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Having a rpm problem

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Old Jul 25, 2005 | 02:57 AM
  #1  
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From: Hialeah/Mia.
Car: 1990 350 tbi l98,
Engine: 5.7 tbi
Transmission: t5
Having a rpm problem

When im driving and crusing at about 1500 rpm, my rpm gauge flickers. And it feels like it is missing. but from 1800-2000 rpm gauge up it doesnt feel that weard problem. At ideling it is beautaful. I have a brand new msd rotor and cap are about 5 months old, msd coil parts store new distributor, new moroso wires, and bosch 2.00 plugs.

Please help[ really sucks. -Eric
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Old Jul 25, 2005 | 12:31 PM
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From: Hialeah/Mia.
Car: 1990 350 tbi l98,
Engine: 5.7 tbi
Transmission: t5
Has this ever have happend to any one?
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Old Jul 25, 2005 | 02:29 PM
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From: Buckhannon, WV
Car: 84' Monte
Engine: 350
Transmission: 700-r4
Axle/Gears: ferd 9" posi 3.50 gears
yep, mine ended up being a loose ground strap inside the dissy. The hold down for the condensor also is a ground, mine vibrated loose.

If thats not it, it's something on the dissy side of things. You won't get a flickering tack unless there is something up with the coil, module or ground.
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Old Jul 25, 2005 | 05:21 PM
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From: Hialeah/Mia.
Car: 1990 350 tbi l98,
Engine: 5.7 tbi
Transmission: t5
This really su**s, i bought a cap and rotor angain and accell shorty plugs. I have the bosch platinums. I read up on them that they are not to good.

I am going to check those grounds that you are talking about. Thanks
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Old Jul 25, 2005 | 06:37 PM
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From: Cincinnati, OH
Car: '90 RS
Engine: 377 LSX
Transmission: Magnum T56
Your 02 could be on the way out. Has that been replaced during your last tune up? If you can't recal if it has ever been changed I would do it now for nothing more that preventative maintenance. A new 02 can make a world of difference.
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Old Jul 26, 2005 | 10:50 AM
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From: Hialeah/Mia.
Car: 1990 350 tbi l98,
Engine: 5.7 tbi
Transmission: t5
Well i changed the cap ,rotor, and plugs. Also that bolt that you were talking about (BMmontess) by the ac bottle was lose and i tightn it . It runs a little better, but still having that little flickering thing.

I also have already changed the o2 seneor. Can it be anything else? -Eric
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Old Jul 26, 2005 | 11:58 AM
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From: Buckhannon, WV
Car: 84' Monte
Engine: 350
Transmission: 700-r4
Axle/Gears: ferd 9" posi 3.50 gears
actually it's no the AC condensor I was talking about, it's the electrical condensor inside the dissy. Small tube shaped object, looks like a capacitor.

You haven't changed or tested any of the major ignition components that would cause your problem, mainly the coil and the module.
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Old Jul 26, 2005 | 12:04 PM
  #8  
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From: Hialeah/Mia.
Car: 1990 350 tbi l98,
Engine: 5.7 tbi
Transmission: t5
What tube are you talking about? What type of distributor do you have? I have a new style distributor that does not have the coil on top. My coil, my whole distributor, cap, rotor, wires, plugs are all brand new.
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Old Jul 26, 2005 | 01:12 PM
  #9  
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From: Buckhannon, WV
Car: 84' Monte
Engine: 350
Transmission: 700-r4
Axle/Gears: ferd 9" posi 3.50 gears
I have the big cap HEI, sorry, didn't mean to confuse you. I will say that your problem is in the dissy, something is causeing the coil not to charge, hence the flickering tack and corresponding miss.
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Old Jul 26, 2005 | 05:47 PM
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From: Hialeah/Mia.
Car: 1990 350 tbi l98,
Engine: 5.7 tbi
Transmission: t5
Dissy you mean distributor?

Can it be a bad connection on the rpm gauge to the coil wire. I have one of those clips, are like a little mouth with a clip to close it. It could be that. i am going to fix that and see if that works.

I also moved the ground wire directly from the battery to the block ,to a different bolt and felt the car run alot better. Thanks for helping
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Old Jul 26, 2005 | 05:54 PM
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From: Buckhannon, WV
Car: 84' Monte
Engine: 350
Transmission: 700-r4
Axle/Gears: ferd 9" posi 3.50 gears
A loose tach wire would make the tach jump, but wouldn't make the car miss. Keep after it, you'll find the problem.
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Old Jul 26, 2005 | 11:36 PM
  #12  
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From: Hialeah/Mia.
Car: 1990 350 tbi l98,
Engine: 5.7 tbi
Transmission: t5
Were are the exact pritty important ground wires that are located that i should be looking for?
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Old Jul 27, 2005 | 12:51 AM
  #13  
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From: Dixon, IL
Car: RS
Engine: 305
Transmission: 4L60
Axle/Gears: 3.42
if I remember right, the back for the block by the AC/firewall.
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Old Jul 30, 2005 | 01:09 PM
  #14  
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From: Hialeah/Mia.
Car: 1990 350 tbi l98,
Engine: 5.7 tbi
Transmission: t5
Well the bolt on the back of the head was kinda lose but not that lose. Still doing it.

I also checked the o2 like shifty said just in case. Nothing there just fixed the wire a little bit. I need to figgure out what this is, it really su**s. If worse come to worse i am going to go carb or something. what else do you guys think it is?
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Old Jul 31, 2005 | 10:58 AM
  #15  
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From: Buckhannon, WV
Car: 84' Monte
Engine: 350
Transmission: 700-r4
Axle/Gears: ferd 9" posi 3.50 gears
pull the modul and have it checked out at the local parts store, I know advanced has a machine to check it, try a new coil, heck just unplug every thing from the dissy a couple of time to see if the connectors have become corroded.
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Old Jun 8, 2010 | 12:43 PM
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From: A.Z.
Car: 89 TTA
Re: Having a rpm problem

Ever figure this problem out?
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