LT1 wont start any ideas
03-10-2007, 03:57 PM
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LT1 wont start any ideas My friend has a 97 TA he SAYS one day he came out and it wouldnt start so he figured it was opticrap problems so he replaced it with a new one. this is where i came in to the problem it definetly has fuel when i left thursday i had it backfiring through the exhaust i pulled the opti to make sure it was timed correctly. wierd thing is on my techforce it said that the desired idle is 3088 rpm it is a stock pcm so i thought maybe that was the problem so we poprd another pcm in it but it had the same problem. the map sensor is no good locked at 30"hg that is the only sensor that doesnt read correctly but it is a maf sistem so i didnt think that is the problem any ideas? I said to swap to ls7 i guess thats an expencive fix for him though.
03-10-2007, 06:23 PM
#3
Did it have a check code for indicating to replace the opti? If it didnt have a DTC for the opti it's a waste of time and money because it wont solve any thing. The opti is either going to be installed correctly or not, the PCM controls timing on the LT1s, this isnt a Gen I SBC when you can making timing changes via the distributor. If it was installed incorrectly the car wont run. What code is the car throwing, if the MAP is bad it will cause driveability issues, even on a MAF car you need it, deals with engine vacum. You check to see if the ICM was good?
Last edited by BizZzatch350; 03-10-2007 at 06:29 PM.
03-10-2007, 06:37 PM
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They say the desired idle is that high when the car is not running. On some of the scan tools. The map should be at 1.000 not running. Only a couple of things will cause a no start on an LT1. Coolant temp sensor in the water pump. Fuel pump. Fuel pump relay. Opti issues and ICM and doubtfully the coil.
03-10-2007, 06:39 PM
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i agree like i said the opti was before i started helping. the icm was replaced and the coil and the crank sensor all before i showed up shotgun approah and not the way i would have done it but he was desperate now hes got alot of money in it and it still dont run. the plugs are completely drenched in fuel my thought was that if the desired idle is 3000 rpm its getting enough fuel to sustain that rpm but not enough air and fire i tried holding the throttle about halfway thats when it backfired so why would it want to idle that fast?
03-10-2007, 11:00 PM
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Not true. The computer sees it as the car is at 0 RPMs and it needs more and 3187 or something like that is the highest it'll go.
What is the Water temp sensor reading? Not on the gauge on the dash, but through a scan tool?
What is the Water temp sensor reading? Not on the gauge on the dash, but through a scan tool?
03-11-2007, 01:31 AM
#7
Have you checked the coil and module ? The ignition module went out on my '94 one day and just died in the middle of 1960. When I got it home, I bought a new coil and module and just plugged them in without removing the original pieces. It fired right up and I was able to trace it down to the ignition module.
Hope this helps.
Hope this helps.
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03-11-2007, 09:24 PM
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when i got there the cts in the water pump read -40 so i pluged it in i think this caused the plugs to foul the only explaination i can think of he replaced the coil module opti and i pluged in the cts we are definetly getting fuel so i had him replace the plugs we are going to try it again tomarrow. thanks for yalls help i really dont like these lt1s.
03-12-2007, 01:35 AM
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When the coolant temp sensor reads -40 degrees, it is usually unplugged or has a broken pin in it. At that point, the car thinks it is really that cold and dumps TONS of fuel into the cylinders.
Oh and maybe unplug the battery for a few minutes. I have had a few times where if the codes weren't clear, the car still would not start. Or unplug the PCM BAT fuse.
Oh and maybe unplug the battery for a few minutes. I have had a few times where if the codes weren't clear, the car still would not start. Or unplug the PCM BAT fuse.
03-16-2007, 07:43 AM
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heres the update i went over there again the cts is pluged in and reads 78 degrees it has a new module now i even switched it with one i new that worked to make sure it wasnt just a bad part the car backfires still. he had a BUDDY run an extension on his o2 sensors for his new headers the right one had a wire completely burned through and the wire had broken. could that cause it to dump fuel before it starts or would it wait till closed loop to read it? i put another o2 in it but it still didnt start. i asked about the extensions they put in and they are butt connected and have 14 gauge wire.i havent ohmed the wires for the o2 back to the pcm yet but i think i will tonight. he also told me last night that the carhasnt been running right since the headers were put on. once again his buddy told him that it was because his rear o2s were not deleted from the pcm yet. I think that the wires for the o2 is causeing to much resistance and giveing the o2 a false reading nothing to do with the no start just want to know what yall think about this type of extension.
03-16-2007, 11:35 AM
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when i put my headers in i tried to extend the o2's as well and it was nothing but problems..... anytime i hit a puddle of water it would run like crap and to the point where it would want to turn off.... ITs probably throwing too much fuel, plugs are probably bad now b/c of so much fuel..... get o2 extensions and a new pair of o2's....
03-16-2007, 01:26 PM
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that would be a good idea but in all the knowledge they spliced into the harness side instead of the o2 side so i have no choice but to try to fix it. then its all hopes and dreams. weve cleaned up the plugs and let the car sit to drain residual gas down do you think o2 is the no start problem. i thought it was only in closed loop that they work.
03-16-2007, 08:04 PM
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alright new update its still got ALOT of fuel we now have spark for a change i pulled the opti and cleaned it up. now it backfires from fuel i believe i pulled the pump fuse to clean up the chambers alittle bit. i think we are going to pull out spark plugs again. but i still cant figure out what would cause it to over fuel it like that. The only thing thats not reading right is the map it still says 30hg. we pulled the plug and it droped it down to 2hg. no change so i dont think thats it either. any ideas?
03-17-2007, 12:01 PM
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no codes in pcm just checked wires last night after i cleaned up the opti it acts like its going to start. i dont know about the regulator any ideas on a way to check it
03-17-2007, 12:11 PM
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well you really cant put the opti on wrong unless your just a total dumbass. The computer controlles it. Its most likely not going to be the opti. If its getting fuel, Id try other things. See if fire is coming out of the coil, coil wire to distributor, then from teh distributor. One of those has to be a bad link. Was for me recently. No matter what is wrong it should still start with spark and fuel.
03-17-2007, 12:12 PM
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Originally Posted by FIREHAWK #07
when i put my headers in i tried to extend the o2's as well and it was nothing but problems..... anytime i hit a puddle of water it would run like crap and to the point where it would want to turn off.... ITs probably throwing too much fuel, plugs are probably bad now b/c of so much fuel..... get o2 extensions and a new pair of o2's....
