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Step on pedal - No power?


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Check timing, points (if it has points).

How many miles are on the engine? Did this problem come on suddenly? or was it a slow progression to what it is now? Will the engine eventually come back out of the bog if you keep the gas pedal down?

Adam

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Have you tried rebuilding the carb? The accelerator pump could be acting up. Float might be sticking also. (you did say this is carbureted, right?) Does it backfire at all when you give it gas? If it does, make sure timing is right. It may need to be advanced.

Adam

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I don't know much about HEI, but that sounds like a possibility...make sure the plugs are clean and check the wires...maybe replace them if they are more than 30000 miles old. It's possible that the plugs have some oil buildup which causes hesitation at throttle.

Adam

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Could be a sticking power piston in the carb. If it is stuck in the "down" or "economy" position and does not move upward to give a richer mixture under load, it'll do just as you mention. Went through that with dad's pickup with a QJet on it. Your carb is probably the front half of a QJet if it has a carb or even a full QJet depending on the year. If it acts reasonably normal when out of gear, but bogs when you load the engine against the foot brake, that's the first thing I'd see about. Everything else can be new or working fine, but if the carb doesn't put any power mixture into the motor, it just doesn't respond. Once the accel pump shot is gone, so is the power.

Some of those carbs also had dual stage accelerator pumps which were controlled by the ECM via a temp sensor. Not to mention the Throttle Position Sensor on the vehicles with computer controlled carbs.

A friend had a Chevy pickup that acted the same way. The first shop that rebuilt the carb left the spring out (or lost it) from under the power piston so manifold vacuum kept it in full economy mode all of the time. Adding a spring again fixed everything.

Otherwise, check for a clogged catalytic converter or a muffler with a bad baffle that's shutting down the exhaust flow. Slim possibility it could be a transmission torque converter issue, but very slim.

Hope this helps . . .

NTX5467

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you didnt mention what year your regal is. does it "kick down" when you step on it? when the transmission is in gear and you are rolling down the road to about 25-30 mph-if you can get that fast-if you step on the gas does it kick down into passing mode? does it also behave this way if you shift it manually? that could be the shifting modulator.i believe some models were engine vacuum controlled and some were ecm [computer] controlled, just like the carb.

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OK. Checked exhaust and cat - no problems there.

Pulled coil from cap and tested - checks out OK.

No codes from the ECM.

EGR - OK.

Now a new development. Start the engine - have to keep tapping lightly on the pedal to keep it running.

Checked fuel pump and filter again - both OK.

Carb problem I'm assuming?

What should be the next step?

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here is someplace you havent looked. you stated your fuel supply was 'ok'. does that mean you have fuel coming out of the fuel line when you crank the motor with the line disconnected from the carb? are you sure of the quality of the gas? do you have any enemies [sugar or water in the gas tank]? if you have GOOD fuel pressure, you are sure it is nothing but good gas, it wont hurt to get a $20 carb kit and just restuff it. while in there, check the carb vs the diagram the kit comes with to see if anything is missing or not quite right. have you checked your compression lately, a steady loss of compression could also cause these symptoms. but i would guess the carb first as it is the easiest to fix. try spraying W-D40 on the outside of the carb body to see if you have any unseen vacuum leaks. carb cleaner will work also but evaporates too fast. use it to clean up after. have you looked at your spark plugs? they will tell you if they arn't living in a healthy enviroment. it started running really bad after you checked your egr? go back a few steps and retry what you checked. now you got me wondering!

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Well,

If carb doesn't work, and you did complete tune up including compression check,no vacuum leaks and exhaust is clear....

Start to suspect the timing chain, cam gear is nylon for silent running and deteriorates naturally over the years, you may have skipped a tooth, yes it will still run with out popping but suffers severe power loss.

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check compression. if you find one cylinder that is low, you have a leaking valve, which can cause hesitation on acceleration.

check timing. (I might have said that already, I don't remember)

Adam

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Timing is right on. All six cylinders have good compression.

This is really a mystery!

If I start it and hold at 1000 rpm it'll keep running. Soon as I take foot off pedal - 15 seconds to stall.

Put in gear - can get to 40 mph by tapping on pedal. Try to give it some gas - nadda! No response.

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glavin!

um...Have you made sure the exhaust system is clear? something is not letting the engine breathe like it should I suspect.

This is odd...just pull it out and throw in a 455. grin.gif

Adam

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Have a '70 455 on my stand as we speak. Doin' the oil mods now.

TA 488/488 cam, dbl groove bearings, super bearings mains and rods, forged 11:1 pistons, cryoed rods, SP1 intake, and stage one heads. No carb choice yet.

WON'T BE THE ONE OFF THE REGAL THOUGH!!!

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I had an occurence that when I had a large amplifier for my stereo system hooked up it drew a lot of current from the battery and created a pretty bad hesitation for a long time. I finally ripped it out and figured out the problem.

Adam

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i will bet you dont have a place to tear the front of your engine apart. and this time of year the front yard sucks. if your ecm doesnt show anything is wrong, how do you know your ecm isnt the problem in the first place? sounds like you need a mechanics advice who is there to have a first hand look at what you have. just a though.

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If the timing chain has jumped, compression will not be within specs. If you want to check for chain looseness, just pull the fuel pump out and check it that way. This really sounds like a fuel delivery or vacuum leak problem. Look for a vacuum leak at the power brake booster, these are sometimes easy to overlook! Good luck and let us know, Tim <img src="http://www.aaca.org/ubbthreads/images/graemlins/wink.gif" alt="" />

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I almost forgot to let you know what the problem turned out to be.

After rechecking all the obvious possabilities a second and third time.

(EGR, manifold leak, finally changed ALL vacuum lines, electrical connections and wiring, entire ignition system, fuel pump, gas filter, gas line, gas cap)

Rebuilt carb twice in case I forgot something the first time. Nothing was solving the problem.

My dad finally stopped by to take a look.(He's a car guy as long as I remember)

I start the car, it runs for about 1 minute and stalls. He looks over the hood, says I need a MC solenoid - costs about $70. Just Like That!

Picked one up the next morning, changed it that evening. Everything is running fine.

Now! I checked both the MCS and the TPS twice with the multitester and dwellmeter and they both checked out OK.

When I called him that night, I asked how he knew.

He told me that when the engine stalled he didn't hear the MCS clicking, then it started clicking, then it stopped. That's how he knew.

I Hate When He Does That!! But I'm glad he does.

And I want to thank everyone who tried to help.

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"MC" = mixture control solenoid; it takes the place of the old power piston I mentioned that could be stuck in the "down" or "economy" position, resulting in no power resulting from no mixture enrichment when needed for extra power; basically, the computer pulses or cycles the metering rods up and down from commands from the ECM to deliver the correct mixture for the operating conditions at that particular time (i.e., idle, cruise, power, WOT). Not the previous "analog" (if you could call it that) system where the power piston was compressed against a spring by manifold vacuum to do basically the same thing.

When you took the carb apart, there most probably could have been some small little circles of what might look like orange-red silicone in the bottom of the float bowl. When those appear, it's the mixture control solenoid that they came out of and failure is imminent or has already happened. Don't feel too bad, though, as not everyone remembers those solenoids are supposed to make a little noise.

Glad you got it figured out and with everything else that got "attended to", things should run pretty good for a good while into the future without further maintenance.

NTX5467

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Thanks NTX5467, Those computer fuel problems are what keeps Holley Carburetor in business I guess. Then, all you have to do is kill the "check engine" light, the longest lasting light bulb in the industry. Wayne

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