420 Breaks up at higher RPMs

[rocker_topper]

ok just got finished with a complete 420A rebuild in my 98 eclipse. Got it running and it sounds great and runs great as long as im not getting on it. If i ever get over around 4,000 or so RPMs it starts to sputter a little bit. I feel confident its a spark problem. Computer throws no codes and Idle and low rpms are great. Car still pulls at higher RPMs just breaks up a little bit. Pulled plugs, checked the gap and regapped. gapped at .050 and replaced. Upon running it down the road the breakup changed to around 5,000 rpms. dont really think its the gap anymore so any ideas guys? getting ready to sell this thing and I want this thing right before i do so people dont try to low ball me(even though I know they are gonna )

74 views and not 1 reply? nobody has any ideas on this? Im at a loss here guys . If you guys got any suggestions let me know this thing has gone to hell and back and runs good now just this one little problem and i really wanna get it fixed cause this is my first engine rebuild and i think ive done a good job considering im not a mechanic . TY HAYNES repair manuals and DSMtuners.com

 

[TheEagle]

IK it may be frustrating. I havn't been on in awhile myself. My question would be hows your fuel pressure holding up.

If that's not it, I'd be looking at your spark wires and ignition coil unless those were fine beforehand.

 

[Fotowntalon]

Did you do a stock rebuild? If not how are you tuning?

 

[Ricardo18]

...What do you mean you're gapping the plugs? If you have to gap them you most likely don't have the right ones. These cars aren't carb'd.

 

[rocker_topper]

Did you do a stock rebuild? If not how are you tuning?

yes stock rebuild

IK it may be frustrating. I havn't been on in awhile myself. My question would be hows your fuel pressure holding up. havent checked the fuel pressure but it doesnt seem to break up if im standing still just revving. It seems like its only under a load

If that's not it, I'd be looking at your spark wires and ignition coil unless those were fine beforehand.

the coil is new, plugs are new, and wires are an old set. I might try changing them out. Any suggestion on a good set for a decent price?

...What do you mean you're gapping the plugs? If you have to gap them you most likely don't have the right ones. These cars aren't carb'd.

I don't even know what to say to this . The champion plugs im running in them require a gap of .050". Carbuerated engines arent the only engines whos plugs need to be gapped. Not trying to be rude, but im pretty sure these plugs do require gapping. My haynes repair manual, and my all-data both says these plugs require a gap of 50 thousandths of an inch and they came gapped at around 30 thousandths of an inch, thefore i would have to gap them to .050".

 

[Fotowntalon]

50 sounds a little high, I gap my to .065 though, granted I am using a creaming demon coil. Are you using coppers?

 

[96 420a-t]

I ran 40 in my 420a. But look at you furl pressure and wires. Best bet for you.

 

[rocker_topper]

50 sounds a little high, I gap my to .065 though, granted I am using a creaming demon coil. Are you using coppers?

yes copper plugs with the factory coil.

I ran 40 in my 420a. But look at you furl pressure and wires. Best bet for you.

ill try regapping to 40. When i first pulled them they were around .030 and it broke up at 4000 then I gapped to .050 and it stopped breaking up at 4000 and started breaking up around 5000. Also how man PSI of fuel pressure should I have for referance when I check it out.

 

[TheEagle]

the manual on the 420a calls for .05 if I remember?

http://www.dsmtuners.com/forums/attachment.php?attachmentid=120188&d=1300040674

Nevermind, found the link.

 

[rocker_topper]

the manual on the 420a calls for .50 if I remember?

http://www.dsmtuners.com/forums/atta...8&d=1300040674

im pretty sure its .050 cause a half inch is a huge gap!!!! and its a manual tranny BTW in case i didnt mention that before.

 

[TheEagle]

Haha thank you for catching that. I was thinking about when last I had to find the spark plug page.

 

[Ricardo18]

What I'm saying is the plugs should come pre-gapped if you bought the right plugs. I've never had to gap any plugs after I buy them and never had any issue with loss of power or fuel economy.

 

[rocker_topper]

these plugs fit numerous vehicles and each having thier own "gap spec". They were gapped from the store at .030", and I have since gapped at .050". Now my next step is to check fuel pressure, Although IDK what a suitable amount of fuel pressure would be.

 

[TheEagle]

Only a guess. Its usually never an issue with stock rebuilding but if your running to lean . But I think what a lot of us want to know is what do you mean by "breaks up a bit"? like is there anything substantially noticeable/unique to whats going on. It may help us get a better/more accurate answer.

 

[Tribal_RS_96]

Hey, I'm just coming off my 420a rebuild, everythings smooth over here, 2gnt.com specifies 47-50 psi stock.
2GNT.com - Specifications

Also, when talking about the break up, I would check your vacuum just to make sure, and how old are the wires, I had to replace mine during the rebuild

 

[rocker_topper]

Only a guess. Its usually never an issue with stock rebuilding but if your running to lean . But I think what a lot of us want to know is what do you mean by "breaks up a bit"? like is there anything substantially noticeable/unique to whats going on. It may help us get a better/more accurate answer.

the engine sputters and RPMS drop a bit and then jump back up. only around the 5,000 RPM mark