Inconsistent bucking when entering 4th under full load (WOT)

[Blood on Blood]

In the past month, the following was installled on my Mach 1

4.30 gear
aluminum drive shaft from a 2000 Mustang GT
Tune

Problem:

This has happened twice in the past couple of weeks (at night, cooler air). When shifting into 4th, under full load (WOT), the car (engine) begins to violently buck as if something sparatically pushing against the front of the car. If I take my foot off the gas, then the bucking stops. This does not happen when shifting into any other gears or when I am already in 4th and then floor it (WOT). And of course, this bucking does not occur every time I enter 4th at WOT.

I was thinking a broken motor/trans mount or wrong driveshaft; however, the inconsistency makes me think it is the tune, bad ignition coil, who knows?

Dave

[G]

Originally Posted by Blood on Blood

In the past month, the following was installled on my Mach 1

4.30 gear
aluminum drive shaft from a 2000 Mustang GT
Tune

Problem:

This has happened twice in the past couple of weeks (at night, cooler air). When shifting into 4th, under full load (WOT), the car (engine) begins to violently buck as if something sparatically pushing against the front of the car. If I take my foot off the gas, then the bucking stops. This does not happen when shifting into any other gears or when I am already in 4th and then floor it (WOT). And of course, this bucking does not occur every time I enter 4th at WOT.

I was thinking a broken motor/trans mount or wrong driveshaft; however, the inconsistency makes me think it is the tune, bad ignition coil, who knows?

Dave

Tune perhaps but it could be fuel related. What is the status of your fuel filter.

When I changed mine it was nasty and I discovered a pinched hard line.

It don't look so bad in the picture but when I pulled it off, it look worse on the other side. I have stuff at work to smooth it out but when I came back from flying the mechanics had made a new part and fixed the dents on the old one.

[Blood on Blood]

I talked with the tuner and the car is going back some time this week. The tune was 12.8 and the timing 28 degrees.

The fuel filter was changed about 10,000 miles ago and only shell/amoco has been put into the car.

I will check the line...

Thanks

[Blood on Blood]

Originally Posted by geoffav

Tune perhaps but it could be fuel related. What is the status of your fuel filter.

When I changed mine it was nasty and I discovered a pinched hard line.

It don't look so bad in the picture but when I pulled it off, it look worse on the other side. I have stuff at work to smooth it out but when I came back from flying the mechanics had made a new part and fixed the dents on the old one.

My fuel line has the same pinch and/or crease in the same location.... I will have that looked at and change the fuel filter as there is 10,000 miles on it... However, whether a dirty fuel filter or pinch in the line, wouldn't the inconsistent bucking issue occured prior to the tune also?

Thanks

Dave

[G]

Originally Posted by Blood on Blood

I talked with the tuner and the car is going back some time this week. The tune was 12.8 and the timing 28 degrees.

The fuel filter was changed about 10,000 miles ago and only shell/amoco has been put into the car.

I will check the line...

Thanks

WOW, 28 degrees.

My Mach1 is lightly mod'd and uses 93 octane only and I don't think my advance is more than 22 at any rpm. The GT with the built motor on the same fuel we tried 25 for mid range and had to back it off to a max of 24. All of these things are a bit different but it sounds like a bunch of timing.

Do a search for timing advance, I found some good info. The computer code seems to effect the tweaks from the stock tune.

[birdman941]

Sounds like an ignition coil failing.
They sputter intermittently and then get worse until they fail.
Pull your coil covers off and see if there's any water in one of the spark plug holes.
There may be rust on a coil boot if you are getting water in there.
If you see that, I would suspect that (or those) coil(s).

[1fast04mach]

Originally Posted by birdman941

Sounds like an ignition coil failing.
They sputter intermittently and then get worse until they fail.
Pull your coil covers off and see if there's any water in one of the spark plug holes.
There may be rust on a coil boot if you are getting water in there.
If you see that, I would suspect that (or those) coil(s).

i agree with birdman i pulled my coils and found one with rust, im putting in new accel coils this weekend, u might wanna check ya plugs, ive had the same bucking problem and new plugs really helped

[Blood on Blood]

An update, the plugs have about 7000 miles on them.

