LT1 misfires
12-17-2002, 10:43 AM
#1
Teching In
Thread Starter
Join Date: Dec 2002
Location: usa
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
LT1 misfires I have a 93 Pontiac TransAm as my daily drive.
Recently I had to rebuild the engine due to a spun bearing (130,000miles)
Well when the car gets hot, it starts to miss-fire.
Let it cool down and its fine again.
I have already replaced plugs, wires and the coil.
Any ideas?
Recently I had to rebuild the engine due to a spun bearing (130,000miles)
Well when the car gets hot, it starts to miss-fire.
Let it cool down and its fine again.
I have already replaced plugs, wires and the coil.
Any ideas?
12-17-2002, 05:53 PM
#3
TECH Addict
Join Date: Nov 2001
Location: TEXAS
Posts: 2,593
Likes: 0
Received 0 Likes
on
0 Posts
Re: Help needed with LT1 Hace you tried using 93 octane or the highest available in your area? I believe these cars are set up to run on premium gas, but they do have a fail safe in them for low octane gas. Your octane may be too low and you're causing detonation. Also, is your coil still mounted on the drivers head or have you done the spacer mod yet? By using some longer bolts and something as a spacer (washers, nuts, anything) you can move the coil about an inch off of the head allowing it to run cooler and not get 'heat soaked'.
12-17-2002, 06:01 PM
#4
TECH Apprentice
iTrader: (3)
Join Date: Dec 2002
Location: Houston, TX
Posts: 391
Likes: 0
Received 0 Likes
on
0 Posts
Re: Help needed with LT1 try cleaning your fuel injectors. they could be dirty. when rebuilding a motor its always recommended to clean your fuel injectors. sometimes injectors get a little dirty and start to cause misfires when reaching eot. also quit being cheap and put 92+ octane. one last thing, check your plugs and make sure none are fouled out. that will also cause a misfire. <img border="0" alt="[Fluffy]" title="" src="graemlins/fluffy.gif" />
12-17-2002, 06:09 PM
#5
TECH Fanatic
Join Date: Nov 2001
Location: I-L-L-I-N-O-I-S
Posts: 1,098
Likes: 0
Received 0 Likes
on
0 Posts
Re: Help needed with LT1 </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by mighty mex:
<strong>try cleaning your fuel injectors. they could be dirty. when rebuilding a motor its always recommended to clean your fuel injectors. sometimes injectors get a little dirty and start to cause misfires when reaching eot. also quit being cheap and put 92+ octane. one last thing, check your plugs and make sure none are fouled out. that will also cause a misfire. <img border="0" alt="[Fluffy]" title="" src="graemlins/fluffy.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I agree, have your fuel filter/injectors checked. And also, only use premium fuel(91+ octane). Your car will run like crap if you don't. That could very well be your problem right there.
Mike
<small>[ December 17, 2002, 06:10 PM: Message edited by: 2000LS1Z28 ]</small>
<strong>try cleaning your fuel injectors. they could be dirty. when rebuilding a motor its always recommended to clean your fuel injectors. sometimes injectors get a little dirty and start to cause misfires when reaching eot. also quit being cheap and put 92+ octane. one last thing, check your plugs and make sure none are fouled out. that will also cause a misfire. <img border="0" alt="[Fluffy]" title="" src="graemlins/fluffy.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I agree, have your fuel filter/injectors checked. And also, only use premium fuel(91+ octane). Your car will run like crap if you don't. That could very well be your problem right there.
Mike
<small>[ December 17, 2002, 06:10 PM: Message edited by: 2000LS1Z28 ]</small>
12-17-2002, 06:19 PM
#6
On The Tree
Join Date: Nov 2002
Location: wichita falls, Tx
Posts: 132
Likes: 0
Received 0 Likes
on
0 Posts
Re: Help needed with LT1 Have you replaced the "OPTI", that would be my guess along with spark plug wires but you say you already changed them. Good Luck
Michael
Michael
Trending Topics
12-17-2002, 08:17 PM
#8
TECH Enthusiast
iTrader: (2)
Join Date: Dec 2001
Location: That Southern Fried Space City
Posts: 658
Likes: 0
Received 0 Likes
on
0 Posts
Re: Help needed with LT1 LOL@some of these responses...
As some have said, are you using the original optispark distributor?
And so you guys will get off this premium kick, 93 octane is not a necessity on a stock motor. If your motor is not knocking than your wasting your dollars at the pump. Octane rating is for reducing knock, not performance. I've owned three f-bodies and only ran premium on my blown car(s).
Personally I'd buy a set of new injectors since they are cheap but if you are going to run a cleaner through them, you should use the Redline SI cleaner.
Oh yea, and I don't know about LS1's but LT1's have no "fail safe" other than a knock sensor for detonation which in turns just yanks timing.
Did you do all the work on the car or did you have a shop do it. More details the better...
<small>[ December 17, 2002, 08:18 PM: Message edited by: The Big Show ]</small>
As some have said, are you using the original optispark distributor?
