cold start problems, leaking injector or just need of tune
Thread Starter
Teching In
Joined: Dec 2011
Posts: 44
Likes: 0
From: Just a small town in far west Texas
cold start problems, leaking injector or just need of tune Sorry for the NooB question but after a search i didn't come up with a satisfying answer...
Question 1`
On *some* cold mornings (20 degrees or so), particulalry after sitting 2-3 days, my 98Z will idle real rough and die. If i raise the idle with the pedal to 1500 rpms for about 2-3 minutes it'll chug some but then it clears out and runs fine when it warms up. It does set off the SES light and sometimes has either a random misfire or #7 misfire codes in it. Ironically it doesnt set off a cat code
. I have done the following within the last 20-30 miles:
Brand new (not reman) stock 99 LS1 GM crate motor
iridium AC delco plugs done w/new motor
new GM wires done w/new motor
new coils with connectors/pigtails done w/new motor
Mods are:
Lid
BBK long tubes done w/new motor
deleted cats, egr and air injection system done w/new motor
LS6 intakedone w/new motor
B&B cat back
I'm thinking that i probably need a tune since its still a stock tune and the emission stuf is gone but I also read up on it possibly being a leaking injectors too since they are originals with a fair amount of miles on them.
I can only do a tune or new injectors at the moment due to low funds and want to make an educated descision.
Qustion 2
Now If I need new injector(s) should i get the stock ones "flowed" by a reputable shop which seems to be cheaper or just new aftermarket ones? Also if i needed new injectors and got 30# injectors for it, would it be too much for the mods I have? I don't plan on doing much more to the car for quite a while and want it to be a good reliable car. Sorry for the long post just trying to learn something on tuning.
Question 1`
On *some* cold mornings (20 degrees or so), particulalry after sitting 2-3 days, my 98Z will idle real rough and die. If i raise the idle with the pedal to 1500 rpms for about 2-3 minutes it'll chug some but then it clears out and runs fine when it warms up. It does set off the SES light and sometimes has either a random misfire or #7 misfire codes in it. Ironically it doesnt set off a cat code
. I have done the following within the last 20-30 miles:Brand new (not reman) stock 99 LS1 GM crate motor
iridium AC delco plugs done w/new motor
new GM wires done w/new motor
new coils with connectors/pigtails done w/new motor
Mods are:
Lid
BBK long tubes done w/new motor
deleted cats, egr and air injection system done w/new motor
LS6 intakedone w/new motor
B&B cat back
I'm thinking that i probably need a tune since its still a stock tune and the emission stuf is gone but I also read up on it possibly being a leaking injectors too since they are originals with a fair amount of miles on them.
I can only do a tune or new injectors at the moment due to low funds and want to make an educated descision.Qustion 2
Now If I need new injector(s) should i get the stock ones "flowed" by a reputable shop which seems to be cheaper or just new aftermarket ones? Also if i needed new injectors and got 30# injectors for it, would it be too much for the mods I have? I don't plan on doing much more to the car for quite a while and want it to be a good reliable car. Sorry for the long post just trying to learn something on tuning.
On a cold start, you will be in open loop so the O2 are not used to calculate fueling. The PCM uses a series of table to calculate the fuel until the coolant temp is high enough.
My guess your VE and MAF tables need to be re-calibrated for your set up.
My guess your VE and MAF tables need to be re-calibrated for your set up.
If the motor itself is all stock, Then you probably just have a bad plug or a bad wire or coil on Number 7 that is missfiring. OR you have a bad fuel pressure issue, or a mass air meter?
Have you checked the plug???
Normally only missfire stuff shows up if you changed the camshaft without readjusting the misfire windows.
Have you checked the plug???
Normally only missfire stuff shows up if you changed the camshaft without readjusting the misfire windows.
Thread Starter
Teching In
Joined: Dec 2011
Posts: 44
Likes: 0
From: Just a small town in far west Texas
Thanks for all the info guys, I am kinda leaning towards doing the tune first now. FWIW all the parts listed listed above are new except for the injectors and MAF. I rechecked the plugs and wires and they are good and tight/ gapped correctly. What Mez said is one reason i thought is was injectors. But didn't think about fuel pressure or the MAF since there are no MAF codes and i havent checked the fuel pressure. Suposedly it is a new GM unit from what i was told by the previous owner .
Would a leaking injector show up all the time or just at first start if it leaked into the cylinder? It almost seems like when the car does act up its bogging like the old carb cars used to do when the choke is stuck closed.
I would have to get a mail order tune because there isnt anyone within 150 miles where i live that messes with LS1's. Would such mail order tuners be able to adjust the cold start up fuel tables without much problem? As stated car is basically a full bolt on car with stock internals. Thanks agian for the help!
.Would a leaking injector show up all the time or just at first start if it leaked into the cylinder? It almost seems like when the car does act up its bogging like the old carb cars used to do when the choke is stuck closed.
I would have to get a mail order tune because there isnt anyone within 150 miles where i live that messes with LS1's. Would such mail order tuners be able to adjust the cold start up fuel tables without much problem? As stated car is basically a full bolt on car with stock internals. Thanks agian for the help!
Get it to do it again, and instead of running it at higher RPM and clearing it out, shut it off right away and pull the plugs - if one is wet and loading up, you will find it. If you need injectors, you should be able to pick up a used stock set cheap...
