1995 Chevrolet Lumina 3.1 (M) Motor>>>>Runs rough at idle and under acceleration

[mp1642]

Hopefully someone can help. I will give all the facts known to me to help aid in diagnosis......
Vehicle info: 1995 chev. Lumina 3.1 Liter (M) motor with OBD 2 system
I recently replaced the head gaskets, lower intake maniofold gaskets, coolant pump, spark plugs and ignition wires. ( all done at same time for internal coolant leak )
I have done this job twice before on my other lumina and a malibu. All vac lines and emission components, sensors, wire looms, connectors ect. were reinstalled in same position and right location.
After all done I started engine and noted engine runs rough at idle and upon acceleration.
-No ses/check engine warning lamp illuminated on dash
-Does not appear to run rich
-I pulled all spark plugs and inspected>>>>no wet or foul plugs
- I placed long screw driver to each fuel injector and the other end on my ear....I can hear all injectors making an audable clicking noise.

Any thoughts or suggestions on helping me with diagnosis.
Please keep in mind I have basic knowledge of engines and diagnosis im not a professional or a mechanic. I follow Haynes manual for all repairs and info.

Thanks in advance

[maxwedge]

Is this a dead misfire? If so suspect maybe swapped pushrods, do a compression test to verify not an internal problem this advise assumes proper wire routing and good spark to all cylinders all injectors operating normally.

[discnik]

You said you replaced lower intake gasket, Does it have an upper intake,(Plentum), gasket ? Was this replaced ? Also did you re-check the torque on your intake bolts ? Have you tried listening for any vaccuum leaks ?

[mp1642]

I was under the impression that a "dead" or random missfire will command the MIL light???
As far as pushrods and the conventional ball/pivot style rockers.....I used a cardboard box marked with engine direction to place all pushrods and rockers in to keep from mixing up.
I have heard that fuel injectors are a common problem with driveability/running rough. I was also told when I put a screwdriver to the injectors I only verified voltage to the injectors and not flow rate. How can I check flow rate without an expensive balance tester?????

Another serious problem that is documented: The 3.1 L vin M engine uses a hollow camshaft with pressed on camshaft lobes which can move on the camshaft. This condition can happen after this engine overheats.
Has anyone had this problem???? and how do you verify this????

Thanks for your posts

[mp1642]

I did replace the upper intake ( plenum ) gaskets as part of the complete job.
I torqued the lower inatke bolts to 115 in. lbs. on both the horizontal and vertical bolts. ( torqued the vertical bolts first and then horizontal )
The upper intake/plenum bolts were torqued to 89 in. lbs.
No apperant vac. leaks>>>> I sprayed carb cleaner around intake and plenum area to listemn for an RPM increase>>>>No increase noted

Please let me know any further diagnosis testing or any questions

Thanks for the post

[maxwedge]

95 will not set a misfire code in the transitional obd11 years. Try and isolate the cylinder by shorting a wire one at a time, do this just off idle and look for no rpm drop on the affected cylinder. Then focus on that area, plug/wire/compression/injector. This is all basic diagnostics for isolating a suspect cylinder misfire.

[mp1642]

Please explain the process in shorting out a wire. Pull ignition wire with wire puller at coil pack with engine running???



Thank you for the post

[maxwedge]

Ground one plug wire at a time.

[mp1642]

UPDATE !!!

With your help I was able to isolate and correct the problem. Here is what I did to find it......

Using 6 paper clips, straigtened and lubed, slide the paper clips between the boot and wire at the ignition coil until the paper clip contacts the metal terminal. I started and ran engine. Using a test light ( grounded to the engine ground ) with the probe end I touched each of the paper clips one at a time to find which cylinder wouldent make engine run worse.
Long behold cylinder #1 would not change engine running rough to worse. It had plenty of spark ( arced to probe nice )
Pulled plenum off and found #1 fuel injector dirty with soot. Replaced injector and now engine runs great!

Thanks for all your help!!!!

[maxwedge]

Well done! Run some Chevron Techron thru the tank per instructions to try and clean up the other injectors.