sugarsn10

iTrader: (2)

Sorry, but this is a somewhat long description. I just put a rebuilt CCC quadrajet on my Trans Am and I can't figure out what is causing the problem. I bought the car knowing the carb was bad so I just figured I'd bolt this new one on and it'd be good to go. It fired right up initially and ran good, but once it warmed up and the choke came off, it started to run really bad. The rpm's gradually fell lower and lower. I tried increasing the idle but once it finally got high enough to idle good and slightly richened the idle mixture screws it started dieseling really bad when I shut it off. When I go to drive it once the choke comes off it just wants to die. You can just pedal it and give it bursts of throttle and it will run, but once you start to hold the throttle steady it just starts to bog down and die. I'm not familiar with this computer stuff so I wouldn't know if it is something like an o2 sensor? I called the guy who rebuilt the carburetor and he said it didn't sound like a problem with the carb(go figure). He said if it is he'd be more than happy to fix the problem. I'm really stumped on this one and would appreciate and suggestions anyone has. Thanks.

rgarcia63

I've have the same problem with my '86 Silverado, but haven't done anything with it because I intend to upgrade to EFI.
While researching I came to the conclusion that it might be fuel related.
Here's a website that talks about the effects of using fuels with ethanol, which in my area it's E-10 (10% ethanol.
I'm not saying this is your problem, just something worth looking into.

sugarsn10

iTrader: (2)

Does anybody else have any input? I'm really stumped, so any suggestions would really help.

Black88Z

How do you know the original carb WAS bad? Maybe that wasnt the real problem.

The ethanol things right tho, theres been talk of that for a while now. Screwing up all carbs and older fuel systems.

Has the fuel pressure been tested? Fuel filter(s) replaced recently?

sugarsn10

iTrader: (2)

I figured the old carb was bad because it wouldn't fire at all unless I poured gas down the carb. The car was parked for 3 years because it wasn't running very good then (but it did run) and he took it in and the guy at the shop told him the carb was causing the problem. I haven't tested the fuel pressure yet. It has a new fuel filter at the fuel inlet to the carb. I looked for an inline fuel filter but I didn't see one, is there one? I just feel like it's not a fuel issue, because the car will run and drive fine when the choke is on, but the second it eventually turns off it run terrible. I'll look into those problems because I'm trying anything at this point. Maybe there's not enough fuel to the carb for the increased air to fuel ratio that occurs once the choke comes off. Thanks for the suggestions.

naf

iTrader: (7)

With the choke on it's running rich, as the choke comes off it's running leaner. I'd look for a vacuum leak.

Since this hasn't run in a while, have you checked for trouble codes that may indicate a sensor or some other component is bad? This can cause trouble when the ECM goes into feedback mode as it warms up.

The carb probably needs to be calibrated for your motor. This involves setting the IAB with a dwell meter. I'd first, however, ensure that the idle mixture screws and IAB are at four turns out on each (after checking where they are now so they can be returned to that setting if necessary.

Fuel pressure is not a problem if it's getting enough to run with the choke on.

Your filter is inside the inlet fitting on the carb, again not a problem here.

sugarsn10

iTrader: (2)

I checked the codes and the only code it ran was code 44 which is an o2 seansor lean exhaust. I've looked all around for vacuum leaks, but I just keep looking around to make sure I'm not missing one. I'll have to try those settings on the carburetor and see if those work. I didn't mess around with it much at all because the carb guy said it should be at a setting that it should run alright but not perfect. Since it was running so terrible, I was going to find the big problem and tune the carb later, but maybe the carb is the problem. Thanks again for the advice.

sugarsn10

iTrader: (2)

Does this sound like an o2 sensor problem to anyone? I know that the system goes into the closed loop system as it warms up which then uses readings from the o2. If its bad could it be the cause for it to start running so bad as it warms up? It also ran that code 44. I think I'm going to replace it unless someone thinks that the o2 really isn't the problem.

rgarcia63

The fact that it does read lean means it is working how well it's working was my concern, but if you replace that removes it from the equation.

five7kid

iTrader: (14)

When the O2 sensor gets weak, it starts reading lean.