And so you guys will get off this premium kick, 93 octane is not a necessity on a stock motor. If your motor is not knocking than your wasting your dollars at the pump. Octane rating is for reducing knock, not performance. I've owned three f-bodies and only ran premium on my blown car(s).
Personally I'd buy a set of new injectors since they are cheap but if you are going to run a cleaner through them, you should use the Redline SI cleaner.
Oh yea, and I don't know about LS1's but LT1's have no "fail safe" other than a knock sensor for detonation which in turns just yanks timing.
Did you do all the work on the car or did you have a shop do it. More details the better...
<small>[ December 17, 2002, 08:18 PM: Message edited by: The Big Show ]</small>
12-17-2002, 08:32 PM
#9
Re: Help needed with LT1 misfires can be caused by bad gas, bad spark, or just plain detonation. the cheapest solutions should be sought after first and i would suggest trying a higher octane gas to see if the misfires stop, if they do, then problem solved, if they dont, then thats one less thing you have to wory about for being the culprit. no harm and no money lost. as for myself, i would check the wires again, make sure no wires are anywhere near the headers, even if they arent stock wires. i would first hook the autotap up to the car and igure outwere the misfires are coming from...are they coming from individual cylinders or from all of them? find out. also, how hot is the car getting when you say its getting hot? it may be developing heatspots on the heads or something causeing detonation...did you put stock heads back on or do any porting to the heads when you rebuilt the motor? more details please.
12-18-2002, 06:50 AM
#11
Teching In
Thread Starter
Join Date: Dec 2002
Location: usa
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
Re: Help needed with LT1 Car is stock. No mods
I have run the "cheap gas" ever since i got it, and never had any real problem.
The higher octanes are to prevent detonation, allowing the fuel to burn more efficiently.
As said, std car should run on even the cheap crap.
When I rebuilt the motor, i did clean out the injectors and replace the plugs and wire (as it had done this before the motor was rebuilt).
I replaced the coil last week.
Now there are 2 things that i have been thinking.
1) only does it after say 30 minles, but temp guage is still at about 160-200.
I believe there is a temp sensor on the block that tell the ecu if the motor is cold (forces more gas for cold starts etc.)
2) the opti has done 138,000 miles, BUT, it doesnt miss when cold. so i think that should rule that out.
When it starts to mis, it gets worse and worse, until it feels like only 4 cylinders are firing, then she dies totaly.(starts missing at 4000,3000, then 2000...etc)
It feels like timing, but when its cold it goes like a rocket (no mis-fire even at 5000rpm)
I have run the "cheap gas" ever since i got it, and never had any real problem.
The higher octanes are to prevent detonation, allowing the fuel to burn more efficiently.
As said, std car should run on even the cheap crap.
When I rebuilt the motor, i did clean out the injectors and replace the plugs and wire (as it had done this before the motor was rebuilt).
I replaced the coil last week.
Now there are 2 things that i have been thinking.
1) only does it after say 30 minles, but temp guage is still at about 160-200.
I believe there is a temp sensor on the block that tell the ecu if the motor is cold (forces more gas for cold starts etc.)
2) the opti has done 138,000 miles, BUT, it doesnt miss when cold. so i think that should rule that out.
When it starts to mis, it gets worse and worse, until it feels like only 4 cylinders are firing, then she dies totaly.(starts missing at 4000,3000, then 2000...etc)
It feels like timing, but when its cold it goes like a rocket (no mis-fire even at 5000rpm)
12-18-2002, 03:16 PM
#12
TECH Enthusiast
iTrader: (2)
Join Date: Dec 2001
Location: That Southern Fried Space City
Posts: 658
Likes: 0
Received 0 Likes
on
0 Posts
Re: Help needed with LT1 To be honest with you, it sounds more and more like the opti to me. Its funny that way cause it will progressively get worse. Ofcourse the 93-94 opti is mucho dollars so it would be nice to put the car on a computer to find out exactly what the misfire is first. I'm not sure how to do that on 93's though as they have the embedded removable prom.
12-20-2002, 07:50 AM
#15
TECH Enthusiast
iTrader: (2)
Join Date: Dec 2001
Location: That Southern Fried Space City
Posts: 658
Likes: 0
Received 0 Likes
on
0 Posts
Re: Help needed with LT1 Wow, AZ is selling complete units now? Do they come with any type of warranty? That price isn't bad at all if they do.
Glad you found your problem without pulling too much hair. Opti can drive you insane...ask me how I know <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />
Glad you found your problem without pulling too much hair. Opti can drive you insane...ask me how I know <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />
12-20-2002, 10:13 AM
#16
Teching In
Thread Starter
Join Date: Dec 2002
Location: usa
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
Re: Help needed with LT1 The Opti unit has the LLT warranty.
Limited LIFETIME....wow, sounds too good to be true <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
Limited LIFETIME....wow, sounds too good to be true <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
12-22-2002, 06:24 PM
#18
Re: Help needed with LT1 been having the same probs with mine did plugs wires. when its cold it runs hard. but give it 20 mins or 20 miles and it misses pops and detonates. might be my prob too.ill have to look into it. hey btw did the opti bearing make any noises b4 it died..
