98 gt
4/29/21, 06:16 PM
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Hope someone can help! Bought this car last year was running a little rough gotvit running great but put it in storage for to months. Went to get it out of storage car would barely run after some research put new fuel pump in helped some and changed mass air flow sensor that helped a little. But after checking things out 6th and 7th cylinder act like they are dead did compression check all cylinders are 155 to 157. After more research checked timing chains one of the chain tensioner was bad so I figured it jumped time so I tore it down put new chains and the parts plus new heads and cams plus new intake .plus new plugs and wires and 78mm throttle body and all new sensors. Still 6th and 7th cylinder acts the same.
4/29/21, 08:58 PM
#3
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Howdy! 
Welcome to the forums!
Air, fuel, compression, spark, exhaust repeat x 8. So it's an intake, fuel, spark issue. You've already got compression figured out. And you swapped plugs and wires. It's unlikely to be plugged exhaust... unless it is, but I'd think that entire side would be unhappy.
98 GT 4.6L SOHC 2V motor, right? And you said plugs and wires... so this is using the dual 4 coil packs at the front of the engine. Each one's 'passenger rear' spark plug wire connector is where 6 and 7 are. Which is interesting... but I don't know if that means both are out...
This is a waste spark scavenge system. The firing order is 1-3-7-2-6-5-4-8. But really, you can break it into this:
1-3- -7-2
6-5- -4-8
What you see (hopefully?) is that 1-6 fire at the same time. Same with 7 and 4, and the rest. Each pair fires twice in a full cycle of the engine (two revs of the crankshaft), one to make the power stroke in the one cylinder, and the other to burn off any excess fuel in the exhaust stroke before/as it exits the other cylinder. And also (hopefully) you see the passenger and driver's side coil packs as you look down from the front of the car. The pairs stay in the same coil pack, and in line with the entire firing order. Simple!
And I learned something I didn't really know about that setup. All these years... Neat!
With that... 6 and 7 are driver's side middle two cylinders, and they are paired with 1 and 4 respectively, the outer two cylinders on the passenger side... Hm. I'd almost want to say those two should be acting up if it were the coil packs... odd that those particular two cylinders in those particular positions in the coil packs are what's happening there...
Probably nowhere thoughts, but hey, if they help, there they are.
I might be inclined to check spark on those plug wires at the other end, myself, just to see. Not impossible both coils are shot...
Also, it could be an intake issue, maybe the gasketing around 6 and 7's port is messed up. It could be an injector issue as well, might be clogged or stuck open. I'd wager you'd probably get a code for those though...? Car is an OBD II, so should be able to just get the codes... Or get a scantool of decency to start reading the computer as the car is running...
And finally, the computer could be suspect. It happens. Or it could be a corroded connector or bad ground...
About all I got. I hope that helps. I hope if I missed something, someone else will chime in. Always learning, after all. Good luck, and do let us know!
Welcome to the forums!Air, fuel, compression, spark, exhaust repeat x 8. So it's an intake, fuel, spark issue. You've already got compression figured out. And you swapped plugs and wires. It's unlikely to be plugged exhaust... unless it is, but I'd think that entire side would be unhappy.
98 GT 4.6L SOHC 2V motor, right? And you said plugs and wires... so this is using the dual 4 coil packs at the front of the engine. Each one's 'passenger rear' spark plug wire connector is where 6 and 7 are. Which is interesting... but I don't know if that means both are out...
This is a waste spark scavenge system. The firing order is 1-3-7-2-6-5-4-8. But really, you can break it into this:
1-3- -7-2
6-5- -4-8
What you see (hopefully?) is that 1-6 fire at the same time. Same with 7 and 4, and the rest. Each pair fires twice in a full cycle of the engine (two revs of the crankshaft), one to make the power stroke in the one cylinder, and the other to burn off any excess fuel in the exhaust stroke before/as it exits the other cylinder. And also (hopefully) you see the passenger and driver's side coil packs as you look down from the front of the car. The pairs stay in the same coil pack, and in line with the entire firing order. Simple!
And I learned something I didn't really know about that setup. All these years... Neat!With that... 6 and 7 are driver's side middle two cylinders, and they are paired with 1 and 4 respectively, the outer two cylinders on the passenger side... Hm. I'd almost want to say those two should be acting up if it were the coil packs... odd that those particular two cylinders in those particular positions in the coil packs are what's happening there...
Probably nowhere thoughts, but hey, if they help, there they are.
I might be inclined to check spark on those plug wires at the other end, myself, just to see. Not impossible both coils are shot...Also, it could be an intake issue, maybe the gasketing around 6 and 7's port is messed up. It could be an injector issue as well, might be clogged or stuck open. I'd wager you'd probably get a code for those though...? Car is an OBD II, so should be able to just get the codes... Or get a scantool of decency to start reading the computer as the car is running...
And finally, the computer could be suspect. It happens. Or it could be a corroded connector or bad ground...
About all I got. I hope that helps. I hope if I missed something, someone else will chime in. Always learning, after all. Good luck, and do let us know!
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