olds8729

Link to another thread or any advice would be appreciated...

Purchased a rebuilt/pre-adjusted E4MC Rochester QJet 4-BBL carb for a 307 in an 87 Cutlass Supreme. Hot air choke.

This was to resolve a couple of service engine soon light issues. (IE TPS sensor, etc, the carb was sweating gas, figured it would be best to go radical.)

Carb seems to be working great, no idiot lights... EXCEPT a slight bit of hesitation upon immediate acceleration. It's very slight and goes away. Secondaries seem to kick in OK, trans shifting fine, no vacuum leaks identified, no service engine soon lights, smooth idle, just this slight hesitation which is more or less a nuisance. Maybe a choke thing?

Realizing this thing supposedly came pre-adjusted, I'm wondering what the issue could be? Timing seems dead on per the factory specs on the fan shroud. Car ran perfectly fine before this with the exception of the carb to ECM problems.

Obviously, I don't want to mess with anything unless I absolutely have to.

Thanks

BILL DEMMER

my first guess is the primary accelerator pump. it may be that the rubber cup needs to seat-in. beyond that i would look at the efe system to make sure it's working properly. make sure the flapper valve in the air cleaner is working too and that the pipe coming off the exhaust manifold, to the air cleaner, is providing hot air. btw, there is no such thing as a pre-adjusted ccc carb. they may have gotten it in the ballpark, but they require fine tuning on each individual engine. you will need special tools to do it.


bill

olds8729

Thanks for the advice, I'll give it a once over and follow up if/when I can get it squared away.

olds8729

Update...

Called the tech guy from my carb place, he was very helpful. He recommended I take the following steps. Also, he recommended having a scan tool, which I have, which provides data stream. I also have a digital voltmeter for the TPS reading.

#1) Set the TPS (Throttle Position Sensor) - I did some research and found that this is a small adjustment screw by the pivot point of the accelerator pump. Most of these come capped from the factory, but I my rebuilt unit had it exposed. I was able to adjust it by pulling the stem out of a ball point pen and boring out the end until it was big enough to fit over the adjustment screw. Found recommended voltage (~.49) here:

http://tlentz.oldsgmail.com/howto.html#TPS

#2) The next thing he said was to adjust the mixture screws in tandem until the datastream from the scan tool provided a 30-35 degree or 50% duty cycle.

I did #1 and I have already noticed an improvement. My TPS was about
.75+ which was way to high. I backed it down to .49 and I as I said, I noticed an improvement.

I'll update on #2 when I have time, it's raining out today so I won't get around to it. Thanks.

joe_padavano

Or any other carb, for that matter. The CCC is particularly sensitive to the adjustment procedure. You must follow the procedure in the CSM exactly in the order noted. If you do, the CCC runs great.