Huge Hesitation

[crouse]

I have a huge hesitation at WOT at 5000 to 6000 rpm, I let off the throttle then back on WOT, and there is at least a 1/2 to 1 second delay before I start feeling acceleration again. But I can hear intake air. It's not bucking or sputtering I'm just not accelerating. I've run two Auto-X events this year noticed it at the first event on June 13th. On the July 18th Auto-X I had an instructor ride with me and he noticed it right away and described it as turbo lag.


I've cleaned the MAF, changed the three O2 sensors and just recently added a can of Sea Foam to a full tank of gas without any change. I'm thinking about changing my throttle position sensor. I'll probably change plugs eventhough they only have about 25,000 miles on them. What about coils? I've got about 72,000 mile on the clock. Any suggestions would be appreciated.


Thanks,
Curt

[bob6364]

This may be a stupid question ...but have you changed the gas filter lately...sounds like you are running out of fuel to me....

[justbob]

My money is on the fuel pump. Have you datalogged it?

[CRUZTAKER]

My money is on the fuel pump. Have you datalogged it?

If so...this would be a great opportunity to upgrade a few delivery options. ;)

[crouse]

This may be a stupid question ...but have you changed the gas filter lately...sounds like you are running out of fuel to me....

Hmmmm... not sure when it was changed last. I'll check tonight and possibly replace it if it's been a while.

[crouse]

Just thought I'd open this thread up again since it's almost Auto-X season.

The fuel filter is in good shape.

Wondering if the MAF could cause my hesitation? I clean it periodically with the CRC MAF Cleaner.

Any additional help would be appreciated.

[RacerX]

Never fixed? That bites. Now when you say it happens 5 to 6k, is that in every gear? Hold 1st, then 2nd, then 3rd (OD off obviously). Does it act excatly the same through gears. Do you have an sct tuner?
Definitely change your plugs!!! 25k and a couple autocrosses, change them. No to tps, doubt maf prob.

[babbage]

Just thought I'd open this thread up again since it's almost Auto-X season.

The fuel filter is in good shape.

Wondering if the MAF could cause my hesitation? I clean it periodically with the CRC MAF Cleaner.

Any additional help would be appreciated.


Dyno session may help - they can see the duty cycle of pump and injectors etc. That will show where the issue is. I'm betting its the fuel pump. Take some carb cleaner and hit the tbody and upper intake, check PCV valve too.

[crouse]

Never fixed? That bites. Now when you say it happens 5 to 6k, is that in every gear? Hold 1st, then 2nd, then 3rd (OD off obviously). Does it act excatly the same through gears. Do you have an sct tuner?
Definitely change your plugs!!! 25k and a couple autocrosses, change them. No to tps, doubt maf prob.

It acts the same in 1st and 2nd. Although I've rarely had it to 5000-6000 rpm in 3rd. It actually happens at a lower RPM like around 4000. Last summer I changed plugs, cleaned the MAF changed the PCV and cleaned the throttle body with no improvement. I damaged the gasket between the throttle body and the intake so I replaced it with a new gasket, so I'm good there.

I have an SCT tuner and had some dyno tuning done by DB Performance in Rogers, MN. So I'm thinking babbage is onto something. I might schedule some time with them this spring to see if we can sort it out.

Thanks for the help, Curt.

[Dragcity]

Kinda sounds like some sort of overlap in the shift schedule or maybe the tune is cutting fuel at those RPMs? Sounds like a tuning issue to me, regardless.

[ctrlraven]

Seafoam in the gas will lower octane, it's not a fuel octane booster so just remember that if you go WOT a lot and have a good amount of timing advanced.

[crouse]

I ran an Auto-X event on Sunday. I had a little less than 1/2 tank of gas. The course was mostly right turns. I noticed on a big sweeping right turn and on the slalom that it seemed like I was running out of gas. It would sputter and then it would go. On the straights, it was fine and it seemed like left turn were not an issue. I don't remember anything like this from last year and I always start with about 1/2 tank of gas. I assume the fuel pickup is in the center of the tank and not to one side? Any help would be appreciated. Thanks, Curt

[ctrlraven]

Yes it is in the center.

[Marauderjack]

Seafoam in the gas will lower octane, it's not a fuel octane booster so just remember that if you go WOT a lot and have a good amount of timing advanced.

I don't have a dog in this fight but......who told you this???:confused:

Almost any lower boiling flammable liquid you add to gasoline will slow the flame front effectively increasing octane but 8-16 ounces of anything other than water shouldn't do diddly squat!!:shake:

[Blackened300a]

http://www.autopartslib.com/wp-content/uploads/2010/04/Mercury-Marauder-Fuel-System-Fuel-Tank-Components-Parts-Diagram.png

According to this, the pump will sit directly in the middle. Have your fuel pressure and fuel volume checked then go from there. Does your pump sound abnormally loud or any hard starts when its cold?

[JoeBoomz]

Was this ever resolved? I know you said it happens in 1st so this suggestion might be way off, but check for TC lockup. This will cause a dip in RPM's and your load values which sounds exactly like you're describing (though you aren't supposed to be able to lockup TC in 1st).