6,500rpm Missfire??

[thxone]

If I floor my engine while driving, it will stumble horribly at 6,500rpm and acts like it is misfiring. My valve covers leak... spark plugs are 100,000 miles old I think and I am running 87 octane. I should be shot right? I don't think the car wants to shift until 7,000rpm from 1st to second gear, it revs all the way to 6,500 and I wait for the shift to second and it falls on its face and I have to lift off the throttle. Could it be the timing and the 87 octane? It is weird because it increases in rpm up to that point then acts like I hit a limiter... like this:

__________---------------/ / / / /
Take off--- 3,950rpm------ 6,500rpm stumble

 

[AREA 91]

If I floor my engine while driving, it will stumble horribly at 6,500rpm and acts like it is misfiring. My valve covers leak... spark plugs are 100,000 miles old I think and I am running 87 octane. I should be shot right? I don't think the car wants to shift until 7,000rpm from 1st to second gear, it revs all the way to 6,500 and I wait for the shift to second and it falls on its face and I have to lift off the throttle. Could it be the timing and the 87 octane? It is weird because it increases in rpm up to that point then acts like I hit a limiter... like this:

__________---------------/ / / / /
Take off--- 3,950rpm------ 6,500rpm stumble

Are you sure that your not hitting the rev limiter?
The tach's in these cars aren't very accurate.

 

[kevinspann]

Fix what's wrong and try again. And as Brian said, it could be the car hitting the rev limiter, but I would think the ATX would shift by that point. There isn't any kind of chip in the computer is there?

 

[thxone]

As far as I know, no chip or tuning of any kind... my thoughts are the same on shifting before the limiter... weird. As soon as I can get the money for the valve cover gaskets I am going to do the plugs as well. I am also going to try just 93 octane for a while... maybe it is an issue with that too. It acts like it is an overboosting Turbo car... alas, I have no turbo. I am going to have to trace all the vacuum lines as well now... My initial thoughts are plugs, O2 sensors and the exhaust leak at the flex pipe. The only active code is for the vacuum solenoid for the butterflies on the intake. I don't even know where the computer is in this car yet.

 

[thxone]

Edit:

That solenoid for the butterflies is in fact leaking at the cap on top of it... it is a vacuum leak for sure... I am using clear RTV silicone on it right now to seal it up... It may help, it may not. Will let you know. I know I checked out one at the parts store and the cap was very tight, no wiggle, no jiggle, no nothing. Fingers crossed.

 

[SHORANGERBIRD]

-um thats like a balance flow port. has a small filter inside. not supposed to be sealed.....

 

[thxone]

-um thats like a balance flow port. has a small filter inside. not supposed to be sealed.....

To late... sucked some still wet silicone into the solenoid... if it wasn't screwed before it is now lol... I have now bypassed the solenoid and am running the vacuum directly off the intake manifold... It's a whole lot better... brakes feel better, it is shifting at 7,000rpm on the nose and it's pulling hard. No doubt the solenoid is causing many issues. Gotta hurry up and replace it.