1986 Pontiac 6000 Engine noise, cuts out above 1k RPM

Tiny
SF_ONENOTE
  • MEMBER
  • 1986 PONTIAC 6000
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 201,085 MILES
Previous history: At 166,000 miles the car had a newly rebuilt engine placed in it from a GM Buick Century comparable. It has about 40,000 miles on the rebuilt engine now.

So far the following has been done:

Replaced Fuel Filter, Fuel Pressure Regulator, Fuel Injector, & Fuel Pump. (Reason: The car was not getting gas from the line to pass through the injector. It was getting gas up to the throttle body.) The fuel pump being replaced solved this. The tank had been full before it sat - so it sat with a full tank for 4-5 years.

It took some coaxing to get it started. But, it was able to idle. There is a lot more noise being generated. Much like a large resonance not in any particular area inside the engine bay but just the overall engine bay area itself. It has made popping noises like it there was a part in the cycle that there was an explosion that did not get contained in the chamber. Because it was running so roughly, I was recommended to "Sea-foam" the car. I was able to do this by pouring half the can in the brake booster vacuum line to the engine. I shut it off immediately, and I poured the other half of the can in the oil of the crankshaft.

After a couple of hours, 1 - 2, I started the car back up and would rev the car in neutral at about 2500 rpm. It was able to do this for enough time to clear out a majority of the Sea Foam. I was going to take it for the road test after this. However, it now will not go above 1000 rpm.

I checked the plugs and they look coated with carbon. The distributor cap looks new, but if I have my history right then the plugs are from the time of the rebuild 40k ago, and the wires themselves may be older. I was thinking of replacing both of those anyway, but is there any other things I should be looking at regarding the following items? :
1.) Overall loud running noise, 2.) The occasional explosions at the end of a cycle (it sounds like it is popping up into the air filter chamber - and if I had the cover off - flames would shoot out of it about 2 out of 10 starts), and 3.) The ability to idle at 1000 RPM, and if you give it gas, then it cuts off
Friday, April 3rd, 2009 AT 3:19 PM

3 Replies

Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
Tune up /wires plugs cap rotor and in your case perhaps a new coil as well, then report back, we may need a compression test and timing check. Do you own a timing light?
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Sunday, April 5th, 2009 AT 2:50 PM
Tiny
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Hi again merlin2021! (I would have used your first name, but I didn't ask you whether it was permissible to use that on a public forum.)

Thanks for continuing to help me out.

Spark plugs, wires, and distributor cap - check. Note: The distributor cap looks new and clean, but I can't be sure as to when or if it was replaced or what may have been done with it.

When you say "rotor, " does it go by any other name or something more specific and where is it located? I looked up rotor in my Chilton's manual but it only references brake rotors.

The Chilton manual I have mentioned that there is such a thing as an HEI distributor after 1982 that requires special spark plug wires than standard. Is this something I need to be looking at, or concern myself with?
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Sunday, April 5th, 2009 AT 5:00 PM
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
It's right under the cap.
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Monday, April 6th, 2009 AT 2:44 AM

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