I own a 1990 LX convertible and dropped a new GT 40 motor in it with GT 40 intake manifold and put 30 lb injectors and calibrated mass air sensor and the motor is still surging. I was told it was because I had stock injectors but same problem with the 30 lb injectors. Ford Tech line said to measure the vacuum pressure at 900 rpms but my car does not idle steady surging up and down below about 1200 rpms. I have the fuel pressure at 40-42 lbs and when I did manage to take a pressure reading, it seemed sufficient. Ford said there is idle recalibration download I can et them to send me but didn't get it from them yet. Maryland performance said it is a common problem and a plug in the intake mainfold you can install that can help. Seems like a band aid for a problem. As I said it seems not to surge if I hold the gas pedal to about 1200 rpms.Any help here?
Surging problem
- Thread starter action
- Start date
gambit90lx
New Member
- Apr 21, 2007
- 8
- 0
- 1
me too
i have a gt40 crate engine also with 30# injectors and a c&l mass air meter and i too am having surging issues sometimes not all the time....the thing sometimes almost cuts off and then surges up to about 1300 and then back to almost cutting off...then sometimes it runs perfect.....what kind of maf are you using i am using a c&l and i have heard alot of people saying almost the same thing
i have a gt40 crate engine also with 30# injectors and a c&l mass air meter and i too am having surging issues sometimes not all the time....the thing sometimes almost cuts off and then surges up to about 1300 and then back to almost cutting off...then sometimes it runs perfect.....what kind of maf are you using i am using a c&l and i have heard alot of people saying almost the same thing
ShortThrow50
Member
I have the same problem with my trick flow h/c/i and am running 24 pound injectors with calibrated C &L maf. I heard c &l ar junk. Mine only does it for about a minute after start up. Soon as I get the cash im gonna buy a diff maf
I am requesting this thread to be moved to the general tech board, as you guys won't get much help here...
http://forums.stangnet.com/showthread.php?t=698148
JR has done a great job with this thread...
jason
http://forums.stangnet.com/showthread.php?t=698148
JR has done a great job with this thread...
jason
My first question would be 30# injectors? That's a little much I would think, how much horse does the crate GT40 engine put out stock? What throttle body are you using? I'm running a C&L and don't have a issue. I also have a tweecer with a custom tune I created. I had a warm starting surge issue, but I checked everything then realized that it's just plain to rich, so I cleared the start-up table (used as a multipler against the base OL fuel table) and then set the global fuel multipler to 1 (lower than 1 makes it richer, higher than 1 makes it leaner, 1 states just use what's in the OL table). This seemed to fix the issue.
So basically my thoughts are that first your running really rich because the computer thinks you have 19# injectors and the computer doesn't know the proper amount air coming through the TB as well as the correct MAF air flow thus, making it rich, (then the computer uses timing to keep the car running as a secondary if the idle drops to low) and your idle comes back then your rich again and it starts all over. (surging)
This is all assuming you are running a stock computer, sounds like you need to go and get it customed tuned to work properly.
So basically my thoughts are that first your running really rich because the computer thinks you have 19# injectors and the computer doesn't know the proper amount air coming through the TB as well as the correct MAF air flow thus, making it rich, (then the computer uses timing to keep the car running as a secondary if the idle drops to low) and your idle comes back then your rich again and it starts all over. (surging)
This is all assuming you are running a stock computer, sounds like you need to go and get it customed tuned to work properly.
Similar threads
