LT1-LT4 Modifications - Need some help




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96Formula6spd
09-13-2009, 11:46 PM
Hey guys I am having a lot of trouble with my rebuilt engine and its looking more and more like the machine shop messed up. Anyways I got my engine back and put it back together. It was running horrible so I checked my plug wires,all my grounds, and all the connections, I even checked to make sure my fuel cap was on. So I took the plugs out and all of them were fouled. So I replaced them all with new ones. It was running a little bit better but not much so were were leaning toward injectors. So I got a noid tester and pluged it into the harness and every one passed. After that I check to make sure we have spark with a made up spark plug tool that you leave out and plug into your wire. Every one passed from the new gm opti. I also Have replaced the icm and coil. Next I took the injectors out and cleaned them by leaving them in chemtool injector cleaner for 2 hours and hitting them with the air compressor. They are much cleaner now put still no change in the running of the car. So today I took out my plugs again. Cylinders 1,4,5,8 looked good however cylinders 2,3,6,7 were fouled already. The car has been run less than 5 mins. I have checked the plug wires many times. I am starting to think that the people that rebuild my short block have the timing set not set correctly. Any thoughts? I am fresh out of ideas and want to sell the car but I know I will get nothing for it so I am stuck trying to fix what should be a perfect running car.


gregrob
09-13-2009, 11:49 PM
Does it have a bigger cam?

If so is it tuned for it?

Sounds to me like its just pig rich at idle.

96Formula6spd
09-14-2009, 01:22 AM
It has a lt-4 hotcam and the pcm was tuned by trificta


96Formula6spd
09-14-2009, 01:16 PM
Anybody got any ideas? I should have just gone over to the dark side with a lq swap.

derekderek
09-14-2009, 01:35 PM
Well how is it running? Is it backfiring any if so is it through the exhaust or intake? Does it have a miss to it and rocker knock? Valves adjusted properly, is there a difference in idle if you unplug the maf? Fuel pressure good? Any vacuum leaks you could have over looked,maybe the temp sensor is unplugged making it run rich. There are a ton of possobilities you have to give us alittle more info. Is it just running rich but idles fine have you driven it yet any stumbles? Hope this will get you on the right track. Ohh and most of all any codes being thrown?

96Formula6spd
09-14-2009, 02:12 PM
Well if you get the car started it will run around 1300 rpm if you hold it there however you can hear a miss. If you try to rev anything over 2500 it backfires. I tested the fuel pump with a gauge and it passed at 43.5 psi with the ingition on and 48 with the car running. The regulator also passed. I have checked the vacuum lines and all of the plug wires. I know I did the rockers right as I have done them before with no issues like this. I also cleaned the injectors and tested the harness. Injectors are nice and clean and the wiring harness passed. So that shows my pcm is good. So I am out of ideas.

derekderek
09-14-2009, 03:33 PM
So its popping out the exhaust? If so double check triple check your plug wires going to the plugs make sure they are on correct plug very easy to swap some around. Also check your maf try unplugging it see if it changes anything. Try checking your temp sensor for connection also. This is going to be a challenge though with out actually being there. Since its a new build there are so many factors in it.

96Formula6spd
09-14-2009, 06:23 PM
well i took the maf off once and it ran horrible. The water temp is plugged in and it works fine. People keep saying plug wires yet I have checked every one many times so its not those.

derekderek
09-14-2009, 06:54 PM
well i took the maf off once and it ran horrible. The water temp is plugged in and it works fine. People keep saying plug wires yet I have checked every one many times so its not those.

People keep saying check the wires because it is the easiest and most common mistake people make. Well if you are sure everything else is fine run a compression/leakdown test see what that turns up. If that comes up good then might have to start tearing into things check the timing what not.

96Formula6spd
09-14-2009, 08:38 PM
sounds like work I dont want to do. Tried to do a compression test but was having the hardest time getting the adapter to go into the spark plug hole. So I gave up on that. So Ill end up spending my weekend working on the car again rather than taking some time off from school. All summer it was work and fix the car which has not been running since February.

96Formula6spd
09-15-2009, 01:50 AM
So I was thinking some of my ruff running could be due to some bad gas along with the bad plugs. So I think this weekend I am going to clean up the plugs and then putting some new gas in it and some gas treatment since the fuel lines have been open pretty much the whole summer. What do you guys think. If this does not work I pulling the engine out for the 4th and hopefully the last time.

shbox
09-15-2009, 07:08 AM
If the plug wires are on right, you may want to double check the installation of the opti. That rich running is going to hamper your rings ever getting seated.

derekderek
09-15-2009, 07:18 AM
So I was thinking some of my ruff running could be due to some bad gas along with the bad plugs. So I think this weekend I am going to clean up the plugs and then putting some new gas in it and some gas treatment since the fuel lines have been open pretty much the whole summer. What do you guys think. If this does not work I pulling the engine out for the 4th and hopefully the last time.


If the gas is just 4-6 month old then I wouldnt think that would be your problem. I left gas in my car for alittle over 2yrs while I was deployed came back cranked right up and drove it out of storage no problems. Did you ever verifiy the Timing alignment or did someone else put it together for you?

96Formula6spd
09-15-2009, 12:42 PM
I never checked the timing however I did install the opti myself. I have installed an opti before and its just a matter of lining up the correct mark onto the pin on the cam. I did not check the timing as he had already put the timing cover and the harmonic balancer on. But now I am thinking i should have.