SUP; guys, got a question, ever since i added my gt 40 intake, bumped timing to 12, car idles better and has more power w/o the iac hooked up,ive tried a diff iac and didnt make a diff, i even replaced wiring harness. dont have any codes accept for the one for egr delete, no vacumm leaks all lines are new. car also has headers and 2 chamber lers.brand new gear drive, msd coil and cap and wires. im thinking its prob not getting enough fuel , so when i unhook the iac it bumps the mixture up?
Did you ever hook the o2 sensors back up?
Yes everything is hooked up except egr delete.
Can I assume that we are working on your 88 Cat? Stock fuel pump? Size injectors?
And I forgot to ask if you have done a base idle reset?
http://sbftech.com/index.php/topic,1031.0.html
Base idle reset was done each time ive changed the iac, fuel pump is stock and injectors are factory psi. idle is ok most of the time but sometimes when cold it will surge for a few seconds, im just wondering why it would idle better and have more power with iac unplugged, im thinking it makes fuel mix richer. or because of my mods injectors are now to small and might have to go to stang injectors.
The IAC just controls idle. Nothing more. Removing it should not increase power.
What size injectors are you running? If it's the stock computer you have to run 14lb injectors.
yea they are the stock injectors 14lbs, im been thinking about changing cam and using a lsc computer and stang 19 lbs injectors.
With a gt40, and assuming HO cam and firing, you really ought to have MAF (calibrated) and 24's 14's aren't even almost close to enough fuel for that. Don't do any WOT pulls if you're fond of your pistons.
No; its a non ho motor, cougars dont come with ho motor. its a so motor with a gt40 intake 65mm tb headers flowmaster, msd ign, air intake kit.
The reason it idles better with the IAC unplugged is because with exhaust, GT40 intake,65mm TB,cold air intake you have exceeded the limits of what the speed density ecm can handle as far as fueling since you have made the engine flow more air in and out with your mods. The ecm is hunting for an idle because its most likely on the lean side. With the IAC unplugged your just taking away the ECM's ability to try and change the idle to stabilize it and its just idling off what ever amount the throttle blade is open on the set screw. Its still running lean with it unplugged and Id be careful with making to many full throttle pulls like this.
Step up to the LSC ecm and 19s at the very least and it should run a lot closer to normal again.
thanx i was figuring it was starving for fuel, im used to carbs lol...i noticed the plugs where more white than tan like usual.
None of ours did, but I'm laying out a common configuration that a lot of guys shoot for. You can't just throw a gt40 and headers on a 150hp SO motor and expect it to be happy, it's speed density for Christ's sake, It operates on a wide set of assumptions. There's a reason guys who mod go for a certain set of parts, it's because they play well together and make good power.
Get yourself some GT40 heads (steer away from P's) for $300, somebody here will probably GIVE you an HO cam if you ask nice and pay shipping. You shouldn't just throw a GT40 on top of E6's and an SO cam. It's not ever going to be happy. You'd have been better off with headers and an HO upper. I've probably still got my 19's in a box somewhere, and with a SD HO EEC, that would probably run pretty happy making around 275, if a little lean at the very top (GT40 heads, HO cam, 19# and HO EEC, GT40 upper and lower). The setup you have now will have slowed your port velocity, and is probably screwing up your MAP reading, skewing it one way or the other, and owing to the greatly increased plenum volume, introduced a nice delay into it's ability to give fast and accurate readings of manifold vacuum. We're only talking milliseconds, but when it's trying to calculate load, a dozen or so ms is enough that it might not ever catch up. It'll just bounce back and forth as it tries to react to and correct for an inaccurate load. If I could guess, your idle is probably happier when you've disabled spark advance, right? With TFI, this would be done by removing the SpOUT connector, I don't know how it's done with your MSD. Spark advance is determined by that load calculation that can't be happy.
thanks for the help sir!!! i figured it was running kinda lean, but im getting no spark knock. im gonna change to h/o cam if i can find one. use the lsc ecm and some 19 lb injectors and go from there, im used to carb cars, im old school...lol if i change to gt40 heads also i will probably have to switch to mass air ive been told.
I found a good deal on a h/o firing order cam its a 270hr cam, for 80.00 never ran. would that work? or is it to agressive for the speed density set up?
You can run GT40 heads and stay speed density, but if you go with any other cam than a stock HO, you must convert to MAF. A couple guys here are running others speed density, but reportedly, selection is critically important. You must have 19# injectors for any HO speed density EEC, anything larger and you MUST convert to MAF and either run a calibrated unit or get a chip with a tune. Post a wanted thread in the marketplace, these guys here will have what you need.
thank you sir!! you have been very helpful, i almost gave up on the fuel infection and went to carb set up. but with all your guys help i should be fine. will post a add, thanks again
shad.
Try this first: http://sbftech.com/index.php/topic,1031.0.html
It should at least idle ok with just an intake swap. You're SURE there are no vacuum leaks correct?
positive, all new gaskets and vacumm lines, plus i checked for leaks, found none.
It doesnt have the problem all the time, drove today ran fine, thats why i thinking everybody is correct in the fact its running to lean,and ive maxed the the factory speed density ecm and 14lb injectors.
How would it have idle problems and run lean AT IDLE from adding an intake manifold (which is THE biggest bottleneck out of all the stock parts whether SO or HO) and a set of headers? For
it to lean out at idle, you would have to add enough air to where the PCM could not compensate for the change; something that would be shown when checking for codes. The specific code would be "Adaptive Fuel Lean limit reached". Code 85. If you've driven the car around and put it under load and not seen it; chances are even less you'll see it at idle (meaning ZERO chance).
You have a vacuum leak. It's a minor one. I wouldn't be at all surprised if it was the shaft seals on the throttle body.
FWIW -- 14 pound injectors would probably handle close to 200 HP at the stock pressure PROVIDED THERE IS ENOUGH FUEL PUMP TO FEED THEM. If you do find a fuel issue with the combo you described, look at the pump first....
Hey found the vaccum leak, it was the pcv the plastic had a crack in it, couldnt see till i got it out...geez