I've been running E10 since 1982, and I've never seen it "eat" carb parts. Rebuild kits have had ethanol-compatible components for a couple of decades now.

sugarsn10

iTrader: (2)

That makes sense because it sent the lean code when I was idling and there was no way it was lean because I was messing around with the idle mixture screws and they were definitely more on the rich side than the lean side.

SDTransAM

iTrader: (5)

Then replace the o2 sensor.

naf

iTrader: (7)

O2 may or may not be bad. It's likely reading lean because it is lean. Fits the other symptoms.

In my experience a bad O2 won't make the motor run like crap so much as just a little off (and worse mileage). Won't hurt to replace it though.

sugarsn10

iTrader: (2)

Well I replaced the o2 sensor and that didn't seem to help at all. The problem is definitely still there. I checked some other sensors too. When I unplug the map sensor it runs way worse like it should. Unplugged the temp sensor by the thermostat and it didn't really do anything, maybe a little worse. I don't know what else to check. I'm going to change the plugs and wires, not expecting much from that but it needs it anyways. I'm starting to lean more towards it being the carburetors fault since there isn't a whole lot left to blame.

sugarsn10

iTrader: (2)

I have another question. Shouldn't I be able to run the engine fine without the crank case ventilation tube that goes from the valve covers to the air filter? When the air filter is off it really runs bad. I thought some people just run like a filter vent instead of that tube or am I wrong?

rgarcia63

It should run fine with no filter. There should be an oil knockout filter pad on the inside where the tube connects to air filter box. Are there any vacuum hoses connected to the air filter box?
The air filter is a restriction so you get more air with it off, it should actual run better without it, but if it's actually running lean more air just makes it worse. Did the code 44 return after replacing the O2?

sugarsn10

iTrader: (2)

It didn't return after I replaced the o2 sensor. This is an aftermarket air filter so the only hose running to it is the big crankcase ventilation hose from the valve cover to the bottom plate of the air filter assembly. It's really odd because I've always thought that hose wouldn't affect how it ran, but it really does. It won't idle on either choke on/off if that air filter is off or if the hose is disconnected from the filter assembly. I don't know if that has anything to do with the main problem or not. It sucks not being able to run it with the air filter off because now it is hard to check for vacuum leaks at the carburetor.

rgarcia63

So if the code didn't return then the O2 was faulty just not the cause of the problem you're having.
I would try plugging the hole in the valve cover first, then the bottom of the plate.

sugarsn10

iTrader: (2)

I just noticed this as I was looking closer to try see if there was a vacuum leak. I thought the coolant temperature sensor was the only thing in the thermostat housing, but I noticed there is what I figured out is the EFE (I'm really new to this emissions and computer stuff). It looks like the thing has a fitting for a vacuum line, but I can't find another vacuum line that is supposed to go to it. Does anybody know if this is supposed to have a vacuum line to it and if so, where it's supposed to be coming from? Thanks in advance.

five7kid

iTrader: (14)

There is a thread with vacuum diagrams on the FAQ forum. It shows the EFE lines.

sugarsn10

iTrader: (2)

Well it looks like one of the previous owners bypassed the efe tvs on the water neck since it was broken. Rechecked all of the other vacuum lines with the diagram and the rest of them are there and hooked up. Still can't seem to find a vacuum leak. Stumped again.

naf

iTrader: (7)

Don't forget about the accessory vacuum port on the manifold behind the carb. Plug it and see. It's a great source for leaks.

The vacuum line to the brake booster is another, although rare, source of potential leakage.

