1984 Z28, 305, non-hypo

After I put an MSD system on it, it got 24 mpg highway

Then OUT OF NOWHERE it started getting 14. Its doing 3 things it didnt before:

It starts, runs at normal rpm's for a few seconds, then dies
It has some kind of miss sound coming out of tailpipe.
And the mpg on it has dropped like a rock

Ive already timed it perfectly and put new plugs/wires on it.

Do you guys think its a timing issue??

This car is pretty solid. No engine trouble, no severe fixes. Very reliable car up until this point.

Thanks.. all the help I can get is appreciated.

 

Of course not. How could it possibly be? The timing is the same for all 8 cyls; if it's off, all 8 screw up, not just one. No possible way for "timing" to cause JUST ONE cyl to misfire.

Why would you need that?

Do a quick compression test first. Make sure you do it with the engine a little warm (doesn't have to be "hot", just, not stone cold); make sure the battery is FULLY CHARGED throughout the whole test; remove all 8 spark plugs before you start; block the throttle wide open.

Post the results.

Shouldn't be too hard to figure out which way to go, from there.

 

Okay - Hey, before I do that maybe you can help me with another question that might pinpoint the issue.

I set the timing on it, but DIDNT do it with the ETS wire disconnected (black/tan wire). I just set it 6-8 deg. btdc and timed it normally. I read on a post though that if you dont disconnect that wire, youre really not setting the timing true to 6-8 btdc.

Is that true?? Cuz I should do that before doing anything else b/c I may not have even fixed the problem last time !!

 

I just realized something. If I compression test, I can also do a little test that will tell me if Ive blown a head gasket. I need to do that first.

 

Yes that is true.

The ECM is under control of the timing; and typically, at idle, the actual spark timing will be about 20° ahead of the "static" timing that you have the dist mechanically set to.

Put it back where it was. Probably won't fix a misfire but should help it not die at idle so bad from being at least 15° retarded from where it belongs.

And besides a compression test, that would be ..... ??

Best test for that is a compression test.

 

Sofakingdom, blow off.

 

 

Okay know-it-all.

Maybe youve never heard of pressuring the cylinder then checking for air bubbles in your radiator fluid after taking off the cap ...... ??

K, now I know you probably believe youre like god when it comes to diagnosing vehicles, but lay off the smart *** tone.

Now go back and feel like your king of something, other than my thread.

 

A head gasket leak doesn't necessarily occur between a cyl and water; they also happen between cyls only. In fact THE VAST MAJORITY of head gasket leaks don't involve water at all; the single most common one, is between the center 2 cyls on one head.

Which is why a compression test is the way to find them.

Compression tests also find rolled cam lobes, valves that don't seal for whatever reason, etc.

But if you want to do extra work and find out NOTHING, hey, that's cool too. WOn't hurt my feelings at all: my car doesn't have ... whatever problem yours has, so it's no skin off my nose if you don't fix yours right away. I'm only trying to help. Just don't hallucinate that if you do that test and see no bubbles in the rad, that your head gaskets are good.