I have a slightly modified TPI and it seems to be running lean. The Air/fuel gauge reads at startup fine, but while it idles its slightly below lean. I checked the plugs and they where greyish white(no its not a blow headgasket) I went with regular AC delco's and went to 2 heat range cooler. I checked the Fuel pressure(disconnect vacuum line) and it read 48psi, I have a replacement stock Fuel pump which was replaced about a year ago along with the fuel filter,Stock Fuel pressure regulator. As for injectors i have the Ford SVO 19# injectors. Should i go with an aftermarket regulator and up the fuel PSI???? How can i get it between Lean and Rich.

 

14 readers and no response, gee thanx

 

if you are just under stoich, its ok....... but if its all the way to lean, check for vacum leaks. that cause "unregistered" air to enter the engine w/ out the computer knowing and causing it to run rich....

 

thanx for the reply, I checked with a vacuum gauge and there dosent seem to be any leaks, Im running way lean. What im confused with is, are the injectors fine or do i have to go bigger?

 

well, it is possible that larger 22# injectors are needed, but i doubt it, if anything, i would try an adjustable fpr. up the psi and see if that helps. other than that, i would need more info. you could also take a noid light, and see if each injector is getting power, maybe there not firing.... or maybe your O2 is off a little, but how far lean is the gauge showing?

 

I did the noid light and yes all injectors are getting a signal. I have the autometer digital gauge and the light goes all the way left towards lean, sometimes going past it and disappearing.

 

Where does your automemter gauge plug in to determine rich/lean? Do you have a scan tool to look at your O2 readings?

 

Vortech, I've got the same problem you have, and the same injectors. I thought after changing to those inj's, I'd be a tad rich, but no. Are you able to borrow/ buy a laptop or scantool?, also, how is your mileage?

 

The SVO injectors are designed to give normal fuel delivery at 36 PSI. Try reducing fuel pressure. I know, this sounds backwards. But from experience, IT WORKS.

 

It works because with more pressure on the injector it takes it longer to open because it has to overcome the fuel pressure trying to hold it closed.

 

Mileage isnt that bad, i cant really give a good estimate, because the fuel level sending unit went bad. I had an access to a scan tool and for some reason it wouldnt connect, I mean, it plugged right in, but scan tool said "Cannot Connect". I have the Painless Wiring harness. Guess i'll go ahead and buy an Adjustable Fuel Pressure Regulator and go from there.

 

You should have done the afpr when you did the motor. Also put a fuel pressure guage on the schraeder valve with a long hose and put the guage under the windshield wiper. Go for a blast and watch the fuel pressure. If it drops more than 5 pounds then you need a booster pump. That's how I found out I needed one.

 

Thus, causing a LEAN condition.

 

I didnt know the SVO injectors worked its potential at 36 psi, I thought that was too low. Since you explained it, i understand it. What i forgot to mention is that at WOT its between Stoich. and rich, but the lean condition only occurs at idle.

 

At idle, the lean condition exist due to the reduced firing rate and having to overcome the 48 PSI fuel pressure. At WOT the ECM is firing the injectors almost constantly over riding the O2 sensor. Designed to operate at 36 PSI and having 48 PSI is causing the injectors to put excess fuel into the cylinders that cannot all be combusted, thus RICHNESS. Can be corrected only by reducing fuel pressure or new firing pulse duration in the PROM.

 

The 19# Ford injectors are designed to be run closer to 38-39 psi, at least that was the stock fuel pressure on my 1990 5.0 coupe. Those are stock injectors for this application. However, the GM system uses batch-fire and the 5.0 HO uses sequential, so I'm not sure if this figures into your lean idle situation. Perhaps a set of stock injectors off an L98 (22#) might work better for you and you could reduce your base fuel pressure to boot.

Some of the Ford guys crank the crap out of the stock 19# injectors and don't seem to have a problem, but again this is probably an apples to oranges comparo given the completely different fuel delivery systems.

Dave

 

thanx guys, appreciate all the help and knowledge you provided, sure is a big help. thanx again.