Common G-Body Problems, Repairs, and Adjustments

My "Check Engine" light is on. What does that mean?
How do I set the timing on this computer controlledengine?
How do I adjust the Throttle Position Sensor (TPS)?
How do I adjust the Idle Mixture?
How do I adjust the Throttle Valve (TV) cable?
How can I check to see if my secondaries are openingfully?
How do I get the dash/gauges out?
Thunking noise from windshield/dash area when turninga corner or hitting a bump.
Torque Converter won't unlock when warm.  Car lugsand/or stalls in lower gears after leaving freeway.
Power Antenna motor whirrs, but no antenna movement.
Factory Tachometer reads at least 30% too high, possibly intermittently.
All of my gauges are reading wacky, or just one is but the sending unit is okay.
Loose tilt steering column.
Speedometer Non Functioning or "Bounces".
Rocker Arm Covers are Leaking Oil.
Car runs hot or overheats.
Leaking coolant around the corner of the intake manifold.
My cruise control doesn't work.
My tape player won't stop auto-reversing, or won't auto-reverse at all.

Pulling the computer codes:

When the "Check Engine" light comes on, it means you should open the hoodand check the engine. Yup, that's an engine all right :-) Now what?

 Don't waste your money on one of the "scanners" from the parts store. A full fledged diagnostic machine is another matter, but a paperclip can accomplish all that the parts store scanners can.

Setting the timing:

Adjusting the Throttle Position Sensor (TPS):

The TPS is simply a potentiometer attached to your throttle. It's located inside of your carburetor and is used to tell the vehicle computer how much throttle you're giving the engine at any time. The computer uses a combination of throttle position and RPM to determine how much load your engine is under and what to set the spark advance and mixture at (by reading from tables located in the EPROM).

On the top of the carb, towards the front on the driver's side you'll see the lever that activates the accelerator pump. Right behind and tothe side of the pivot point of this lever is the adjustment for the TPS.The adjusting screw is normally covered by a small metal plug.

Setting the idle mixutre:

This is done in one of two ways, depending upon what type of carburetor you have.

To tell the difference, you need to remove the cover from over the idle mixture control solenoid, this is the cover, about 3/4" x 3/8" on top of the carb, about in the middle. There is a rivet on one side that you must drill through (cover the carb good so metal shaving don't go down it),and a hole on the opposite side you can slide an allen wrench in to push the cover out. Once you have the cover removed, you'll see the adjuster with a large slot on top to adjust with a slotted screwdriver. On the adjuster will be stamped either a number or a letter. If it's a letter (like Z in my case), use procedure A. If it's a number, use procedure B.

If you have an '84 Hurst/Olds like I do, I can save you the time and say you don't have to remove the plug from over the solenoid. In this case, use procedure A.


First, you need to gain access to the idle mixture screws. These are in the front of the carb, way down at the base, recessed in, one each side. If anyone has rebuilt or monkeyed with the carb in the past, these may already be exposed. If not, you need to remove the carb, use a hacksaw to cut two slits in front of the screws, about 1cm apart, and then remove the blockage with pliers or a light hammer tap. Uncovering these screws is not a "bad thing". If your idle mixture is way out of whack, like if you just rebuilt the carb and moved these screws, start with the screws 3 turns out from lightly seated. That should be a good baseline.

Next, you'll need the tool to adjust the mixture screws. This is commonly available at most auto parts stores. Tell them you want a tool to adjust the mixture screws on a late-model Quadrajet and they'll know what you need.


Setting the TV Cable

The TV, or Throttle Valve, cable is used by the 200-4R transmission to control shift points and line pressure. Much the way the vacuum modulator on a TH-350 does. A loose TV cable will cause sloppy, early shifts. An extremely loose or disconnected TV cable can burn up a transmission in short order!

The TV cable can be found on the driver's side of the carburetor. Towards the back of that side of the carb you'll see a bracket with two cables in it. The lower one is the throttle cable, the upper one is the TV cable. You should be able to follow it down in back of your engine,where it goes to the tranny. The end of the cable attaches to the throttle linkage on the carburetor. You'll notice where the cable comes out of thefront of the bracket there's a square part (maybe 3/8" in diameter) with ridges on it. In back of that bracket there's a release button on the passenger's side of the cable. Squeeze that release button in (almost takes two hands for mine, it's pretty stiff) and then you can move that square part withthe ridges fowards and backwards. To adjust it to factory specs, push the release button in and push the square part all the way back into the bracket (this is "tight", out is "loose"). Then quickly open the throttle fully (wide open) and release. The cable should pop out a few ridges. For performance use, press the release button in and move the cable back one ridge from there. If it pops back out (mine hasn't yet) then I guess you're outta luck, figure it's tight enough and that's the way it was meant to be.

