mrdap
Full Access Member
- Joined
- Jul 15, 2012
- Posts
- 199
- Reaction score
- 142
- Location
- USA
- First Name
- C/K_Lover
- Truck Year
- 81-91
- Truck Model
- C20/K30/V15/V2500
- Engine Size
- 350/454
Strange problem with my 1988 GMC Jimmy today.
350 TBI, 700R4, 120,000 miles
104° F Arizona
Driving, everything is normal.
Good oil pressure, over 30 psi.
Not overheating, under 210° around maybe 200 or 190
Alternator working properly, voltmeter at over 14 volts.
All of a sudden the engine seemed to lose RPM and responsiveness and I heard a medium loud tapping sound.
My immediate thought was I lost a rod bearing or a rocker arm.
But the sound did not really sound to me like a rod bearing or a crank bearing or a rocker arm, and unfortunately I've heard those before.
It was a tapping sound but more of a muffled tapping and the engine wanted to die.
Turned off the engine as quickly as possible and coasted into a parking spot.
I assumed I had run it out of oil although there are no leaks of any kind.
It's been about 7,417 mi since the last oil and filter, Shell Rotella T4 15W-40. 4,338 mi since last oil top off.
It's been using about one quart of oil per 3,500 mi. Seems normal.
Turned the engine off. Checked the oil. Looked like the crankcase was dry. Damn.
Assumed I ran it out of oil, it burns a little bit. About 1qt per 3,500 miles.
Went to Walmart got some more oil and funnels.
When I got back to the car I checked the oil again.
After the oil had drained back down into the pan, about 1 and 1/4 quarts low but definitely not empty.
I topped off the crankcase.
Started the engine. The muffled tapping was there but it sounded better or less loud.
The engine refused to idle, it would run as long as I gave it about half throttle but then it would want to die and it wouldn't idle. Quick to start and restart.
The tapping noise lessoned.
Oil pressure was good, above 30 psi, the voltmeter was working at 14+ volts, and the coolant temperature was low.
Instead of calling a tow truck I decided to just drive it home.
Whatever damage was done was done and I'm going to have to pull the engine anyway, I thought.
As I kept driving, in about one block the tapping noise went away.
However still the engine refused to idle.
Driving home everything was normal no unusual sounds no vibrations.
Just as peppy as usual.
Although I'm not standing on it.
Completely smooth and quiet in cruise.
All gauges look normal.
But it refused to idle without giving it significant throttle.
One time at a light I did see the check engine light come on so there might be a code in there, but as soon as the engine RPM increased the light went out. I'll pull the code later.
Made it home. I'm going to let it cool off.
The vehicle is well maintained by an avid enthusiast and professional engineer.
Not long ago all of the front accessories were rebuilt or replaced.
Water pump, alternator, power steering pump and hoses, fan clutch, belts all replaced.
Also fuel tank, fuel pump, fuel level sender, and fuel filter were replaced.
Also coil HV wire
All rubber vacuum hoses were replaced.
I was consistantly getting an average of 13.5 MPG in the city.
Any ideas?
Lock up converter stuck on?
Cat converter plugged?
350 TBI, 700R4, 120,000 miles
104° F Arizona
Driving, everything is normal.
Good oil pressure, over 30 psi.
Not overheating, under 210° around maybe 200 or 190
Alternator working properly, voltmeter at over 14 volts.
All of a sudden the engine seemed to lose RPM and responsiveness and I heard a medium loud tapping sound.
My immediate thought was I lost a rod bearing or a rocker arm.
But the sound did not really sound to me like a rod bearing or a crank bearing or a rocker arm, and unfortunately I've heard those before.
It was a tapping sound but more of a muffled tapping and the engine wanted to die.
Turned off the engine as quickly as possible and coasted into a parking spot.
I assumed I had run it out of oil although there are no leaks of any kind.
It's been about 7,417 mi since the last oil and filter, Shell Rotella T4 15W-40. 4,338 mi since last oil top off.
It's been using about one quart of oil per 3,500 mi. Seems normal.
Turned the engine off. Checked the oil. Looked like the crankcase was dry. Damn.
Assumed I ran it out of oil, it burns a little bit. About 1qt per 3,500 miles.
Went to Walmart got some more oil and funnels.
When I got back to the car I checked the oil again.
After the oil had drained back down into the pan, about 1 and 1/4 quarts low but definitely not empty.
I topped off the crankcase.
Started the engine. The muffled tapping was there but it sounded better or less loud.
The engine refused to idle, it would run as long as I gave it about half throttle but then it would want to die and it wouldn't idle. Quick to start and restart.
The tapping noise lessoned.
Oil pressure was good, above 30 psi, the voltmeter was working at 14+ volts, and the coolant temperature was low.
Instead of calling a tow truck I decided to just drive it home.
Whatever damage was done was done and I'm going to have to pull the engine anyway, I thought.
As I kept driving, in about one block the tapping noise went away.
However still the engine refused to idle.
Driving home everything was normal no unusual sounds no vibrations.
Just as peppy as usual.
Although I'm not standing on it.
Completely smooth and quiet in cruise.
All gauges look normal.
But it refused to idle without giving it significant throttle.
One time at a light I did see the check engine light come on so there might be a code in there, but as soon as the engine RPM increased the light went out. I'll pull the code later.
Made it home. I'm going to let it cool off.
The vehicle is well maintained by an avid enthusiast and professional engineer.
Not long ago all of the front accessories were rebuilt or replaced.
Water pump, alternator, power steering pump and hoses, fan clutch, belts all replaced.
Also fuel tank, fuel pump, fuel level sender, and fuel filter were replaced.
Also coil HV wire
All rubber vacuum hoses were replaced.
I was consistantly getting an average of 13.5 MPG in the city.
Any ideas?
Lock up converter stuck on?
Cat converter plugged?
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