95 Vette LT1 rough idle
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95 Vette LT1 rough idle I have a 95 Vette LT1 motor in my 1948 Chevy truck. I have a Howell engine harness and reprogrammed CPU. Non emission set up. My motor starts up but idles rough. It sounds like an old Harley.
I have confirmed that my fuel presser is in spec.
Here is what I think are the possible causes.
1 - The motor sat for 7 years. I am thinking that I need to have the injectors cleaned.
2 - I am running open headers. insufficient back pressure.
3 - Opti
Looking for feedback.
Thanks in advance
Marc
I have confirmed that my fuel presser is in spec.
Here is what I think are the possible causes.
1 - The motor sat for 7 years. I am thinking that I need to have the injectors cleaned.
2 - I am running open headers. insufficient back pressure.
3 - Opti
Looking for feedback.
Thanks in advance
Marc
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Honestly, I'm going to have to say a combination of 1 and 2. Try cleaning the injectors first, see what happens. If you've still got a nasty idle problem, then see what you can do about increasing backpressure a bit. I don't mean go to the extreme and put 1.5" piping after the headers, but to be honest, I've never seen a problem with an LT1 in the past while running open headers, so cleaning the injectors should clear everything up.
Can you pull data off the ECU? An air-fuel ratio would be perfect in order to find out what exactly's going on in those combustion chambers.
Can you pull data off the ECU? An air-fuel ratio would be perfect in order to find out what exactly's going on in those combustion chambers.
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From: cheyenne wy
i have a very similar project. same exact motor,open hooker headers right now, just got the fuel cell and lines all plumbed up and i also gutted all emissions. i am almost ready to start it, and i would be very interested in how your progress goes and what you did compared to what i did, thanks o ya its in an 83 chev sb 2wd slammed (same concept as yours)
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Honestly, I'm going to have to say a combination of 1 and 2. Try cleaning the injectors first, see what happens. If you've still got a nasty idle problem, then see what you can do about increasing back pressure a bit. I don't mean go to the extreme and put 1.5" piping after the headers, but to be honest, I've never seen a problem with an LT1 in the past while running open headers, so cleaning the injectors should clear everything up.
Can you pull data off the ECU? An air-fuel ratio would be perfect in order to find out what exactly is going on in those combustion chambers.
Can you pull data off the ECU? An air-fuel ratio would be perfect in order to find out what exactly is going on in those combustion chambers.
I am running my own exhaust (2.5" stainless with 50 series Flowmaster mufflers with an x-member) and I just about have everything I need. After I get the injectors cleaned it wouldn't take much to hook up the exhaust.
I should also mention that when I felt the headers, I noticed some of the tubes were much hotter then the others, which also lead me to believe that it is an injector problem. I did run all new taylor plug wires and new plugs.
Thanks
Marc
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i have a very similar project. same exact motor,open hooker headers right now, just got the fuel cell and lines all plumbed up and i also gutted all emissions. i am almost ready to start it, and i would be very interested in how your progress goes and what you did compared to what i did, thanks o ya its in an 83 chev sb 2wd slammed (same concept as yours)
Your project sounds cool.
Good luck.
Marc
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From: South Wales, UK
Swap your injectors around and see if the cool pipes move with them. Are you running a MAF? If not you'll need to tune it a little to get your idle right. Even with the MAF mine needed work, and without the MAF it was rough.
Sweet truck too.
Sweet truck too.
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After doing all of that I should have a better idea if it is an injector problem.
Thanks for the reply.
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to test the injectors you do not need to swap them. you can unplug them one at a time. when you get to one that does not change the idle you may have found a problem. normally i would doubt that it is an injecor issue but you did say 7 years. if you can borrow another maf. getting the motor scanned at a shop of course is the best choice of all. very nice truck.
the last car that had a rough idle that I looked at was not throwing any codes at all and it was a broken valve spring (2002 6.0 ltr. with 200k)
the last car that had a rough idle that I looked at was not throwing any codes at all and it was a broken valve spring (2002 6.0 ltr. with 200k)
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to test the injectors you do not need to swap them. you can unplug them one at a time. when you get to one that does not change the idle you may have found a problem. normally i would doubt that it is an injecor issue but you did say 7 years. if you can borrow another maf. getting the motor scanned at a shop of course is the best choice of all. very nice truck.
the last car that had a rough idle that I looked at was not throwing any codes at all and it was a broken valve spring (2002 6.0 ltr. with 200k)
the last car that had a rough idle that I looked at was not throwing any codes at all and it was a broken valve spring (2002 6.0 ltr. with 200k)
I also tried tapping on the injectors while the motor was running and it seemed to get a little smoother.
I must admit I am confused by the MAF comment. When you say MAF do you mean the sensor or the duck work? This was brought up before and I was not sure what they meant. Please explain.
Thanks for the feedback
Marc
the MAF sensor would be between the throttle body and air intake. I do not even see one in your engine photo!? look up LT1 MAF sensor (google it) and you will see a photo, your computer should be hooked up to it.
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Does that sound right?
You are probably on to it, OP, if you tapped on the injectors and it sounded smoother. You probably freed one up. Go out and get a mechanics stethoscope. You should be able to hear a pretty good click, click, click, from them with your stethoscope. If you dont hear that, then they're stuck. Tap on them with a brass punch and a hammer. You can wack em pretty good. I been doing that for 15 years. I think I'm the one that came up with the idea. LOL
Now, even if you hear a click, it doesnt mean the injectors good. It could be moving the pintle, and just be clogged. If thats the case, you need to pull them and get them cleaned.
When you go out to buy your stethoscope, get an infrared temp gun too. They are the best thing since rubber tires!! LOL
You can use it to find dead cylinders, just point and shoot the header tubes.
Also good for finding draggin brakes, hot and cold spots in the rad, countless uses.
Yes, you probably are setup to run speed density. Which is typical of conversions.
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Looks like hes setup to run SD. Typical of the conversions.
You are probably on to it, OP, if you tapped on the injectors and it sounded smoother. You probably freed one up. Go out and get a mechanics stethoscope. You should be able to hear a pretty good click, click, click, from them with your stethoscope. If you dont hear that, then they're stuck. Tap on them with a brass punch and a hammer. You can wack em pretty good. I been doing that for 15 years. I think I'm the one that came up with the idea. LOL
Now, even if you hear a click, it doesnt mean the injectors good. It could be moving the pintle, and just be clogged. If thats the case, you need to pull them and get them cleaned.
When you go out to buy your stethoscope, get an infrared temp gun too. They are the best thing since rubber tires!! LOL
You can use it to find dead cylinders, just point and shoot the header tubes.
Also good for finding draggin brakes, hot and cold spots in the rad, countless uses.
You are probably on to it, OP, if you tapped on the injectors and it sounded smoother. You probably freed one up. Go out and get a mechanics stethoscope. You should be able to hear a pretty good click, click, click, from them with your stethoscope. If you dont hear that, then they're stuck. Tap on them with a brass punch and a hammer. You can wack em pretty good. I been doing that for 15 years. I think I'm the one that came up with the idea. LOL
Now, even if you hear a click, it doesnt mean the injectors good. It could be moving the pintle, and just be clogged. If thats the case, you need to pull them and get them cleaned.
When you go out to buy your stethoscope, get an infrared temp gun too. They are the best thing since rubber tires!! LOL
You can use it to find dead cylinders, just point and shoot the header tubes.
Also good for finding draggin brakes, hot and cold spots in the rad, countless uses.
I don't think that I am tapping on then injector hard enough. I was just slightly tapping on them.
I think that I am gaining on it.
Thanks for all of your help.
