Yellow Bullet Forums banner

1 - 20 of 23 Posts

·
Registered
Joined
·
407 Posts
Discussion Starter #1
I have a freshly rebuilt iron 408 LS1. Went to start it last night and it is lighting off some HUGE backfires at idle. Not every cylinder but they are coming through the exhaust about every 4 seconds, maybe less. Before the rebuild the car was idling decent, still needs a tune, but was not hammering out some backfires. The only things which changed are a smaller blower pulley (16psi) and a wideband gauge.

any thoughts?


Details on build:

6.0 LS1 (408)
EFI - accufab t/b
F1A procharger
TH400
stock computer
Speartech wiring harness
 

·
Registered
Joined
·
407 Posts
Discussion Starter #3
I double checked everything last night, not to say that I didnt over look something. I am going to do just as you said tonight, make sure I didnt make a stupid mistake. From what I can tell at this point everything is pluged in correctly.
 

·
Registered
Joined
·
407 Posts
Discussion Starter #6
It does need a full tune. The car was at the dyno and lost oil pressure. At idle it was not backfiring when it was at the tuners. I knew I would leave out some important information.
 

·
Registered
Joined
·
1,387 Posts
id worry more after the tune is finished if its still doing it. untill then id wait till car is tuned. thats saying everything is in order liike plugs, plug wires, coils, 02s and etc
 

·
Registered
Joined
·
407 Posts
Discussion Starter #9
That is my first thing to look at. I pulled them last night and none of them looked "too" bad. I also got a new cam sensor on the way just in case. I am going to mess with it tomorrow morning. I am just trying to get some ideas while I am sitting here in the office.
 

·
Registered
Joined
·
116 Posts
Did you check pushrod length? I had that issue a year or so ago and they were too long and the car did what you're explaining. Might be something to check.
 

·
Registered
Joined
·
407 Posts
Discussion Starter #12
I have some 85# injectors in it, I am also spraying meth. It was tuned with the F1A last year with 60#'s. I never thought about that but the plugs may just be shot. I will try that first. Sometimes the simplest solutions are easiest to overlook.
 

·
Registered
Joined
·
291 Posts
I have some 85# injectors in it, I am also spraying meth. It was tuned with the F1A last year with 60#'s. I never thought about that but the plugs may just be shot. I will try that first. Sometimes the simplest solutions are easiest to overlook.
If the car has not been tuned for the 85# injectors, that is your issue. That is alot of extra fuel over the 60's. Get it properly tuned for the new injectors.

Zach
 

·
Registered
Joined
·
407 Posts
Discussion Starter #14
Just trying to clarify. They did some initial tuning on the car and had it running ok. It did not receive a full tune, partial tune only. The car lost oil pressure on the initial pass. I cannot tell you exactly what was done since I am not a tuner and dont pretend to be.

I REALLY appreciate everyones feed back. It just seems weird for it to start doing this all of a sudden. I will change the plugs and see what happens.
 

·
Registered
Joined
·
291 Posts
Just trying to clarify. They did some initial tuning on the car and had it running ok. It did not receive a full tune, partial tune only. The car lost oil pressure on the initial pass. I cannot tell you exactly what was done since I am not a tuner and dont pretend to be.

I REALLY appreciate everyones feed back. It just seems weird for it to start doing this all of a sudden. I will change the plugs and see what happens.
If it was tuned for the 60lb injectors and still has that same tune in it, the other injectors will not run well without the fueling corrected for them.

Zach
 

·
Registered
Joined
·
9,246 Posts
Whereabouts are you in Chicago? Do you have HPT or a scanner? You'd see the fuel trims all maxed out with the pcm pulling max fuel (25%) if the injectors are not scaled right. I have some really cold plugs and a maf translator (I seriously have one lol) if you needed to pull fuel just to get the car on a trailer or something.
 

·
Registered
Joined
·
407 Posts
Discussion Starter #18
It was running and idling with the 85's in it, I drove it on the trailer to take it to Speed Inc. The idle was not perfect but it idled well I thought for having much larger injectors. I took it to speed, they did about an hour of tuning and on the first full pull the engine lost oil pressure. I took the motor out, AES fixed it right up, and now its back in. Only change is the wideband install and a smaller pulley for more boost. It seems as though this came out of no where. Nothing really changed.

It may be the plugs, and I am also hearing the cam sensor could be acting up. I will get new plugs in it in the morning and see what happens. I just got home from class and I am sure my wife would not be happy if the car dropped a huge backfire and woke up out six month old at 10pm.

Update to come in the morning.

Thank you for all of the help and advice.
 
1 - 20 of 23 Posts
Top