Joe King

New engine build diving me nuts! My latest issue is when I am accelerating all is fine but when I start to lift on the accelerator it has a dead spot. It only does it while driving and once I start to lift never while accelerating. It just started this about two weeks ago after I set the timing and dwell but I think the dwell is set a little low but when it was really low it didn't have this issue. I used to love carb motors and hate efi but this car has me feeling a little different...

garage goat2

where in Florida? Sounds like a vaccum leak?

Sugar Bear

Please post year, model, engine, etc.

The symptom is similar to a binding EGR valve that does not close quick enough when backing off the throttle, try unplugging it as a test to see if it changes anything. Don't drive with it disconnected for long if you hear engine ping/detonation.

Does it occur after opening the secondaries? They may be sticking/hanging open a little, check for free movement and total closure of the secondary throttle plates.

Good luck!!!

Joe King

I live north of Orlando and South of Daytona but closer to Daytona.

The car is an '89 Cadillac Brougham, I ripped out the 307 and built a '72 350 bored out .040, Edelbrock cam & intake, balanced, headers, quadrajet modified, recipe #2 from Cliff ruggles book. The modified qjet made all the difference in keeping the ccc. I was ready to rear it all out but that was a game changer for sure.

I will check the egr and secondary butterflies for sure. But it seems to do even when not running hard/no secondaries.

droldsmorland

Dwell isn't set low or high. Its 30* or .016"-.018" gap... period. Do you mean timing?
What are your timing specs...base timing, then with vacuum and then all-in with centrifugal. Are the centrifugal weights and springs clean and serviceable? How are you signaling the vac advance can? Ported or straight intake vac?

What kind of cam profile are you running? What is the vacuum reading at curb idle? What RPM is the idle set at?

Is this a 72 engine with a 72 spec intake? A 72 shouldn't have an EGR neither should the 72 spec Edelbrock intake. Do you, in fact, have an EGR? If so the symptom is typical of a failing EGR, its vac signal or a vac leak elsewhere. I'd eliminate the EGR with a block off plate if it is there or put a non EGR intake on.

Next, read the plugs. White means lean either on the carb circuits or a vac leak.

After determining that the timing events (including dwell) are set correctly for what the engine wants I'd look at vacuum leaks. Carb base gasket, intake gasket (is the intake "matched" to the heads?), throttle bushings, PCV valve(bad) and brake booster etc...

Hammerdrop

If this is an E4ME carb, isn't this still a CCC Computer Controlled Carb, OBD 1 setup?

Hammerdrop

I "mispoke" on the meaning of CCC. I know it's Computer Command Control.
How did this turn out with checking the EGR and the secondaries? Those sounded like good ideas.
I think drolds didn't know that the dwell you were referring to is the Air Fuel Solenoid dwell.

droldsmorland

Ahhh yes Hammer...A/F sol dwell would make sense...

Joe K, this a somewhat cryptic post especially for an old skooler and the king of refrigerator eyes(me). Sugar Bear and I are still gona go with an EGR or vacuum leak problem. Isolate the EGR and road test to rule it out.

Is this one of the dual valve EGRs as seen on the late 80s, mid-90s GMs? I have seen one side fail on that style of EGR causing various stumbles/flutters at part throttle acceleration and deceleration.

Next step...see what the O2 sensor(s) is up to in general and when the problem occurs. That is if you still have all the OEM OBD1 stuff hooked up??? Read the O2 signal while decelerating.

Does the Edelbrock intake have an EGR on it?

Calling Joe K....

Joe King

Thanks for the pointers, I am still running the CCC obd-i . I am out on vacation but once I return I am going to test the egr and see if that helps. To be honest I have been suspecting my intake is leaking but I can't find anything definitive that it is. It's an Edelbrock aluminum intake with the egr port which I did keep hooked up.

Thank you again for the help

Hammerdrop

Best way to find a vacuum leak is a Smoke Machine and the best way to wake that Cadillac up is to change the rear axle gear ratio.

Joe King

I blocked/ capped egr port and no difference. I also realized the lean mixture, timing and replaced carb base gasket. Running much better but still hiccup when letting of the accelerator. What I did find out is the check valve to the a/c and cruise is malfunctioning (not checking, air blows/sucks through both direction) which explains why when accelerating ac goes to defrost.

I will try smoking it out Sunday after I replace the check valve in it. And I absolutely agree, changing the 2.56 great ratio on this tank would make high difference but after engine build, no more funds for that. I went WAAAYYYYYY over budget on the engine.

Hammerdrop

I have a 1993 Caprice Police axle with a 3.42 open diff that I won't be using. If you come to Chicago I will let it go cheap.

