Just bought a new one, Had the shop install it, put a new oxygen sensor, MCS is clicking even while running, and tps is good.


The exhaust smells like pure gasoline and burns my eyes, and the engine lacks serious power. Essentially it's doing the same bull**** the previous Q-jet was doing. The Ecu clearly isn't liking something it sees, or can't see for this matter.


I'm very skeptical of putting this setup on the new engine, or else it's gonna coat the fresh cylinder walls with carbon.


I'm suspecting the knock sensor is causing the ecu to retard the timing. I even pulled the connector off the knock sensor, and it didn't change anything. Is the knock sensor the cause, or does it not really cause any of the issues i listed?



Distributor is stock, in case you ask.

 

if you got the carb rebuilt and we will assume it is working good.
could it be your timing is off ?

 

ditch the pos and buy a donor late model TBI f-body and convert it. Did that to my 82 trans am and loved every second of the car after that

 

How about, no.

 

Yeah, its a completely remanufactured q-jet.


Anyways, I do feel like my timing is off, I'm just curious if a dead knock sensor is doing this.

 

Enjoy that carb then man .... Gonna be a battle you will never win.

 

I understand your hate for it, and clearly tbi is a better choice, but for me i'd prefer to get it running right especially since I just payed decent cash for it.

 

Can't win a battle when your only weapon is ignorance.

Does the choke open?

 

Have you been here?

http://forum.grumpysperformance.com/...hp?f=55&t=1144

This site has tons of valuable information. I've linked to a Q-Jet thread to start you out. I've got a Q-Jet also and I'm fighting tooth and nail with my hot rod friends on sh!tcanning it. They want me to ditch the ECM, intake, dizzy, and Q for another set up. If I'm going to spend that sort of cash on an upgrade I'd consider a FAST system, a Holley EFI, or an MSD Atomic EFi system. But until then I'll work on the Q.



.

 

i would think not.just because my truck witch is a tbi truck has none(because i took it off) and it runs fine.
but maybe look in to it. as i know more about non CCC stuff. and can't give you a definite anser.

 

Yeah choke opens normally. I've ran diagnostics and no trouble codes are stored as well.


Can anyone answer if the water coolant sensor plays a role in the Ecu's decisions for the fuel/air mixture?

 

no i haven't yet. Thank you, I'll start reading through it right now.

 

i would think it does. as there is a dedicated sensor for the ECU for temps. it should play a role in the mixture.

 

Hmm, I'm gonna replace it then, and see what happens.

 

there is 2 of them one in the driver side head witch is for the gauge.
and one in the intake witch is for the ECU.
i am sure you already know. but thought i would mention it anyways

 

did not know that one. Always wondered what it was. lol

 

actually your "dedicated" CTS for the ecm is located in the thermostat housing. The ones in heads are for temp gauge and fan switch. You'll be looking for a connector with yellow/white wires IIRC

 

Whats the m/c dwell reading at idle?

 

You need to take the car to a shop that has a legit OBD-1 reader that displays all sensors. Your service manual will have the numbers you SHOULD be reading at idle.

If a sensor is bad/off it will affect everything and could lead to the carb dumping fuel into the engine as a 'limp home mode' type of deal. Granted, your case seems a bit excessive, but it's worth a shot.

 

We hooked a snap on scanner to it at my school, didn't want to communicate at all with the scanner. I even replaced the ecu, still did the same thing.

 

check grounds at rear of heads and there are two more on passenger front intake bolt then also check ecm fuse.

 

OBD1 came out in 93.......

Very simple to put a dwell meter on the pigtail(pass side fire wall). Should be reading 30 at idle, and 30 at what ever your cruise speed is.<6cyl scale/motor warmed up.
If the carb is running rich, and the computer is trying to compensate,, Then your reading is gonna be like 45-50. If the ecm is richening the mix, then it closer to 0.
Thing is, this is just a carb. The ecm will make adjustments a little richer or leaner via the primary needles depending on the carb settings. IE, idle mix screws/lean stop/rich stop/air bleed. < these should be set on any install to factory spec's for a starting point.
You sure the needle and float is OK?

 

Don't swap in a new CTS. You can simply jump the leads to confuse the ECM into thinking the motor is full hot. Although the CTS rarely fails, the pigtail to it takes some abuse and can cause an open or short. If open, the ECM will think the motor is forever in warm-up mode.

Disconnecting the KS takes knock retard out of the equation. This ECM is not as sophisticated as the later TBI ones, where they did a self-test of the KS on start up. With a timing light you should be able to verify that the timing is around 20 or so at idle and increases smoothly as the throttle is opened. The exact amount is not as important as verifying that it increases linearly and not incrementally.

Any new or rebuilt ccc-qjet has to be adjusted for dwell on a new motor. If the carb is outside of that narrow range where the O2 is sending rich/lean flags to the ECM it will never go into closed loop and stay in rich, warm up mode. If you want to get your ccc-qjet running properly, post back and I can walk you through the process.

 

The old one did the same exact thing, for the record.

What do I do first?

 

Make sure you've got the ignition system straight: install a new cap, rotor, plugs and wires and set base timing with the ESC unplugged at about 4 degrees before TDC. Reconnect the ESC and verify the timing is near 20-22 at idle and advances correctly.

