30lbers too big?

[chemical5l]

Hey guys, I took my car thats not idleing and running like crap to a few speed shops and they told me that the 30lb injectors are too big, is this true? Mods are in signature.

[mheinjr]

No, I have a 75mm Pro-M cal'd for 36lbs and I have 36lb Injectors, and my car is fine...

I have a chip,fuel psi-48, timing is 14*

Most people on here have timing at 10*, fuel psi-38-40

If your MAF isn't cal'd for #30's it won't run right, cause when you say not idling it sounds to me that thats your problem, but who knows it could be a few things...

[chemical5l]

my mass air is 80mm, calibrated for s/c and 30lbers. what fuel pressure should I be at with vaccuum on?

[regattacoupe]

did you try clocking the meter?

[mheinjr]

well vaccuum on I don't know but everyone done there's with vaccuum off. start at like 38 and just keep adjusting upward. Try clocking the MAF first though that could be the problem too

[TheHawk05]

It almost sounds like you may have a connection problem with the meter. Make sure the meter is grounded through it's ground wire. I mention this because in the latest issue of 5.0, there is article on MAFS and how they work with all tech info provided by Pro-M. They say the two most common problems with they see with MAFS is improper ground and the actual element of the sensor getting contaminated with debris or oil ( Which is why they do not recommend K&N filters). Check all your grounds on the engine and make sure they are good. If the motor has been out of the car this is where alot of probems can be caused like the ones you are experiencing.

Check:

The ground strap that runs from the back of the driver side cylinder head to the firewall (looks like braided steel with two brass ring ends.

The ground wire that runs from the front driver side of the block near the timing cover to the neg battery terminal. A lot of problems occur here when people pull the motor, paint it, then forget to clean the paint off the mounting tab where this cable fastens causing a bad ground.

You should not need to clock a Pro-M as what is common practice with a C&L. I installed mine @ 12 o'clock like the tech from Pro-M told me and have no problems. Be patient and good luck as it's bound to be something simple that is causing this problem, it's finding it that can be tough sometimes.

Pro-M tech tips and troubleshooting

[frank woodall]

I use 30 's with a 70mm mass-air and no chip.....FP at 41 (no vac.) on the street and 65 (no vac.) at the strip. timing at 15* pulling 1 1/2* per lb on 93 gas

[ersunl]

I use 30's and they're damn near maxed out. You could use 42's if you tune them... lot's of people do. The injectors are fine.

-Eric

[chemical5l]

well, the speed shop over here is telling me that my car is not idling and running pig rich because my injectors are too big and they cant get the pressure down below 32, does this sound right?

[mheinjr]

Well I am only trying to help you by saying this. This was the same thing that was happening with mine.

Surging idle, ran pig rich so rich I smelled it in my oil.

I braught it to a mustang tuner and he could not get it right. He said the same thing he thinks the injectors where too big. He couldn't get the mass air flow correct with the computer. I had a Lightning MAF that needed to be tuned with the comp. So what he did was was get it to run the best he could through the comp. and I drove it home "it was good to drive", put on a 75mm Pro-M MAF, and this thing started idled perfect and never ran better. I just had to up the fuel psi to 48 to make the AF ratio 11.8.

So moral of the story was by adding that maf it ran perfect. It's hard to say what your problem is it sounds to me like your MAF isn't cal'd for #30's like you say it is. It sounds like it is cal'd for 42's or somthing higher making it tell the comp. to give it more fuel cause it's a big injector

But hey I got that response that my injectors were too big, I showed him after I put on the 75mm MAF like he reccomended

[chemical5l]

so the mass air flow was no good hey, I wonder if thats the same problem mine is having.

[mheinjr]

well I think it has somthing to do with..


See a lightning maf is cal'd for 42's "yours has interchangable filters in them lightnings don't", but they tell me you need to calibrate it through the comp. "I don't know" I don't really care about the lightning all I know is I put this75mm cal'd for 36 and it runs like a charm.. I had to put a AF meter on it to make sure at high rpm's it wasn't running lean.

I defanitly think it has to do with it. If you have a spare to throw in it would be great, but It is either it doesn't have the right calibration air meter, or like I read up top it maybe a ground or a lose connection I don't know, but I would bet thats your problem

[chemical5l]

thanks for the help, so can I test it or do I just have to send it in?

[regattacoupe]

I had 30's on my car and it idled like a baby........sounds like a mass air issue or possibly the o2's...

[fanglemeister]

Hi everyone, been a while. A couple points:

1) factory mass air meters are not "calibrated" for a particular injector size, they are actually calibrated for a specific processor. The MAF transfer curve of the oem meter is embedded in each variant of processor, so you cannot install a Lightning meter on an A9L computer with 42# injectors, nor can you install a '93 Cobra meter with 24#ers on a T4MO, etc. etc. because the bigger factory meter is not setup to match the smaller transfer curve in the processor. OTOH an aftermarket MAF meter such as the Pro-M is tailered to make a specific injector size work using a specific processor's MAF curve, so a set of 30# injectors and matching Pro-M designed to work on an A9L computer probably wouldn't run very well on a newer T4MO computer, because the MAF transfer curves are different between the A9L and T4MO - it's not just the mounting flange that is different.

2) The "blower" calibration Pro-M meters are set up notoriously rich, probably a good 15% to 20% richer than stock. This can cause some problems, since the stock A9L programming is designed to run at a nice fat 11.8:1 at WOT, running a "blower" Pro-M will cause it to target as rich as 11.78 - 20% = 9.42:1 a/f.
To get back to where you need to be you'd probably need to reduce your fuel pressure lower than most AFPR will allow. I would strongly encourage you to sell the blower calibration and buy a standard Pro-M calibration.

3) It is very rare to develop an injector problem that causes rough running; if they fail, you usually won't even get the car started for lack of fuel, it is almost unheard of that an injector will hang open and flood an engine. Over the years I've noted that 80% to 90% of all rough idle problems on the lean side are caused by a vacuum leak. Please make certain that all your vacuum lines are plugged in and sealing well, and none of the hard lines are cracked. In some rare cases I've even seen the vacuum booster on the brakes causing a leak. OTOH rough rich idle is usually caused by a FPR problem.

4) Have you pulled any codes off the eec? Even the cheapest of eec code scanners today can put the eec into what's called a cylinder balance test - it will shut off one injector at a time and note the drop (or rise) in rpm, if any single cylinder does not drop within the correct range it will flag that cylinder in the test results.

5) the 30# injectors are not too big as you probably have figured out, unless you are trying to run a really low rpm idle. Realize that the 30#ers were oem on the 3.8L V6 Tbird SC, which on a fuel capacity per cylinder basis isn't all that different from a 5.0L V8.