No Power/Misfires

[SHOBen]

Much like another post I bought a 90 Model that was not running. It had the intake off and sat for 7 months. I have sinced put the car back together, basically did the 60k upper, all valves were inspec. The cam lobes looked good. This was all I knew about the car when I bought other than the kid telling me it would not pass emissions. After I put a new battery in it today it fired off, but has a "miss" it sounded like electronic miss, but it is not. It has brand new plugs.

My father-in-law and I thought we heard a mechanical sound coming from the front bank as you look at the cylinder bank the hole closet to the cam gear. We did a compression test it made it up to 150psi (not sure how accurate the gauge is) anyhow it leaked down on all 3 cylinders immediately, we did not do the back. I also drove it down the street it made no power, and the oil light came on just for a split second. I am not sure if the car with 66k, had ever had the timing belt or the valves looked at before. The valves being in spec lead me to believe it was, and I think the cam gear is off a notch or two and is causing the immediately leak down on the compression test. THoughts, suggestions, comments.

 

[92inPA]

The power loss could be caused by lots of things. With the car sitting for an extended period, bad fuel comes to mind first. Also, are you 100% sure you have the plugs wires on correctly? That is well worth double checking. They should be routed like this...
Spark Plug Routing photo

 

[SHOBen]

Bump this sucka, and lets see what you guys come up with after work hours.

 

[SHOBen]

no one knows anything?

 

[SHOBen]

New Update:
The compresson gauge was leaking not the cylinders. I checked the timing this way... Took off the top timing cover turned the engine by hand, the crank pulley mark lined up on 0 degrees and the cams were dead on. Is this thorough enough or did the crank pulley need to come off to verify? I am taking the y pipe off today to see what that will do, now that I know the compression gauge was bad.

 

[92inPA]

Look no further as far as the timing is concerned. You have verified that is okay. It also sounds like compression is good, even though the gauge isn't.

Have you double checked the spark plug wire routing? Use think link I provided earlier to get the correct routing. You say the plugs are new. Did you check their gap before installing? Have you pulled them back out to see if you can spot which cylinder isn't firing?

 

[SHOBen]

I know the plug wires are ran correctly. I started it last night and the backfiring has gone away. However when I manually moved the throttle a loud tapping noise came from the engine again, same piston and or area, front bank cylinder closest to cam gear. I was going to drive it and see how it ran. I also believe that taking off the y-pipe might reveal that the cats are somewhat clogged due to the lack of power. There was a new thermostat in the trunk when I got the car when I bought which leads me to believe it was running rich. Perhaps the fresh gas and marvel mystery oil burned out the cats somewhat and is reducing the restrictions at the cats decreasing the back fires. The noise coming from the cylinder bank with the engine shuddering at the sametime is what is confusing me.

 

[93rev2sev]

Codes?

Cylinder balance test.

 

[SHOBen]

Update:
The car has 50% more power, but that is still 50% less than it should. ALL engine noise is now gone (sigh of relief) however I still have intermittent backfires.
I also did get a Check Engine Light, but I had to turn the car off, and it did not come back on. Questions:
1) Can I retrieve this check engine light
2) How do you do it on these cars, on my OBD I GM I just cross the terminals with a wire, thanks for the help.
Any thoughts on the intermittent back fires? Bad plug wires with 66k??? Is that possible. I think my cats are shot. I am going to take off the y pipe and run open headers and see how much power there is then. Is there any precautions i.e. fire and things getting hot I need to worry about for a few short trips down the street?

 

[SHOBen]

Codes

Time to talk to myself again...
Got these codes on KOEO 91 and 81'
KOER 021, 091, 025, 074, 052
I forgot I had the front O2 unplugged ignore the lean front cylinder condition. Thoughts? I still have random backfires.
I took off my y-pipe and the backfiring seemed to stop with just open headers. I broke my shifter cable so I am installing my rod shifter now so I can drive it with open headers and see if the power is where it should be.

 

[92inPA]

I would do the cylinder balance test to see which cylinders are causing the issues. Then clear the codes, install fresh plugs and wires, and run all the tests again (KOEO, KOER & cyl bal). Running your SHO at all without the Y pipe installed won't help, since you need the O2 sensors installed and functioning properly.

What makes you believe your cats are shot?

 

[projectSHO89]

If you're getting a mechanical knocking, you probably either spit out a shim (which would also cause low power as the valve wouldn't be working) or you've got a spun rod bearing.

Steve

 

[SHOBen]

Cylinder balance test.

I did another test, without the ypipe on (Yes i know!) I got 21, 41, 91, 25, 74, 52. A cylinder balance test said #5 and #6. I am going to put the y-pipe back on and do it again, but what about the cylinder balance test?

 

[SHOZ123]

Is the power plug secure and properly inserted in the coil?

 

[SHOBen]

Is the power plug secure and properly inserted in the coil?

It is in there. I did a cylinder balance test again now 1&3 showed up and not 5 &6. I pulled all the plugs except the middle rear and all of them were different colored than the next one, literally everyone of them was different. I am starting to get really ****** at this car. How the **** can it be so jacked up with 66k miles.

 

[SHOZ123]

Dirty Fuel Injectors? :type:

 

[SHOBen]

I was going to put a vacuum line on the port on the back of the intake and send some sea foam through the engine...
Think the fuel filter could cause this?
Could my wires be bad? I had to previous SHO's and never had any problems with the wires or coil.
Is there any SHO mechanic's in Houston?