HIGH RPM HESITATION NOW

M

MSTANG5O

New Member

Aug 7, 2003

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West Chicago

Apr 11, 2004

#1

• Apr 11, 2004

• #1

I have a '92 5.0 with the following mods: 1.7 roller rockers, accel 48,000v coil, adj. fuel press. regulator, cold air intake, 9mm motorsport wires, BBK off-road h-pipe, flowmasters, 3.73 gears, pro 5.0 shifter. Here's my problem. I installed the fuel press. reg. and the coil at the same time and now the car feels like it picked up 10 hp untill I hit 4500 rpm. It pulls hard untill then and seems to "run out of motor" sort of speak. It stumbles at high rpm and makes no more power. The fuel press. with the stock regulator was 35 with the vac line on. I set the new one the same to start with. This problem is new since the coil and reg. install. the timing is set at 12. I was low on gas when i test drove it and it had shell gas in it. I filled up with Amoco and it got a whole lot better, but not gone. Any ideas would be appreciated!

 

M

MSTANG5O

New Member

Aug 7, 2003

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West Chicago

Apr 11, 2004

#2

• Apr 11, 2004

• #2

BTW - cap, roter, plugs and wires are all new.Thanks

 

B

b1gp1mp1n247

New Member

Feb 19, 2004

159

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Pittsbrugh, PA

Apr 11, 2004

#3

• Apr 11, 2004

• #3

i would say fuel pressure is set too low. im running 42 vacuum on. 35 seems a bit low. also what plugs are you running???

 

M

MSTANG5O

New Member

Aug 7, 2003

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West Chicago

Apr 11, 2004

#4

• Apr 11, 2004

• #4

Running standard autolites

 

M

MSTANG5O

New Member

Aug 7, 2003

12

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0

West Chicago

Apr 11, 2004

#5

• Apr 11, 2004

• #5

I cranked the pressure up a bit and did not seem to help. reset at 35 vac. on

 

M

MSTANG5O

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Aug 7, 2003

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West Chicago

Apr 11, 2004

#6

• Apr 11, 2004

• #6

I have ohm tested all injectors and they passed!!

 

M

MSTANG5O

New Member

Aug 7, 2003

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West Chicago

Apr 11, 2004

#7

• Apr 11, 2004

• #7

LOL...all the little things I forgot to add..I also have a 255 fuel pump if it matters.

 

B

b1gp1mp1n247

New Member

Feb 19, 2004

159

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Pittsbrugh, PA

Apr 11, 2004

#8

• Apr 11, 2004

• #8

id just check to make sure all plugs are in tight and wires are connected right. how is the idle??

 

M

MSTANG5O

New Member

Aug 7, 2003

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West Chicago

Apr 11, 2004

#9

• Apr 11, 2004

• #9

Idle is perfect. No surge or hesitation. All vacuum lines are good. engine runs good and strong untill 4500 rpm.

 

ECU5.0

Banned

Jan 10, 2004

1,803

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raleigh, nc

Apr 11, 2004

#10

• Apr 11, 2004

• #10

it could just be running out of steam. if you have stock intake. the 1.7 rockers are letting out more air than is coming in. i dont know thats just my guess.

 

P

PRO50SC

New Member

Dec 28, 2003

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Olney, Maryland

Apr 11, 2004

#11

• Apr 11, 2004

• #11

MSTANG5O said:

BTW - cap, roter, plugs and wires are all new.Thanks

Click to expand...

What about the fuel filter?

 

M

MSTANG5O

New Member

Aug 7, 2003

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West Chicago

Apr 11, 2004

#12

• Apr 11, 2004

• #12

Fuel filter is new.

 

P

PRO50SC

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Dec 28, 2003

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Olney, Maryland

Apr 11, 2004

#13

• Apr 11, 2004

• #13

MSTANG5O said:

Fuel filter is new.

Click to expand...

Installed in the right direction? All this replace to try to cure this problem?
What kind of coil? Have you put the old one back on to rule the new one out and same for the regulator? Any time you make a mod and the car runs worse then when you started, always try going back if it's easy enough to do.

 

M

MSTANG5O

New Member

Aug 7, 2003

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West Chicago

Apr 11, 2004

#14

• Apr 11, 2004

• #14

I have to pull the plenum to swap the regulator, so forget that. Ill try putting the stock coil back in, but I have a brand new Accel coil in now.It might be defective, but not likely.

 

M

MSTANG5O

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Aug 7, 2003

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West Chicago

Apr 11, 2004

#15

• Apr 11, 2004

• #15

The car runs much better all the way around after the mods with the exception of the high rpm stumble. Pulls real hard untill about 4500-4700 rpm. I lowered the fuel pressure a little and it seemed to help, but now it's lower than it was stock. Stock was 35 vac. on. Now it's 30 vac. on. I can try going lower, but why would lower fuel pressure help that? It also seems to pull harder with lower fuel pressure. Any suggestions or comments are appreciated! Thanks everyone!

 

ECU5.0

Banned

Jan 10, 2004

1,803

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raleigh, nc

Apr 11, 2004

#16

• Apr 11, 2004

• #16

it pulls harder because its running lean which makes more power....but is bad for the engine because it runs hotter and other reasons which i dont know. i was having the same problem you are having for a while and couldnt figure out until this weekend when my friend looked at it and noticed my #3 wire had been sittin on the header and wasnt getting spark. stupid me, but you might just want to check all the wires to see if thats the case.

 

P

PRO50SC

New Member

Dec 28, 2003

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Olney, Maryland

Apr 11, 2004

#17

• Apr 11, 2004

• #17

What plugs are you using and what are they gapped at?

 

M

MSTANG5O

New Member

Aug 7, 2003

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West Chicago

Apr 11, 2004

#18

• Apr 11, 2004

• #18

Gapped at .054..stock

 

M

MSTANG5O

New Member

Aug 7, 2003

12

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West Chicago

Apr 12, 2004

#19

• Apr 12, 2004

• #19

PROBLEM SOLVED! Accel coil was no good. second one I've had problems with. put the stock coil back in and the car runs fine. No hesitation. Set the fuel pressure down to 40 vac off...30 vac on. Runs great, pulls hard all the way up. Got an MSD blaster coil on the way. Maybe I'll have better luck with it. Will post results with MSD coil in. If anyone has any ideas of why it would run worse at top end with a higher voltage coil rather than the stock one (other than the Accel was bad) let me know. Thanks guys!

 

T

tdo9250

New Member

Mar 23, 2004

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Apr 12, 2004

#20

• Apr 12, 2004

• #20

Man, I have been racing cars for a long time. Screw all Excell and MSD equipment. If your coil needs to be replaced, go to the dealer and get a new one. There is a big difference in the quality of Factory parts vs most garbage aftermarket parts. If you need further proof, buy a factory distributor cap and compare it to a pep boys cap.