daniel dekay

ed maher told me that it would be a good idea to post my message here as well as the general tech board.

ok, i replaced the lg4 in my 86 camaro with a gm 350. i still use the stock q-jet 4bbl. when i replaced the engine i bought a carb kit and replaced the gaskets. (actually my dad did cuz he knows his was around a carb). only a few weeks ago the car was running like crap. i took it into the shop and they fixed the stuck choke becuause i had no idea how to do it. that cost me 105 bucks, a pretty standard price i thought. well, the car ran great for roughtly 2-3 days. then i tried to start the car, i cranked it only a moment then killed it for some reason, i forget. a few seconds later i tried again, this time it just cranked and cranked but it wouldnt turn over. i finally got it started after waiting 5 mins, but as it started soo much blue smoke came out the exhaust and it reeked of fuel. when it finally calmed down it ran fine except for a rich fuel smell. thus i think the car is running rich. it threw no codes, thats when i took it into the same shop that fixed the choke. he said that my 02 sensor wire was fried cuz its too close to the headers. he also said that is highly unlikely that, that would cuase the car to run rich. he said that the TPS is probably the culprit and wanted 260 more just to diagnose it further and replace the o2 wire. i said "no thanks" and i am gonna retrieve the car later today. that cost me 80 bucks.

my ? to the carb gurus is, would the TPS cause the car to run rich? Ed gave me the website of a place where i can buy a tool to get to the TPS. how hard and how long is this procedure? any tips?

thanks

daniel

Damon

Don't throw away your money. you can diagnose this yourself. Beg borrow or steal a scan tool. You can't tell crap without seeing things as the computer sees them. A wacky TPS should be pretty obvious- the voltage reading will be out to lunch or simply won't move at all when you step on the gas.

I suspect the guy who "fixed" the choke might have screwed something else up. There are so few people who really know how to work on a QJet, let alone a computer controlled one.

jrr

All you need to check a TPS is a common volt-ohmmeter with a needle meter movement. Disconnect the plug from the TPS and connect your ohmmeter to the center tap of the TPS and then to either end. Open and close the throttle. The needle should move SMOOTHLY with no jerky movement. With the TPS plugged back in and your engine idling, around 500 +/- 50 RPM, the TPS voltage from the center tap to ground ought to be about 0.5V.

If the TPS is OK, see if you didn't accidentally mess up the O-rings that go around the air bleed valve. I did that one time and I couldn't figure out what was wrong until I took the air bleed valve off and found two torn O-rings. Gotta use WD-40 on those O-rings before screwing that air bleed valve back in.

Also, Q-Jets are NOT forgiving if you overtorque them, especially the two hold-down bolts up front. Overtorque those two bolts once and that casting is toast! That Q-Jet will NEVER run right again.

Nordbert

The oxygen sensor is not operational when
your engine is "cold" (open loop). Therefore
I would look for another problem such as
the choke or its linkage STILL sticking or
the electric choke not functioning properly.
The choke coil or its heater may be bad, or
electricity may not be getting to the coil.
Check to see if the choke pulloff is opening
the choke upon startup.

Ed Maher

OK, it sounds like you are describing a cold start problem foremost.
With that said, nordbert is right, the computer runs in open loop during warm-up, and is supposed to run rich. However that it stalls after it fires, then gves problems restarting/blows smoke suggests that your choke is either:
1-the heater element is bad (couldn't be out of adjustment, cuz you sia dit was just running fine, and it wouldn't tighten itself.)
2-the vacuum pull off is missing/out of adjustment
3-the choke linkage itself is still binding