Checking the secondary air valve:

Instructions provided by Rick Watts

With the car off and no vacumn on the pull-off, open the secondary airvalve with your finger. look and make sure the valve opens fully, approx. 90 degrees. If not, check where the pulloff linkage hooks to the secondaryvalve. there will be a "limiter" made into the linkage hook-up in the same location as the spring valve . this limiter comes in contact with the carb body prohibiting the secondary valve from fully opening. this can be filed down to allow full opening. checking the secondary metering rods will be necessary because they will be calibrated for the "part opening" secondaries.Replace with a performance type ie:hurst\olds- 442

How do I get the dash/gauges out?

Easy once you know the trick.  You probably already found the screws along the bottom of the dash and removed them, but now you need to pull the plastic woodgrain bezels from around the light switch and the centerA/C vents.  They are held in with ? shaped metal clips at each corner. Use something stiff and curved (I use an old PC expansion slot cover thatI bent the end on into a hook), and hook behind each corner, near the clip if you can tell or guess where it is, and pull straight out.  You have to pull pretty hard sometimes, often to the point where you're worried about breaking the panel, but I haven't broken one yet (knock on wood). Repeat on each corner until it's free.  It's easiest to do this when the dash is warm so the plastic is pliable and gives up the clips easier,so if it's the middle of winter you may consider hitting it with a hair dryer first.  Once the bezels are removed you'll see some 7mm (or is it 5/32nds?) hex-head screws.  Remove those and the dash will come off.

To remove the gauge cluster, first remove the trim around the bottom of the steering wheel column.  You'll see a clip on the right-hand side of the column attached to a thin cable.  This cable moves your PRNODL gauge when you shift gears.  Remove the clip and let it hang. Remove the 7mm screws from around the gauge cluster.  Gently pull the gauge cluster forward and snake a thin hand over the top ("Oh wife [or child], could you come here for a minute?") to press the release clipon the speedometer cable.  Gauge cluster is now free!  On older models (78-82 I think) with non-electronic cruise control, it's easier to disconnect the speedo cable from the cruise brain under the hood than from in back of the gauge cluster.

Thunking noise from windshield/dash area when turning a corner or hitting a bump.

Although it sounds like the windshield or dash is to blame, it's commonly caused by the hood rubbing against the rubber stops.  Open the hood a little and drive to see if the problem goes away.  To fix, lubricate (with lithium grease) or adjust the rubber hood stops, especially the one at the center rear of the hood.  You may have to reapply the grease every 6 months to a year.

Torque Converter won't unlock when warm.  Car lugs and/or stalls in lower gears after leaving freeway.

Caused by the Torque Converter Lockup Solenoid (TCC Solenoid) sticking and not disengaging.  Fresh tranny fluid will sometimes help, but usually only temporarily.  Permanent solution is to replace the TCC Solenoid.  It's about $40-$45 (and that's full retail price) from your GM dealer.  You need to drop the tranny pan and filter to see it, then it's right there on the bottom of the tranny, attached with two bolts and two wires.  You don't need to know your way around a transmission to service this solenoid, it's right there on top and very obvious how it's bolted in.  If you have a tranny shop do this, I wouldn't expect it to cost more than the price of a tranny fluid/filter change plus a half-hour labor and the cost of the TCC Solenoid (if you don't bring it with you).

Paul Carriero, an owner of an '86 Monte Carlo SS (which shares the 200-4R tranny), has documented this procedure very nicely at

Power Antenna motor whirrs, but no antenna movement.

The mechanism inside the power antenna is broken.  You have two options, a repair kit from GM, or a new antenna. The service manual says you need to pull the fender to service the antenna (ugh), but if you unbolt the fender bolts around the rear of the wheelwell, along the bottom of the fender, and inside the door jamb, then you can gently pull out the bottom of the fender and drop it through there.
Replacement mast and cable kit Part # 022038195 $14.95
Bolt Kit, consists of nuts, screws, washers and spring clips to hold the antenna housing together (required with mast/cable kit unless it's been fixed before). Part # 022020281 $6.23
New Antenna Part # 22048604 $103.00
Bracket (required with new antenna unless it's been replaced before) Part # 22038589 $10.00

Factory Tachometer reads at least 30% too high, possibly intermittently.

