Find your vacuum leak first. You probably hosed up a runner gasket.
New Ford injectors causing fast idle
Thread Starter
Advanced
Joined: Aug 2006
Posts: 96
Likes: 0
From: Spokane Washington
New Ford injectors causing fast idle
I just installed Ford (Bosch) injectors in my '91 L98 engine. They are
24lb blue top M-9593-A302 type that I was told could be used instead
of the stock Multecs that came on the car. Everything went fine on the install but my idle is to about 1800 rpm at idle. I let it warm up but it never slowed down.
Anybody have any suggestions? Thanks in advance for the help.
Gary
24lb blue top M-9593-A302 type that I was told could be used instead
of the stock Multecs that came on the car. Everything went fine on the install but my idle is to about 1800 rpm at idle. I let it warm up but it never slowed down.
Anybody have any suggestions? Thanks in advance for the help.
Gary
Supporting Vendor
Joined: Mar 2008
Posts: 1,762
Likes: 14
From: Cumming Ga
I just installed Ford (Bosch) injectors in my '91 L98 engine. They are
24lb blue top M-9593-A302 type that I was told could be used instead
of the stock Multecs that came on the car. Everything went fine on the install but my idle is to about 1800 rpm at idle. I let it warm up but it never slowed down.
Anybody have any suggestions? Thanks in advance for the help.
Gary
24lb blue top M-9593-A302 type that I was told could be used instead
of the stock Multecs that came on the car. Everything went fine on the install but my idle is to about 1800 rpm at idle. I let it warm up but it never slowed down.
Anybody have any suggestions? Thanks in advance for the help.
Gary
to run 24 svo's in your car you need a retune of the prom. The 91 needs 22's to match the stock tune. First of all, they are rated at 39psi. If your pressure is 43.5 like it should be they are flowing 26lbs. Injectors should not affect the idle speed. In your case it should be real rich but at 1800 its will be hard to tell, especially if its sucking air leaning it out a little . Its sucking air somewhere. look for a vac leak, if they were new in the box they have ford 14mm o rings on the bottom. GM uses 15mm. so, it could be there, How did it run prior to the swap? vac leak is my vote.
Team Owner
Joined: Dec 2000
Posts: 21,094
Likes: 282
From: Phila., PA burbs
Not sure about your idle issue, but I agree with Jon that you probably need a tune. I'm running the same injectors in my 91 and I had to have a prom burned to keep it from running ultra rich. The MAF guys seem to be able to get away with them without tuning, but SD is less adaptable.
Melting Slicks
Joined: Jan 2002
Posts: 2,238
Likes: 4
From: Milan
The injector constant in your tune is 22 lb/h
This should be changed to 24 or near so.
The old debate on the Ford Injectors rated at 39 psi (instead of 43.5 psi) it's another story.
A 24 lb/h injector rated at 39 psi should deliver more than 24lb/h at 43 psi.
I had in the past 24 Ford injectors and I changed the injector constant to some more than 25.
BLM went in the leaner side.
Put back the constant to 24 and the BLM (dead perfect to 128 with old 22 injectors) returned to 126-128.
Now I have 30 lb Ford injectors and the constant in my chip is more than 30, ONLY because I have raised the fuel pressure.
The calculation to increase the injector constant I used, is based to the difference from 43 psi to my actual fuel pressure of 49 psi. (not based from 39 psi).
-Beppe-
This should be changed to 24 or near so.
The old debate on the Ford Injectors rated at 39 psi (instead of 43.5 psi) it's another story.
A 24 lb/h injector rated at 39 psi should deliver more than 24lb/h at 43 psi.
I had in the past 24 Ford injectors and I changed the injector constant to some more than 25.
BLM went in the leaner side.
Put back the constant to 24 and the BLM (dead perfect to 128 with old 22 injectors) returned to 126-128.
Now I have 30 lb Ford injectors and the constant in my chip is more than 30, ONLY because I have raised the fuel pressure.
The calculation to increase the injector constant I used, is based to the difference from 43 psi to my actual fuel pressure of 49 psi. (not based from 39 psi).
-Beppe-
Thread Starter
Advanced
Joined: Aug 2006
Posts: 96
Likes: 0
From: Spokane Washington
Thanks for the suggestions guys. I'm not much of a mechanic so it looks like I'm headed to a tune-up shop. The injector job was just about the limit of my abilities. The mechanic that I have used for a number of years wanted $600 to do the injector install so I thought I'd save some money.
