Go Back   Corvette Forum > C4 Corvettes, 1984 - 1996 > C4 Tech/Performance
Sign in using an external account
Register Forgot Password?
Register Search Today's Posts Mark Forums Read FAQ Vendor Directory
Search
C4 Tech/Performance
L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine Sponsored by
J&D Corvette

Welcome to Corvetteforum.com!
Welcome to Corvetteforum.com.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, at no cost, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, join Corvetteforum.com today!


Corvette Store
 
 
C7 Parts & Accessories
C6 Parts & Accessories
C5 Parts & Accessories
C4 Parts & Accessories
C3 Parts & Accessories
C2 Parts & Accessories
C1 Parts & Accessories
Wheels & Tires
Sponsored Ads
 
 
Vendor Directory
  
Reply
 
 
 
 
Thread Tools Search this Thread
Old 07-04-2013, 08:55 AM   #1
Midnight 85
CF Senior Member
 
Midnight 85's Avatar
 
Member Since: May 2004
Default Need some ideas

Hi all and Happy 4th of July! I am finally getting everything sorted out on my Pro Flo XT project. It turned out the injectors I had were not the size they were supposed to be so I got a set of remans from FIC. 30 lb. set at 43.5 with vacuum disconnected. I now have a huge hesitation when I stab the throttle, if I just roll in to it it just starts pulling & won't stop but if I just hit it hard, be it rolling or sitting still it just won't go. I just need some things to look for that will cause this. If I set the tps down to where it is supposed to be it is real bad, if I set it up to just over 1 volt is gets better but is not eliminated and the high setting causes it's own problems. Timing is at 10 degrees just what the tune calls for, if I try to advance it a bit more it won't run right at all. If you have any ideas let me hear them.
I should add that I had to open the throttle blade more with the new injectors which makes it hard to set the tps down where it is supposed to be.
__________________
Praise the lowered!

Last edited by Midnight 85; 07-04-2013 at 08:58 AM.
Midnight 85 is offline   Reply With Quote
Old 07-04-2013, 10:42 AM   #2
cumbercr
CF Senior Member
 
cumbercr's Avatar
 
Member Since: Mar 2008
Location: Santa Maria CA
Default

I wonder if the tune tables for accel enrich need to be looked at.
cumbercr is offline   Reply With Quote
Old 07-04-2013, 12:59 PM   #3
THE 383 admiral
CF Senior Member
 
THE 383 admiral's Avatar
 
Member Since: Sep 2010
Location: East Nassau NY
Default

that's Strange I'm sure the Pro Flow will end up similar to a HSR 10 deg was just a starting point... 12 -16 deg on my previous 89 build... made a huge difference...
THE 383 admiral is offline   Reply With Quote
Old 07-04-2013, 02:17 PM   #4
Midnight 85
CF Senior Member
 
Midnight 85's Avatar
 
Member Since: May 2004
Default

I did some more playing around and I noticed the fuel pressure would either stay the same or even drop a few pounds when I would rev it. I jacked the pressure way up and all the problems went away but I had 70 lbs of pressure. If it is the pump, would I be able to raise the pressure that much? And if it is the regulator how can I be sure?
Midnight 85 is offline   Reply With Quote
Old 07-04-2013, 02:36 PM   #5
THE 383 admiral
CF Senior Member
 
THE 383 admiral's Avatar
 
Member Since: Sep 2010
Location: East Nassau NY
Default

Ok it would appear your pump is weak.. your adjustable regulator is doing its job...
Maintaing pressure untill you command more fuel.. 70# would just about double your injector flow! What happens when you pull the vacuum from the regulator? An no if you pulled the regulator you would not have pressure..