The EFE valve plumbing is exposed to a lot of heat and can suffer corrosion and deterioration as a result. Best to cap it and leave it alone in most cases.

sugarsn10

iTrader: (2)

I was just looking around at the map sensor and noticed it has no vacuum hose going to it at all. So it obviously isn't getting any reading. Can I just pull and vacuum hose from the carb or does it have to come right from intake manifold? I have a feeling this could be the source of the problem.

sugarsn10

iTrader: (2)

I see on the vacuum diagram it talks about a vacuum sensor. That isn't the same things as the map sensor is it? I tried following where the vacuum hose for the "vacuum sensor" goes, but it goes behind the distributor and into a wire loom. I think it may be the same hose coming out of another harness on the passenger side of the vehicle by the firewall, but then it travels across the firewall and into a "t" over on the driver's side with a bigger vacuum hose coming from the nipple on the intake manifold. This line then goes into another loom behind the brake booster. Is the small vacuum hose off the back of the carb supposed to go to the map sensor or does it follow the route I just explained? I'm somewhat confused and just want to know which hose is supposed to go to the map sensor and where to find it. Thanks.

naf

iTrader: (7)

There is no MAP sensor on your car. It uses both a:

VAC sensor which is located near the brake booster and connected to the rear of the carb through a hard plastic line that runs through the ECM wire harness loom;

AND a:

BARO sensor which is located on the right side of the firewall and has NO vacuum line connection.

The two pieces look otherwise identical. The BARO provides an atmospheric pressure reading that the ECM uses to correct the 'gage' pressure reading of the VAC sensor to an 'absolute' reading.

sugarsn10

iTrader: (2)

That makes a lot of sense. I was thinking the baro sensor was a map sensor and couldn't figure out why it didnt have a vacuum line going to it. I found the vacuum sensor and it does have vacuum line to it. I tried unplugging it and the vehicle didn't seem to run and worse or any better. Does this mean that the sensor is bad because the default setting isn't worse than the sensor's readings? It still wont idle when the choke comes fully open and surges up and down between 500 and 1000 rpms. Again when I rev it, it revs up, but when I hold it somewhere its starts to bog down and die. It really seems like a computer related problem to me because of how well it runs when the choke is on. Is this similar to something that would happen is the actual computer is bad? Thanks.

naf

iTrader: (7)

Try these:

Clear the ECM by disconnecting the power line to it. It's the single wire that comes off the battery terminal along the right fenderwell. It should have a little plug on it there that can be pulled apart. This should clear your trouble code.

Check your CTS pigtail and plug. Disconnect it from the CTS on the water neck and short the leads. This will 'confuse' the ECM into thinking the motor is full hot.

Disconnect the TPS connector on the front of the carb. This will cause the ECM to command a full-rich, limp home mode. You won't want to drive like this but see how it reacts.

Check your timing. Make sure it's around 0-6 degrees advanced at idle with the ESC connector (4 wire) to the distributor disconnected (you may need to temporarily block open the throttle some to do this. The motor should be below 1000 rpms for this check because the ICM will command a 'limp home' timing advance at a certain rpm threshold. Check the timing with it reconnected. It should look to be around 22 or so degrees advanced and increase with throttle. The exact amount is not that important, just that it is fairly steady and does advance.

This issue was a problem before you came into the car, so don't assume its carb related. Have you replaced the dist cap, rotor, plugs and wires? And inspected the dist rotor for play/wobble? All that should be done to a new-to-you car this old before any in-depth trouble shooting.

The ECM is not likely bad if it showed a code. They usually either work or don't.

Do the ignition stuff, make sure they're known good and go from there.

sugarsn10

iTrader: (2)

Thanks for the advice. I just replaced the plugs and wires the other night and by cousin (the previous owner) put on a new mallory ignition cap probably a year before he stopped driving it. I would think it would still be good, or should I replace that also? I'm gunna try all the steps you talked about tomorrow when I'm done with work. To short the CTS leads do I just use a wire to jump to terminals on the pig tail leading to the sensors?

rgarcia63

Once the CTS is disconnected put the jumper on the leads going to the ECM.

Zwrench

What method are you using to check for vacuum leaks? If visual, you wont notice any but the most obvious such as missing or damaged hoses. I use carburetor cleaner spray to check for vacuum leaks. I spray the hoses and gasket mating areas. If I were you, I'd pay particular attention to the carb base gasket since you just replaced the carb. If it's new, it might be the wrong one. If you reused the old one, it may be damaged.

