timing issues..

[lancescott67]

I replaced the timing chain on my 93 gmc 4.3 tbi because of excessive "slop" Now, when i accelerate, there are "flat spots"( at certain rpms you can noticeably feel the power reduce, then come back when the rpms get higher) in the power band. Most noticeable in third or OD. I thought it was a bad set, so removed the first replacement set, checking the marks before removing the chain and gears, now have the same issue with the second set, which is a different brand. Also, I get ping and run-on when the engine is hot, I have double checked the ignition timing marks, and the only way I can stop it is to advance the timing 3 to 4 degrees. What the heck am I over looking?

[sector95]

Some thoughts.....

I am assuming your engine was running fine before you decided to swap the timing chain....yes?

My first action would be to make sure I had not forgotten or inadvertantly disconnected any sensor leads..... easy to do in the "heat of battle".

How many miles are on your engine? You may have upset the delicate balance of a high mileage engine and it's collective component wear by putting in a new cam chain.

There may also be some "learning" required of your engine computer since your valve timing may have changed with the old chain.


Mike
98Sierra

[maxwedge]

Did you disconnect the electonic timing control wires before timing the engine?

[2000CAYukon]

What shape is the dist in? More specifically, the pickup coil and upper shaft bushing. Any play in the shaft or a bad pickup coil can cause a low rpm miss.

Where the valves readjusted? If so how did you set them (i.e zero lash plus 1/4 turn)?

//2000CAYukon

[camaroguy_1967]

Originally Posted by maxwedge

Did you disconnect the electonic timing control wires before timing the engine?

Hello I am new to this forum and need to ask a question. Can you help me find the wire you are refering to. My truck refers to 1 wire behind the electical junction box cover, 1994 GMS Sierra. My truck pings when shifted into the next gear, 5 speed K1500. Also pings during heavy acceleration. It has 170K miles, no smoke does not use oil. I need to check the timing but can not find that wire.

[horse482]

Originally Posted by camaroguy_1967

Hello I am new to this forum and need to ask a question. Can you help me find the wire you are refering to. My truck refers to 1 wire behind the electical junction box cover, 1994 GMS Sierra. My truck pings when shifted into the next gear, 5 speed K1500. Also pings during heavy acceleration. It has 170K miles, no smoke does not use oil. I need to check the timing but can not find that wire.

Welcome to af. You should create your own post when asking a new question, but since we are already here. The wire on your truck is in the cab under the dash on the right side below the glove box.