I am stumped...
Thread Starter
On The Tree
Joined: Mar 2013
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Never disconnected the wires, just left the coil packs hang on the side. I did unplug the sub harness, but plugged them back in when i was done. I have checked those.
Yeah, there is always "that guy" I am going to start doing the compression test now, hoping to rule out a possible bent valve. I have checked fuel pressure at idle, reading at 60 psi. I just checked over the whole top end vacuum and no leaks. Just cleaned my IAC and that didnt help a thing. I really am hoping there are no bent valves. I havent even gotten to go WOT on this engine yet...
First off, when you post on ls1 tech you're gonna run into jacka$$'s that wanna make you feel stupid! They know it all. Do a compression test on the cylinders to rule that out. If this happened after messing with the valvetrain there is always a improbable chance that a valve got bent somehow. This would cause the dead miss and popping. Once you establish that you have good compression in all cylinders you can move on to fueling and ignition issues. We all run into problems with our cars. There are some guys on here that know there **** and hopefully will chime in. You'll know who they are right away because they'll try to help you instead of criticizing you bud.
Thread Starter
On The Tree
Joined: Mar 2013
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Desired RPM (what engine speed the PCM wants)
Actual RPM (what the engine is doing, should be within a few RPM of desired)
IAC Counts (what position the PCM has commanded the IAC stepper motor to)
In the meantime, if you work the throttle long enough to get the engine up to temp and the PCM into Closed Loop mode does the idle smooth out and manage on its own without you pedaling it to keep it running?
Thread Starter
On The Tree
Joined: Mar 2013
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That video is actually really helpful...if you can get access to a scantool and read the following data it will help rule out a bad IAC:
Desired RPM (what engine speed the PCM wants)
Actual RPM (what the engine is doing, should be within a few RPM of desired)
IAC Counts (what position the PCM has commanded the IAC stepper motor to)
In the meantime, if you work the throttle long enough to get the engine up to temp and the PCM into Closed Loop mode does the idle smooth out and manage on its own without you pedaling it to keep it running?
Desired RPM (what engine speed the PCM wants)
Actual RPM (what the engine is doing, should be within a few RPM of desired)
IAC Counts (what position the PCM has commanded the IAC stepper motor to)
In the meantime, if you work the throttle long enough to get the engine up to temp and the PCM into Closed Loop mode does the idle smooth out and manage on its own without you pedaling it to keep it running?
Ok, lets look at this and do some diagnosing just from the information given, it ran good before the p-rod trials and the trunion upgrade, then it did'nt so whenever there is backfiring out the exhaust and once in a while the intake and You've messed with the valves , thats a sure sign that 1 or more valves are staying open maybe .002 or .003" ,,,,,,or if 12 or less valves are a little open They could be open more than .002 or .003, if all are a little open than only open .001 or .002 or maybe .003".I say either the trunion upgrade changed it just a little or more likely is that You put oil into the lifters and it needs to self adjust the amount of oil and then it will run right ,,,,,,,not very long 10 or 20 minutes running should do it
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On The Tree
Joined: Mar 2013
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Ok, lets look at this and do some diagnosing just from the information given, it ran good before the p-rod trials and the trunion upgrade, then it did'nt so whenever there is backfiring out the exhaust and once in a while the intake and You've messed with the valves , thats a sure sign that 1 or more valves are staying open maybe .002 or .003" ,,,,,,or if 12 or less valves are a little open They could be open more than .002 or .003, if all are a little open than only open .001 or .002 or maybe .003".I say either the trunion upgrade changed it just a little or more likely is that You put oil into the lifters and it needs to self adjust the amount of oil and then it will run right ,,,,,,,not very long 10 or 20 minutes running should do it
A few days ago you posted that you were going to start doing the compression test...how's that coming? Post your readings (make sure you have the gas pedal at WOT and the fuel pump relay or both INJ 1 and INJ 2 fuses pulled) when you get done.
Thread Starter
On The Tree
Joined: Mar 2013
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Well I just let my car run for 20 minutes. It seemed to run significantly better... so i decided to drive it down the street and back. It runs better than it did, but still not right. Its rough (not as rough as before) untill about 2200 rpms. When it hits 2200, it seems as if a switch hit and runs smoother right away. You can even hear the valves flow immediately better when it hits 2200. It did not backfire this time either. So you could say, its "kind of" driveable at this point. Does this point to my valves?
As for the leak down test, it will most likely be this weekend. Swamped at work and working OT.
As for the leak down test, it will most likely be this weekend. Swamped at work and working OT.
just throwing this out there you may have bent a valve when you put those longer push rods in there. With those 5.3 heads and depending on what head gaskets you are running you may have had PTV clearance issues with the longer push rods. A cylinder leakdown test or even a compression test should/will point this out.
Thread Starter
On The Tree
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Hes coming out to me this weekend, going to data log and see what its doing. If its nothing with the tune, Its most likely going to CBI street cars for valve job, port and polish, assembly, etc. This way i know it gets done right and will have a warranty on the work. Obviously something that i did caused this. Hes an LSX specialist locally here. Very good rates for labor. Im the DIY kind of guy, just getting frustrated with this thing.
TECH Addict
Joined: Aug 2005
Posts: 2,305
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From: Monroe,NY
Always check the simple thinds first. I had a similar problem and it ended up being a bad coil. If you have an infared temp gun while its running check the temp of each header primary and make sure none of them are way off on temp. If one is way off on temp that is your bad cylinder. Also check your spark plugs and wires.
Teching In
Joined: Nov 2008
Posts: 23
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From: Utah
the video sounds like valve train noise compression check or leak down would answer your questions. double check the truion upgrade I have never done one but maybe something went in the wrong way ive seen people put roller rockers on with the flat side down towards the head and the round part facing up with the bolt on it and have major issues
Thread Starter
On The Tree
Joined: Mar 2013
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The problem ended up being in the injector wiring harness. One of the wires had slipped out of the plug on cylinder 5. Which was weird but it never threw a code. And the odd chances of that happening while i was working on the PRs/rockers. All in all, I got a whole new MSD ignition, learned to look over everything, got pretty good at installing rockers... lol, and car runs stronger than before. Thank you all for the input. With the exception of "Assholio"
Last edited by Fast98Z28; Nov 5, 2013 at 04:21 PM.
TECH Addict
Joined: Mar 2013
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Funny how little things can bite yer azz.
I was working on my jeep changing valve cover gasket, then it wouldn't start......about drove me crazy. I found a tiny stone fell into one of the connectors for the engine harness when I unplugged it. When I plugged it back in it forced the contact inside back. Took me about 6 hrs to find it.
I was working on my jeep changing valve cover gasket, then it wouldn't start......about drove me crazy. I found a tiny stone fell into one of the connectors for the engine harness when I unplugged it. When I plugged it back in it forced the contact inside back. Took me about 6 hrs to find it.
Last edited by RockinWs6; Nov 5, 2013 at 04:43 PM.