Stupid ignition problem

OverBoardProject · #1 06-07-2006, 09:34 PM

85 S10 Blazer 2.8L. Factory ignition system. Carburated!

I've recently replaced my Distributer, coil, cap, router, wires, plugs, ignition module.
It idels perfectly, but when I give it some throttle it starts to miss. And badly.
I've even replaced all the parts except the wires the second time, and it hasn't changed a thing.

When I pull the plugs it looks like 4 are running rich, and 2 aren't even firing.

At times it sounds like it's trying to run on all 6 cylinders as well making it realy weird.

Any ideas what might be wrong.

I've now got a retired mechanic as stumped as I am.

I pulled the plugs days before this all started, and they all looked like the perfect burn.

Edit, Yes it is timed right!

Rmbodie · #2 06-08-2006, 02:49 AM

I got an idea , lets convert it to desiel . HAHA . I was reading your mind . Heres my thought . When mine gave me trouble it was the wires . Try this , get someone to hold the brake and put it in gear and put some load on it at night . See if you see arcing from the wires to ground when it is pulling a load . this is how I found mine . they were new autolite wires too . Rob

OverBoardProject · #3 06-08-2006, 09:22 AM

Thanks Rob, I never thought of trying that. Althoough yes I've done it before.

The Diesel will come and faster now, but I still need to be able to drive it. I'm suposed to be moving tomorrow and have to get there.

As a result my mom will be in town tonight to drive 1 of my vehicles back tonight. I can get her to give me a hand with that. From the sounds of it I'll probably see a light show under there

Southern Comfort · #4 06-08-2006, 09:30 PM

What about the mass air flow sensor. tap it and see if the idle changes.
SC

blazee · #5 06-08-2006, 09:33 PM

Quote:

Originally Posted by Southern Comfort

What about the mass air flow sensor. tap it and see if the idle changes.
SC

That would be a possibility on other years, but his 85 doesn't have a MAF.

old_master · #6 06-08-2006, 10:29 PM

You mentioned that some of the plugs were running rich and some lean. The intake manifold runners on a V6 are configured so that one barrel of the carburetor feeds the front and rear cylinders on one bank and the middle cylinder on the opposite bank. Every other cylinder in the firing order fires alternately between the barrels. This is true for V8's as well, and designed that way for many reasons. With this in mind... it is possible for the idle, transition, or high speed circuit to be restricted in one barrel of the carburetor causing what appears to be random rich/lean burning. Check closely which plugs are rich and which are lean. This may explain the “no rhyme or reason to the fouling”.

OverBoardProject · #7 06-09-2006, 02:06 AM

I think that you hit it on the head Old Master. I popped the hood tonight, and absolutely no arching there. That's with a full load at 2500 RPM. The 2.8L carbs are lousy, and I've had issues with this carb before. (it's flooded while driving over really rough terrain)

I'm leaving it alone (parked) while I move, and will get the carb re-built in the next few weeks when I have the time. Even if it doesn't cure the problem it will still cure a problem.

BlazerLT · #8 06-09-2006, 02:13 AM

Sounds like a gummed up carb.

I heard this stuff does wonders in getting rid of the deposits.

Redline SI-1 Complete Fuel System Cleaner

OverBoardProject · #9 06-09-2006, 02:16 AM

Thanks BLT. I should give that a shot before I get it re-built. Why spend the coin when the plans are to yank the motor sometime this summer anyways.
Although I want it to run good so I can sell it.

Plus I do like redline products

Rmbodie · #10 06-09-2006, 06:06 AM

That is a good point about the carb barrels . My original TBI did not divide the intake plenum like my Edelbrock does . So I did not think of that . Good luck on the move . wish was something simple for you though .Rob .

BlazerLT · #11 06-09-2006, 07:19 AM

Quote:

Originally Posted by OverBoardProject

Thanks BLT. I should give that a shot before I get it re-built. Why spend the coin when the plans are to yank the motor sometime this summer anyways.
Although I want it to run good so I can sell it.

Plus I do like redline products

It is supposed to do wonders, I have heard nothing but praises on it.

One whole bottle for the first tank, then 3oz per 20 gallons after that.

This product is recommended by BMW and some other manufacturers. You might be seeing a couple gummed up jets due to the poor fuel we have been getting in the last 3-5 years.

OverBoardProject · #12 06-10-2006, 01:19 AM

Thanks everyone. I'm now 1/2 moved (using my car) and will go back for the Blazer next weekend if at all possible. I know that it'll be running within a short period of time now.

I'm hopefully going into Kelowna (the biggest inbterior city in BC Canada), and will be looking for the next powertrain in the wreckers. I'll let you guys know if I find what I want (and take pic's now that my camara is fixxed)

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