Hammerdrop

Been thinking about it and maybe you should try disconnecting the EGR, just for fun, and see if the problem changes. You still running the stock exhaust?

Joe King

I tried disconnecting the egr but no joy. Car is far from stock exhaust, she has headers running true dual into a pair of FlowMasters.

I wish I could remember what I may have changed for this to start happening but I have no idea.

Joe King

I just pulled my egr valve off, any chance these leaks could be the culprit?

Hammerdrop

If that gasket is shot, I think that could create a nice vacuum leak or an exhaust leak that you could hear or both.

You have no trouble codes, right?
Could you better describe the hesitation you experience? So this is only when you lift off the gas pedal? The rest of the time, driveability is fine?
Does the engine stall?
Read my thread on the 1989 Custom Cruiser pinging; I am pretty sure that without any back pressure in the exhaust, your EGR is not functioning at all, but I'm not saying that is the cause of your problem.

olds 307 and 403

I would switch over to the same EGR as Hammerdrop. The early 307's advance curve was less aggressive than the later swirl port 307's. Did you check the TPS? Make sure the movement on a volt meter with the key on is .5 to 4.5 volts in a smooth curve to start.

Joe King

Interesting you suggested the T.P.S. I have made some adjustments but did not readjust the tps and I was just thinking about it yesterday. The new gasket didn't make a change and maybe on Friday I can adjust the tps.

Problem: after accelerating and I get up to speed, I slowly lift my for to stop accelerating and get ready to hold my speed it had a flat spot. Right as I am lifting off the gas pedal. I was starting to wonder if maybe she wanted premium gas. I'll try the tps first then see where I am at.

Hammerdrop

In the beginning, you said the Cliff Ruggles did your carb. Was the TPS replaced at that time.

You have no trouble codes, right?

Joe King

I rebuilt the carb using Cliff's recipe #2. Tps was new but today I tried to adjust it but it would not go under 7.9-8.0 I had the screw practically all the way out but the numbers wouldn't drop anymore than 7.9. I could screw it in and the number would go out but there was a spot where the number just stopped coming down. I tried to loosen the lid and tap with a hammer but no joy. So I'm not sure if the tps is bad or if it is just hung up inside. Ugh!
Tps number being high can explain why on the interstate the tranny doesn't lockup, it thinks I am accelerating while I'm just holding steady. At lower speed it locks up fine.

Hammerdrop

Still looking for an answer on the trouble code question.....

Thinking you can check that TPS with a old analog ohmeter.

Joe King

No trouble codes, no engine light.

I have a spare tps I will install next chance I am free

Joe King

So finally this morning I got around to working on the TPS. After taking the top of the carb off the times and finally testing both TPS sensors I found out that the spare sensor was bad (glad I never hooked it up) and the new(er) one is good. Still unable to make adjustments though.

Finally I spotted that the green spacer that goes from the arm to the tps sensor inside the carb was stuck. I tried to tap it with a punch but still nothing. Lastly, removed top of carb again, clean the green spacer and the bore it slides in then sprayed the **** out of it with some wd-40. FINALLY!!! I was able to make adjustments and it was no longer sticking. Haven't driven it yet but will shortly.
xxxxxxxxxxxxxx
Still flat spot, ordered a 73 Cutlass 350 egr, should have in a couple of days

Hammerdrop

I am surprised that a non functioning TPS did not trip the Check Engine Light. The bulb is functioning with the ignition on and the engine not running, correct?

Joe King

Bulb works fine. TPS kept sticking so I bought a new one, with a new pusher thing and I put on a new gasket and a different carburetor lid and finally that problem is gone but now I have been chasing a surging issue when cruising. Worst at lower speed, 70+ no issues. I think I am in the right track right now cause it is nearly all gone. I just have to figure out if plugging the new egr did the trick or if screwing in the lean/rich screws did it.

Hammerdrop

Some thoughts:

The TPS has a specified voltage range. I think at idle it should be like 0.4 volt and at full throttle like 5.0. Is that what you are reading on your scanner now? Check those voltages with the manual.

Pulling the hose off the EGR will disable it to eliminate that as the problem. Possibly restricting the EGR could help if the EGR exhaust flow is too much. I noticed that my 73 EGR valve had something in the instructions about restrictor washers for use in certain applications, but I mine had none included, so I installed it without any.

I did put a restrictor in my EGR vacuum hose to slow down the opening a little. This is similar to what you would do to the Choke pulloff connected to the secondaries on a Quadrajet to slow down their opening to avoid a secondary bog.

Do you have the idle air valve in the top of the carb adjusted to give about a 50% (or 30° dwell) duty cycle at idle?

