1994 Cutlass Supreme hesitation/sputter

[doberdog]

1) Car hesitating, sputtering and missing off the line
2) While in park, rev engine and during decal you hear a clicking sound almost like a shift solenoid trying to engage
a) Replaced throttle position sensor – no change
b) Swapped out each ignition pack – no change
c) Replaced missing vacuum line grommet in top of intake plenum – fixed issue
3) Car ran great for 2 days then problem resurfaced, including decal clicking sound
a) Toggled EGR with Tech-1, did not show change in idle performance
b) Only codes were related to disconnecting/reconnecting TPS and Idle Control sensors
c) Replaced spark plugs
4) Car still hesitates poorly off line, seems to run better >2500 rpm but can still feel miss
a) Replaced fuel filter
b) Checked fuel pressure which is showing some signs of being erratic
c) Cleaned throttle body and re-sealed
d) Cleaned EGR and re-sealed
e) Replaced vacuum sensor near rear bank of cylinders
f) Drilled hole in cat to check for back pressure
5) Car runs slightly better, hesitation not as severe, but still feel miss, and decent accel >2500 rpm
6) Going to try:
a) Compression check at each cylinder, suspect possible valve spring fracture
b) Changing fuel pump
c) Upper/lower intake manifold gaskets

[Tech II]

What do you mean:Checked fuel pressure which is showing some signs of being erratic

What is the pressure?


Toggled EGR and no change with a Tech I? This a linear , electrical EGR? If yes, and car did not fall on it's face as you opened it? If so, sounds like the upper plenum may be plugged, or the tube to the EGR is pugged or the EGR is not working.....this should have set a code....


You replaced the spark plugs....did one plug look different compared to others? Did you use OEM plugs? Did you change the wires? Did you check the coil terminals for carbonning or arcing? Did you check coil output with a spark tester?


Are you losing coolant?


Have you checked vac line to F/P regulator for the presense of gas?


Have you checked for vac leaks around the engine with carb cleaner?


Are there any codes?

[maxwedge]

Originally Posted by Tech II

What do you mean:Checked fuel pressure which is showing some signs of being erratic

What is the pressure?


Toggled EGR and no change with a Tech I? This a linear , electrical EGR? If yes, and car did not fall on it's face as you opened it? If so, sounds like the upper plenum may be plugged, or the tube to the EGR is pugged or the EGR is not working.....this should have set a code....


You replaced the spark plugs....did one plug look different compared to others? Did you use OEM plugs? Did you change the wires? Did you check the coil terminals for carbonning or arcing? Did you check coil output with a spark tester?


Are you losing coolant?


Have you checked vac line to F/P regulator for the presense of gas?


Have you checked for vac leaks around the engine with carb cleaner?


Are there any codes?

Great questions, I was just going to do about the same thing, Shep

[doberdog]

Here's the latest (from the mechanic doing the diagnosis). Fuel pump at about 20-25 psi, should be 35 and above. Used injector tester, shop air and a couple of cups of fuel in a reservoir to confirm fuel pump issue. Engine ran very well. Heard a hissing at lower intake and confirmed a gasket leak with some carb cleaner aimed at the area of concern. The issue still remains with a snapping sound when the throttle is rev'd quickly. The concern is a more serious issue that may present itself in the future, either near or far, that could include something in the valve train, valve hitting a piston, or a piston wrist pin. Tough to isolate without serious teardown. Need to decide at this point if the car is worth the pump and gasket band-aid repairs based on my son's budget.

Just wanted to update so future readers could use the diagnosis and information in their troubleshooting efforts. Thanks to all that offered their input to this thread.