Thread: Motor sputtering

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Hello everyone. Have a problem with a 1975 camaro with factory 350. Took motor & trans out to paint engine & compartment. Ran perfect! Did not take distributer out but painted motor on engine stand. New plugs,wires,cap rotor. Fuel pump,water pump.Took original quadrajet 4 barrel off intake. Tilted slightly to clean the outside with carb cleaner. It was never upside down. Put it all together & drove it. Was hesitating & not running good. Did not realize distributer wasent tight & it moved while motor was taken out-in. It's a 4 speed car. Timing supposed to be 6 degrees. I disconnected advance,plugged vac line, motor hot at 900 rpm set timing 6 degrees. In neutral revs normal,sounds good. From a stop driving normal it spits-sputters under a load. it kind of clears up around 2,500 rpm. If I hold it to floor it takes off normal & higher rpms seems fine ? Moved timing to 8,10,12 & same thing ? Has egr valve that tested fine with vac test. Car is original & kept it original. Any suggestions where to start looking ? Is it carb? Had no issues before. Thanks for your time !

I would check your spark plug wires to make sure their in the right order. I've had two switched around before and it can run almost ok like that. Could be a wire that's arcing the spark to somewhere also. That's where I would start.

Thanks for the reply. Yes I checked the order 2 times as well. Sprayed carb cleaner in carb & then the carb vent as it was running. Gave it throttle to run & clean it out. No difference after carb cleaner. But I was thinking I might have got a bad wire in the new set. Tomarrow I'm going to remove each 1 when its running too see if it makes a difference

Do you have a vacuum gauge? If not see if you could borrow one from a friend maybe.
Since you've checked firing order and plug wire location, verify that #1 cylinder is on compression stroke (TDC) and then verify the distributor cap is in the proper location, it should have an indexing tab. Then verify the plug wire locations are still correct. These checks won't cost you anything and there needs to be an organized diagnostic procedure.

Maybe you could do a short YouTube video on how it runs, it can be very hard to describe how a Motors running using words.

Check ground. You painted the block, make sure you have a ground strap.

Originally Posted by firebird77clone

check ground. You painted the block, make sure you have a ground strap.

bingo.........
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Can you not use caps on this site anymore? Not even for emphasis? Like the post above, I wanted to use caps for emphasis, like in zowie......
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Don't know how long it took you to do this but maybe bad gas from sitting a long time?

Thanks everyone for taking time to post. I do have a vac gauge. Before I realized the distributer was loose & moved. I turned motor to around 0 on timing chain cover & lifted distributer to see where rotor was pointing. It was towards #1. I did not remove distributer at any time,but checked anyhow. Did not have alot of gas in tank,but I did this in a 3 month span. Added $20 in gas since then. I have ground strap off firewall to motor-trans bolt where factory had it. Strap is like new but don't think I sanded the area. There's another ground off neg Batt terminal to fender. Then off neg batt to alternator bracket. I did think about a video. Might try to tap cell to windshield or something. Driving me crazy because this motor absolutely purred before I took it out! No problems. I'm at work another 4 hours yet. Will try sanding neg ground areas. Thanks again everyone!

It sounds like you're knowledgeable enough about Motors where you tried all the usual fixes.

ZOWIE!

Yes, it sounds like you've "done this before"... So I'd say you need to verify the grounds are clean and solid, maybe test voltage supply into the coil? Solid voltage?

HMmmmm CAPS seems okay..

under edit.
I re-read your original post and am curious why your idle is 900 rpm. Seems very high to me, No I didn't go looking for specs but it does seem high to me. My memory thinks it should be more in the 700 to 750 range. For giggles, if you're curious also.. Set your timing light up and start the motor, let it warm up if needed. Pull the vacuum advance hose and plug it, then watch the timing marks while you lower the idle rpms. I'm curious if the dizzy isn't already moving the mechanical advance weights and changing the timing due to the (perceived) higher rpms... If the timing also changes then either the mech'l advance springs are weak or the dizzy setup might need to be different?

Hey everyone. Thought i would have time today to work on car but have to wait till the morning. Yes I started turning wrench about 30 years ago, but haven't really done it for 5 yrs or so. So posting this to see if I'm missing something (having a brain fart) the 900 rpm is for standards..if it was a auto it should be 600. This is while advance is unplugged & vac line capped. I'm Getting info of radiator tag from factory. I'm the 4th owner of this car, had it over 10 yrs now. But just got to painting car,doing interior,etc...i am going to try that timing recommendation with weights after going over grounds. Will post tomarrow any results. Also will try to get a video if nothing works. I know it will help seeing & hopefully hearing this. Thanks everyone !

Carb base gasket correct one and on correctly?

Well after checking things I decided to put a Holley carb on to see if this was it. Runs perfect now so it's the carb. I have rebuilt alot of holleys. I have a few quadrajet carbs as anytime I had problems I swapped them out for Holley & never had issues. BUT I want to keep this car original with this quadrajet carb. Anyone rebuild 1 ? Or rebuilt Holley & quadrajet. Are they a pain or a pain compared to holleys? should I just take it somwhere? Can't believe this carb got messed up after taking extra precaution to not turn upside down & mess float up,etc..