Joe King

The TPS is set to .4 and the idle air valve is adjusted according to my service manual 1.346 I believe. I would have to pull out my book again to make sure but it is set according to the Factory service manual.

I'll have to look into the egr restrictor, I installed a 72 350 egr but I do have the original egr valve that I could put back on since that want a problem before but the tps was. Maybe I will try that.

Curious about the idle air valve adjustments with dwell, where can I find more info on that?

Hammerdrop

What is the TPS Voltage at full throttle? It should be like 5 volts, I think.
The Idle air is right on top of the carb and can be adjusted to give a 50% duty cycle (or a 30° dwell). If you have no Check Engine light, you are probably within specs on both. My little restrictor in the EGR vac line simply delays the valve opening for just a very short time.
All you have to do to disable the EGR is pull the vac line off and plug it.

Joe King

I reinstalled my original egr and the surging went away. I noticed the port for the vacuum on it has a very small home compared to the 72 egr valve. I had a high idle so I tried to adjust the idle down but Everytime I would back the screw out the idle would just bump up again. I need to check tps again now that I changed the idle screw and see if that fixes my idle. It is way too high and runs on when I shut it off.

Still no check engine light and I double checked the idle air bleed on top of carb with my mic and according to the book specsi have it adjusted down at 1.756 whish gives it .125" of up and down movement which, again, according to the book specs. I'm not sure if there is a better adjustments to be made for the bigger and modified engine that replaced the 307 that it used to control. Maybe I should look into that.

Joe King

So I have done some research and as it turns out, I have been doing it all wrong. I have been setting the top idle air screw to 1.756 and seeing the dwell to the air fuel adjustment screws on the base.
what I just read is I need to set the air fuel mixture screws out at 3 3/8 turns out and set the dwell with the upper screw. If I can get the numbers right then I need to turn the lower screws out some (evenly) then try again.

Hammerdrop, thanks for pushing me to research a little more. Tomorrow I will dig into this and see if I can't get it right. I know right now my lower air fuel mixture screws are out 4.5 turns each so about 1.25 to far which might be some of my problems.

Hammerdrop

Yea, I don't think that I ever messed with the setting of idle screws on the base plate. I just put them back where they were set at the factory. There must be a adjustment procedure in the manual for that.

The air fuel solenoid takes care of the fine adjustment to maintain the exact mixture adjustment. The way I understand it, when the solenoid pulses more to hold the fuel rods down to get to a leaner mixture, at the same time the plunger in the idle air valve is being let open more to also lean out the mix. The opposite is that on a rich command the rods are held up more for more fuel and the idle air is open less. It's a complicated deal to figure out.

I would say that if the engine diesels on shut off, the idle speed must be too high. I have yet to figure out how that throttle kicker works exactly, but there is a cracking screw on the body of the carb that, I think, maintains the curb idle. I don't think that the throttle kicker should be active (sticking out) at curb idle. I'm pretty sure that mine is retracted at idle and the cracking screw on the body of the carb is controlling the idle speed at engine shutoff. I think that kicker is a more a pollution control think that holds the throttle open when the car is coasting down. But I am not 100% sure if that is the only time it is active.

So do you think that you are getting too much EGR? Did you get any restrictor washers with your 73 valve? By the way, there were not any EGR valves in 72. That started in 73. I suppose a restriction plate could be fashioned to decrease the gas flow.

Joe King

I just read my factory service manual again and it said to not adjust the air bleed any further than the 1.756 and only just the idle mixture screws to between 10-50 dwell. Weird, 2 books with 2 different ways of adjusting the same carb. I might try the other way and see if I get different results. My manual is from 1989 model so it is at the end of time... Carburetor speaking ...

Your right, my egr is from a 73, my engine is a 1972, mixed the t years up a little bit. It did not come with a restrictor and the instructions had nothing about one either.

Joe King

Not to get off topic here but I just wanted to say that today I installed a Dorman 55101 manual choke for my E4me carburetor and it was A GREAT investment! My car hasn't started with just two pumps since I sent my old carb off to be rebuilt. Man, it felt great to not have to pump this sucker up 6 times, crank, steak, pump 6 times, crank, steak, pump 6 times, barely run, been it to stay running, feather gas enough to keep it running...

Any ways, car has been shooting for a few days, purposely so when I installed this kit, I would know if it worked and but did it!

Hammerdrop

If you block off the hot air feed to the choke, you should know that amount of air going through there functions like bypass idle air.
I would expect that to affect the idle. The carb is calibrated for that amount of air going through there. Usually, the shaft seal on the choke shaft leaks and prevents proper operation. I even had a rebuilder forget to install one.

That hot air choke is a PITA. I know.