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Having Trouble Getting Engine To Run Right

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Having Trouble Getting Engine To Run Right

ChevroletSS ChevroletSS
New User | Posts: 1 | Joined: 11/12
Posted: 11/18/12
09:51 AM

I have a 1994 C1500 that I put a 305 in.  This is my daily driver.  I reused everything that was in the truck before like cylinder heads, intake, and throttle body.  There used to be a 350 in this truck.  I have everything back together, new plugs and wires.  The truck has a miss in it very bad.  I have the timing right.  I have the plug wires right.  I did a compression test and all cylinders are at 90.  One thing I noticed about my plugs are they are all black now.  I thought maybe its cause I have a 350 throttle body but called the parts store and a 350 and 305 throttle body is the exact same thing except injectors.  I dont hink its my injectors.  Why am I having this issue.  It ran fine before with the 350.  

76Skylark 76Skylark
Guru | Posts: 853 | Joined: 12/11
Posted: 11/18/12
12:34 PM

Check the spray from the injectors does it dribble or do the both make a nice spray pattern.I usually see problems with one side not spraying at all so then it isn't rich are you sure the valves arent too tight, as an even 90 psi is good it is half of a new engine,so is the cam big?  

Dave632 Dave632
Addict | Posts: 2220 | Joined: 07/08
Posted: 11/18/12
01:15 PM

If your plugs are black you're running rich for some reason or other.

The fouled plugs are the reason you're engine is missing.

I would suggest you check everything in relation to your fuel mixture.  

pepsi1 pepsi1
Guru | Posts: 1718 | Joined: 09/11
Posted: 11/18/12
02:57 PM

Make ure you have a Battery that has been fully charged.
  Did you use the correct head gaskets for the 305 and not the 350 head gaskets. 90  PSI is even, but very low. You really want a minimum of 125PSI. If the engine won't make compression it won't make power. I would recheck the valve adjustment and make sure you don't have any tight intake valves. Like Dave said if your spark plugs are black they are fouled. Put a set of AC R45TS. Don't throw the other plugs away unless there old.


waynep71222 waynep71222
Enthusiast | Posts: 448 | Joined: 03/12
Posted: 11/18/12
11:20 PM

grounds ground grounds.... did you manage to get them all hooked back up????

how about the oxygen sensors...    installed and plugged in...    do you have a volt meter.. can you get it fired up and see if the oxygen sensor voltages are NOT stuck in one position. these engines require oxygen sensor feedback to operate..  if the previous motor lost its head gaskets it could have contaminated the head gaskets...

could the exhaust system be plugged up.. melted clogged cats..  shop rags wedged into the head pipes that did not get removed but pushed down??? do you own a vacuum gauge??

is the MAP sensor hooked up to MANIFOLD vacuum properly...

is the engine coolant temp sensor with 2 wires properly plugged in....  it has an oval connector..
if the sensor is bad.. or not plugged in.. the computer will think the engine temp is -20F..  so it will dump fuel...

is there any chance that the fuel pressure regulator has failed??? or that the fuel lines that were disconnected from the throttle body got dirt in them...

you can use a TIMING light to look at the fuel injector spray pattern. .

how is the ignition timing???    there is a wire to disconnect to set the base timing...

you can set the base timing with the engine off...   there is a label on the core support to say what the base timing is...   10 degrees probably.. could be 15 or could be 0.. i don't recall right this second...  but you can rotate the crankshaft in normal direction of rotation and stop without going past the base timing mark you have...   you can remove the distributer cap and see if the reluctor teeth and the pick up coil teeth line up perfectly...   if they are not aligned.. you can rotate the housing till they do and lock it there....  that should be really close to perfect base timing..   if the timing is off.. it will run horrible..

do you happen to have an OBD1 scan tool to allow you to access the LIVE DATA stream not just the trouble codes..

are all the spark plug wires properly inserted onto the distributer cap... and properly latched to the spark plugs???