The tuner and I are going to drive the car around at night later this week with the wide band, data logger, etc., hooked up.

Initial thoughts:
*ignition coil failure
*too much timing
*plugs are improperly gapped

We will be changing the fuel filter.

Thank you for all of the insight.


Dave

[G]

Keep us updated, we can all learn from this.

[4a7191a]

my car had a problem like that when i had a bad coil.

[Blood on Blood]

I wanted to wait until tonight (Friday) as the tuner/I just finished working on the tune.

I was out near Elburn and we headed the car East on a country road. Two runs, from 2nd into 4th. No problems. Then we did one run heading towards the storm, where cold air from the storm was blowing in through the shaker and the car bucked after entering 4th. It began to rain almost immediately after that run.

The bucking was as if you accidently downshifted the car from 3rd to 2nd and popped the rev limitet. It was so violently that the *** end of the car was skipping.

The mass air meter read fine and the timing was at 28 degrees during WOT. We did not have time to hook up a wide band due to how quickly the storm was coming in. Only the Predator was hooked up.

We dropped the timing down to 26 degrees, turned off the knock sensor, moved the rev limiter up to 7300 rpms and made a couple other adjustments. Again, the car was acting as if you down shifted and popped the rev limiter when in actually to did properly shift to the next gear and the rpms dropped as they should.

After the roads dried and the air still cool, I did 5 separate third to fourth gear pulls and the car was fine.

Again this is an intermittent issue, so if it occurs again we are going to remove the tune and assess. If it continues, we will then at the ignition coils.

I will keep everyone posted as this does not appear to be a common issue...

Dave

[Blood on Blood]

Ran the car at the drag strip and almost every run was a train wreck. This gremlin (bucking) issue still remains as if when you shift the 4th, the car acts as if you shifted to 2nd, when in all actuality you are in 4th gear.

After the event, the ignition coils were inspected, which the look new. The spark plugs were also clean. The gapping was at 54 and now we brought it down to 35.

We performed 8 highway runs after regapping the plugs, which the bucking issue did not appear. Maybe closing the gap on the spark plugs resolved the issue, but I doubt it.

Going to wait and see if the issue returns. We are going to check the Mass Air meter to determine if it is dirty and the IAC too. Also, if the issue returns, test the ignition coils and possibly replace the plugs with a colder set.

I am going to continue posting on this subject so that it is documented if someone in the future experiences similar symptoms.

Dave

[Linumup]

Originally Posted by Blood on Blood

Ran the car at the drag strip and almost every run was a train wreck. This gremlin (bucking) issue still remains as if when you shift the 4th, the car acts as if you shifted to 2nd, when in all actuality you are in 4th gear.

After the event, the ignition coils were inspected, which the look new. The spark plugs were also clean. The gapping was at 54 and now we brought it down to 35.

We performed 8 highway runs after regapping the plugs, which the bucking issue did not appear. Maybe closing the gap on the spark plugs resolved the issue, but I doubt it.

Going to wait and see if the issue returns. We are going to check the Mass Air meter to determine if it is dirty and the IAC too. Also, if the issue returns, test the ignition coils and possibly replace the plugs with a colder set.

I am going to continue posting on this subject so that it is documented if someone in the future experiences similar symptoms.

Dave

Id bet to say its your Mass air meter . Are you still running the stock one ?

[3150Mach1]

Originally Posted by G

Tune perhaps but it could be fuel related. What is the status of your fuel filter.

When I changed mine it was nasty and I discovered a pinched hard line.

It don't look so bad in the picture but when I pulled it off, it look worse on the other side. I have stuff at work to smooth it out but when I came back from flying the mechanics had made a new part and fixed the dents on the old one.

Sorry to steal your post.
I have this same pinch and was searching a little bit and saw another picture where someone had it as well. I know its from the rear housing hitting it in a to soft setup.
Is it hard to fix?
How do you fix it?
Can you cut out that portion of the line and run a rubber line from the filter to just beyond it with clamps?
Should I run a new and better line from the filter to the fuel rails????
Sorry but this would be a new area for me.