Last edited by THE 383 admiral; 07-04-2013 at 02:41 PM.
THE 383 admiral is offline   Reply With Quote
Old 07-04-2013, 02:38 PM   #6
Midnight 85
CF Senior Member
 
Midnight 85's Avatar
 
Member Since: May 2004
Default

Thanks, that's what I was thinking but wanted to be sure before I bought the wrong part. Looks like a new Walbro is in order.
Midnight 85 is offline   Reply With Quote
Old 07-04-2013, 02:46 PM   #7
THE 383 admiral
CF Senior Member
 
THE 383 admiral's Avatar
 
Member Since: Sep 2010
Location: East Nassau NY
Default

Did the incorrect size injectors have the same hesitation??
THE 383 admiral is offline   Reply With Quote
Old 07-04-2013, 03:07 PM   #8
Midnight 85
CF Senior Member
 
Midnight 85's Avatar
 
Member Since: May 2004
Default

No they did not, this all started with the new injectors.
Midnight 85 is offline   Reply With Quote
Old 07-04-2013, 03:33 PM   #9
THE 383 admiral
CF Senior Member
 
THE 383 admiral's Avatar
 
Member Since: Sep 2010
Location: East Nassau NY
Default

Hmmmm.. that is not a good sign... what are the specs on the remans.. & flow chart tested?? What about your tune????
THE 383 admiral is offline   Reply With Quote
Old 07-04-2013, 03:34 PM   #10
383vett
CF Senior Member
 
383vett's Avatar
 
Member Since: Apr 2003
Location: moraga ca
Default

With my ACCEL dfi management system there are a couple adjustments similar to the throttle squirt of a carburetor. Sounds like you need to find this and increase the acceleration enricbment
383vett is offline   Reply With Quote
Old 07-04-2013, 03:34 PM   #11
Midnight 85
CF Senior Member
 
Midnight 85's Avatar
 
Member Since: May 2004
Default

30 lb remans from FIC and a pcmforless tune and another tune from another source, both act the same.
Midnight 85 is offline   Reply With Quote
Old 07-04-2013, 03:45 PM   #12
THE 383 admiral
CF Senior Member
 
THE 383 admiral's Avatar
 
Member Since: Sep 2010
Location: East Nassau NY
Default

Can you Data log???
If you where close i would test with my 30# ads super injectors..
You need the complete spec sheet for the injectors and compare your tune constants
THE 383 admiral is offline   Reply With Quote
Old 07-04-2013, 03:45 PM   #13
Midnight 85
CF Senior Member
 
Midnight 85's Avatar
 
Member Since: May 2004
Default

Quote:
Originally Posted by THE 383 admiral View Post
Hmmmm.. that is not a good sign... what are the specs on the remans.. & flow chart tested?? What about your tune????
Quote:
Originally Posted by 383vett View Post
With my ACCEL dfi management system there are a couple adjustments similar to the throttle squirt of a carburetor. Sounds like you need to find this and increase the acceleration enricbment
You both may be on to something, it does act like it needs a pump shot. I pulled the regulator off & took it apart to see if there was anything wrong inside, it looks good. I really find it hard to believe that two different tunes would both act pretty much the same, the pcm tune is calling for more fuel than the other one but it doesn't seem to make any difference which tune is in the ecm.
When I did have the old injectors in the engine I took it to Bloomington Gold and I had been getting a code 24 for lean then so I raised the pressure to try & compensate but it did no good I still had a check engine light coming on all day.
The fact still remains that when I rev the engine the pressure either stays the same or drops a few pounds, if it was in the tune this would not happen would it?
Midnight 85 is offline   Reply With Quote
Old 07-04-2013, 03:51 PM   #14
Midnight 85
CF Senior Member
 
Midnight 85's Avatar
 
Member Since: May 2004
Default

Quote:
Originally Posted by THE 383 admiral View Post
Can you Data log???
If you where close i would test with my 30# ads super injectors..
You need the complete spec sheet for the injectors and compare your tune constants
I can datalog and that will probably be my next step once I exhaust all other possibilities. I have complete faith in FIC's injectors and I just have a gut feeling it is the pump. I changed the filter already this morning hoping that might be the cause but it was not.
Midnight 85 is offline   Reply With Quote
Old 07-04-2013, 04:12 PM   #15
THE 383 admiral
CF Senior Member
 
