4.3 vortec misses on 3 cyl

gbic1 · 11-29-2004, 03:22 PM

I have a 94 s10 4.3 vortec which is missing on #s 2 4 6. Compression is good. spark is good. injector is new,fuel pressure is good. plugs are new. converter is gone. What would cause a miss on those 3 cylinders? It happened all of a sudden. Engine has about 70, 000 miles. It appears to be flooding the plugs on that bank. O2 sensor reads rich all the time.

OverBoardProject · 11-29-2004, 03:48 PM

Try replacing the wires, router, and the distributer cap.

gbic1 · 11-29-2004, 04:10 PM

Cap and rotor are new and wires scope out fine. Thanks

Mikado14 · 11-29-2004, 06:37 PM

Check your distributor shaft for play. Have seen more than one with bad bearings. What happens is that the reluctor hits the pickups and will cause a no fire.

BlazerLT · 11-30-2004, 12:22 AM

I think the injector is faulty.

When a bad injector is seen, it will flood a bank like that.

Nitekry · 12-01-2004, 11:43 AM

I have been there this baffeld me for a whiel You may have already replaced the injector spider and seen fuel on one side of the manifold
the issues it the lines in the back of the manifold that feed the fule are very high pressure and the tiny hairline cracks in then after they get old dump fule into the manifold whiel running .. so if they have never been replaced then you will need to do that. it is all one kit that includes the piece that the lines are attached to. you take them off from the back of the manifold and slide the new ones in. Good luck tis fun.

BlazerLT · 12-01-2004, 03:59 PM

This can be diagnosed by seeing washing in the passenger side of the plenum.

If it is on the passenger side, it is the CPI injector again.

gbic1 · 12-01-2004, 06:14 PM

I will see in the morning. I have another new injector and ordered a Nut kit also. I cant see how the nut kit can cause a leak on the passenger side but the lines have 176K miles on them and has a small rub mark where the injector line were rubbing. Is it possable that the vacuum is pulling fuel past the pressure regulator orings even though it is new 0 miles? I pressureise it with the upper plenum off and it does NOT leak. Gary

gbic1 · 12-02-2004, 12:05 PM

Well, Another new injector and a new nut kit and same thing still. Not running on the right bank and the plugs are flooding out still. Tested the wires with a ohm meter also and still ok. Seams to run ok at high rpms just not below 2000 or so. Distributer shaft seams to be tight. What else could cause a miss on 3 cylinders?

Mikado14 · 12-02-2004, 05:28 PM

Ok, let's go through your list:

Compression is good
On your second CPI unit
Plug wires ohmmed out good
Fuel pressure is good
New plugs

1. Have you checked your cap for any cracks?
2. Have you inspected the reluctor in the cap for cracks?
3. Do you have a brownish color dust on the inside of your cap?
4. Since it is the entire passenger side that is not firing, have you checked to see if all 3 wires are not pinched or twisted together?
5. Was any work done on the engine prior to this happening?

BlazerLT · 12-02-2004, 05:37 PM

Yea, seems like maybe a bad cap and rotor problem.

gbic1 · 12-02-2004, 09:40 PM

Cap and rotor are new. They were really bad but no change. Wires are correct and have the correct resistence. There is plenty of spark to the plugs. When sprayed down with water they do not arc. Changed the plugs twice. Distributer shaft is tight. Going to try a different distributer tommorrow but dont put any faith in to it. I actually ran better with the big hose to the brake booster off (got in hurry and forgot to hook it up by accident) so it is diffently getting too much gas. Scanner shows rich condition all the time. Egr is closed. ECT is reading correctly. Going to try a different ecm tommorrow even though it doesnt make any sence. As far as I can tell this injector fires 6 times for every revolution and is common to both sides. Worked on a freind tow truck 2 weeks ago and it was missing on one bank and it was beacuse the ecm was loosing ground to one side under load.

Mikado14 · 12-02-2004, 09:46 PM

Hold on a minute. You sound like you have a little knowledge here. What you are saying can be true but the CPI has only two wires to it. If the one bank works the other will also.

As far as the distributor goes, when you changed the cap, was there any brownish rust in it?

Mikado14 · 12-02-2004, 09:48 PM

I just reread your original post. Did you just install the CPI unit?

gbic1 · 12-02-2004, 09:57 PM

Quote:

Originally Posted by gbic1

Cap and rotor are new. They were really bad but no change. Wires are correct and have the correct resistence. There is plenty of spark to the plugs. When sprayed down with water they do not arc. Changed the plugs twice. Distributer shaft is tight. Going to try a different distributer tommorrow but dont put any faith in to it. I actually ran better with the big hose to the brake booster off (got in hurry and forgot to hook it up by accident) so it is diffently getting too much gas. Scanner shows rich condition all the time. Egr is closed. ECT is reading correctly. Going to try a different ecm tommorrow even though it doesnt make any sence. As far as I can tell this injector fires 6 times for every revolution and is common to both sides. Worked on a freind tow truck 2 weeks ago and it was missing on one bank and it was beacuse the ecm was loosing ground to one side under load.

Well I though I had a lot of knowlage untill working on this truck now I am wondering. Cpi is new on Monday and again to day. I dont think there was any rust but the carbon from the center electrode of the cap was gone. Could not see the gas stain on the fuel regulator like I saw a year ago when I dd one of these on a 95 Blazer. Fuel pump holds pressure very well and trucks starts perfect. Nothing else was dont to this truck. It was running fine till 48 miles ago and it happened all of a sudden. ?

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