The factory used the same tachometer for both 6 and 8 cylinder cars, placing a selector clip on the back over the proper selection.  This gets loose or corroded over time.  Remove the gauge cluster,and on the back towards the driver's side you'll see that plastic clip with a metal springy bit underneath.  If you're confident in your soldering abilities, it's best to lose the clip and solder across the contacts (don't forget to use a heat sink!).  Alternately, you can clean the clip and contact with a pencil eraser, slightly bend the springy part for more tension, and re-install.  I did this once and had to re-do it right (solder) 3 years later since the problem has recurred.

All of my gauges are reading wacky, or just one is but the sending unit is okay.

Probably caused by a bad connection (usually ground) to the gauge cluster. Remove the gauge cluster, you'll see the connector on the back where it plugs in.  Clean each connecter on both gauge and car sides (especially any with a black wire!) with a pencil eraser or electric contact cleaner.  Optionally lube them with a light coatingof conductive grease, and re-install.  You may also want to remove each bulb socket and clean it's contacts too.  You can also get creative and bend the pins on the connector slightly so they seat better.

Loose tilt steering column.

You have to pull the steering wheel (you'll need a steering wheel puller and a lock plate compressor), and mostly dissasemble the column. You'll find two bolts in there that need tightened.  They're odd shaped,12-point I think.  Use locktite on 'em so it doesn't happen again!

Speedometer Non Functioning or "Bounces".

The speedometer cable seems to fail frequently on these cars, I'm not sure why.  A bouncing speedometer needle is a sign that the cable has a burr in it.  Lubing the cable may alleviate it temporarily, but it'll come back sooner or later.  Replacing the cable is the only permanent solution. 

Rocker Arm Covers are leaking oil

Rocker Arm Covers (aka Valve Covers) leaking oil is a common occurrence on older cars. Sometimes it gets so bad that oil will drip down onto the exhaust manifold and cause smoke from underhood. You need to replace the gaskets.

Remove what you need to to access the rocker arm covers. Driver's side isn't so bad (you can get it around the EGR, but I think it's easier to just remove the EGR valve), but there's several hoses and wires over the passenger's side.

Remove the bolts and then remove the rocker arm covers. Use a gasket scraper (aka putty knife) and optionally gasket remover spray (or something like carburetor cleaner or brake cleaner) to remove all traces of the old gasketfrom the valve covers and from around the cylinder head. When cleaning theheads, try not to get any stuff to fall into the heads. Maybe stuff a rag in there if you're clumsy.

Check the flanges around the bolt holes in the rocker arm covers to makesure they are flat. They frequently get pushed in due to over-tightening of the bolts (in an attempt to stop the leak probably). If they need it, turn them upside down and place the flange on the edge of a workbench and tap it down flat with a hammer.

When you get new gaskets, ask for the composite rubber ones (NAPA has them) rather than the cork ones. Cost about twice as much, but much better quality,will hold a seal a lot longer, they won't flatten out and get hard like cork ones do, plus you can reuse them if you don't tear them getting them off. Install the new gaskets dry (you don't need any RTV or other sealer with the composite rubber gaskets), and re-install the bolts. Don't tighten the bolts down too much. I do mine with a nut driver rather than a ratchet. Snug by hand with a small nut driver is about right. With a ratchet it's too easy to over tighten them.

Car Runs Hot or Overheats

Overheating and running hot really isn't any more of a problem with G-bodies than it is with any other car, but still, it's a common source of frustration.

Here are some tips, and things to check. I'd check them more-or-less in this order,depending upon when the overheating occurs (at speed, at idle, hot weather only, etc):

Radiator in good shape? No leaks. No severe corrosion on the inside. Not encrusted with bugs and leaves out the outside. Modine makes a replacemnt3-row core radiator that's a direct drop-in. About $140 from your local radiator shop.

Coolant in good shape? Not brown and rusty. Preferably less than 2 years old. Flush the system if not and add 50/50 antifreeze/distilled water (30/70 if in a warm climate). Water Wetter isn't a bad idea either, not a miracle, but it does seem to help. You can probably find the radiator petcock on your own, but there are plugs on either side of the block (down low) to drain the coolant from it.

