FireDemonSiC

Usually I like to take only one problem at a time, but with the money this is costing me in gas prices my speedometer has to take the back seat for now.

When I first bought my 85 Z28, the check engine light would be on constantly. The computer was throwing a code 44 which of course most you probably know, means the oxygen sensor is reporting a lean burn. I replaced the O2 sensor and since I got the exhaust manifold fixed with new studs and gaskets, the check engine light is scarce. I managed to drive the car for about 2 days after getting it out of the shop without it coming on. But then...

Code 44 returned. I cleared the ECM, and drove it for another day before it came back on. Now shutting off and restarting the car will get the light to go off until I drive it for awhile. You can also tell the rich burn from the overwhelming smell of fuel whenever you have the car stopped and idling especially with the windows down.

What would be the next most obvious step in determining what the problem is here? The guy I bought the car from mentioned something about the EGR valve needing replacing, but the ECM hasn't shown any signs that It's going bad.

Damon

Is the choke opening all the way when the motor is fully warmed up? Choke problems on the factory computer controlled QJet are not uncommon. No power or inadequate power to the choke heating element (it uses an electrically heated choke- is the power wire to the choke even hooked up??), choke element just worn out, binding choke linkages, etc.

That's just a shot in the dark, since there are quite a few things this can be. Most of the things it can be are related to the carb itself, but certainly not all. Probems with the evaporative emissions system (miles of vacuum lines and various diaphragms and vacuum switches), excessive fuel pressure from the fuel pump, etc.

The EGR system can cause a check engine light, but it won't cause an over-rich condition that I've seen. If the valve is open when it shouldn't be like at idle or on a cold engine, your idle will go to heck in a handbag, usually. If it's shut when it shouldn't be (never opening, for instance) it will eventually throw a check engine light, but usually only after a fair bit of constant-throttle highway driving.

FireDemonSiC

I replaced the O2 sensor myself but I do not 100% trust my newcomer skills/miscellaneous mingling of the 4 previous owners. How do I verify that the O2 sensor is hooked up and receiving power? I have a volt meter but I read that using one on the sensor can damage it.

I think the next step I might take is replacing the CTS. Only issue is, where is it located on my car?


Also a bit off topic but I figure I might as well throw it in here to get my oil pressure gauge to stop reading off the charts 24/7. Where is the oil pressure sending unit located? This one I looked for in my Chilton manual but couldn't find anything

BTW, what is the Choke light for on the instrument cluster? I see an indicator for Choke on mine but it never lights up. Then again, never does my fasten belts indicator. Blown bulb maybe?

Pat Hall

iTrader: (31)

The CTS is usually located in the intake manifold, near the thermostat housing. It's brass and has a 2 wire plug. Your OP sending unit should be behind the intake manifold, right next to the base of the distributor. It's a fairly large, metal, bell-shaped deal. On your choke, when the engine is cold, find the power lead to the choke, turn the ignition key on, and check the power lead with a test light. It should light up when the motor is cold and the ignition is on. Another thing you can do is after the motor is good and warmed up, while it's still running, remove the air cleaner lid and check to see if the choke butterfly is all the way open.

FireDemonSiC

Just sourced a new sensor. Theres several options I have to go by.


Sorry for the copy and paste, but It's an online java based catalog. So I figured it would be the easier route.

I'm guessing I want to go with the ACDelco 213928?

FireDemonSiC

Out of curiosity, If the oil pressure sender was not plugged in at all would the gauge read 0 or off the charts?

darkride86T/A

The oil press. gauge would be pegged high if the wiring harness isn't connected. Also, check the voltage on the TPS. It should read .54 volts at idle and no more than 5 volts at WOT. You could check the EGR valve, but before you go and take the plenum off to get to it, check the EGR solenoid and vacuum line first. My '89 IROC had a bad O2 sensor in it and it ran really, no REALLY RICH!!!! But it also had code 32(EGR malfunction) stored in the ECM. It idled real rough too. I read that an issue with the EGR system will cause rough idling and possibly an over rich condition.

FireDemonSiC

That's exactly where my needle sits. Pointing straight up reading off the charts 24/7.

While I was snooping around the back of the engine, I didnt find the pressure sender yet but i DID find a single wire connector in that general location that was just resting not plugged up to anything. I suspect foul play...

She's in the shop now getting worked on. Tilt column took a dump on me and the entire steering column needs to be replaced. I should get her back tomorrow and I'll return with pics/results.


The O2 sensor being bad isn't the case since I just replaced it. The problem is though no one has responded to my question on how to check if It's getting power.

Pat Hall

iTrader: (31)

If that loose connector back there is a female, blade style plug, then that should be your OP wire. On your CTS, make sure you get the one for the computer, and not the one for the gauge. They're 2 separate deals. The one for the gauge is usually located in the driver's side cylinder head, and the one for the computer is usually near the water neck on the intake manifold. The one for the temp gauge only uses one wire, so that's another way you'll be able to tell if you get the right one. I wish I could answer your question regarding the 02 sensor, but I have no idea how to check it for power. If you can hook up a scanner and verify that the computer is going into closed loop operation after the engine is warmed up, then that should indicate that the 02 sensor is functioning. The 02 sensor doesn't operate when the computer is in open loop, and the only time it's in open loop is when the motor is cold, or when you mash the gas all the way to wide open throttle. Btw, when the other guy said his car was idling really rough due to the EGR valve, it's probably because his was stuck open. If it gets stuck open, it causes a huge vacuum leak, which will result in a terrible idle. That can also cause a really rich condition since the vacuum leak is introducing a lot of extra air into the motor, which causes the 02 sensor will detect a lean condition and richen up the mixture to try and compensate. My diverter valve for my smog pump broke on my car a while back, causing it to pump air into the exhaust manifolds while the computer was in closed loop, instead of diverting it down to the cat, and that caused mine to run too rich. Since the air tubes introduce extra air into the manifolds before the 02 sensor, it also caused the computer to richen up the mixture too much.