The job was pretty straight forward and I think everything went together correctly, but some of those torx bolts on the tubes can be a bitch to get at.
The job was pretty straight forward and I think everything went together correctly, but some of those torx bolts on the tubes can be a bitch to get at.
Team Owner
Joined: Jul 2004
Posts: 28,474
Likes: 3,291
From: Hartford WI
Thanks for the suggestions guys. I'm not much of a mechanic so it looks like I'm headed to a tune-up shop. The injector job was just about the limit of my abilities. The mechanic that I have used for a number of years wanted $600 to do the injector install so I thought I'd save some money.
The job was pretty straight forward and I think everything went together correctly, but some of those torx bolts on the tubes can be a bitch to get at.
The job was pretty straight forward and I think everything went together correctly, but some of those torx bolts on the tubes can be a bitch to get at.
You ain't seen nuttin yet. Try the bolts that go from the runners to the manifold on an Accel Superram for the first time. You'll wish you had what you have.
Le Mans Master
Joined: Jun 2006
Posts: 5,642
Likes: 5
From: One day you're a Comet...the next day you're dust... Arkansas
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Thread Starter
Advanced
Joined: Aug 2006
Posts: 96
Likes: 0
From: Spokane Washington
I don't have any special tools to check for vacuum leaks. All of the hoses look good. The tube gaskets installed without a problem. I checked a second time for tight bolts. How do I check for leaks?
Racer
Joined: Jul 2006
Posts: 315
Likes: 0
The injector constant in your tune is 22 lb/h
This should be changed to 24 or near so.
The old debate on the Ford Injectors rated at 39 psi (instead of 43.5 psi) it's another story.
A 24 lb/h injector rated at 39 psi should deliver more than 24lb/h at 43 psi.
I had in the past 24 Ford injectors and I changed the injector constant to some more than 25.
BLM went in the leaner side.
Put back the constant to 24 and the BLM (dead perfect to 128 with old 22 injectors) returned to 126-128.
Now I have 30 lb Ford injectors and the constant in my chip is more than 30, ONLY because I have raised the fuel pressure.
The calculation to increase the injector constant I used, is based to the difference from 43 psi to my actual fuel pressure of 49 psi. (not based from 39 psi).
-Beppe-
This should be changed to 24 or near so.
The old debate on the Ford Injectors rated at 39 psi (instead of 43.5 psi) it's another story.
A 24 lb/h injector rated at 39 psi should deliver more than 24lb/h at 43 psi.
I had in the past 24 Ford injectors and I changed the injector constant to some more than 25.
BLM went in the leaner side.
Put back the constant to 24 and the BLM (dead perfect to 128 with old 22 injectors) returned to 126-128.
Now I have 30 lb Ford injectors and the constant in my chip is more than 30, ONLY because I have raised the fuel pressure.
The calculation to increase the injector constant I used, is based to the difference from 43 psi to my actual fuel pressure of 49 psi. (not based from 39 psi).
-Beppe-
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
Or just plain old water which will cause the engine to stumble when it gets in the cylinders. Get a small spray bottle, turn the nozzle to "stream" and spray around the runners, top and bottom and also at the top and bottom of the injectors. The spray bottle will give a more concentrated stream so pinpointing the leak is a bit easier. If the leak is bad enough you may even see white smoke coming out the tailpipe.
Safety Car
Joined: May 2006
Posts: 4,290
Likes: 140
From: Salem NH
I'm guessing the 'light blue top' 24s are really 26s and people think they are 24s and started this horrible 39psi rumor, or someone plugged in the wrong specific gravity for gasoline when testing them
What specific gravity are you flow testing your injectors at? 93 octane around here is about .73ish, depending on ethanol content. Some guys use a test fluid with a specific gravity of .6, and forget to convert before they print.
I still owe you a phone call, just been busy.. I'd like to chat sometime.
-- Joe
Thread Starter
Advanced
Joined: Aug 2006
Posts: 96
Likes: 0
From: Spokane Washington
The reason I changed the injectors was that the service soon light came on and one of them checked out with very low resistance (2 ohms). The idle was very rough. The engine has 50,000 miles and I just figured it was probably time to install new ones.
