MIA, engine is missing under boost

[ThikStik]

Hello guys,
Iv'e got a gremlin uglier than my 1975 AMC. Its a miss 1 outta 3 times i punch it. And it is just when motor has been run for 20 minutes or so. Two weeks ago I had a full time miss under boost. Found a bad plug-that fixed it for about 6 days. Then i found an open (infinite resistance) plug wire. That fixed it for a day. Now it doesn't miss consistantly on each WOT just 1 outta 3 times.
I also have very inconsistant idle smoke. I have put in new valve springs and intake seals, less often but just as smoky when it does it. My turbo is new and I just removed it and vacuum test shows OK. I mention smoke because im wondering if it is related to miss. Plugs are not oily at all. Static FP=44, O2's are 790-850, retard not over 4, boost set at 16, usually run 18, and yes, turning it down seems to cut miss some. 93 octane. I am a GN newbie and just have my little Auto Xray 240 which Im hoping is giving accurate knock readings. Plugs are set @35. Reds wires are on the way. The car does have a periodic miss at idle and under a free 2000 rpm or higher it does miss fairly often. Coould that bad plug/wire have hurt module. The ohm test shows good on coil. HELP
Thanks

 

[Sleeper]

Sounds like a bad coil pack/ module. Ohming the towers is not a true representation of coils condition. It will tell you if it is definitely bad, but the test is not done under load. It may show good sitting on the bench, but break down at 2000 RPM. The only real way to test it is with the Caspers Coil Pack tester. It tests under simulated RPM load. If you can't get your hands on a tester, see if you can borrow a friends (known to be good) coilpack/ module setup and see if that cures the problem.

HTH
Paul

 

[Carolinaturbot6]

Well, ohming the coilpack doesn't always work. It's a good test & all, but sometimes it may ohm ok but still be problematic. Popping is usually related to an ignition problem, but can also be detonation (knock).

Are you able to monitor the fuel pressure rising under boost? Your o2's do sound ok...but o2 readings don't always tell the whole story, if you know what I mean.

You may want to keep your foot out of it until you get the plug wires, that may be all you need to stop the popping.

What color is the smoke? I recently went to Autozone & borrowed a coolant pressure tester (with a deposit of course) & made sure I didn't have any coolant leaking. If there's one near you, & the smoke is white, testing the coolant system may be in order.

What plugs are you using Rick? I've had good results with AC R43TS plugs at .035 gap. Try turning the boost down a few more lbs, & see if the popping stops. Either that or put some higher octane gas in the tank & see if that helps. If it does, then you know you're experiencing detonation.

Maybe some others will help you further. Let us know what you find. HTH

 

[Carolinaturbot6]

http://www.turbobuick.com/forums/showthread.php?s=&threadid=33444

Paul mentioned the Caspers coilpack tester, which comes in real handy. You may want to think about getting a spare coilpack & ignition module from John (above link). Nice to have spares just in case yours give out one day, & also good for troubleshooting. HTH

 

[ThikStik]

Thanks Carolina and Sleeper. Yea, I am going to run some race gas next day or so. I am running your plugs @ 35 and they are new. Gotta borrow a coil pack for sure.
As far as the smoke, it doesnt have that sweet coolant tinge to it and does smell like oil burning. The inconsistancy is amazing! It just really makes you think its gone and then whoosh. Prolonged idling is the main time it does it. There are no seals on the exhaust side of valves , normal?
Oh yea, would a driver's side header cause the boost miss? Or just tip in stumble and Higher? O2s?
Dont know if fp rises with boost. Have 233 thats adjustable. Will check.
Thanks once more.

 

[Sleeper]

Your right, no seals on the exhaust side. I would replace the O2 sensor just for good measure, and if it's not the problem you will have a spare. Depending on how bad the DS header leak is, it will cause the O2 sensor to read false conditions and send that info to the ECM to try and correct. During the transition into boost it will yo yo trying to compensate.

Paul

 

[ThikStik]

I can remember one person having the same or similiar problem on this board and a new o2 senser solved his prob. So, maybe a fooled o2 sensor will act like a bad o2 sinser. I thought WOT parameters were choosen by chip and o2 ignored. ????? as usual! Oh well, time to fix a header-which means, time to let someone who doesn't car about my car or me mess something up and not listen to my advice about bolting header to a head during welding. Kmart exhaust putty?
Thanks Sleeper, I think you'r e on to something.

 

[ThikStik]

wires

Red's wires did it. The ohming didn't uncover problem of Accels.