Hesitation/Miss under WOT from 3-4k?

[BAM614]

Just picked up my SHO this past weekend and noticed it's not as fast as my buddies 94, and also noticed its if I floor it through 3-4k it seems to stutter or something. It seems down on HP all around, but its definitely hesitating/missing in that range.

I have all records, 60k maintenance was done 5 years ago/8k miles ago along with plugs/wires/etc etc. Car was very well maintained from what I can see so I'm not sure where to start.

Car is bone stock, 5spd, 65k miles on the odo.

Thanks
Matt

Oh yeah, I did search but didn't see anything directly relating to my issue.

 

[Eric VerValin]

Cam sensor maybe? I'd also be suspect of the 02's maybe. Cleaning the MAF is the cheapest option tho.


I've seen all three of those pop up and not give a code but changing it sure did help. See if your car has any codes yet. That'll be your first step for sure. A paperclip will be your new best friend.


Oh another thing that may also help that is cheap is the fuel filter, check infront of the rear passenger side wheel and see how old that thing looks. These are a few things I can think of off the top of my head.


But then again... what about your buddies car you are comparing this too... I'm thinking his Y pipe and that UDP is chaning the way the car gets over that 3-4k **** there before the secondaries open. Also is his chipped in anyway? That changes a lot too over that bump in the powerband.

 

[BAM614]

Cam sensor maybe? I'd also be suspect of the 02's maybe. Cleaning the MAF is the cheapest option tho.


I've seen all three of those pop up and not give a code but changing it sure did help. See if your car has any codes yet. That'll be your first step for sure. A paperclip will be your new best friend.


Oh another thing that may also help that is cheap is the fuel filter, check infront of the rear passenger side wheel and see how old that thing looks. These are a few things I can think of off the top of my head.


But then again... what about your buddies car you are comparing this too... I'm thinking his Y pipe and that UDP is chaning the way the car gets over that 3-4k **** there before the secondaries open. Also is his chipped in anyway? That changes a lot too over that bump in the powerband.

Yeah, I found out how to check codes and such last night while googling, so I'm going to try that today. Luckily I have another car that I can just swap parts with to see if anything helps.

I mean I know a ypipe and udp is supposed to be good mods, but his car is downright mean compared to mine, all the way through the powerband, start to finish. It'd just ** the crap out of mine if we ever lined up. As far as he/i know it isn't chipped, but I don't think he's checked either.

The best way to describe his is it feels more 'raw' power, where mine feels more subdued or 'glazed over'. Like you can feel mine accelerate its just not like any special. Funny thing is I swear it feels faster with partial throttle than with WOT.

Will check those things and report back this afternoon.

Thanks!

 

[Jh8990]

definatly replace those even if they are not throwing codes, if you can. you will be happy if you did in the future. as for acceleration that restrictive stock y-pipe is definatly holding you back.

-Justin

 

[Vnuk1]

Cleaning the MAF is the cheapest option tho.

^^THIS^^ or try unplugging it and driving it to see if it has crapped out completely..

 

[BAM614]

I'm happy to report the SHO is a new animal after a few hundred dollars and ALL day in the garage.

Cleaned the MAF and it made everything all better, it pulls smooth 100% and REALLY picks up in the secondaries!

Put an old K&N cone filter I had from a previous car on and it sounds awesome now, probably try and relocate it into the fender soon.

Went to replace the rear pads/rotors as they were not wearing correctly (small 1inch groove in the middle of the rotor, and major rust build up everywhere else on the rotor).

Anyways that turned into needing a passenger rear caliper because it wouldn't compress.

Then that turned into needed BOTH rear flex lines as they were collapsed and wouldn't get ANY fluid to the calipers, found this out when trying to bleed the new caliper. Fun! NOT!!!!

Then I moved to the front and bought MOOG oem springs and cut 2 coils off them to drop the front a bit and in the process noticed the drivers side axle boot was torn so I bought a new axle and replaced it as well.

BUSY day in the garage and I'm BEAT.

Cliff notes for those that need it:
New rear pads/rotors led to new caliper which lead to new flex lines
Cleaned MAF = excellent performance again.
Dropped the front a couple inches.
Installed new drivers axle.



Thanks for all the help guys, really appreciate it!

 

[SHOhopefull]

Hmm... I cleaned the MAF and it made no difference...O2's?

 

[BAM614]

Figure I'll post in here to see if anyone wants to chime in, rather than waste another post about it. I did search and as you all probably know, it gave tons of info but wasn't really all that helpful...

Anyhoo...I've got all records from the original owner on my car, and I'm due for an oil change. Just rolled 66k last night, and the PO had all dealer oil changes done, motorcraft filter and 5w30 oil, i'm assuming regular because it doesn't specify, just lists the part number and 5w30....

So should I switch to synthetic now and keep using the motorcraft filter, or keep doing what he was doing?

I assume I'll be harder on the car than he was (he was in late 60s, early 70s) and when I took it on the test drive and mentioned the hesitation/not pulling hard above 4k his answer was, oh, I'm not sure, I haven't taken it that high in ages. LOL.

So I won't say I'll beat the shit out of it but I'll definitely enjoy the pull and sound of the secondaries opening quite often...

A common answer was Castrol GTX, didn't mention synthetic or what, and also seemed a bunch of people mentioned using 10w30...but I don't know much about oils so I'm not sure what difference this makes.

What do you guys think? I'm gonna do my own oil change this weekend and also am debating on doing rod bearings at the same time...since I'm reading mixed opinions on that as well.

Best deal I found today was 5quarts of pennzoil full synthetic for $20 and a motorcraft filter for $3.27. $24 for a full syn oil change is a deal! Do it?

Thanks
Matt

 

[Eric VerValin]

You can get Mobil 1 5 quarts at Walmart for $20... they make 4 quart jugs and sell those at AZ and Advance / Orileys for about $24. Stick with the Motorcraft filter... FL-1A if you want a little larger one.


And don't feel bad about stepping on the gas, its what the car was made to do.


Glad that MAF cleaning worked out for ya! Gotta love the easy fixes!

 

[Eric VerValin]

Hmm... I cleaned the MAF and it made no difference...O2's?

That is where I would probally guess next man. Amy's car was a little "poochy" I like to call it, and the O2's woke hers up. And she didn't have any codes yet pointing to the o2's... I'm almost thinking I'm due for a set too now that you say something..


Good thing we only got 2 and not 4..

 

[jonheese]

My usual suspects for hesitation/reduced power (and actions to resolve), in order of likelihood from most to least likely:

1. Oil/water in plug wells (soak out w/tampons, replace plug well seals)
2. Dirty MAF (clean w/electrical component cleaner)
3. Old/bad plugs and/or wires (replace)
4. Old/clogged fuel filter (replace)
5. SPOUT accidentally unplugged (plug back in)
6. Crank cancer (http://wikisho.com/krazgeo/CrankCancer.html)