Distributor swap

1998 GMC SONOMA
244,000 MILES • 4.3L • 6 CYL • 4WD • AUTOMATIC
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RCA195203
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Hi guy's! I have a 1998 GMC Sonoma with the 4.3 in it. But a 1990 engine was swapped out before I bought it. My question is, can I use a 1998 distributor on a 1990 engine? My manual is from a 1994 to 2004 and it says somethings that question like, using the number four cylinder instead of the number one cylinder when timing the engine and that the 1/6 are correlating cylinders. I am having a misfire problem according to my scanner on number six and although the compression is 125 in that cylinder as apposed to 130 to 140 for the rest. I cannot seem to line up my timing marks together! I replaced my timing chain and gears and made sure that the dots were lined up, and made sure that the number one was up on number one TDC to put my distributor in and lined it up on the number six on the distributor base. I was just wondering if the incorrect distributor was the problem of not lining up my marks! Everything runs alright, although my scanner says that I have a misfire on the number six, but it starts good and cuts off good. I am very confused!

Thank you
Sep 24, 2018 at 9:21 AM
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ASEMASTER6371
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Good afternoon.

The simple answer is no.

The 1998 is actually a cam sensor, not a distributor. The 1990 has a module and a pick up coil that the other does not have.

What distributor is in the engine now? Is the engine in a 1998 or in a 1990?

Roy
Sep 25, 2018 at 11:09 AM
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RCA195203
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It is the 1998, the one with the cam sensor, the non adjustable one.
Sep 25, 2018 at 8:08 PM
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ASEMASTER6371
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What leads you to believe that it needs to be replaced?

What is your exact issue?

Roy
Sep 26, 2018 at 3:21 AM
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RCA195203
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Scanner says it has a misfire on number six cylinder. Plugs, wires, distributor, all gaskets, heads, rockers, harmonic balancer, and lifters are all new. It starts and stops good, but has a small miss somewhere. All vacuum hoses were replaced. But for some reason the two marks will not line up for timing. My engine is on the number one TDC and the distributor is pointing to the number six on the base.
Sep 26, 2018 at 8:06 AM
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ASEMASTER6371
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Okay, that may be if you are not on compression on number one. If you are on valve overlap, then it will be 180 degrees out.

The fact that it runs tells me you have it set correctly.

Did you check the compression?

Roy

https://www.2carpros.com/articles/how-to-test-engine-compression
Sep 26, 2018 at 9:45 AM
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RCA195203
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Yes the compression is as follows: #1/140, #2/130, #3/135, #4/130, #5/135, #6/125 this one is the lowest and it is the one with the misfire!
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Sep 26, 2018 at 10:03 PM
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ASEMASTER6371
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Okay, good.

Did you insert a small amount of oil in the cylinder and re test?

If it goes up more than 15 lbs. The rings are worn. If it does not go up, it could be a burned valve.

Roy
Sep 27, 2018 at 3:15 AM
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RCA195203
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Yes I did, and it did go up. I know it could be the rings but I was just wondering if a 125 compression was enough to cause the misfire. Some how I am leaning towards a vacuum leak. I have not changed out the catalytic/converter or the right and left bank O2. My scanner does not read these two items.
Sep 27, 2018 at 7:53 AM
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ASEMASTER6371
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125 should not cause the misfire. If your ignition system is good, cap, rotor, wires, plugs, and coil, then it could be injector pattern not correct.

Have you tried any injectors cleaners?

Roy

Sep 27, 2018 at 9:50 AM
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RCA195203
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Injectors are all new. The spider system is what I have and the regulator is part of that unit. Like I said in my last reply to you, the only thing I have not replaced is my O2's and the catalytic converter.
Sep 27, 2018 at 6:41 PM
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ASEMASTER6371
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Okay, neither one will cause the misfire.

It could be a vacuum leak as well. You can have the engine smoke tested to look for a leak. It may be the intake manifold. Remove the oil fill cap with the engine running. Put your hand over the oil fill and see if you feel the vacuum. If you do, it may be the intake gaskets.

