seriously, id like to keep this thing. But i'm at my wits-end here. Ive been fighting with this for atleast 2 months now.

firstly i have an 86 LG4 with hedman shorties and a 3 inch exhaust with no cat.

The carb is an E4ME off of a 88 caprice (350). It was supposedly rebuilt recently and it apears to have been so on the inside and out.

The problem is i cannot get it to stop stumbling under light throttle, and or cruising speeds. I have tried NUMEROUS combinations of mixture screws, IAB, lean stop, rich stop, always having 1/8th inch MCS travel and it doesnt go away. The problem started the day i put this carb on.

I had it running great (for 15 minutes) before i messed with the mixture screws, that was atleast 2 months ago. When cruising my 02 voltage is .900, when it stumbles it goes nearly full lean. WOT it stumbles just slightly at throttle dip-in and goes very strong out of the idle circut. Its not the secondaries bogging.

I've tried the mixture screws everywhere from 2 to 7 turns out. With the Lean and Rich stops set at various "benchtop" settings i've read around TGO and the internet.

I've tried 4 turns on the idle screws, 4 turns on the Lean stop and set the Rich stop for 1/8th inch travel. With the IAB 4 turns out and the car wont run. The idle doesnt even smooth until the IAB is almost completely tightened. And even then it stumbles lean and runs rich.

The kicker is that i cannot really get any IAB "authority" until atleast 5 1/2 turns up on the lean stop (the highest it will go is about 6 turns). Anything less and you cannot "over-richen" the IAB. Turning the IAB richer, while checking the throttle/rpm, it will either stumble on throttle dip-in or stumble through-out the entire power-band, before coming so rich it doesnt idle well.

The accelerator pump works fine, i checked it just yesterday. It looks new and squirts fuel.

i'm very frustrated here sorry for the long post. any help would be great.

 

Anyone??

This is my only car. I'm open for any ideas..

 

What kind of air cleaner do you have on it?

Have you made sure you don't have any vacuum leaks?

7 turns out isn't a bad starting point. The threads are a lot finer on CC q-jets than they are on most carbs.

Or, you may have a clogged circuit and it's only operating off of one idle circuit. Overtightening an idle mixture screw can also damage the circuit. Those are complete shots in the dark, though.

Who supposedly rebuilt it?

 

thanks for replying Five7Kid. A shot in the dark or not, i'm at a loss here, any help is welcome.

The Air cleaner is a paper open element. It does it with the air-cleaner off in Park as well as driving with it on.

A vacuum leak is possible. Though i've gone over all places i could think of with a peice of large hose to my ear and couldnt find anything. Thats not to say there isnt, i'm going to pick up a vacuum gauge this week-end hopefully. Someone also recomended trying carb cleaner at the hose ends. About how much vacuum should i have with this engine at idle?

Would vaccum leaks cause it to run nearly full rich ( .9 volts)? The whole reason i messed with the idle screws was to try to lean it out some. But "duh" the IDLE screws are for the IDLE..

The carb was rebuilt by a TGO user. I searched and found him asking questions and stating he rebuilt his carb quiet a while ago. I believe him for sure. It looks new as can be on the inside, nothing like my 160k old E4ME.

I'm seriously thinking of taking the choke and TPS out of this thing and slapping it in my old carb. Because that is all that was wrong with it.

 

bump

 

What kind of dwell readings are you getting? and how do they look as the engine rpm's increase?

 

I'm not sure what the dwell is, naf. I was hoping i could atleast get it running decent with-out one and fine tune it once i have one. You figure the law of numbers would be on my side after 2 months of tuning, but no

I ordered a kit with a dwell/tach, timing light, vacuum gauge and compression tester so i will let you know once i get it.

My new motor is going in soon (its been sitting for 4 months now) and i'm HOPEFULLY putting this qjet on the performer RPM i have for it. If it gives me many more headaches, though, i'm considering putting a double-pumper on it.

What all do you need to convert to a non-computer controlled setup? Do i need a new fuel pump and or a regulator aswell as the distributor?

Thanks again for all the help

 

The dwell meter will tell you how much the solenoid is cycling to richen or lean out the idle mixture. It can only adjust within a small range and all the other settings help the mixture solenoid get within the right "window" to effectively manage the primary circuits. Without the meter you're hit and miss. Once you get the meter hooked up and running, you may find that one of your sensors is bad, could be coolant, o2, tps, map, whatever but once you're tuning with the right tools it's cake. You're unlikely to get better mileage out of another carb'd system and the ccc qjet will still support a good amount of power.