Another question: How old is the gas?

sugarsn10

iTrader: (2)

I used some wd-40 to check for vacuum leaks. I didn't really spray the carb gasket yet. I got a new one but it looked identical to the one that was on there. I'm gunna spray by it just to make sure.

sugarsn10

iTrader: (2)

I checked the timing and it was all good, right at 0, I could maybe advance it a little. It ran about the same but lower rpms and what not with the ESC connector unplugged from the distributor and eventually died out as the choke came off as usual. I then plugged it back in and started it just for the heck of it. It seems to run great now. It idles instead of stalling and even holds a somewhat steady rpm and doesn't bog down when it is warmed up. It seems like it miraculously fixed itself when I plugged those wires back in. Is there any reasonable explanation to this? I just feel like it's a fluke.

Anyways, the rpms still jump around slightly when idling and when reved up. It maybe surges between 100-250 rpms. Would this mean that maybe the TPS needs to be adjusted?

Also, earlier in the day I unplugged the computer to clear the codes and unplugged the TPS and shorted the CTS like you suggested. I didn't really notice a huge difference. I could tell it was different, but couldn't tell if it was running better or worse. Tomorrow I'm going to start it and play with it again to see if this was all just a fluke or what. If it starts to run like it did before, I'll repeat the steps you said to try and really try to notice what seems to be better or worse. Once again thanks for all the suggestions!

naf

iTrader: (7)

Could have been a loose connection at the dist causing erratic timing? You'll have to check the timing while it's doing it.

Go ahead and check your TPS. Make sure it reads near 0.4-.5 volts at idle and steadily increases to around 4 volts at WOT. You can do this by backprobing the B and C terminals (plug must be connected). Don't need the engine running though, just ignition in run. A bad TPS can send erratic throttle position signals which can affect timing and what-not.

sugarsn10

iTrader: (2)

I finally got around to checking the tps and it was at .95 at idle so I adjusted it down to .48 at idle and it was 3.98 at wot. So that all seems to be good. I started it after that and the throttle response seemed to be a little better and didn't fluctuate as bad, although it did still fluctuate.

I decided to check the cap and rotor and I think I'm going to replace them. I have some pictures of them if anyone has input as what you think of their condition. There is some wobble to the shaft. It has approximately 1/8 in. of up and down travel. It also turns about the same, and when you lift up you can feel it turn since it's got that helical gear at the bottom. It has no wobble directly side to side though. Is this kind of the norm. I think I remember the shafts of the last couple distributors I dealt with had this up and down motion, but then again they were not new. You can see in the picture of the rotor that the thin piece of metal that goes to the center looks bent and somewhat mangled.




I also again shorted the CTS sensor and unplugged the TPS. It was once again very similar to how it acted normally. Seemed a little more boggy and the throttle response was a bit worse as I kind of expected. It did idle and not stall once the choke came off. It normally doesn't do this unless unless I've pedaled it to keep it alive for a while or been starting it multiple times. Either way it seems to run better once the coolant temp is up to about 220. I'll try the process again tomorrow after I either reassemble the distributor or put a new cap and rotor on, depending on what you guys think I should do. I'm leaning towards new stuff just to take it out of the equation of things that could be wrong.

sugarsn10

iTrader: (2)

Also, I need to buy a vacuum gauge still so I haven't set the idle mixture screws perfectly yet. Right now they are both at about 3 turns out. I've seen a lot of guys say that around 4 turns out is pretty close to being right so it probably is running slightly lean right now.

naf

iTrader: (7)

You won't use a vac guage to set the idle mixture screws. Just set them at 4 turns out then use a dwell meter to set the IAB. The dwell meter connects to the green diagnostic lead near the blower motor. With the engine warmed up and the dwell meter on the six cylinder scale, you'll want the dwell to be near the center of the scale (at idle) and wavering slightly back and forth. The wavering tells you that the ECM is in feedback mode and is adjusting the mixture slightly for changes in O2 readings.

