98 4.3 midrange misfire

[MT-2500]

Originally Posted by need_a_new_truck

On the 98's there is a marking on the distributor cap (number 6) that the rotor should point to when the #1 cylinder is top dead center of compression stroke. Then I think the cam and crankshaft position sensors adjust the timing automatically(No timing light needed). So if you adjust the dist cap a little from the marking on the cap, the sensors should compensate for that adjustment.

Here is the markings on dist to set it for installation.
http://files.automotiveforums.com/ga...hp?photo=51302

But the PCM/VCM will not adjust anything if you turn the dist.

The dist only has a camshaft sensor in it to let the computer know where the camshaft retard setting is.
In - or + degrees.

The camshaft retard setting set as close to 0 - or + degrees centers the dist rotor to fire dead on or straight at the plug wire terminal.

If it is to far off you will get a code for it being off and if to far off you may get miss fires.

Also if it is to far off you will get a large spark gap which can result in high voltage spark that can damage plugs and engine from to hot of spark.
MT

[1996LTOwner]

Originally Posted by MT-2500

Read my lips.
Turning the dist has no affect on the engine [timing].
You can turn it all day and not change the timing or fuel delivery.
The crankshaft sensor sets base timing.
It is timed off of the crank shaft sensor.

The dist only delivers the spark from the coil to the cylinders buy turning the rotor to the right cylinder at.
Turning the dist centers the rotor to fire dead on with the plug wire terminal.

Read my lips? Get real. Your words, "Turning the dist centers the rotor to fire dead on with the plug wire terminal." You couldn't be saying that turning the distributor positions the rotor in such a way that the sparked is sent to the plug wire terminal at a specific time in order to coincide with the compression stroke and fuel delivery. Saying that would lead me to believe that turning the distributor would change when the spark is sent to the plug wire terminal. But that couldn't be since turning the distributor has no effect on when the spark is sent to the plug.
Since I obviously don't understand this and what you say must be right, if I put a timing light on my vehicle and turn the distributor while it is running, the timing marks under the gun will not be affected? Gee, I thought that a part of timing the engine ment you were timing the spark to be delivered at a specific time. Silly me.

[534BC]

MT is correct, the distributor is only that. It merely distibutes the timed spark to the correct terminal. It does not change the timing, it only changes the rotor to post relationship.

Think of it as loosening just the cap itself and swinging it only.

[need_a_new_truck]

YIPPPPEEEE. IT'S FIXED!!!!

Well....I called the junk yard today to see if they had a distributor to put in my Blazer. They did....$40 bucks. So I thought, what the heck, I'll give it a try. Put her in and bam.....runs like a champ. But I'm thinking it may not have been the distributor that was bad, but the cam sensor. Not 100% sure but I didn't really see anything wrong with the distributor itself. Plus.....I think what was happening is the cam sensor needed to be warm in order to work correctly and it took time for the heat to reach the distributor area so it would work correctly. Just my guess....so I'm sticking to it.

I want to thank the people on this site. You guys sure know your stuff and it helped me solve the problem.

Thanks again!!