If you swap it out you'll have to change your distributor and rewire the controls for your lockup converter (for autos).

In the meantime, unplug your tps and see how it runs. Let me know when you've got the meter.

 

My TPS is fine, its in the correct range.

I think my MAP sensor may be bad though. It sets off the SES light on long high-way cruises. Could it cause problems like this? It was my understanding that the MAP sensor didnt do anything while the motor was warming up at high-idle, or while the engine was below 110F.

How do i test the 02 sensor? This is the second one i've had in the last 2 months. I have it wired to the inside of my car so i can see the voltage while driving. Its pretty-much always .900 volts, accept for the first minute you start it while its warming the sensor.

Thanks again, naf.

 

Sounds like your carb is running full rich and the solenoid is not adequately adjusting the mixture. Are you getting crappy mileage? The MAP sensor can cause this as can other bad sensors. If you've got a manual, you may want to test all of them. O2 sensor sounds ok, though. You'll need the dwell meter to test your solenoid and carb settings.

 

The first thing you need to do is focus. You stated you had the car running fine prior to messing around with the carb's idle mixture... so re-trace you're steps. By the way, turn the mixture screws all the way in, then back them off three full turns a piece (this is a good enough reference point).

Go with the basic's, first. How are you're plugs? Are the gaps set too narrow? How are the plug wires? Check you're dizzy's cap and rotor, do you see any crack's? Did you yourself ever touch the valves (rocker arm adjustment)? Maybe their a little too tight?

Moving towards the Carb, you stated that someone said it was recently rebuilt. You know, this honestly scares me when I hear something like this... I'd rather rebuild them myself. But anyways, again, go with the basics;

You already mentioned that you're air cleaner is not dirty. Did you accidentally put the Carb's gasket on backward, with the secondaries on the primary side, and the primaries on the secondary side? Do you know how to properly set you're float level? Did you check to see if youre float valve is leaking? Are you're jet's loose?

Get yourself some Carb cleaner, and spray some around the Carb's throttle shaft, and intake manifold base.... does the engine momentarily rev higher while it's idling? If it does, then there's you're vacuum leak.

You mentioned that the accelrator pump seems to be working, and that the secondaries are set properly. If you're basing this on what was said to you, I wouldn't trust it. You have nothing to lose, re-set you're secondaries, and check to see if the accelerator pump piston/diaphragm is leaky....

 

Naf, my gas mileage is bad. Its not quiet as bad as my other carb was with the bad TPS and choke, but its pretty bad. Nothing like the near 20 mpg i read some people getting with their CCC setups.

Street Leathal, thanks for giving me a hand here.

The distributor should be in good shape (i'll check it though). There is less the 2000 miles on the cap, rotor, plugs and wires. I have one of those "fancy" accel super coils with 4+ bosch plugs (waste of money) and they look to be burning rich. I put some new ac delco's in to see if the plugs were the problem and it was still doing it.

I tuned the secondaries my self. I know they are on. On a good day i can lay it down from a slow roll and break the tires loose with this wimpy lg4. It has a G hanger with DR rods.

When i had the air-horn off i pressed down on the accelerator pump and it squirted fuel, so im basing my assumption its "good" off of this. It looks new as can be as well. Notthing like my other one.

When i first got the carb on there the engine would die, or try to, as soon as you touched the throttle. I fixed it by adjusting the IAB down and it was running like a beast (beast of a LG4 mind you ). But i tried to fix the over rich problem with the mixture screws and got it all out of wack. Then i decided to "start fresh" by retuning everything according to info i found searching TGO. No luck there.

i havent touched the heads.

By carb gasket do you mean the base gasket? Its on there good, and its new. I'll try the carb cleaner trick though, i got some somewhere.

Do i need special tools to set the float? I havent a clue how to set it. enlighten me.

I even tried putting the primary metering rods from my old carb in this one and it was no help. It had 57's in it and i put in 56's from the cars original carb.


Thanks again for all the help here.

 

Get a dwell meter and connect it to the diagnostic cable at the passenger side firewall. You need to see what your mixture solenoid is doing. From there you can adjust it or find the problem.

 

It will still pump, even though it might be a little leaky. Since you had the air-horn off, did you check to see if the accelerator pump passages were restricted?

There is a metal 'tang' that needs to be adjusted, a set of fingers will do...

"Flat Spots", if related to the float (as the cause of them come from more than just a bad float setting), indicate too low of a float level.

Here's a question for you, when you make a full turn at idle speed, does the engine immediately want to stall?

 

You won't be able to know anything for sure until you get a dwell meter. Get one, test it, and report back.

 

~30$ at autozone.