3.2 Hesitation/Pict

[CrossT]

I thought I had cured the hesitation/bucking I was experiencing [as are a few other]. Car was running great, after I swapped out for new plugs, for a about two months, then out of the blue, the bucking stars up. I thought I previously had a bad plug [#4]. So, I removed #4 again and again found it was somewhat fouled. So, something in #4 is amiss.

Here is a pic of two plugs. The one on the left is representative of all the plugs except #4, which is on the right. It's blacker than the photo would suggest.

I suspect this is a symptom of what is causing the bucking, so I would like to remedy.

What can cause a single plug to foul?

Injector?

Wire?

??

thanks for any thoughts

todd
86 coupe

[Udo]

Todd,

as you mentioned, could be the injector, the wire but also a piston ring or the wrong plugs!
Since it started after changing the plugs I would suggest either a problem with the plugs (try to mount the old plug again and make sure you have the same plugs as before) or the connector/wire.
Are you sure that the plug was sitting tight? Sometimes dirt or a bad thread make you think it is tight!

[stlrj]

Had the same thing happen to me, the same plug fouling a week later without fail. This went on for years until found that the wire going to that plug was shorting out.

My plugs looked exactly the same and you could always tell which one was bad.

[CrossT]

thx guys

The wires are - IMHO - a potential, but not immediate suspect. Two yr. old Magnecores. So I got a new Dist cap, and will see tomorrow, if that's the cuplrit. Replaced the rotor very recently.

The top end was redone < 30k ago, so rings are unlikely. The car has bucked with two week old Bosch coppers as well as NGKs.

I'm hoping there was an issue with the 3 yr old Dist cap and the #4 plug bridge.

I'll report back tomorrow morning after driving to work.

thx again
todd
86 coupe

[CrossT]

Immediately it was obvious that the dist cap was NOT the problem.

I've ordered a new #4 wire and we will see . . .

todd
86 coupe

[PatrickB]

How many miles on the engine?

[CrossT]

Patrick

In total, the engine has 181K miles on it. The top end was redone at about 155K, tho. So, one might say it has the equivalent of about 25K - 30K on it.

I had all the wires out just before this bucking started a few months ago and I cleaned them off to look nice and red again. Maybe possible I damaged one in the process.

todd
86 coupe

[stlrj]

If it's any consolation, I installed a brand new set of Magnecores only to experience some missing problems.

[jet911]

I'm sure if there is a problem with the Magnecor wires, Magnecor with correct it. I've been running Magnecor KV8.5 for three years and zero issues. They are great wires.

[CrossT]

You are right on. Good wires

I called Magnecore and they are sending a new #4 wire. Not free of course, but pretty cheap nonetheless.

If it turns out that the wire is not the issue, this car is off to the wrench. I'm not gonna start throwing expensive parts at it.

todd
86 coupe

[PatrickB]

Just for kicks...
Is your car CA car?
Mine is, and had the brown quick connect wire attached right before where the harness attaches to the DME. Disconnect it. It just took care of about 90% of the rough running problem for me.

[CrossT]

Patrick

It is a CA car and mine seems to run pretty much the same connected or not. I've disconnected it.

I might be wrong, but I thought the effect of disconnecting this wire makes it a 49 state car and gives a few more HP near the top end. A few full throttle redline runs would probably reveal a noticeable diff.

todd
86 coupe

[PatrickB]

Actually, just the opposite.... I think it makes the mix richer at idle, and at part throttle. This is where i have been experiencing all of my stumbles... medium throttle between 3-3.5k rpm's. Completely eliminated now. Just a small blip around 4200 rpm... I too have replaced or swapped everything. Just recently replaced the distributor, cap & rotor & plugs. The dizzy, cap/rotor, & platinum plugs really cleaned up about 90% of the problem. Disconnecting the brown wire did the rest. The only real complaint is that under full throttle, my engine pukes out a bunch of grey smoke between 5800 & 6100 rpm. above that to 6500 it is clean?? It might be time to break down and get a SW Chip... Gas mileage is up from 19 to 21.5 now as well...

[stlrj]

under full throttle, my engine pukes out a bunch of grey smoke between 5800 & 6100 rpm.

If I'm not mistaken, isn't that the rpm where the fuel maps go full rich? If that's so then what we might be experiencing is an over rich miss.

With that in mind, I made some adjustments on my air flow meter which seems to have totally eliminated the high rpm puke on my 86 3.2.

[PatrickB]

I just reconnected the brown wire, and the car is running fine... For now... I ran it through the redline after warm up, and no over rich at the high rpm.
I might be wrong again, but I seem to remember people saying on the board that the AFM adjustments really only affect the idle and lower rpm rang, not the full throttle and high rpm range??? I'm not saying I necessarily agree with that, but it seems as if my car tends to defy all common reason and logic.....

[stlrj]

AFM adjustments really only affect the idle and lower rpm rang, not the full throttle and high rpm range???

Not if you make your adjustments inside the meter on the spring and pointer. Now we're talking global, not just at idle.

Joe