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Old 10-13-2011, 02:01 PM
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Berns Berns is offline
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Default Tracing problem 1993 Caprice 5.7L

Hello All,
I have been replacing sensors as I try to fix my surging problem, also at the same time doing any maintenance following my FSM for my car. Yesterday I was revving my car and noticed that when I rev it and hold it the needle on my tachometer seems to jump. Could it be misfire or dist going bad?
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1993 Caprice LTZ/LS
Smoked headlight, tinted 91 tails, LED interior and exterior, JET chipped, MSD ignition, sounds with Kenwood unit, 20" IROCS w/ 255/35 20 Falkens, dual after cat exhaust and bowtie tips, modded air box, WAY MORE TO COME.....
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Old 10-13-2011, 09:09 PM
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Quote:
Originally Posted by Berns View Post
Hello All,
I have been replacing sensors as I try to fix my surging problem, also at the same time doing any maintenance following my FSM for my car. Yesterday I was revving my car and noticed that when I rev it and hold it the needle on my tachometer seems to jump. Could it be misfire or dist going bad?
Could be a lot of things. Does the engine actually change speed when this is happening? What specifically have you done? Have you checked fuel pressure (which is more of a pain on TBI's, you need an adapter)?
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Old 10-14-2011, 10:28 AM
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I had a 92 that had a similar wierd problem, when you started it up cold, it would "surge" rpms would go up to 1000 then lower down to almost stall then back to 1000 then back down, etc etc. it would do it for about 3 mins then idle normally. If you put it in gear it would usually idle fine, but every once in a while die as soon as it went in gear.

I tried all kinds of stuff, new intake gasket, O2 sensor, IAT sensor, ECM. I never could figure it out.

Eventually somewhere in the 100,000+ miles I put on that car, the problem went away on its own.
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Old 10-14-2011, 11:23 AM
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Originally Posted by fuzzcar View Post
I had a 92 that had a similar wierd problem, when you started it up cold, it would "surge" rpms would go up to 1000 then lower down to almost stall then back to 1000 then back down, etc etc. it would do it for about 3 mins then idle normally. If you put it in gear it would usually idle fine, but every once in a while die as soon as it went in gear.

I tried all kinds of stuff, new intake gasket, O2 sensor, IAT sensor, ECM. I never could figure it out.

Eventually somewhere in the 100,000+ miles I put on that car, the problem went away on its own.
Mine does that every once in a while and would love to know what the hell it is lol
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  #5  
Old 10-14-2011, 12:28 PM
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Try a distributor with a new pick-up coil.
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Old 10-14-2011, 03:37 PM
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Try a distributor with a new pick-up coil.
Agree.
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Old 10-14-2011, 05:46 PM
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It is usually caused by fluctuating fuel pressure. The rubber hose between the fuel pump cracks, and allows fuel to vent back into the tank. If you are going to replace the hose, you should replace the pump at the same time. Use an AC Delco. I used a cheaper one, and had to replace it one month later, then again after a year and a half.

The tach jumping could be a signal issue from the crank sensor, or a short. The short could be the wires at the distributor connector(s) The insulation gets brittle, and can crumble. the wires can come in contact, and you will have an erratic run. This would be more of constant problem, as opposed to the fuel issue which causes rythmic fluctuations in idle.

Another issue might be the ground at the thermostat housing. It is the ground for the O2 sensor, and the ECM. I used a gun barrel brush to clean the threaded hole, and some WD 40/PB Blaster. Clean the bolt and the lugs too. Do it when the engine is cold so that the thermostat housing does not leak.
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Old 10-27-2011, 02:13 PM
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Ok. Cleaned out the bolt in the t-stat housing, cleaned off the wiring as well by sanding any corrosion. Is the connector for dist the one that plus on the side by the coil, if so, it is in good condition. I will have to check the crank sensor as I have not replaced this one. I did notice yesterday that the hose in the evap canister are all shot, all cracked and brittle to the touch, will replace those as well this weekend. My car's FP had left me stranded 2 yrs ago and had it towed to a shop, I told them to replace any hoses while the tank was down. When I picked up the car they stated that all the hose were in good condition and did not need to be replaced.
I will keep you posted.
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1993 Caprice LTZ/LS
Smoked headlight, tinted 91 tails, LED interior and exterior, JET chipped, MSD ignition, sounds with Kenwood unit, 20" IROCS w/ 255/35 20 Falkens, dual after cat exhaust and bowtie tips, modded air box, WAY MORE TO COME.....
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Old 12-02-2011, 10:33 AM
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I replaced all emissions hoses from the TB to the Canister to the Tank, some just crumbled at the touch and one had a leak from a crack. I re-routed the spark plug wires and added wire cover to the wires so they do not touch and cause cross fire. Checked plugs and they are in good condition. Still have a surge. I was reading my FSM and it stated it could also be the spark control module and knock sensor that are going out. Has anyone updated any of these? Module is pretty expensive.
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1993 Caprice LTZ/LS
Smoked headlight, tinted 91 tails, LED interior and exterior, JET chipped, MSD ignition, sounds with Kenwood unit, 20" IROCS w/ 255/35 20 Falkens, dual after cat exhaust and bowtie tips, modded air box, WAY MORE TO COME.....
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