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Post by legendaryacura8 on Mar 2, 2012 21:21:26 GMT -5
Again with hoping I explain this well enough. My '75 Monaco has a 360 4-Barrel in it. When I'm at a dead stop, the car idles great, as soon as I put it into drive and step on the accelerator (gradually) the car will start to go, and then bog down a little bit, and then start going again just fine. Once it's up to speed I don't notice any issues. I took it over to my mechanic to let him take a look and we did some troubleshooting. Once moving along at a decent speed (35 mph) I would stomp on the gas, and the car would react great. He said this proved that the accelerator pump in the carb was working fine. Then e started playing with timing and vacuum. All he documentation I have shows that the timing is supposed to be set at 8 degrees. When we checked it, it was up at 15 degrees! However, once we bumped it down to 8, the car would idle ok, but it didn't sound as good as with the timing up at 15, and the problem with the acceleration got worse. Then he checked the vacuum with a gauge and even with the timing set at 15 the vacuum pressure was low. Tomorrow I'm going to go over and we're going to tear the carburetor apart and look at it's insides. One thing I noticed in one of his books about the carburetor was that it supposedly has a a stage pump inside. one possibility he mentioned that I thought made sense might be that one of the "stages" isn't operating correctly. He also said that if we didn't find anything there that we cold check out the timing chain, just to be safe. Anyone here have any ideas about what could be going on? Just looking for any advice.
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Post by blusmbl on Mar 2, 2012 23:47:17 GMT -5
It might be the flyweights sticking in the distributor, might be hanging up on acceleration and not advancing smoothly. It might then be sticking and showing the timing advanced. Hope you find the problem.
Jeff.
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Post by Lord Vadus on Mar 3, 2012 23:11:06 GMT -5
Another option is a bad EGR. I'd check that and the catalytic converter, as a plugged cat will do the same thing.
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Post by legendaryacura8 on Mar 4, 2012 16:20:44 GMT -5
So we ended up jury rigging it. Switched the vacuum line to the distributor and the way my mechanic explained it to me, at idle, with the timing set at 15, the vacuum now advances it to around 28-30. With this set up, when I step on the accelerator, the vacuum still drops, but ti's not enough to kill the car. We decided since I'm going to be dropping a 440 in eventually, we wouldn't bother searching for this problem too intensely. How difficult is it to replace the EGR valve? He mentioned it but we never got too in depth for it.
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Post by countrybunker on Mar 4, 2012 17:59:58 GMT -5
ive had the same thing going on with my car. However its a 360 2 barrel car. The car runs fine at idle and accelerates and drives fine. But from a dead stop with slow acceleration you can feel some hesitation. I had the carb rebuilt, intake pulled and cleaned. But that didnt seam to really cure it. I did put a mopar performance coil along with a tune up and that really seemed to help it. Idk if it was the hotter spark or what. Well that was years ago and im starting to feel it a bit again.
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Post by Lord Vadus on Mar 4, 2012 23:30:35 GMT -5
I'll have to look at my car to check on the difficulty of replacing the EGR; I did the job a little over a year or so ago and my memory isn't 100% on it since I've fiddled with several different exhausts since then; a '74 Monaco Custom, '77 New Yorker, '76 Eldorado, 440 header system, etc. and I know my Brougham had a slightly modified exhaust, so I'll have to check and see how it'll be on the stock system, though it should be easier. I know it took longer for the parts to arrive and that its a one-day job, if that helps.
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Post by spanks79 on Mar 5, 2012 0:16:48 GMT -5
EGR should have no affect on acceleration, unless it is stuck open or opening when it is not suppose to. You can unplug the vacuum line to the valve and plug the line with a golf tee. See if it makes a difference, it likely won't, but if it does the valve is bad. The valve could be stuck open, you can take the valve off and make sure the pintle is seated and does not have some carbon holding it open. I would check the chain. If you have low vacuum a loose chain can cause this. Vaccum will always drop under accleration, vacuum at idle is what you care about. To check the chain take the distributor cap off and turn the crank shaft center bolt with a big ratchet. Turn it counterclockwise until you see the rotor button move, mark your crank pulley, then turn the crank clockwise until the rotor button just starts to move again and stop. Then see how far you had to turn the crank, if it is any more than a few degrees of crank rotation the chain is loose. I personally would check the function of the secondary circuit of the carburetor. The secondary's on a thermoquad are mechanical but they have a vacuum operated air valve over the top of them. You need to make sure it is operating properly. Check this site for some good TQ info www.nybclub.org/m-r/carburetor/CarterThermoquadInformationPage.htm |
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