eddie jr

Hi guys,
I have an 88 L98 TPI that recently overheating for only a few minutes due to a pulley problem that dumped the belt. I then did a coolant system pressure check to verify no damage/leaks, which checked out. Oil is good, no water. And then compression check showed good and strong and fairly even. So i started it up and it runs fine, no leaks, temp stays in check but the needle seems to bounce around more at idle. When driving it seems smooth to 2000 but then there is a definite vibration after 2000 for a bit.

I put a timing light on each wire and all are firing but 2 or 3 seem to have an erratic flashing, so i am assuming they are misfiring?

Last fall when i put it the motor in i put on new wires, plugs, cap, rotor, timing set and set timing and minimum air where it should be.

Any idea what this could be? Could the extra heat have done something to one of the ignition parts?

thanks.

AlkyIROC

I was looking for something about changing ignition stuff.

Recheck the plug wires. It's very easy to get 5 and 7 mixed up.
Rotation is clockwise. 18436572

eddie jr

Thanks for the reply. I was travelling for a few days so couldn't back to it. The double-checked to order and it is fine, but if they were wrong, would you not still detect spark just fine on the wire since it would ground through the plug to block?

I just checked the resistance of several of the wires to (Taylor Streetfire i believe) which were 1.3 - 1.7 Kohms which puts it right about the 500 per foot spec. I also pulled the cap and there were not huge buildups on the posts, just what you would normally expect to see......i cleaned them anyway though.

So now i am stumped, what could cause erattic spark only on some cylinders?

Queball

check those spark plug gaps..make sure theres no physical dmg

eddie jr

They look fine. all new and gapped (with 700ish miles on them).

I did some more checking and for some reason on #3 the timing light flashes nice and consistent up high on the wire but erratic/faster down near the plug???

When i switched the plugs in 1 and 3 and back, that was not conclusive.

Queball

could just be bad wires regardless.
i purchased a set of brand new wires ..installed them an some how i destroyed the end of a wire putting it on the plug..dunno how but oh well..replaced it again n all was good.

anything can happen to them wires..so easy to f*** up,,

AlkyIROC

If 5 and 7 are mixed up, the engine will still run but those 2 plugs will be firing at the wrong time. Because they are right beside each other in the firing order, they will still ignite the fuel in the cylinders but at the wrong time. This will produce a lack of power and popping or a miss when under load.

Using a timing light on each cylinder like you're already done is a good way to tell if the plug is firing on that cylinder. If you say 2 or 3 are erratic then suspect a problem with those cylinders. Plug wires may not seated properly on the cap or plugs. Those plugs also may be defective. Try swapping the plugs to a different cylinder to see if the miss detected with a timing light also moves to that cylinder. If the erratic light moves with the plug, replace the plug.

eddie jr

Well , i had tried what you said and it was kind of inconclusive as to whether or not it was following the plugs, but then it flashed erratic (or much faster) down low by the plug but slower and consistent up high, so i thought for sure the wires.....nope. At the same time new delco plugs just cuz they are cheap.....no go there either.

Then i thought for sure it had to be in the distributor, so i pulled it and put in a used module and new pu coil i had laying around. I also cleaned the reluctor and piece on the shaft. Magent looked good with no cracks. You hear a tiny "ting" as something still barely touches at one point when you spin it but moves really nice now. I can't see where it touches. Thought for sure that would cure it......nope!

So now i am at a total loss, i don't know what the heck is going on. It seems you get the faster spark on many and different wires......i am wondering if it isn't even spark issue now?

If there were a fuel problem and the engine runs a little rougher (which it does), could that cause you to see erratic spark with a timing light? That is why i keep thinking it is ignition related.

I checked fuel pressure.....48psi. 38psi when running. varies a little when revving by about 4psi either way. Bleeds down very slowly. All injectors at 16.6 ohms, one at 16.2. That doesn't mean they are opening properly though, but i am hesitant to pull them since it is a lot of work to find out they are fine.

I am lost now......anymore thoughts?

eddie jr

anyone? this is killing me, still can't figure it out. i have been through literally everything.

Queball

check fuel filter..
check vacum leaks (throw some water on the intake man, see if see bubbles..
check compression ?
check fuel inject/carb/ clean it

if u over heated check for water in the oil..(possible blown head gasket inner instead of outwards)

id def compression check your cyl's and oil/water

Queball

also get it code scanned? see if any codes pop up

redneckjoe

what was the pulley problem that dumped a belt? perhaps its related to your current issue?