Overfuelling problem
Thread Starter
Teching In
Joined: Nov 2005
Posts: 6
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From: Rugby, Warwickshire, United Kingdom
Overfuelling problem Hi guys,
I am new to this board and need some help. I have recently bought a 93 Trans Am that i am having some problems with. The car will start fine every time from cold but will load up almost immediately, and when it warms up it becomes a right pain, struggling to idle. We have plugged a Tech 1 onto it and the only things that seem amiss are an injector pulse width of 5.4 at idle and QDM3 relay fault in the ECU.
The engine has got some major mods, ported polished heads/intake, headers, Comp Cams #305 roller cam, 1.52 roller rockers, SVO #24 injectors, K&N intake, MSD coil and custom burn chip from TPI Chips.
Living in the UK its hard to find anyone who is in the know about modded LT1's. Any help would be great as I want to get the car on the road but at the moment I'm pulling my hair out with it.
Thanks guys.
I am new to this board and need some help. I have recently bought a 93 Trans Am that i am having some problems with. The car will start fine every time from cold but will load up almost immediately, and when it warms up it becomes a right pain, struggling to idle. We have plugged a Tech 1 onto it and the only things that seem amiss are an injector pulse width of 5.4 at idle and QDM3 relay fault in the ECU.
The engine has got some major mods, ported polished heads/intake, headers, Comp Cams #305 roller cam, 1.52 roller rockers, SVO #24 injectors, K&N intake, MSD coil and custom burn chip from TPI Chips.
Living in the UK its hard to find anyone who is in the know about modded LT1's. Any help would be great as I want to get the car on the road but at the moment I'm pulling my hair out with it.
Thanks guys.
Thread Starter
Teching In
Joined: Nov 2005
Posts: 6
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From: Rugby, Warwickshire, United Kingdom
Me again, any ideas??
Really need to get this thing running as it is getting cold over here now, if anyone can suggest anything I will listen and take advice. I am going to check the obvious like EGR, vac leaks etc tomorrow, but feel it is something not so basic. HELP!!!!!!!!!!!!!!!!
Really need to get this thing running as it is getting cold over here now, if anyone can suggest anything I will listen and take advice. I am going to check the obvious like EGR, vac leaks etc tomorrow, but feel it is something not so basic. HELP!!!!!!!!!!!!!!!!
I am not sure injector pulse widths are supposed to be but you sound as if that's incorrect. Better fix that before you start looking for other problems. Also, have you had this car in an English winter before? Since 93's are speed density, it might not be compensating for the cold well enough. Just a theory. A mass air system might be able to adjust for such temperatures.
Thread Starter
Teching In
Joined: Nov 2005
Posts: 6
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From: Rugby, Warwickshire, United Kingdom
Yeah, pulse width is definitely too much, its just figuring out why and whats causing it. No I haven't used it thru a winter before, only had it about a month, but when I started it the other night it was worse, but I suspect that because it was so cold the overfuelling problem has been made worse.
Thread Starter
Teching In
Joined: Nov 2005
Posts: 6
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From: Rugby, Warwickshire, United Kingdom
Have had the car on a Tech 1, and it seems all injectors are runnng at 5.4, if you adjust the pulse width to 1.4 on all injectors it will idle great, as soon as tech1 is influencing it, it goes back to 5.4, no trouble codes are thrown up and all sensors appear to be fine, only problem that is thrown up other than pulse width is the QDM relay #3 is coming up as faulty, trouble is I can't seem to find out what systems this relay controls and whether it would give the symptons that I have got.
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Thread Starter
Teching In
Joined: Nov 2005
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From: Rugby, Warwickshire, United Kingdom
Adjust them down to 1.4 with Tech1 diagnostic tool, as soon as you take your finger off the button on Tech 1 the pulse width will return to 5.4. Tech1 will only adjust settings temporarily and will not set the PCM for good, it only works as a diagnpstic tool to try to add or remove problems temporarily. Just a small point, twice since I have been running the car I have actually smelt the cat, so whatever is causing it has cleared momentarily twice. All other times the car smells really rich and you can't smell the cat at all.
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Verdad Gallardo Ahh I see. Do you have a friend that has similar injectors that maybe you could swap out? You could see if they do the same. Being in the UK I doubt it. With a mass air system and flash PCM, you could just simply adjust the pulse widths via your laptop and you could easily see if that fixed it. You could get a PCM, harness, and MAF sensor from a junkyard for less than $300 (just a guess--in pounds I guess it would be about 540).
TECH Regular
Joined: Feb 2003
Posts: 444
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From: Bahrain
Did you check the oxygen sensors reading through tech 1. If the sensors are giving wrong lean reading then the injectors are commanded to dump more fuel. Also worth checking is the coolant temperature sensor on the water pump. Again check it's reading with key on engine off when the car is cold and see if it's reading is close to ambiant and when. The input from this sensor affects the fueling.
Last edited by transamtom; Nov 20, 2005 at 09:14 AM.
Also, doesn't the SVO injectors rate higher when used in the LT1? I remember hearing someone saying that the 24# were closer to 30# when put in an LT1. I had mentioned to someone about putting a set of 30#'s in my LT1 when I got it built and he stated they would be closer to 36's instead.
Originally Posted by Klortho
Also, doesn't the SVO injectors rate higher when used in the LT1? I remember hearing someone saying that the 24# were closer to 30# when put in an LT1. I had mentioned to someone about putting a set of 30#'s in my LT1 when I got it built and he stated they would be closer to 36's instead.
Thread Starter
Teching In
Joined: Nov 2005
Posts: 6
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From: Rugby, Warwickshire, United Kingdom
Thanks for your replys, I think I may have got to the bottom of the problem. I decided to get off my rear and have a look at the car, took it for a run today ( bearing in mind we've got temps of about -1 here at the moment ) anyway i noticed the air coming out of the vents with the dial on HOT was to say the least only very slightly warm, although the car was idling OK, not popping and banging and the strong overfuelling smell had gone. Got back home after about 30/40 minutes driving and opened the hood to check the coolant, first thing I noticed was the cooling fan was running, which seemed strange as when I took off the rad cap there was no pressure and the water was cold enough for me to put my finger in and leave it there.
Am going to change the rad cap, stat and cooling fan relay this week and see how we go from there.
Also think I have got to the bottom of the uneven O2 readings, the AIR pump has only been hooked up to one header ( other side is blanked ), funny enough the one with the higher reading is the one without AIR. Will order a new connector and hook the other side up as well.
Hopefully this will sort it, thanks for everyones help, will let ytou know how I get on.
Am going to change the rad cap, stat and cooling fan relay this week and see how we go from there.
Also think I have got to the bottom of the uneven O2 readings, the AIR pump has only been hooked up to one header ( other side is blanked ), funny enough the one with the higher reading is the one without AIR. Will order a new connector and hook the other side up as well.
Hopefully this will sort it, thanks for everyones help, will let ytou know how I get on.