I haven't tried the starting fluid method for finding a vacuum leak yet. I have done that on other cars. The idle is so high that I'm not sure I could detect any increase. It sounds like I need to change the prom anyhow.
Supporting Vendor
Joined: Mar 2008
Posts: 1,762
Likes: 14
From: Cumming Ga
All the SVO injectors we've tested on the the ASNU machines have come out to the 'advertised' rating at 43.5 PSI. Yet this "39psi" thing keeps popping up like weekly. I have NOT had a pair of 24s tested, but I've had 30s (red top), 36s (dark blue top), and 42s (green top). My buddy has 3 ASNU machines and does R&D work for them, so I'm going to have to trust his testing
I'm guessing the 'light blue top' 24s are really 26s and people think they are 24s and started this horrible 39psi rumor, or someone plugged in the wrong specific gravity for gasoline when testing them
What specific gravity are you flow testing your injectors at? 93 octane around here is about .73ish, depending on ethanol content. Some guys use a test fluid with a specific gravity of .6, and forget to convert before they print.
I still owe you a phone call, just been busy.. I'd like to chat sometime.
-- Joe
I'm guessing the 'light blue top' 24s are really 26s and people think they are 24s and started this horrible 39psi rumor, or someone plugged in the wrong specific gravity for gasoline when testing them
What specific gravity are you flow testing your injectors at? 93 octane around here is about .73ish, depending on ethanol content. Some guys use a test fluid with a specific gravity of .6, and forget to convert before they print.
I still owe you a phone call, just been busy.. I'd like to chat sometime.
-- Joe
the 2008 ford motorsports catalog (published and written by ford motorsports) clearly states that the svo's are rated at 39.15 psi. So that must be who started this rumor. Download the cat. and look at page 137.. heres a small excerp:
"Ford Racing’s fuel injectors are also rated at 39.15 psi delta, so the fuel injector sizing discussions found below will
assume a fuel pressure of at least 39.15 psi delta"
Also the asnu machine flows in ccm. What formula are you using to convert to lbs/hr. The calculator in the new classic machine is formulated on a british liquid pound so we found the calculator inacurate. We use the same formula Russ Collins uses of RC engineering. I speak to Phil Ellisdon of asnu frequently, He is the owner of Asnu which is a British Company , we talk about new things needed like special fuel rails for testing and bigger tubes for larger injectors etc. I should ask him why he never told me he had R&D guys in the states.
Instructor
Joined: Mar 2007
Posts: 117
Likes: 0
From: San Luis Obispo California
Safety Car
Joined: May 2006
Posts: 4,290
Likes: 140
From: Salem NH
A buddy of mine dug up some ford catalogs and states:
"As far as the ford racing catalog, it just appears to be screwed up. Every one since 2004 list a different delta test pressure, the 2008 one lists 39.15psi and list the same flow numbers for the same part numbers as they did in 2006 at 40psi and earlier at 43.5. I'd believe that the catalog is wrong before I'm going to believe that the same injectors change flow every year..."
Here is some links to injectors that we had tested in 2004:
http://www.thirdgen.org/techboard/tp...ow+ford+cruzin
Since then I've become pretty close with Rich and we talk about injectors regularly.
When you guys first started selling injectors on here, I was a little confused until I realized you are not FIC you are FICINJECTORS.
formulated on a british liquid pound so we found the calculator inacurate. We use the same formula Russ Collins uses of RC engineering. I speak to Phil Ellisdon of asnu frequently, He is the owner of Asnu which is a British Company , we talk about new things needed like special fuel rails for testing and bigger tubes for larger injectors etc. I should ask him why he never told me he had R&D guys in the states.
-- Joe
Race Director
Joined: Aug 2000
Posts: 11,470
Likes: 764
nobody has asked the OP what fuel pressure he's running. everyone seems to be getting into a pi$$ing contest on what pressure the injectors are RATED by the factory. going from factory 22's to 24's, is not going to cause the idle to increase some 1200 rpm. yea, the 24's may be dumping a little more fuel (at the same operating pressure), but that alone, is not going to cause a jump in idle rpm. there's some other issue involved here... i wouldn't start by reprogramming anything! 
Safety Car
Joined: May 2006
Posts: 4,290
Likes: 140
From: Salem NH
However, I think his plenum has a vac leak.
-- Joe