Set idle speed at around 600 and adjust TPS for near 0.40 volts at idle. Verify the TPS voltage goes to near 4.0 volts at WOT.

With a dwell meter connected to the diagnostic cable (green single wire near the AC blower) see what the dwell is doing at idle. Set on the V6 scale it's supposed to hover around 50 % (or 30 degrees) at idle. It should waver back and forth 10 or so % to indicate that the ECM is using the O2 sensor readings to trim the mixture. If it's rock steady, the mixture's likely too far out at current settings for closed loop. If it wavers, but is out of the 50% range it can be brought into range by adjusting the IAB screw in the center of the carb. Turning out adds air/leans mixture. The dwell should respond by decreasing, adding fuel.

Complete the first steps and connect the meter (or scanner capable of reading ALDL-I have an Autoxray 6000) and come back.

 

I think i found the problem. Fuel pressure is too high.

 

How'd you determine that? Has either fuel pump been replaced?

 

I hooked a gauge up and it was reading 7-8 psi Is that normal for a carburetor?


The fuel pump was indeed replaced, but ran rich with the old one as well.

 

For a carbed motor about 5.5 is about right.

 

So definitely out of the ordinary then...I have some cheapo edelbrock fuel pressure regulator I never opened, do you think I should use it and limit the pressure to maybe 4 psi?

 

What pump are you using?

 

Its a no name stock replacement pump.


I think I'm gonna just go ahead and swap engines this week, and run the edelbrock carb thats already on the 355.


In the meantime, I'll just tuck the ecu harness into the fenderwell, and store the Q-jet away.

 

I'm using a Holley fuel pressure regulator w/ return line and a GM fuel pump. Remember, my application is different. I chucked the LG4 (mech. fuel pump) for a ZZ3 crate that necessitated I install an in-tank fuel pump and a fuel pressure regulator. The Holley regulator has a rubber diaphragm that can turn rock hard over time. I've replaced that once already. I can only help so much since I don't have a factory set up any more.

 

And swap out the distributor. And the torque converter lock up.

It's getting harder for me to become vested in these threads lately because as soon as things get a wee bit difficult, the 'swap to edelbrock' seems to come up. Good luck though.

 

If it makes you feel any better, I cringe when I say edelbrock.

 

I think, correct me if i'm wrong,

The Q-jet needs the oxygen sensor, mixture control solenoid, TPS, and water coolant temp sensor to operate correctly?

 

Plus: Distributor (provides engine speed input to the computer), manifold vacuum sensor, barometric sensor.

 

oohh, As in the sensors on the stock airfilter? I removed that for a snorkless one.

 

oh wait, I'm thinking about maf.

 

lol, TBI, E4ME, im sorry man its all a loss. all you can do is find out what is working and what isnt. maybe you can get a hold of shop manuals? try mitchells or identafix? unfortunately everyone seems right that this is a loosing battle BUT... if this is the only venue for you is fixing this thing, check intake airtemp sensor? coolant too? MAP, MAF, maybe just maybe the new carb is faulty? mechanics (sorry technicians) rarely see a carb today, maybe they forgotor overlooked something. if i am not mistaken maybe you can get some live data from this thing from a scanner?

 

Too late now, Already began swapping engines. I just wanted to fix the Q-jet problems, because without a doubt, it is superior to any mechanical carb.

So the cheapo average edelbrock carb will do, for now.

 

Honestly, make a trip to the junkyard and pull off a E4ME. Clean it up a bit and see if that solves your problem. This will make it easier to figure out if you have a sensor problem or not.

I fired my new engine up last weekend and am having the exact same problem as you are. I suspect a stuck float. Keep us posted and I'll do the same.

 

It isn't ignorance, I fought these feedback carbs once on my 82 Trans Am. After trying 4 rebuilt ones from various places and neither really made the car run any better, I went to my local chevrolet dealership and yes got reamed for IIRC 1,300.00 for a brand new one (that was when you could still buy them new) anyways after buying that I never had a problem again until it started acting the same as the original carb did. Then bought a wrecked 90 firebird with the LO-3 and transfer all electronics and everything else to my 82 Trans Am and never had a driveability issue ever again.

Yes, a time consuming project however when you can't pass smog or the car isn't driveable sometime you have no choice but to throw in the towel and upgrade.

Some states that are lucky people can rip off all emissions equipment and go old school to get around a problem. I live in California so it isn't that simple to just replace the feedback carb with a holley or other types. Other times it is just a engine harness that has finally just gave up the ghost. I'm not saying don't try to fix it but there comes a time when something can't be fixed and you have little choice to upgrade.

 

Yeah, It's certainly pissed me off, But I'm still leaving the harness in tact, and placing the sensors and carb in a box for the future.

 

Sounds like the float level,...also.. Check that the little plugs at the bottom of the bowl arn't leaking....need to take the carb off, fill the bowl with fuel and hold it up overhead so you can see under.

Get an Air/Fuel ratio guage and a duty cycle meter. Duty cycle should be around 45-65% idle and cruise. 80-90-100% at WOT