Thermostat okay? You can test them in a pot of boiling water with a thermometer, but they're so cheap once you go through the trouble to remove it you might as well replace it. I swear by the Robertshaw or Mr. Gasket high-flow thermostats (180 or 195, your choice). These things have worked miracles for me!

Lower radiator hose okay? These can collapse under high flow. It should have a spring inside to keep it from doing just that.

Fan clutch working? If you see oily residue around it, it's probably leaking (silicone). To test, run the car until it's hot and you think the fan should be working. Open the hood and then turnoff the engine. Fan shouldn't "free wheel" for more than a turn or two after the engine stops. After the engine is stopped, if you can spin the fan by hand and it free-wheels more than about 1 turn, it's bad. A new one should go less than a half-turn.

Air flow unobstructed? Is the factory air dam still underneath the radiator? Are the air flow diverters still attached to both bumper supports? Do you have a tranny cooler, fog lights, bra, or anything else obstructing the grille or radiator? Is the fan shroud still there and in one piece?

Check the timing. Incorrect timing can cause an engine to run hot.

Check the fuel system. If you are running too lean, it will run hot.

Well, everything else has been eliminated so now it's time to change the water pump. Ugh. Plan a whole Saturday, or a whole weekend if you go slow (like I did) to remove everything and change it.

Leaking coolant around the corner of the intake manifold.

Leaking coolant at the front or rear corner of the intake manifold,where the manifold, head, and block all meet, is a common problem on all Oldsmobile engines with aluminum intake manifolds. The leaking is caused by the different thermal expansion rates of the aluminum manifold and iron block, and additional corrosion is caused by an electrolytic reaction between the aluminum, iron, and stainless steel intake gasket. The fix it to replace the gasket, and do a better job than the factory did.

Removing the intake and manifold is pretty straightforward, so I won't go into all the details. Just make sure to label all the hoses and wires well so that you can reattach them. Also, you don't have to pull the distributor (try THAT one on a Chevy!), but removing the cap can give a little extra clearance. Expect to take most of a day, or possibly two for this job.

Clean off the old gasket well. The surfaces should be smooth and clean. Clean enough to eat off of. I prefer to use the Fel-Pro valley pan (aka"Turkey Tray") gasket. It comes with sealer and instructions. Follow the instructions, using the brush-tack sealer around the intake ports and the RTV around the water ports. What you'll do different comes when installing the rubber end-rails. There are four ways to do it:

  1. Just put the rubber seals in place like the factory did. But if that worked, you wouldn't be here now, right?
  2. Place a big drop of RTV silicone on either end of the rail, where the head,block, and intake manifold meet. Then put the rubber seal in place.
  3. Same as #2, except first make two rows of dimples on the rail with a centerpunch. Mondello recommends this method to keep the rubber seal from pushing out. I've done it with and without the dimples, and haven't had one leak again either way.
  4. Lose the rubber gaskets and use a bead of RTV silicone instead. Edelbrock and a few Olds engine builders recommend this method.
Clean the bolts off and dip them in engine oil. Reinstall the manifold and torque down in the proper sequence to the recommended torque. You'll need a service manual of some sort to find the exact torque specs and torque sequence.

Once everything is back together and you're confident it works, then it would be a good idea to change the oil. It's always a good practice to change the oil after a procedure like this which "opens up" the engine, just in case anything fell down in there.

Troubleshooting the Cruise Control

Mine broke too. I checked a few things, but replacing the solenoid assembly under the hood finally fixed it. I found both the solenoid and the "black box" on a car at the junkyard and grabbed them both.
  1. Unplug the wire at the base of the steering column that goes up to the cruise control stalk. Verify power at that point (I think a yelow wire). Use a continuity meter or an ohm meter to verify that the switches in the stalk work properly.
  2. Check the vacuum switch above the brake pedal. Make sure the hose is good (not cracked) and hasn't come off or the switch isn't broken.
  3. Replace the "black box" above the gas pedal. Remove the wiring harness, push down on the clip and it slides right out. Clean the contacts and try it then, if that doesn't work, then either replace it or do step four then replace it if it still doesn't work.
  4. Check vacuum hoses to solenoid assembly. If they're good, replace the solenoid assembly under the hood.
Really easy to replace things on this! Nothing is hard to get to. The parts are still available from GM too if you're really rich. They wanted $350 for the solenoid, and $250 for the black box. Junkyard wanted $11 for both!

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