You will diagnose these in reverse order. To check the linkage for binding is easy. When you go out to the car in the morning, open the hood and take the air cleaner off. The choke should be wide open. Now work the throttle, you should see the plates snap closed. Now open the throttle a little with one hand, and with the other hand push down on the little lever behind the choke housing pointing towards the front (kinda squre/trapezoidish shaped) That lever is just an extension of the fast idle cam. It should feel smooth with no sticky parts to it. If there are, give the whole linkage a carb cleaner bath. If it's still messed up you'll need to remove the choke...
For #2. Hit the throttle to close the choke and start the car (with the air cleaner still off.) Watch the choke plates as it starts. They should open up a little bit (~1/8"-1/4".) If they don't open at all, and at the same time the engine is running rough/stalls, it would appear the choke pull off is either not working or out of adjustment. The pull-off is the vacuum can on the front pass. side of the carb. It pulls in with vacuum applied (like when the engine starts), and the lever on the bottom pulls a tab on the choke linkage to open the choke a bit. If it pulls in, but the choke plates don't open much/the engine runs rough, you need to wind the screw on it out to get more choke opening from it. If it doesn't pull in you need to replace it.
#1-if the choke is bad it won't open...usually more of a problem after it's warmed up a little rather than immediately after starting up.

No, the TPS will not give you problems with cold starting, but if the mechanic already checked it and said it was bad, it will cause you to run rich all the time, hurting gas mileage and fouling your plugs/combustion chambers.
the easy check is like jrr, said (except i wouldn't do it with the engine running.) With the key on and the throttle closed (choke off) you should see 0.5V between the top and bottom wires coming from the front DS of the carb. If it is much higher than that it needs to be adjusted. Also check it through the range of motion to make sure it isn't jumpy as jrr said.
The tool i linked you to is for adjusting the TPS. To do so you need to remove the plug covering the adj. screw. It's on the top DS of the carb, on the right side of the acc. pump arm pivot point. Carefully drill a small hole in the cap, then screw a self-tapping screw in, then pull it out with pliers. From there you just adjust it with the tool to get 0.5V. If you can't adjust it to 0.5V or it is jumpy, then it is bad and needs to be replaced, which requires taking the airhorn off the carb.
Fixing the TPS is a great idea. If it is currently bad you will see a HUGE gain in gas mileage, not to mention reduced likelihood of detonation from carbon build up from being too rich.

...ed

daniel dekay

thanks for all the info guys. my only problem with this is: i am currently 200 miles away from my home and my tools. i am at college, and i dont much enjoy working on my car in the parkin lot of my apartment. it will be a couple weeks until i can go home and work on this problem. so my ? is, what effects does 'running rich' have on my car. i heard that i should change my oil since the excess gasoline may find its way into the crankcase. will by plugs be covered with carbon deposits, more than usual? is this one of those problems that only get worse with time?

see, thats the reason i took it to the dealer, is so i wouldnt have to worry about what happens since i dont have the resources to do the job myself.

oh yeah, my car started right away today, no fighting or anything, she idled fine as well. i can still smell a strong gasoline odor tho.

thanks alot,

daniel

Nordbert

Thanks,Ed! I knew someone could describe
how to check this without a long post! LOL!!

Ed Maher

No sweat that you're away from home Dan. You can still check the choke out and make sure everything is good there. All you need is a can of carb cleaner and a phillips screwdriver (to adjust the pull-off if it isn't opening enough.)

Can you relate the starts fine / gives trouble thing with temperature. For example, if it gives problems when it is very cold (<30) but not when it's warmer out (40+) then i would tend to want to point my finger at a too tightly adjusted choke. In the extreme cold it's too tight and causes you to run too rich, stalling you out or causing a miss.
If it's the opposite, it could be the opposite, the choke could be too loose. It could also be that the pull off isn't opening the choke enough.

All of that can be easily fixed in your apartment parking lot (assuming the dealer guys didn't rivet your choke cover back on.)
...ed

daniel dekay

well,

the car is really easy to start in the morning, like 9-10 am. temp is prob in the 30's or 40's here in san luis obipso ca(central coast). it really surprises me how fast it kicks over. my friends brand new volvo doesnt even start as fast.

the bad thing is that, if i take the key out for some reason, and try to start it again soon, it wont kick for the life of me. it takes about 5 mins of waiting, then it will kick but just barely. i get alot, and i mean alot of blue smoke out the pipes, and i have to keep revining it witht he gas pedal to keep it from dying. after about 30 seconds it will go back to normal operation, no smoke or anyhting, but i still smell the gasoline odor.

daniel