[birdman941]

Originally Posted by Blood on Blood

Ran the car at the drag strip and almost every run was a train wreck. This gremlin (bucking) issue still remains as if when you shift the 4th, the car acts as if you shifted to 2nd, when in all actuality you are in 4th gear.

After the event, the ignition coils were inspected, which the look new. The spark plugs were also clean. The gapping was at 54 and now we brought it down to 35.

We performed 8 highway runs after regapping the plugs, which the bucking issue did not appear. Maybe closing the gap on the spark plugs resolved the issue, but I doubt it.

Going to wait and see if the issue returns. We are going to check the Mass Air meter to determine if it is dirty and the IAC too. Also, if the issue returns, test the ignition coils and possibly replace the plugs with a colder set.

I am going to continue posting on this subject so that it is documented if someone in the future experiences similar symptoms.

Dave

It's a coil.

[hawk]

Originally Posted by 03Mach150BP

Sorry to steal your post.
I have this same pinch and was searching a little bit and saw another picture where someone had it as well. I know its from the rear housing hitting it in a to soft setup.
Is it hard to fix?
How do you fix it?
Can you cut out that portion of the line and run a rubber line from the filter to just beyond it with clamps?
Should I run a new and better line from the filter to the fuel rails????
Sorry but this would be a new area for me.

Hey fellas, mine has the exact same "pinch." I don't think anything could hit that line considering where it is (waaay high up above the rear axle bits). Since we have seen it on multiple cars, I am thinking it is supposed to be that way. I have no idea why it is there, but I ain't gonna sweat it.

Edit- added pic

[Blood on Blood]

Originally Posted by birdman941

It's a coil.

What draws you to thinking a coil is bad?
If a coil, how can we tell which one is bad (can only a dealership verify)? Via visual inspection, they all looked good.


The Mass Air Meter is stock.


Thanks

Dave

[Linumup]

Originally Posted by Blood on Blood

What draws you to thinking a coil is bad?
If a coil, how can we tell which one is bad (can only a dealership verify)? Via visual inspection, they all looked good.


The Mass Air Meter is stock.


Thanks

Dave

Pull your mass air apart and visually inspect , go ahead and clean filter , re-install . Mine bucked at WOT .

[birdman941]

Originally Posted by Blood on Blood

What draws you to thinking a coil is bad?
If a coil, how can we tell which one is bad (can only a dealership verify)? Via visual inspection, they all looked good.


The Mass Air Meter is stock.


Thanks

Dave

Let's see,
you closed the gap, reducing the power required to fire the plug.
If a coil is weak, that would cover it up,
but not necessarily fix it.

[Blood on Blood]

Originally Posted by birdman941

Let's see,
you closed the gap, reducing the power required to fire the plug.
If a coil is weak, that would cover it up,
but not necessarily fix it.

I understand. Since the issue is inconsistent, we would probably have to wait for the issue to get worse before it would show up on a scope, or is there another way to test the coils to isolate which one is bad?

Again, thank you and everyone who has posted with advice.

Dave

[birdman941]

Originally Posted by Blood on Blood

I understand. Since the issue is inconsistent, we would probably have to wait for the issue to get worse before it would show up on a scope, or is there another way to test the coils to isolate which one is bad?

Again, thank you and everyone who has posted with advice.

Dave

It will skip under load, or if moisture is present.
Have you pressure washed your engine lately?
Driven in heavy rain?
Have you had the coil covers off?
Water may have gotten in there
where the COP harness goes between the coil and cam covers.
This will drastically shorten the coil's life.

[pdmustgt]

Check wire connections for the engine

[Blood on Blood]

Originally Posted by birdman941

It will skip under load, or if moisture is present.
Have you pressure washed your engine lately?
Driven in heavy rain?
Have you had the coil covers off?
Water may have gotten in there
where the COP harness goes between the coil and cam covers.
This will drastically shorten the coil's life.

Only took off the coil covers when we put it on the dyno, but no water got in...

Dave

[STREET BULLY]

IS the crease from the factory? I am being told it is not and probably came from someone taking of the fuel filter possibly before you got the car and it should be fixed. Does anyone know the best way to fix this issue DYI,

[falcongtho3]

Probably a dead issue considering the previous posts date.