Check engine light

[1994GrandAm]

Hi, this is my first post here. My mom has a 1994 Grand Am SE, 4 door, 2.3 SOHC, 82K miles.

I recently put a new water pump on, and of course had to remove the exhaust manifold to get access to it.

One of the two bolts that connect the exhaust pipe to the manifold broke off, and after getting the manifold off, I tried to drill it out, after dulling my drill bits, I just took the manifold to a machine shop to have them get it out.

Note, I never removed the oxygen sensor.

Got the car all put back together, and after a few miles the service engine light came on, is not always on.

The car is getting bad MPG as it drank through a tank of fuel quick, and feels like a misfire.

I took the car to O'Reilly for the free check engine light scan, the guy said cigarette lighter fuse must be out, as his scanner was not working.

So, later that day I decided to pull the spark plugs (I had replaced them about 25K miles ago as it had a misfire, along with the plug wires/coil to plug connecters, whatever they are called) the plugs were pretty carbon fouled.

So, I bought some new AC Delco plugs, took it for a spin, felt kinda better. I did disconnect the battery for at least a hour while changing the plugs, so that should reset the service engine light codes right?

After taking it for about 5-10 miles the service engine light came back on.

Checked the cig lighter fuse, it's fine, took the car to Autozone to have them try, they did not have a scanner for it, and gave me the little jumper key, I tried no flashes of the light.

So, they told me I could buy a scanner for 29.99, but looking on the back it only said it did Camaro and Firebird and other cars for 1994, so I held off.

Next day took it to O'reilly again, different guy, he asked if the light was on right then I said no, it comes and goes, so he did not even wanna hook up his scanner saying the light has to be on to work.

Then he told me I could take it to a shop to have it scanned, and I said that's ok, I figure it out before paying someone.

So, it appears from the manual this 1994 year is at the change from OBD1 to OBD2, and the older years the jumper wire/key between the pins was the way, and 1995 and newer you use a scan tool.

I'm thinking the oxygen sensor got damaged during the removal of the broken off exhaust bolt in the manifold, as this problem started after doing the water pump replacement.

Is there a scanner that will work on this car for sure to see what the code is?

 

[1994GrandAm]

Also, since putting the car back on the road after doing the water pump, there is a "smell" coming from the engine area.

At first I assumed it was the oil I had put on all the exhaust bolts to help soak them before taking them off, but it is still there, after 2 tankfuls, so I would think any residual oil would have burned off by now.

Maybe it's a exhaust leak.

After getting the car back together I started the car and felt all around the manifold for any leaks, and the pipe that connects to the manifold, felt nothing, and hear no sounds, I had did this just as a precaution while the car was on the ramps.

Of course I put a new exhaust manifold to head gasket on, and cleaned the manifold and head before going back together.

I noticed the smell at red lights, and sometimes at night after sitting at a red light for a while, looking in the mirror as the light turns green, I can see smoke in the lights of the car behind me as I take off.

Can't see anything with the hood up and the engine idling.

I have checked with my hands again to try to feel any exhaust gasses blowing out, of course when the car is cool and just started.

Still no exhaust leak sounds.

 

[melsg5]

Are you sure you dont have an unrelated oil leak from somewhere. Buying a scanner capable of really determining the issue is not worth while. Take it to a shop that has the equipment.

 

[1994GrandAm]

I don't see any oil leaks. This smell (I'm thinking exhaust) just started after doing the water pump replacement, which I had to remove the exhaust manifold for access. Maybe taking it to the shop is a good idea.

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[melsg5]

would think an exhaust leak would be heard at the gasket. Have you tried retightening the manifold?

 

[1994GrandAm]

Ok, I think I have it fixed.

This may sound weird, but I put soapy water on the exhaust manifold to try to see if I could find a leak with it running, right after starting the engine.

This cleaned it as it boiled off right away, so I rinsed it with the hose, then ran a errand, to warm up the engine, for the oxygen tester voltage test as the manual says it needs to be warm.

Tested the oxygen sensor, and got no change.

As I was looking down at the oxygen sensor after using the multimeter, I saw 2 small carbon spatter marks on the exhaust manifold heat shield, this was just clean before running the errands.

I got a shop rag and the carbon spatter marks wiped right off.

It appeared the oxygen sensor was leaking exhaust in 2 very small places, sorry I forgot to take a picture.

Replaced the oxygen sensor, and the old one was very filthy with carbon, looked plugged up.

Took the car for a spin, seems to idle better, and did not notice that smell.

Oh yeah, the manual said to reset the service engine light, disconnect the positive battery terminal, which I did while replacing the O2 sensor.

I'm not 100% sure it's totally fixed, but time will tell.

 

[melsg5]

glad you found the problem, hope it's resolved.

 

[1994GrandAm]

I'm sure if I had access to the proper scanner, it would have said O2 sensor, the good thing about this car, 4 new spark plugs just a tad over 10 bucks for the AC Delco brand, and just under 20 bucks for the O2 sensor Bosch, of course 10 bucks for the O2 sensor socket.

If I had not had cleaned that exhaust manifold, I would have never saw the carbon spatter marks.

Did not even intend to clean it, was trying to squirt soapy water at the manifold to head areas to look for bubbles, but the heat of the manifold, even after only running for about a minute made the soapy water just boil off, and take a lot of crud with it instantly.

I would have never heard that tiny leak at the O2 sensor, by guessing I would say the 2 leaks where where that top piece of aluminum is pressed into the plug.

I'm glad I joined this site, the car has some other issues I need to iron out, hopefully what I found might someday help another person here!

Mike

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[1994GrandAm]

P.S. Forgot to mention the car having another issue while having the troubles , the auto trans was shifting kinda weird.

Very subtle, such as when cruising down a road at 40-45, or maybe even 50 mph, it "felt" like the trans was "hunting" shifting back and forth between overdrive and 3rd gear, or maybe going into and out of torque converter lock up, back and forth like it could not make up it's mind.

It is not doing that now.

I would have never thought a faulty O2 sensor could cause automatic trans shifting issues.

 

[Nathan L]

Could be a little low on tranny fluid is all...