1993 LT1 Idle surging
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I think we just found your problem. Accel anything sucks...... They are not known for their quality.....
Also, they are very likely to have a different voltage offset. That can give you long term fuel trim issues and sometimes immediate driveability issues (like throttle tip in response). So, you'll need a tune with those injectors. And if you need a tune anyway, replace those injectors (sell em to some Ricer on Craigslist) and get some quality injectors. Reconditioned/refurbished ones on ebay from GM or Ford usually do the trick.
Also, they are very likely to have a different voltage offset. That can give you long term fuel trim issues and sometimes immediate driveability issues (like throttle tip in response). So, you'll need a tune with those injectors. And if you need a tune anyway, replace those injectors (sell em to some Ricer on Craigslist) and get some quality injectors. Reconditioned/refurbished ones on ebay from GM or Ford usually do the trick.
My wife threw a fit when I baught these new injectors and opti, I don't even want to imagine what will happen if I have to buy another set...
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From: Maricopa, AZ
As far as injectors go, I don't know the stock PN from GM. But, you can find some great deals on Ebay (less than $100 for 8) for some rebuilt Denso's or Bosches.
Honestly I think you best bet with the fuel injectors (if that is the problem), is to go to the local junk yard and find some working ones off an LT1 or L99. Have them cleaned and replace the orings and install those.
But, before you go shot gunning parts. Get that OBD port hooked up and get that thing scanned.
Also, did you eliminate all the exhaust leaks?
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Tune's vary in price. But, since you're a 93, you need to burn a chip and replace the one in your PCM. I have a 95 and do my own tune (via flash), so I can't help you there.
As far as injectors go, I don't know the stock PN from GM. But, you can find some great deals on Ebay (less than $100 for 8) for some rebuilt Denso's or Bosches.
Honestly I think you best bet with the fuel injectors (if that is the problem), is to go to the local junk yard and find some working ones off an LT1 or L99. Have them cleaned and replace the orings and install those.
But, before you go shot gunning parts. Get that OBD port hooked up and get that thing scanned.
Also, did you eliminate all the exhaust leaks?
As far as injectors go, I don't know the stock PN from GM. But, you can find some great deals on Ebay (less than $100 for 8) for some rebuilt Denso's or Bosches.
Honestly I think you best bet with the fuel injectors (if that is the problem), is to go to the local junk yard and find some working ones off an LT1 or L99. Have them cleaned and replace the orings and install those.
But, before you go shot gunning parts. Get that OBD port hooked up and get that thing scanned.
Also, did you eliminate all the exhaust leaks?
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From: Maricopa, AZ
Yes, can't find any more exhaust leaks. And good news with the injectors is I baught them off Amazon and they are very good with returns/refunds. It's February in MT, so a junkyard trip is kinda out of the story. If you could give me exact info of the injectors you suggest on ebay, please let me know so I can search and see what you mean. It's crazy, these injectors where $250 I want to say, and a $80 set off eBay are better? Crazy..guess I got to research before spending.
Yes, new parts tend to cost more, but that doesn't make them better. I got my 36# injectors on ebay, rebuilt, for $90.94 Shipped. They are SVO take offs.
But, again, you want to see the data log FIRST before you replace parts.
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The issue with the injectors are you'll need to find stock GM units, other wise you'll have injector offsets that don't match between what the PCM thinks and what is actually installed. IIRC, LS1 fuel injectors work on the LT1 with no needed mods. It may be worth a google search for you. You are looking for EV1 style plugs, 24#/hr rated at 3 bar. Don't get Accel, TRE, or some other cheap brand. Look for OEM stuff. Something like this.
Yes, new parts tend to cost more, but that doesn't make them better. I got my 36# injectors on ebay, rebuilt, for $90.94 Shipped. They are SVO take offs.
But, again, you want to see the data log FIRST before you replace parts.
Yes, new parts tend to cost more, but that doesn't make them better. I got my 36# injectors on ebay, rebuilt, for $90.94 Shipped. They are SVO take offs.
But, again, you want to see the data log FIRST before you replace parts.