Screwing the IAB in restricts air (richer) and the dwell should respond with less fuel (higher reading). The measured dwell represents the amount of time the rods are down in the primary jets, restricting fuel.

sugarsn10

iTrader: (2)

I have definitely found a vacuum leak now. I decided I was just going to replace all the vacuum lines since they aren't very expensive anyways. The first one I pulled off was going from the carb to a check valve which then went to the diverter valve for the smog pump. I got to pull the vacuum line from it and notice the hard plastic elbow on the valve is broken. So that was definitely broken. I took the sensor-like part of the valve off hoping I could replace that since that's all that is bad. Now I find out that I can't buy only that part and I have to buy the whole diverter valve which is like $380 from rock auto and I'm waiting for a price check from O'reilly's. There is no way I'm gunna pay that much because that stupid piece of plastic broke. Does anybody happen to have one of these I could buy from them? I know a lot of people seem to take all that emissions stuff off. I've thought about taking the AIR system off buy I've heard it throws off the o2 sensor. Anybody have experience with that? I'm just looking for some suggestions because I can't afford to pay $400 for that little valve, there's other things that money could be used to improve on the car. Thanks in advance for any ideas.

naf

iTrader: (7)

Let me look and see what I've got in the shed.

sugarsn10

iTrader: (2)

I've been reading some different threads to try to find out what happens if I just remove the air system. Most of the threads I read all talk about the TBI and TPI. What about us LG4 guys with the CCC? Does this affect O2 readings in the LG4 ecm?

The other threads seem to say it will make the TPI systems run lean, but not the TBI systems. I would figure the CCC setup is closer to the TBI setup so that would mean there is no affect to it? Does anybody have factual technical experience with removing AIR from the LG4?

naf

iTrader: (7)

It will run fine without it. The AIR is not supposed to be engaged during open loop operation, when the ECM is looking at the O2 anyway. I'm running both my 87 (vortec manifold/headers) and my 85 (otherwise stock) without the systems with no issues.

I had intended to keep the AIR on my 85 when I replaced the motor several years ago but a good bit of the piping had corroded from the inside and crumbled on removal. It just wasn't worth the cost and trouble to replace the broken bits.

So, I wouldn't spend too much money or effort to keep it, but I wouldn't go out of my way to remove it.

I've still got both valve setups. Let me know which piece you need specifically and I could ship it to you at cost. If you still want it.

sugarsn10

iTrader: (2)

I think for now I'm just going to disconnect it and plug the vacuum line to it. I don't have the serpentine setup, so I'm just going to remove the belt for now. If I decide I want to run I'll definitely take you up on your offer. I'm hoping this vacuum leak was the sole problem.

Here is a picture of what the valve looks like on my car.
http://www.oreillyauto.com/site/c/de...2124&ppt=C0018

rgarcia63

The air pump is also used to provide air to get the 3-way cat to light up faster, or it will take longer to warm up, increasing time in open loop, resulting in higher emmisions, well that's what the ECM is for right - emmisions?

sugarsn10

iTrader: (2)

I've read that it heats it up to help the cat reach it's maximum effectiveness sooner. Does the cat have a temp sensor on it to tell the ecm when to transition from open to closed loop? I didn't see anything going to it besides the air tube, maybe I missed it. I just figured the ecm based the transition on feedback from like the choke and CTS. I just figured that it wouldn't stay in open loop longer, but just have higher emissions until it warms up. This is probably the wrong attitude, but I really couldn't care less about emissions. My state has emissions testing in only like 2 counties I think. My county doesn't have emissions testing at all on anything and my car hit the 25 year mark last year.

naf

iTrader: (7)

It will have no affect on open/closed loop. The drawbacks are that the catalytic may become more prone to clogging without the fresh air line AND subsequent higher emissions. The ECM cares nothing about anything past the O2 sensor.

five7kid

iTrader: (14)

Let's clear up the function of the air injection reaction system.

The factory used it in the early days of emissions controls before catalytic converters. So, it ain't there to "light up" the converter.

It's there to provide additional oxygen to the exhaust stream to oxidize any unburnt hydrocarbons. During open loop operation, the flow is sent to the exhaust manifolds, where the exhaust is hottest and reaction is more likely. During closed loop operation, the flow is sent to the cat, where the oxygen can better be utilized in the catalyzed reactions.

