Fully Built LQ9 Missfiring/Stalling/Sputtering/Backfiring At Any TP when warm
09-26-2017, 04:12 AM
#1
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Fully Built LQ9 Missfiring/Stalling/Sputtering/Backfiring At Any TP when warm Sorry if this doesnt belong here....i couldnt find where to post this.
Ok so a little history if you don't already know. 2 year project of mine, lq9 iron block fully built, by fully built I mean .30 over, sleeved, pistons, rods, heads, intake, ARP yada yada yada. Built by me to support well over 1500whp. Sent it to the same state that I bought the shell from to have it and the trans installed this year, tuned by a shop out there (it's a SD "speed density" tune so no maf guys) flew out, drove it back, lots of issues on the way back....none of which had to do with the engine...in fact I still think my work is good as I don't think my problem has anything to do with my engine and so far all the other problems haven't either, o2's, plugs, wires, thermostat, MAP, crank sensor, iat sensor, TPS sensor, alternator, battery, basically all the stuff I paid them to do/install/check before they let the tuner do his work then check before I drove it back which was 1800 miles. Anyways, after all that it seemed to be fine...not even 3000 miles on it yet. Today driving to LA all seemed well, on the way back it all of a sudden started backfiring...and we're not talking like 1 or 2 every once in awhile, I mean like anytime I went anywhere near part throttle or 25% throttle and got way worse as I progressively got further in the throttle until WOT. So I stopped gave it a break and looked stuff over, didn't see anything out of ordinary so after it cooled I started up and it took off fine and cruised fine until it warmed up again then all hell broke loose again....literally, fire ***** as if I had my 2 step turned on and was using it....or dat naawwwsss. Anyways, so I got it home and now she sits because I'm stumped, not much that can go wrong with speed density and my AFR are normal at 12-14 cruising and 11-12 on it (I'm boosted making nearly 1000whp on pump gas so that's normal for me especially with the compression ratio I built the engine for) and not a single speck of smoke or oil in the plugs.....I'm in the engine alone $30k not including the shell and everything else so im kinda broke at the moment so be gentle.....thank you in advance for help.
Ok so a little history if you don't already know. 2 year project of mine, lq9 iron block fully built, by fully built I mean .30 over, sleeved, pistons, rods, heads, intake, ARP yada yada yada. Built by me to support well over 1500whp. Sent it to the same state that I bought the shell from to have it and the trans installed this year, tuned by a shop out there (it's a SD "speed density" tune so no maf guys) flew out, drove it back, lots of issues on the way back....none of which had to do with the engine...in fact I still think my work is good as I don't think my problem has anything to do with my engine and so far all the other problems haven't either, o2's, plugs, wires, thermostat, MAP, crank sensor, iat sensor, TPS sensor, alternator, battery, basically all the stuff I paid them to do/install/check before they let the tuner do his work then check before I drove it back which was 1800 miles. Anyways, after all that it seemed to be fine...not even 3000 miles on it yet. Today driving to LA all seemed well, on the way back it all of a sudden started backfiring...and we're not talking like 1 or 2 every once in awhile, I mean like anytime I went anywhere near part throttle or 25% throttle and got way worse as I progressively got further in the throttle until WOT. So I stopped gave it a break and looked stuff over, didn't see anything out of ordinary so after it cooled I started up and it took off fine and cruised fine until it warmed up again then all hell broke loose again....literally, fire ***** as if I had my 2 step turned on and was using it....or dat naawwwsss. Anyways, so I got it home and now she sits because I'm stumped, not much that can go wrong with speed density and my AFR are normal at 12-14 cruising and 11-12 on it (I'm boosted making nearly 1000whp on pump gas so that's normal for me especially with the compression ratio I built the engine for) and not a single speck of smoke or oil in the plugs.....I'm in the engine alone $30k not including the shell and everything else so im kinda broke at the moment so be gentle.....thank you in advance for help.
Last edited by CodyCamaro13; 09-26-2017 at 04:19 AM.
09-26-2017, 08:49 AM
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If it's fairly consistent that it runs good until it warms up almost sounds like it goes closed loop and starts acting up. That it runs good cold pretty much rules out mechanical issues IMO
09-26-2017, 02:37 PM
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Darth_V8r I agree
2xLS1
my means of data logging is my tuning guy at the moment, I'm still in the process of this build so I don't currently have anything I personally can data log with, buying the shell and having everything installed and tuned in a different state and by a different tuning shop than my usual guy set me back money wise because I've had to replace alot of things the shop that installed everything was supposed to install/check before they let me drive off with it so funds are currently down until I get paid again sadly. And I didn't mean NOTHING can go wrong with an SD tune, it's just IMO alot less to go wrong with SD tuned vehicles. The problem is the shop that tuned my car (not my normal tuner) decided to turn pretty much all my check engine codes off except MAF codes which confused me but either way I'm pretty blind at this point because of that and I didn't even ask them to do it.
2xLS1
my means of data logging is my tuning guy at the moment, I'm still in the process of this build so I don't currently have anything I personally can data log with, buying the shell and having everything installed and tuned in a different state and by a different tuning shop than my usual guy set me back money wise because I've had to replace alot of things the shop that installed everything was supposed to install/check before they let me drive off with it so funds are currently down until I get paid again sadly. And I didn't mean NOTHING can go wrong with an SD tune, it's just IMO alot less to go wrong with SD tuned vehicles. The problem is the shop that tuned my car (not my normal tuner) decided to turn pretty much all my check engine codes off except MAF codes which confused me but either way I'm pretty blind at this point because of that and I didn't even ask them to do it.