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Old 09-17-2010, 12:49 PM
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1994 TBI issues

My new engine has been in for awhile and runs hard but will not idle properly all the time. I have relaced injecters, O2 sensor, IAC valve rebuilt throttle body and checked for vacuum leaks 100 times. What could my problem be? a timing issue? i have a oem replacement cam chain in it which has retardation built into it. In order to compensate for this i ahve the timing advanced 18 degrees! it does not ping either. Do i need to put the timing chain in the truck that is made for the cam? and also there is a funny buzzing noise coming from top of injector housing that matches RPM level...wierd... Please help Me!!

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Old 09-17-2010, 01:33 PM
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Originally Posted by shane.,herold
My new engine has been in for awhile and runs hard but will not idle properly all the time. I have relaced injecters, O2 sensor, IAC valve rebuilt throttle body and checked for vacuum leaks 100 times. What could my problem be? a timing issue? i have a oem replacement cam chain in it which has retardation built into it. In order to compensate for this i ahve the timing advanced 18 degrees! it does not ping either. Do i need to put the timing chain in the truck that is made for the cam? and also there is a funny buzzing noise coming from top of injector housing that matches RPM level...wierd... Please help Me!!
The injector shouldn't be making buzzing sounds, though in concert with engine RPM would be something to expect if they do as the injectors cycle very rapidly and that is in concert with RPMs.

You cannot defeat the timing set up without changing the chip in the computer to go with the change in timing set. The engine won't detonate because there is a detonation sensor that pulls out the timing advance when it hears pinging. If the engine is tripping that sensor, the engine will run run crappy with poor gas mileage, low power and rough running.

Operating temp is also sensitive, the engine needs to get to and above 176 degrees to get out of cold start mode (choke). If per-chance you dropped the thermostat to less than that, it isn't getting out of start up mode which will be excessively rich for a warm engine to always be running on.

Bogie
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Old 09-17-2010, 03:26 PM
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Tbi trucks! You just can't throw in an old cam and expect it to run right with out a lot of modding! chip tuning and so on! I send everyone to this site to where all the truck modding is going on. Some people don't thing you can make a lot of power with tbi but you can. It will help you out alot. www.fullsizechevy.com

Craig
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Old 09-17-2010, 07:14 PM
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That cam chain may be causing your problems. Why didn't you just use a stock replacement?
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Old 09-18-2010, 10:47 AM
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i used a stock replacement is the problem. The eddelbrock 3702 cam is made to use a older style cam chain with no retardation. i bought a chain to match it but have not put it in yet. The operating temp is correct that was my first thought.

yesterday at one point when it was idling correctly i un hooked the IAC and continued to drive it. It stumbles once on startup then runs fine after. i am at a loss but definately need to fix the timing situation. I backed it down to about 4 degrees once, it absolutely was gutless.
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