I just put in a new set of 21# accel fuel injectors and my truck barely starts. once the truck does start it runs fine tho. I was wondering if anybody knew of a solution or really anything that i can do to fix this.

 

should have 19#

 

21 is to much go with 19's

 

When you installed the injectors did you disconnect the battery? If not do so and try again. This will erase the old idle air trim and casue the PCM to learn the new values.

JMC

 

I answerd this same type of question just awhile ago.
You cannot do this and have everything run right and look for more power.
It does not work that way.
First, the injectors and the Mass Air meter have to match.
What you did was increase the fuel into the engine and made it away to much (rich).
The stock air meter is still operating on it's 19 lb tranfer curve, while the injectors are dumping at the higher 21 lb flow rate.
Clearing the PCM doesnot change this created condition.
Your stock engine does not need this much injector in any event.

 

None of the books that I have read tell how much of a change in flow rate the PCM is capable of accomodating. Stock injectors can be off as much as 6-7% so the jump to 10.5% is not all that great. If the PCM is capable of turning them down it will not attempt unless you reset it. Of coarse the engine will run rich becasue it is getting more fuel and it is trying to shorten the injector pulse width. If it can't then BigJohnStud is SOL and he will have to go back to 19# injectors. We won't know unless he tries or has already tried.

JMC

PS. The fuel trim will also be reset.

 

if you want to get the 21# injectors to work right you will have to get a custom tune

 

Well the reason i replaced the injectors was because two of my old injectors were shot not because i was looking for a HP increase. I have disconnected the battery cable not too long ago because i had to when i was putting my headers on. That didnt help tho. So where would i go to get the custome tune? I have plenty of upgrades on my truck so i figured that going up 3#'s would not be much. So i am getting 2 different opinions here, shoudl i take the injectors out and get different ones, or should i get a custom tune?

 

by the way...my upgrades i have are an airaid intake kit, granatelli high-flow mass air sensor, 75mm BBk throttle body, BBk headers, and a magnaflow exhaust kit. i dont know if that makes a dif or not

 

John, you will have to do what you will.
I explained it in as simple a terms as possible.
You upset the system design by using the larger injectors without other compensating changes. This you see by what the results are.
Yes the EEC is capable of retrim to about a 20% limit.
Is the air meter calibrated for the 21s? It has to be.
If not, this is part of the design upset.
Then there are the limits the ox sensors will lean out for normal driving, then there is the concern the WOT air/fuel ratio may be to rich.
A tune is the only way to find out if you can ultimately get away using them.
Good luck

 

The MAF has NO other job beside metering air. There is no calibration in the MAF that tells the EEC what size injectors your using.


The EEC is what you'll have to modify what size injectors you are using.

Some people try to FOOL/TRICK the EEC by using a C&L air meter with a larger metered opening, but thats all its doing.


Chris

 

like i said before for all of you,you can use larger injectors, i have 24# injectors on mine, the only diff is that i have mine super chiped 9100 custom tune by mike troyer, give him a call at troyer performance and he will explain everything to you his # is 540-862-9515 hope this will help

 

sweet, your absolutly wrong on the air meter.
It does measure airflow and responds to the EEC with a signal in proportion to the the airflow.
It's called a transfer function.
Your right, it is not adjustable as said but the transfer function should match the injectors.
These engines work no different than the 5L Mass air engines.
Consider the Cobra in the mid 90s. They had 24 lb injectors and a matching air meter from the factory.
There should be a matchup with the air meter and the injectors size for proper all around running.
If you don't want to consider it, then do some home work and find out what these systems do.
There are ways of tricking within limits but is is not wise to get into all the greif that can result from it.
I didn't just crawl out from under a rock, a few days ago, on all this.

 

Alright, well thanx for all of your help. i really appreciate it and i hope i get everything worked out.

 

Did you not read my post?!?!?
Injector changes can ONLY be made properly with a Chip or and EEC reflash.



Chris