THE 383 admiral's Avatar
 
Member Since: Sep 2010
Location: East Nassau NY
Default

You are correct your pressure is manually controlled from the AFPR.. two upgrade tunes & 2 sets of injectors most likely lean. Just for giggles email your tune to check your constants, PE, LV8, accel enrich tables..
THE 383 admiral is offline   Reply With Quote
Old 07-04-2013, 04:31 PM   #16
Midnight 85
CF Senior Member
 
Midnight 85's Avatar
 
Member Since: May 2004
Default

I just went out & put the regulator back on, I set it at 39 lbs. vacuum off, just for the purpose of testing. Vacuum on, 38 lbs. and dropping 1-2 lbs when I rev the engine. No climbing of pressure under load, (revving). It used to climb between 5-10 lbs when I would rev the engine. My neighbors are about ready to lynch me since I am messing around making noise while they are enjoying the holiday so I am done for today.
Midnight 85 is offline   Reply With Quote
Old 07-04-2013, 04:34 PM   #17
cumbercr
CF Senior Member
 
cumbercr's Avatar
 
Member Since: Mar 2008
Location: Santa Maria CA
Default

You mentioned having trouble adjusting your TPS. One of the accel enrich tables adjusts fuel using delta TPS.
cumbercr is offline   Reply With Quote
Old 07-04-2013, 04:36 PM   #18
THE 383 admiral
CF Senior Member
 
THE 383 admiral's Avatar
 
Member Since: Sep 2010
Location: East Nassau NY
Default

Fuel pump just like i mentioned first *****Happy 4th*****
THE 383 admiral is offline   Reply With Quote
Old 07-04-2013, 06:49 PM   #19
Midnight 85
CF Senior Member
 
Midnight 85's Avatar
 
Member Since: May 2004
Default

Quote:
Originally Posted by cumbercr View Post
You mentioned having trouble adjusting your TPS. One of the accel enrich tables adjusts fuel using delta TPS.
The reason I was having trouble setting the tps is because it is not really adjustable so I had to elongate the holes so it would rotate enough to set it. Then with the new injectors I had to set the idle up so much that I could not adjust it down far enough to be in a reasonable range. This should go back to normal once the fuel pressure is right again.




Quote:
Originally Posted by THE 383 admiral View Post
Fuel pump just like i mentioned first *****Happy 4th*****
Thanks, I have a new Walbro ordered.
Midnight 85 is offline   Reply With Quote
Old 07-04-2013, 07:17 PM   #20
bjankuski
CF Senior Member
 
Member Since: Sep 2001
Location: Glenbeulah Wi
Default

This is not a fuel pump problem, it is a tune problem. You need more acceleration fuel. The pressure will drop when you rev the engine in the driverway because your intake vacuum goes up. On the road at wot the vacuum will drop and pressure will go up. You already raised pressure to 70the psi, if the pump was shot that would not happen. One other note doubling fuel pressure only raises output 41%.
bjankuski is offline   Reply With Quote
Old 07-04-2013, 07:17 PM
 
Go Back   Corvette Forum > C4 Corvettes, 1984 - 1996 > C4 Tech/Performance
Reload this Page Need some ideas
 
 
 
Reply


Thread Tools Search this Thread
Search this Thread:

Click for Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
1992 misfiring badly at autocross vinniemc C4 Tech/Performance 4 07-08-2014 03:22 AM
IAC count on modded engines Midnight 85 C4 Tech/Performance 4 05-01-2014 09:54 PM
Possible to restore factory A6 Tranny settings after tune? NinjaBum C6 Corvette General Discussion 5 04-05-2014 11:37 PM
How to Set up 1984 C4 Crossfire TB's & TPS ProjectC4 C4 Tech/Performance 1 03-23-2014 08:40 PM
1984 Vette Crossfire Won't stay running wolfsinc C4 Tech/Performance 35 08-22-2012 05:43 AM


All times are GMT -4. The time now is 06:44 AM.


Emails & Password Backup

Search Engine Friendly URLs by vBSEO 3.5.2