low boost low power

superdadsc

Registered User
When driving the car I am only seeing 7 to 10 max boost at WOT. The car will start to sputter at around 4K. When on the highway in 5th at 70mph if I floor it it goes REALLY slow with about 3 to 4 lbs of boost.

Mods
fresh rebuild 4k miles
94/95 blower ported/plenum
ported heads
exhaust manifolds ported
FMIC
70TB
MAF ?
36lbs injectors have 57 need to put them in
mild cam
10% JS
5% SC
underdrives
Bianary tune moetes QH
true Duel exhaust
New O2 sensors
New cats
The car ran very strong when I first bought it. Seemed a little faster than my 95 that dyno'ed at 270rwhp. Then I had a surging bucking issue. Replaced DIS and I found out the MAF was on all the way. It went away. Then I had coupler issues. It also has a custom raised top and the coupling started blowing of at WOT. Scared the crap out of me the first time it went BOOM! Fixed the issue and now I have loss of power. I put it on a smoker no leaks.
Have new plugs that I need to put on with new wires.

I have new MP springs, seems like it might be slipping still. Those tensioners were clocked and I was wondering if the springs or the tensioner wasn't working properly. Switched tensioners from my 90 and same issue.

From reading I was looking at and checked
IC leaks
Tensioner
SC fluid level
new JS to SC belt, JS to crank belt.
Have shorter belt for JS to SC. The belt is tight.

The accessory belt is not so tight and needs to be replaced. Have AC delete so the stock belt I bought won't work need to find the right size. Can this cause slipping cause a surge at the top end?

Aby suggestions?

Gonna go down soon and see Mike Puckett maybe he will see something.
 
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I move the linkage on the bypass valve and it seems to move in a full range of motion. I can hear a suction sound when doing so. Is that normal?

Also on the bypass vavle. On the ouside of it is a male end coming out toward the drive side that the vaccum line connects to. Mine is pointed downward at an angle. Is that normal, just wondering if it got bent downwards?

Could my MAF be bad?

Clueless in Georgia!:eek:
 
Betting it's a coupler issue. There is no leak with the smoker as there is no PSI in the system. Double check the couplers and install T bolt bands.

Speaking of popping those. Should hear them about about 45psi let go. ;)
 
most sputtering issues are spark or fuel related

because of your sputtering you wont see full boost so it might not be a boost related issue

does all your data on your editor check out?

what happens when you go 3/4 throttle all the way up the rpms?

does it only sputter @ 4k+ or does it do it at 70mph in 5th too?
 
you have a ? next to the MAF. Is it calibrated to your 36 injectors if not this car is loading up with fuel especially under load and boost and is probably drowning in fuel.
 
most sputtering issues are spark or fuel related

because of your sputtering you wont see full boost so it might not be a boost related issue

does all your data on your editor check out?

what happens when you go 3/4 throttle all the way up the rpms?

does it only sputter @ 4k+ or does it do it at 70mph in 5th too?

I was thinking the same as I read through the posts. Later posts had good pts. Assuming all is good, bad spark plug wires can cause all kinds of trouble. I had a new set of Motorcraft be bad. I replaced with a set of Beldon wire from NAPA with good results.

yes when you manually work the bypass valve it will make a suction noise. You should also be able to see it open and close if you grab the throttle linkage with your hand and goose it a couple times. Also fix that belt issue with the coorect size. With all cares cover the basics before starting the wild goose hunt. It just makes sense to eliminate the known possibilities.
 
At one point the car ran great. Tune is for 36lbs. It only sutters at WOT. 1/2 throttle or so it runs smooth thru rpm range.
No suttering at 70 in 5th, just a dog.

I have not gotten to the plugs and wires as far as changing them but what ones on there are tight.

I need to figure out what I need to do to get this hooked up to my laptop in regards to the QH. I am sure I need some software and a wide band a/f gauge etc.
Need more money still recovering from everything else.

Thanks there is one coupling or 2 without t bands. need to check that out today.
 
Not checking your plugs is ignoring an easy diagnostic step. I've had the same problem, twice. Both times, it was the spark plugs. The last time, one plug was broken in half. Here I was stressing about all kinds of repair scenarios, turns out all I needed was a new set of spark plugs. If this same issue ever shows up on my car again, the 1st thing I'll check is the plugs & wires.
 
Another observation I had with mine was a leaky IC pipe involved a lot more violent sputtering than either the cracked/fouled plugs/wire

Keep us posted
 
Well I double checked the tubes, couplers etc. There was a T-band that was tight, as it was tight, hard to turn but the clamp wasn't tightening so I replaced the T-band.

Definetly made an improvement. Now I have 11lbs of boost and there is no hesitation.

Still seems low on power and boost is low for 15% OD. Was about 15lbs with 10%.

I will spend more time on it tomorrow as I am quessing it all lies in the IC.

I noticed oil in the tubes.:eek: Is this normal or is there a larger issue.:mad: My quess would be blow by, pressure related but I will have to search. Maybe I need a catch can or something for it.
 
Problem fixed. I had some tband clamps that weren't working properly. They looked tight but wouldn't tighten real tight causing a leak under load! Thanks everyone for your help and Birds of prey for pointing me to the issue! Started running better but still low boost and the it got worse. So this morning I took all the tubes off and started from scratch and double,triple checked everything working from one end to the other. Just took her out for a ride and now she feels like a little beast again.:D Car has been having issues for a month or two so it is really nice having it run right.

Couldn't be a better time as I am meeting up with some 928 guy's and am looking forward to showing them how an SC can run! SNOBS!:eek::D
 
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Good to hear all is better! Feels even better when you can fix it yourself. Now get your Binary Editor purchased and enjoy the QH1.
 
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