Vista Cruiser suddenly developed a miss! ={

To get some ideas on what it could be, I shot this video.

I also posted in the classic Olds forum, but not many bites. Maybe some of you guys might know.

I literally started the car up the day before yesterday, took it for a drive, got on the highway, and when I got off the highway, it started running like this. Since the rebuild in Sept, the engine has run beautiful. I recently took it to Pensacola, and it ran beautifully. I don't know where this miss comes from. The vacuum gauge jumping like that is brand new. This engine normally pulls about 19in of vacuum steadily. My books say that the sudden rhythmic drop of 3 points or so is most likely an ignition malfunction, but I'm not so sure. It's definitely not any crossed wires or anything like that. Distributor, wires, coil and plugs are all new. It literally started running like that when I exited the highway.

I tried the test where you pull plug wires, and it still runs like that. I plan on purchasing an ignition tester and hooking it up to see if I'm losing spark somewhere along the line or a couple of places and that's why I can't tell. I'm just hoping it's not a valvetrain issue. The heads are reworked #7 heads, cleaned and machined back in sept with the rest of the engine rebuild.

I'm hoping the video might provide some insight. Any advice would be appreciated.

http://s22.photobucket.com/user/arro..._7571.mp4.html

 

Have you pulled any of the plugs to see what they look like?

 

Since the miss definitely sounded to me like it was coming from driver's side since I hear it thru the driver's side exhaust, I didn't pull the plugs on the passenger side, but I will. The driver's side plugs all look normal.

 

Had an overly-long plug wire make contact with an edge of the exhaust manifold once. Burned through and shorted that plug out. Check for corrosion on the contacts of the wires. Are you running an old style points ignition? If so, make sure the coil isn't seeing 12 V because the resistor wire is bad.

 

Cannot watch the video is it a new points dist or a new HEI? Are the cap and rotor new and points if it has them?

Did you replace the rocker arm Holders when you refreshed the heads? A loy of these were aluminum and would wear out and cause a miss. ( check compression after verifying the ignition system is functioning properly)

 

The ignition is HEI. I made sure to keep the wires away from the headers using brackets fastened to the valve covers. Also, I did inspect the wires for burns and stuff like that and no dice.

Definitely replaced the rocker arms and lifters when i refreshed the heads. didn't replace the pushrods though, because they all looked good and cleaned them out as well.

Guess I'll run a compression test next chance I get and see what turns up. Gut feeling tells me that it's a valve because the ignition system passed every test I could think to throw at it. =/ Hopefully it won't require pulling a head.

 

Does it have an electric choke? Check that if it does. Also, check the fuse.

I've had that happen, went from running great to brutal. Same fuse designated for electric fans also powers the electric choke. This does not show on the wiring schematic. The fuse was melted, (a cheap piece of crap made in China) but it still worked intermittently. Swapped the fuse, the car cleaned up nicely.

I had already checked timing, plugs and wires, the choke looked like it was working correctly. I even thought maybe bad gas so added a $12 bottle of octane boost all with no success.

Unplug the choke wire or wire the manual choke open and see if that does the trick for you.

 

sorry i cant watch the video..my sound card is out... but you seem to have eliminated most of the ingnition sources of a miss..new parts dont mean much i have had many "new " parts fail..including spark plugs. i have also had things like new lifters fail so a compression test would be a good idea .. take out all the plugs (keep them in order for a good inspection) and block the throttle open and disable the ignition system.. post the results.. .. with the vacuum gauge jumping a valve or related parts are suspect....

 

You replaced the rocker arms and lifters the part I am asking about HOLDS the rocker arms down and bolts to the head. Basically it is the rocker arm pivot. If these wear they cause slop in the valve train and can cause a miss. This can happen with or without a tick noise to accompany it.

As said above wire the choke open to be sure it's not mussin ya up.


a compression check should tell the tale on the valve possibility. You can have compression but it would be greatly fluctuated from the better cyls.

And there is the possibility of a faulty new lifter rare but it happens.

 

I keep the choke disconnected, actually. It's always open. I had so much trouble adjusting the electric choke on this edelbrock that I simply disconnected it and opened it up.

I'm sorry, yes, the rocker arms, pivots, and lifters are all NOS.

Definitely gonna do a compression test after this weekend's festivities. And I wanna pull the valve covers so bad to have a look that I'm actually thinking about postponing the party. But... nah.

And I guess I'll pull the spark plugs and see if they're all firing at least, so I can rule that out. Didn't do that test yet.

 

They not only wear, they can break. I had a 70 Delta 88 that had that happen. After determining that ignition and fuel were decent, I ran a compression test and found number 5 bad. When I pulled the rocker cover, it definitely was evident it had snapped right in the middle, and the intake rocker had rotated enough for it to not work.

 

I ran a compression test and I have good compression on all 8 cylinders. 125psi of pressure, which is where it was when we rebuilt the engine.

I have installed a new distributer cap and rotor, thinking that was the problem, but I still have the miss big time.

Should I try brand new plugs and wires next, even though the plugs and wires are all, in fact, brand new when I did that in december?!

I took the valve covers off when I ran the compression test, and I see nothing out of the ordinary. Everything is working on the valve train flawlessly.

={

In addition, I tested all the plugs and they seem to be firing a yellow spark. Not a very white or blue spark. If the engine is running, and I remove any of the spark plug wires, that makes no clear difference. If I remove two wires at the same time, however, it will definitely make a difference. Any ideas? I'm lost.

 

The spark (in air) should be fat and blue. So it's possible you have a bad coil or bad coil hookup (if it's HEI, sometimes people forget the ground strap that goes in before the coil is installed).

 

And if you have HEI make sure you use say 1975 style AC R46SZ or equivalent spark plug with the correct gap of 60-80

May also want to check that you have the engine to body grounds to the firewall hooked up and in good condition

 

Good idea, Killer. I've seen customer's cars have all kinds of weird problems just because the ground straps and harness ground wires are broken off or not connected!