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From: Maricopa, AZ
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1993 LT1, in a Jeep, wire harness is missing needed components to be able to scan this engine. New MSD opti, new spark plugs, new wires, new msd ignition, new IAC
Problem I need help with:
After initially starting this engine all is fine, goes up to 1500rpms or so the settles down near 800 after a few seconds (great!). But after about 2 minutes of idling at 800, the rpms start going completely crazy....Up to 1500, back to 800, up to 1800, back to 1000, up to 1500 and so on. This doesn't stop until the engine is shut down. When I give it a bit of gas manually, I can notice a definate hesitation. I figured it was a bad IAC so I just replaced that this morning, and same thing. The 93 doesn't have a maf sensor...what else could this be? What gives the IAC it's signal? Seems to me that the IAC is just opening and closing on its own. I'm very frustrated and need some help.
No known vacuum leaks, vacuum gauge stays steady. Just strange it runs OK for a minute or two before going whonky.
As the idle is fluctuating, I can hear air escaping/entering the throttle body area. Almost like a sucking sound like it's starving for air.
Problem I need help with:
After initially starting this engine all is fine, goes up to 1500rpms or so the settles down near 800 after a few seconds (great!). But after about 2 minutes of idling at 800, the rpms start going completely crazy....Up to 1500, back to 800, up to 1800, back to 1000, up to 1500 and so on. This doesn't stop until the engine is shut down. When I give it a bit of gas manually, I can notice a definate hesitation. I figured it was a bad IAC so I just replaced that this morning, and same thing. The 93 doesn't have a maf sensor...what else could this be? What gives the IAC it's signal? Seems to me that the IAC is just opening and closing on its own. I'm very frustrated and need some help.
No known vacuum leaks, vacuum gauge stays steady. Just strange it runs OK for a minute or two before going whonky.
As the idle is fluctuating, I can hear air escaping/entering the throttle body area. Almost like a sucking sound like it's starving for air.
Last edited by 93Euphoria; Feb 1, 2016 at 12:29 AM.
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From: Little Rock, AR
93s came with 22# injectors. 94-97 had 24#. So, if you had no compensation done in the computer, you will be running richer than normal. Couple that with only one O2 sensor, no check engine light or way to scan, a boatload of parts thrown at it without real diagnosis, kinda leaves you in a maze. Evaluating some live data should help get you on the right path. Better get reading on engine data parameters.
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From: Kernersville, NC
You are kinda in a tight spot right now as the wrong size injectors are in the car...and money looks to be tight.
I think it would be better to get those you posted in the car rather than have the car over fueling.
The fuel trims may be able to absorb 2#'s over of the bigger injector...but since you only have only one O2, the car may be stuck in open loop all the time...as such, the PCM can't use the fuel trims to try and get the fueling right. So...you've kinda got a mess right now.
I think it would be better to get those you posted in the car rather than have the car over fueling.
The fuel trims may be able to absorb 2#'s over of the bigger injector...but since you only have only one O2, the car may be stuck in open loop all the time...as such, the PCM can't use the fuel trims to try and get the fueling right. So...you've kinda got a mess right now.
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You are kinda in a tight spot right now as the wrong size injectors are in the car...and money looks to be tight.
I think it would be better to get those you posted in the car rather than have the car over fueling.
The fuel trims may be able to absorb 2#'s over of the bigger injector...but since you only have only one O2, the car may be stuck in open loop all the time...as such, the PCM can't use the fuel trims to try and get the fueling right. So...you've kinda got a mess right now.
I think it would be better to get those you posted in the car rather than have the car over fueling.
The fuel trims may be able to absorb 2#'s over of the bigger injector...but since you only have only one O2, the car may be stuck in open loop all the time...as such, the PCM can't use the fuel trims to try and get the fueling right. So...you've kinda got a mess right now.
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From: Kernersville, NC
That is correct....
Most likely you've been open loop....so the ECM has been using no feedback to adjust the fueling. This is all well and good as long as the components for measuring the air and delivering the fuel are correct. Since the injectors are now bigger, that could be causing over fueling. Now I don't know that 2#'s over will cause idle problems...however it's something that has not been adjusted for in the ECM.
