JB

What can cause a car to suddenly lose power and starting pinging and rattling like the timing is off (timing is fine)?

Car's running fine one moment, the next, it will barely go up a small hill in 1st gear it's pinging and rattling so bad, power's almost completely gone. Idle is very rough, timing seems fine when tested at normal idle speed with a light. In the last two weeks I've pulled the intake and distributor, set the timing and dwell, & replaced the fuel pump and in-carb filter. Was running okay before (a little jerky and sluggish, but nothing like now), and very good after for a few miles before this happened. No obvious vacuum leaks, but I'm having such trouble keeping it running it's hard to check.

Whatcha think?

JB




[Modified by JB, 2:36 PM 6/23/2002]

4_inch_Bore

I would guess timing gear or chain, or possibly cam bearings. But since this is a bear to replace, I suggest you get a stethoscope or a piece of conduit and listen to see where the noise is coming from (sorry about ending that sentence with a preposition).

RAM73

JB,

What does the plugs look like? Rich?

Is the Q-Jet is on it or hs it been replaced?

RAM73

JB

Gary, I shouldn't have told you what I do for a living! :D

I thought a slipped timing chain or something, too, but if it were something like that, would the timing look the same & steady with the strobe on it? (I honestly don't know).

Rich--I should have mentioned I just replaced the plugs and wires maybe 50miles before this started. The old plugs looked perfect, fine brown ash and nothing else. Should I pull the new plugs and take a look? It has a virtually "new" rebuilt Q-jet, though the previous owner put it on there, not me. It was running just fine with it, though, at least for 5 or 6 miles worth.

JB


[Modified by JB, 3:22 PM 6/23/2002]

MasterDave

Well, I'm gonna guess a bad set of points (shorting) or worn dist bushings OR your advance springs have broken/stuck. Cracked dist cap. Dist related IMO.

RAM73

Does the Q-jet still have the thick gasket under it? If not the reinstall it. The Q-jet are also well know for a leaking problem. There is a kit available for the Q-jet that help the leaking problem.

If the exhaust smells rich as well, I would look at the carb. If you have access to a carb you can borrow, then I would try a different carb.

There is another problem I ran into on the old points type distributor. It cuased me to change a perfectly good timing chain and gears. The rotor had broken one of the position tabs which hold the finger in place. This allowed the finger to slip into a retarded position when I accelerated. Strange occurance but it would do about the same as your talking about now. Worth a double check.

RAM73

JB

Hmmm, that's intriguing. It was running moderately crappy (kind of a jerkiness on mild accel and on decel), and I discovered a fuel pump leak and that the dwell was set five degrees off. I replaced the pump and set the dwell at 31degrees and it was running very good, no jerkiness. Maybe four or five miles later and boom, starts running very crappy as described. Distributor cap is brand new, springs LOOK okay and don't seem stuck (we are talking about the two springs on top of the centrifugal advance weights just underneath the rotor, yes?) Could my changing the dwell from 36degrees to 31 have pushed the points over the edge somehow? They're cheap so I'll just go ahead and replace 'em and see if that makes a difference.

Ram 73--when I put the carb back on, I used three gaskets, two new metal-sandwich felpros and the very thin stainless sheild that was already on there before. Help out the ignorant here--what's a finger? [EDIT: ah, I think by finger you mean the rotor itself? The two tabs underneath, one square so you don't put the rotor on wrong, those tabs? If so, I also should have mentioned that the rotor is brand new, too]

JB


[Modified by JB, 3:41 PM 6/23/2002]


[Modified by JB, 3:45 PM 6/23/2002]


[Modified by JB, 3:47 PM 6/23/2002]

73-454

Sounds like your old rotten engine has finally packed-it in. Best way to fix is pull the engine and get a pro to rebuild it or buy a new GM crate engine they have many types of engines to fit all budgets.

bence13_33

73-454:
I disagree, I don't think it would be too smart to assume that "his old rotten engine has finally packed-it in" without further investigation.

JB:
Take it one step at a time and eliminate some of the possible problems. Checking out your distributor is a good place to start. This might sound stupid but was your distributor properly secured with the distributor hold down? I've had my hold down work its way loose before and it retarded the timing so much that it could barely run. Just a suggestion.

RAM73

By finger I was refuring to the distributor wiper on the rotor.

I agree with Bense13_33, Take it one thing at a time and eleminate them that way. Since you just replace the fuel pump I would tend to lean to something related to that. The new pump could have over powered the needle and seat on the carb.

You might recheck the points settings again or better that than replace them if you haven't already.

Good luck!

RAM73

JB

Bence--if it sounds stupid, I've probably done it. :D Not the distributor hold-down this time, though--that's the first thing I checked because it did feel like the timing suddenly went off. It was tight and hadn't moved & when I got it up to idle speed and put the timing light on it, the timing was dead on. I loosened it and moved the distributor around and could not get it to idle any better.

73-454--nah, you're not gonna get me to bite on that one. Besides, the motor's got less than 50K on it, so I'm hard put to believe the "old rotten" theory.

Ram73--more ignorance on my part. How would I know if the new pump had overpowered the needle and seat--is this something I would see as physical damage to the needle and seat if I took the top off the carb?

Thanks, guys, I sure do appreciate the help & the patience with my lack of car-sense.

JB




[Modified by JB, 5:19 PM 6/23/2002]

bob

Just a thought, when you checked the timing it was with the vacuum advance disconnected and vacuum line lugged--right? Any chance of a vacuum advance stuck in the full advance position.
bob


[Modified by bob, 3:39 PM 6/23/2002]

4_inch_Bore

"There is another problem I ran into on the old points type distributor. It cuased
me to change a perfectly good timing chain and gears. The rotor had broken
one of the position tabs which hold the finger in place."

That would certainly cause erratic firing and loss of power. But the knocking? Did yours knock?

JB

That sounds like a possibility--I don't quite understand what difference checking the timing with the distributor vacuum plugged would make if that's the case, though (I did indeed check the timing with it plugged). Again, bear with my ignorance, here.

JB



[Modified by JB, 6:23 PM 6/23/2002]

bob

If the timing was checked and had correct idle advance with the vacuum advance connected, you would in fact have your initial set waaay retarded and as soon as you put any load on the engine the vaccum advance would retard and you would be left with your very retarded initial plus of course what ever your centrifical was giving you. In your case with the fact that you are getting pinging you probably aren't retarded.
bob


[Modified by bob, 4:09 PM 6/23/2002]


[Modified by bob, 4:09 PM 6/23/2002]

JB

Bob, I know a few people who might disagree with you on that one. :D

JB

hudman

Can we revoke 73-454's user id?

He is ragging on everybody lately. Keep your trap shut unless you can add something positive!

Stevo81

Don't bother searching for a problem. This is just a bad dream and when you awake, all will be well. Just avoid that spicy Mexican food late in the evening. I am real curious to see the bottom line here. :yesnod:

Jughead

What's your engine temp during this problem?

JB

Overheating was also one of my first suspicions. I learned the hard way with my '78 you can't trust these factory gauges. The gauge showed a nice steady 190 and I saw no steam and heard no boiling. After it cooled, I looked in the overflow tank and saw water in it (I guess that's how you tell with these cars? This is the first one I've ever had where you couldn't just take off the cap and look directly into the radiator to see the water level and core condition--kinda frustrating!)

JB