Beyond that, it could be mechanical. The valve covers and inspect the operation of the valves to be sure they are moving correctly.

Roy
Sep 28, 2018 at 3:32 AM
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RCA195203
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Well, I have been leaning towards the vacuum leak myself. I do not have a smoke machine but could figure something out. I will try the hand on the oil fill neck thing and I will let you know. The rockers are all new. There are different from what cam with the engine. The one's that came with the engine was a roller rocker and when I ordered the heads I ordered it for a 1998 4.3 but when I got the heads it was for a different year rocker, these were just plane rockers. I adjusted them at book specs of 22 pounds and they seem to be working good. What can you tell me about the vacuum lines for my 98 GMC Sonoma? There is a three way valve on the drivers side of the firewall. One line goes somewhere behind the engine or down near the transmission, and the other two goes somewhere down the right side of the drivers side inner finder. Maybe this is part or all of my misfire!
Sep 28, 2018 at 7:15 AM
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ASEMASTER6371
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I attached a vacuum diagram.

Can you upload a picture of the three way valve?

Roy
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Sep 28, 2018 at 7:23 AM
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RCA195203
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Here is the three way value I was talking about. The long line to the left connects to the manifold not really sure where the one short one was, it was like that when I bought it. And the one to the right goes down and wraps into the electrical wires harness but do not know where it comes out at.
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Oct 1, 2018 at 9:57 AM
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ASEMASTER6371
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That line is for the operation of the vacuum motors inside the truck. That is a vacuum check valve that uses manifold vacuum to the control head for the AC.

The blocked off line is okay. originally, there was a big vacuum tank. The replacement was this valve and they said in the instructions to block off the line.

Roy
Oct 1, 2018 at 10:01 AM
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RCA195203
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So from what I am reading from your reply is that it is okay, where it is? If so, any ideas on why my timing marks do not line up on time. I put the number one on TDC and the distributor dropped right in tight with the manifold. The rotor is on number one(6) on the distributor base. Yet the marks are off about 10 degrees retard. I changed out my timing chain/gears and made sure that the two marks in the gears were at 12/6 position.
Oct 2, 2018 at 7:40 AM
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ASEMASTER6371
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Okay, the cam retard should be 0. You can move the distributor a small amount to try to get the adjustment.

If you cannot, then check the gear on the bottom of the distributor. They wear out and very sharp on the edges. It should be a good square gear end.

Roy
Oct 2, 2018 at 9:55 AM
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RCA195203
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This is a non-adjustable distributor and it is new. The harmonic balancer is new with a key way so it goes on only one way. This is the problem, all parts is new, the number one is on TDC and the distributor is on the number one (6).
Oct 2, 2018 at 4:24 PM
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ASEMASTER6371
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The distributor is adjustable. There is a tab the is on the bottom. I remove it when I have to get it to turn. Then it will turn

New or not, I would check the gear.

Roy
Oct 2, 2018 at 4:39 PM
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RCA195203
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A tab on the bottom of what? The only piece of metal around the distributor does not come off it is pressed on for the reason of it being non adjustable.
Oct 2, 2018 at 8:12 PM
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ASEMASTER6371
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If you remove the hold down, the distributor sits in a notch. It allows a small movement. If the notch is removed, it will rotate.

Roy
Oct 3, 2018 at 3:34 AM
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RCA195203
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That is what I am trying to say, the hold down clamp is pressed on the distributor and cannot be removed.
Oct 3, 2018 at 9:04 AM
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RCA195203
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This is the problem, the distributor I have is not for my year of engine. I have a 1990 engine but it is into a 1998 4x4 Sonoma. It was like that when I bought it. I did not know this when I ordered the distributor, I ordered it for a 1998 4.3. It is the one with the cam sensor on the distributor. The 1990 does not have one on the distributor so it can be adjusted, mine cannot! If I ordered on for a 1990 my question would be where my cam sensor would be on my engine so I could use the 1990 distributor.
Oct 3, 2018 at 9:09 AM
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ASEMASTER6371
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Can you post a picture of the distributor?

Oct 3, 2018 at 9:35 AM