Jacobs454

Whaddya Saay, Fellow F-body Enthusiasts!!! I Gotta '89 Rs With A 305tbi/700r4, Stock Besides A Hypertech Chip. The Car Has 165k On The Clock. Everything Was Fine Until A Month Ago I Was Getting On The Gas Pretty Good To Beat The Train When My Car Started "coughing." By The Grace Of God I Beat The Train, But It Left Me Wondering What The Heck Happened. I Stopped The Car, Hit The Gas About 3/4 And It "coughed" Again. By Coughing I Mean That It Kind Of Dies For A Second, Detonates Back Through The Intake And Then Takes Off After Coughing A Few More Times. It Also Does This If I'm Climbing A Hill In Overdrive Right Before It Downshifts Into Drive. I Replaced The Timing Chain/gears And The Coil, But It Still Does It From Time To Time. Any Suggestions As To What The Heck Would Be Causing This Would Be Greatly Appreciated!

Pneumatic_Tire

You say it does this in overdrive? Try getting it to do it in just drive. If it still does it then hook up a fuel pressure gauge and see if you got good fuel pressure. If that's ok, then i'd pull your spark plugs, inspect them and replace if necessary. Check the gap as well before putting them back in, or if you get new ones.

aklim

IF you hit the gas, the OD would probably slip out into D. I would check fuel pressure and quality of spark and also the wires. Do the wires in the dark where you spray a fine water mist at them. If you see alightning storm, the wires are bad. How long since you did a tune up?

Jacobs454

Thanks for the replies! Well, it's been nearly 40K since I changed the plugs, wires, etc. I'll probably give the car a tune-up anyway since it's getting close to that time. I'm using Accel 8.0mm and Splitfire plugs. What is another good but less expensive combo? I was told by a mechanic that the car would miss if the plugs/wires/cap needed to be replaced, but he said that wouldn't explain the detonation through the intake and that it sounded more like a timing issue or valve malfunction?? What's your take?

90rocz

First Jacob, get rid of the "novelty" Split-Fire spark plugs. Keep the Accel 8.0mm wires if they're the Super-Stock spiral core ones. $39.95. If they pass a visual inspection like, bend them and look for cracks, burns etc...They'll take a lot of miles if you take care of them like cleaning them occassionally and keep them off of the exhaust. Get an Accel or Moroso Cap&rotor button(don't skimp $$ here..) and stick with a tried and true set of "Auto Lite" copper-core plugs. Fancy, novelty plugs are prone to detenation, especially of a SBC running near 200* all the time. Change ALL of the filters, especially the "fuel filter", on EFI cars they're critical! Also TBI cars are hard on the TBI base-gaskets, often a source of "high idle" and "back-fire" under a load. You can check it by spraying "carb cleaner" with the straw, around the base gasket (COLD ENGINE!!). If the idle drops down significantly, the gasket IS BAD..And chase down any other vacuum leaks on hoses, EGR etc too.
After the tune up refer to files at 3rdgen.org for set up methods for your TPS, Idle(air bleed) timing etc..
A GOOD, Quality tune up and Set up are essential for any performance or before any modds...

IROC-T

One more thing to check would be the chip,if you have the stock chip try replacing the Hypetech see if that helps. Sound like a timing or vacuum issue to me also.

Jacobs454

I'll Giver Er A Tune Up This Weekend And Take It To A Buddy Of Mine Who'll Check The Timing Out. Hopefully That'll Do It Without Having To Mess With Anything Else. Thanks!

aklim

Inspect the plugs and see if any one differs from the other. Also, see if the plug wires are still good. While the car is running at night, spray a fine mist of water at the wires and see if there is a light show. If so, change the plug wires too.