Other things could be to blame too, but the O2 situation, incorrect injectors, SES lamp install, and code pulls need to be addressed.
Before spending too much money, pull the codes.
Most likely you've been open loop....so the ECM has been using no feedback to adjust the fueling. This is all well and good as long as the components for measuring the air and delivering the fuel are correct. Since the injectors are now bigger, that could be causing over fueling. Now I don't know that 2#'s over will cause idle problems...however it's something that has not been adjusted for in the ECM.
Other things could be to blame too, but the O2 situation, incorrect injectors, SES lamp install, and code pulls need to be addressed.
Before spending too much money, pull the codes.
Thread Starter
On The Tree
Joined: Feb 2011
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That is correct....
Most likely you've been open loop....so the ECM has been using no feedback to adjust the fueling. This is all well and good as long as the components for measuring the air and delivering the fuel are correct. Since the injectors are now bigger, that could be causing over fueling. Now I don't know that 2#'s over will cause idle problems...however it's something that has not been adjusted for in the ECM.
Other things could be to blame too, but the O2 situation, incorrect injectors, SES lamp install, and code pulls need to be addressed.
Before spending too much money, pull the codes.
Most likely you've been open loop....so the ECM has been using no feedback to adjust the fueling. This is all well and good as long as the components for measuring the air and delivering the fuel are correct. Since the injectors are now bigger, that could be causing over fueling. Now I don't know that 2#'s over will cause idle problems...however it's something that has not been adjusted for in the ECM.
Other things could be to blame too, but the O2 situation, incorrect injectors, SES lamp install, and code pulls need to be addressed.
Before spending too much money, pull the codes.
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I got a question about the placement of the drivers side O2 sensor. I have factory exhaust manifolds. How far away from the manifold is the O2 sensor?
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From: Kernersville, NC
Are you asking where the O2(bank 1 or 2, sensor 1) mounts in relation to the head exhaust ports?
I don't know the exact measurement, but less than 12" from the head exhaust ports. OEM's generally put that sensor where all the exhaust ports come down into a single collector for each side(as close to the exhaust ports as they can after all the ports collect together into a single pipe).
Here is bank 2 sensor 1.....lower left of picture....
http://s12.photobucket.com/user/rkmd...ce-01.jpg.html
My stock driver's O2(bank 1 sensor 1) was just before the exhaust manifold flange.
B1S1 - Bank 1 Sensor 1(Driver's Side)
B2S1 - Bank 2 Sensor 1(Passenger's Side)
Seems like I've seen pics of pre-dual cat LT1's where the B1S1 is placed just after the exhaust manifold flange.
The important thing is to get B1S1 in a pipe with the mixed exhaust gases of cylinders 1, 3, 5, and 7. Get B2S1 in an exhaust pipe with the mixed exhaust gases of 2, 4, 6, and 8. In general, the closer to the engine the better.
I don't know the exact measurement, but less than 12" from the head exhaust ports. OEM's generally put that sensor where all the exhaust ports come down into a single collector for each side(as close to the exhaust ports as they can after all the ports collect together into a single pipe).
Here is bank 2 sensor 1.....lower left of picture....
http://s12.photobucket.com/user/rkmd...ce-01.jpg.html
My stock driver's O2(bank 1 sensor 1) was just before the exhaust manifold flange.
B1S1 - Bank 1 Sensor 1(Driver's Side)
B2S1 - Bank 2 Sensor 1(Passenger's Side)
Seems like I've seen pics of pre-dual cat LT1's where the B1S1 is placed just after the exhaust manifold flange.
The important thing is to get B1S1 in a pipe with the mixed exhaust gases of cylinders 1, 3, 5, and 7. Get B2S1 in an exhaust pipe with the mixed exhaust gases of 2, 4, 6, and 8. In general, the closer to the engine the better.
Last edited by ACE1252; Feb 4, 2016 at 10:37 PM.