rebuilt engine, lt4 hot cam kit-runs like crap
11-19-2009, 02:39 PM
#1
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rebuilt engine, lt4 hot cam kit-runs like crap
i have a 95 z28, we just completely rebuilt the engine, stock bottom end, we put the lt4 hot cam kit in it with the mr. gasket 5716 headgaskets to up the compression a bit (prob around 10.8:1 right now)has hooker shortys with the air tubes welded shut. EGR is deleted. stock 24# injectors, etc. had the pcm reprogrammed by a guy locally to delete the egr and AIR pump. Car runs like crap, we did hook a muffler up right at the ypipe to see if it made a difference, but none. At idle, the engine shakes and doesnt stop shaking until roughly 2200 rpm. When you rev the engine up, the rpms come back down very slowly. When you drive it down the road, it has very little power until you get into the higher rpms. I do have a Snap on scanner and i hooked it up, i have a code 27 which is for Exhaust Gas Recirculation (EGR) vacuum control signal solenoid valve circuit-QDM. i also watched my knock sensor parameters and it was detecting some knock and retarding the time 1-2 deg. at idle(prob. because the roller rockers). i didnt see any obvious vacuum leaks, but does that code mean that the guy that reprogrammed my ecm didnt fully delete the egr? any help would be great..thanks
11-19-2009, 02:48 PM
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Make sure you didn't over tighten your valve. 1/8 to 1/4 turn past 0 lash then tighten.
Did your car run like crap prior to the tune? How did it get tuned and it still runs like crap? Mail order? Do you have a stock PCM to try?
And is your fuel pressure maintaining around 40 at idle? or below 2200.
Did your car run like crap prior to the tune? How did it get tuned and it still runs like crap? Mail order? Do you have a stock PCM to try?
And is your fuel pressure maintaining around 40 at idle? or below 2200.
11-19-2009, 03:03 PM
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After we got the engine in and running, i ran the valve adjustment with the engine running method, 1/2 turn past zero lash..(stock lifters). i had him tune the pcm while i was putting the engine together so it would be ready to go and i dont have another 94-95 pcm to use as a test. fuel pressure is 42 psi at idle
11-19-2009, 04:20 PM
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I would make sure they were set properly. Not sure how many you've done or your experience/comfort with them.
If the engine revs down slowly when your off the gas I'm thinking that the exhaust valves are letting gases out of the engine. Would also cause it to shake bad. Like if you put long tube headers on your car it revs down quicker than if you had manifolds
thats where I would start
If the engine revs down slowly when your off the gas I'm thinking that the exhaust valves are letting gases out of the engine. Would also cause it to shake bad. Like if you put long tube headers on your car it revs down quicker than if you had manifolds
thats where I would start
11-20-2009, 12:13 AM
#7
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Crossed plug wires or one or more lifters set too tightly can cause your problems too.
Tell us how you went about setting the lifter preload.
Jake
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Tell us how you went about setting the lifter preload.
Jake
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11-20-2009, 10:46 AM
#8
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The drivers side wires are somewhat crossed because the clip broke. As far as valve adjustment, I started the eng up and went down the row on the left bank loosening the nut until it started clicking, then I tightened them until the clicking stopd plus an additional half turn. Then I set my poly locks and did the other side.
11-20-2009, 11:48 AM
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You need to repair the EGR problem first.
Fortunately I've never had a vacuum leaking EGR problem but I've read posts from others who have. If your EGR is leaking vacuum that's, well, a vacuum leak and will cause the engine to run badly.
There's a tool used to test whether the EGR can hold vacuum. I hope someone who worked with it before can post more details for you on how to use it.
Jake
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Fortunately I've never had a vacuum leaking EGR problem but I've read posts from others who have. If your EGR is leaking vacuum that's, well, a vacuum leak and will cause the engine to run badly.
There's a tool used to test whether the EGR can hold vacuum. I hope someone who worked with it before can post more details for you on how to use it.
Jake
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11-20-2009, 12:16 PM
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As stated in the first post, I don't have egr, its deleted and I had the ecm reprogrammed to delete it.I blocked off all open ports at the intake as well..is this code normal when egr is deleted? Maybe I need to put a resistor in the connector..what does Quad Driver Module mean at the end of that code?
11-20-2009, 12:31 PM
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The "EGR problem" indicated by DTC 27 is for the missing solenoid/electrical circuit. It has no affect nor could it cause a vacuum leak.
QDM means you used the wrong code list (or the generic info from the scanner). The last year that used a "QDM" (Quad Driver Module) was 93. Use Shoebox's code list.
You can minimize false knock from the roller rockers with the LT4 knock module, if you can verify its the rocker noise causing the retard.
QDM means you used the wrong code list (or the generic info from the scanner). The last year that used a "QDM" (Quad Driver Module) was 93. Use Shoebox's code list.
You can minimize false knock from the roller rockers with the LT4 knock module, if you can verify its the rocker noise causing the retard.
11-20-2009, 12:45 PM
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Would a 120 ohm resistor make the SES light go out? The only way I could really verify the roller rockers were causing the knock retard would be to get an lt4 module and see if I'm still getting any retard correct? Would 2 degrees of retarded timing cause a tremendous loss of power and cause the rpms to come down slower?
11-20-2009, 04:28 PM
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As stated in the first post, I don't have egr, its deleted and I had the ecm reprogrammed to delete it.I blocked off all open ports at the intake as well..is this code normal when egr is deleted? Maybe I need to put a resistor in the connector..what does Quad Driver Module mean at the end of that code?
Sorry, I missed the part where you'd deleted the EGR.
My EGR has been deleted also. In fact, the LT1 intake I'm running has had the EGR opening welded shut and I don't have the solenoid mounted either.
PCMFORLESS tuned my PCM and Bryan turned off the EGR. I haven't ever gotten a EGR code and didn't install any resistor.
So, based on that, i suspect that your programmer didn't do something Bryan did to mine. Of course, mine's a 96, maybe that makes a difference.
Jake
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Last edited by JAKEJR; 11-20-2009 at 04:49 PM.
11-20-2009, 04:36 PM
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Run some high octane, unleaded racing fuel, to see if it eliminates the knock retard. If it doesn't, its probably false knock, and you will have to track down the source of the noise. The rockers would be a prime suspect.