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Unread 09-09-2009, 10:18 AM   #1
labman1
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2.5 runs but not well

Replaced cracked head with a re-manufactured head. Installed rocker arms and pushrods in the exact order they were removed. Torqued per specs. Have not been able to get it to run right since. Loss of power and back fires through the engine. We did not do this right after re-assembly, but since having trouble we have located TDC of piston #1 (compression stroke) and verified rotor pointing to cylinder #1 wiring terminal while timing marks are aligned on "0". Same problems exist, loss of power and back fires through the engine. Any ideas? Help!

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Unread 09-09-2009, 11:32 AM   #2
redjeep669
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cam timing.
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Unread 09-09-2009, 01:29 PM   #3
EABiker
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It could also be vacuum leaks in the intake manifold assuming the spark and valve timing is correct.
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Unread 09-10-2009, 03:06 AM   #4
labman1
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i think you may be right, how does the cam timing change with the changing of the head? we never have pulled the timing chain cover or timing chain, looks like it's going to be an interesting weekend.
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Unread 09-10-2009, 05:33 AM   #5
EABiker
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Quote:
Originally Posted by labman1 View Post
i think you may be right, how does the cam timing change with the changing of the head? we never have pulled the timing chain cover or timing chain, looks like it's going to be an interesting weekend.

If you didn't touch the cam or chain, then you can certainly rule those out. Are you sure piston 1 was at TDC on the compression stroke rather than the exhaust? The distributer could be 180 deg. out!
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Unread 09-12-2009, 04:25 PM   #6
labman1
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As far as cam timing as you said EABiker we did not mess with the chain or cam, but while we were changing the head we did not have the parking brake set. It was in park, no parking brake. Could us leaning on the vehicle while replacing the head move it enough to move the cam timing?

I have tried to verify that we are at TDC of the compression stroke today. I have removed the valve cover so I can see the position of the valves for cylinder 1. With the #1 plug removed and both of the #1 valves closed the #1 piston reaches TDC between 6 degrees and 0. I am sticking a clothes hanger into the #1 plug hole and letting it rest on top of the piston as I turn the crankshaft with a ratchet and socket. The clothes hanger appears to stop rising between 6 degrees and 0. I know this is primitive, but as you can tell I'm not a mechanic.
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Unread 09-12-2009, 04:49 PM   #7
MJMPC
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Maybe a stuck valve ?
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Unread 09-13-2009, 06:02 AM   #8
labman1
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How do I check to see if a valve is stuck?
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Unread 09-13-2009, 06:27 PM   #9
RandyYJ
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The fire is going to be set by the CPS in a 94. I would put a timing light on it, and if the white line is anywhere around the 0 degree TDC then you're not 180 out. IIRC #1 will be firing a touch late until it fires up then it will start firing a little before TDC. Pull your IAC and spray it down with brake cleaner real good and clean all the carbon off of it. If your IAC is stuck it will spit and sputter and backfire when you give it starting fluid, but will not run. These are some things I learned swapping in a 4.0, so they may not all apply, but that's my little bit of experience.
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Unread 09-14-2009, 03:12 AM   #10
labman1
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My son has replaced the CPS (Crankshaft Position Sensor) did not change a thing. Randy I appreciate the feedback, help me out though with the acronyms IIRC and IAC. Thanks, Charlie
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Unread 09-14-2009, 04:14 AM   #11
RandyYJ
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If I Remember Correctly, and Idle air control.

The IAC is a sensor on the back side of the throttle body with I think 4 torx screws. I couldn't get my 4.0 to run, and once I pulled and cleaned that it fired right up. It might be coincidence, but worth a shot.
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