Either way, it won't have any effect on how the engine runs (with the exception of tailpipe emissions).

sugarsn10

iTrader: (2)

Thanks for clearing that up. Well I just got done running all new vacuum lines and it is still doing the same thing. I think it runs a little smoother but it eventually stalls out again. I was thinking maybe the fuel pump is starting to go? I have a rubber fuel hose going from the pump to the carb and I can completely squash it even when the engine is running. It doesn't feel very firm at all. I know they only have like 5-7 psi in them, but I would think it would be somewhat firm. I thought I remember the fuel line being somewhat firm on my last sbc.

Also, There seems to be a decent amount of oil on the fuel pump itself. More towards the top like which is where it would be wet if it was leaking between the block and the pump. Does the pump going bad seem like a logical explanation for it stalling and surging? The pump is only $20 but is kinda gunna be a PITA to change since there so much crap in the way. Responses are much appreciated.

rgarcia63

I know it doesn't affect how the the engine runs, but for those who unfortunately have to worry about passing emissions let's clear it up a little bit more.
My AllData online manual for my '88 Camaro describes the function of the A.I.R system as follows:

SYSTEM DESCRIPTION

This system is used to reduce Carbon Monoxide (CO), Hydrocarbon (HC) and Nitrous Oxide (NO,) emissions. It also heats up the catalytic converter quickly on engine start-up so conversion of exhaust gases will start quickly...

CONTROL VALVE DESCRIPTION

PRESSURE OPERATED ELECTRIC DIVERT / ELECTRIC SWITCHING VALVE (PEDES)

This valve, is ECM operated similarly to the ED/ES type (older A.I.R. system), but uses air pump pressure rather than intake manifold vacuum to operate control valves. Air pump pressure builds up against a control valve which is operated by the ECM through 2 solenoids...

Words in italics are mine.

Raul.

sugarsn10

iTrader: (2)

I was poking around testing the CTS and noticed that the purge TVS is cracked. I've tried to research to see if this would cause any problems besides causing a vacuum leak. From my research it seems like it is something I should replace and not just block off. Is this correct? I think I've found the right part from the auto store. They have two types of TVS valves. The cheaper one looks like what is used for the EFE system, and the more expensive one looks like the one for the purge. Is there a difference in these or could I just use the cheaper one? They both have 2 vacuum lines going to them, but the EFE one has a little piece of plastic sticking out. If anyone has any experience with this and has some suggestions I appreciate the help.

five7kid

iTrader: (14)

The two TVS's operate differently, so you need to get the one for the function for which it was intended.

sugarsn10

iTrader: (2)

Well here's my latest update. I finally gave in and bought the stuff I need to properly do some testing. I tested the MAP sensor and it was only giving me .65 volts at 0 vacuum and actually went UP slightly as the vacuum increased instead of decreasing. I also checked the CTS and that was bad also. So I replaced both of those and the purge TVS that was bad. I went to start it and it revs a little better but still dies. I didn't spend a whole lot of time fooling around with it once I got the parts installed seeing as it was -5 up north here in Wisconsin today, and I didn't have the heater. I did take time to hook up the vacuum gauge to the carb and it read 20 in. at 1900 rpm and 15 in. at 1100 rpm. I'm guessing that means I have a nice big vacuum leak somewhere. It was stalling before I could get a good reading of it around 600 rpm. I'm guessing it would be something like 10 in, which is well below the suggested 18-20 I've seen.

I think tomorrow I"m gunna cap off all the vacuum ports and see what kind of reading I get. Idk if I mentioned this before, but as I was installing the brake booster line into the back of the carb, the fitting in the carb cracked when it was about half threaded in. I called the carb guy immediately to see how to deal with this problem(I figured it would cause a vacuum leak) and he told me it shouldn't be a problem and they do that all the time on him. I've sprayed around by it, but it didn't seem to have any effect. I also did notice some wetness in one spot between the intake and head. I tried spraying there too, but couldn't really notice anything. I plan on hooking up the gauge with the ports blocked(exc brake booster) and if it's still leaking I figure it has to be one of the two suspected problem areas. And if so, that carb is going back and I'm pulling the intake off. Does anybody have any suggestions or tips for my plan? This is kind of a last ditch effort. I leave to go back to school on Saturday and I really wanted to get it running good by then. Thanks in advance!