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Discussion Starter #1
I signed on to the forum years ago (2004). My 95 DCM is stock and had I had hopes of building it after putting 5 kids through college. If there was any money left. I have one more kid with one more year. Unless he goes to grad school.
Sadly, I was out of state for years and my family left the car outside, uncovered. The paint and rubber is a wreck.
But still I have hope. Probably just build it to a nice driver.

So it has 151K miles. Changed Spark Plugs this weekend.
I had checked wires for 2 nights before the plug swap and saw no arcing.
Only thing recently changed were the plugs. I just used the Autolite 104's.
I wasn't sure the car was going to pass smog this year so cheaped out on plugs. Probably not the best idea.
The engine ran great for a few spirited run through the streets. On the freeway she pulled well.
But on the way to gas up it started to stumble at the off ramp light.
I headed straight home so I didn't stall on the street that night.
I checked today. Started up OK and rev fine. Then as it sat there idling it started to have a rough idle.

I checked exhaust while revving and at idle. No smoke. I saw wet spray on the pavement behind exhaust pipes. I figure condensation from better combustion. Before changing plugs the exhaust was dry and rich smelling. Then I noticed the Right Exhaust bank (dual exhaust) is where the miss is coming from. Irregular miss. No backfires.

Maintenance History:
I had the OPTI & Water Pump changed at 125K miles
O2 sensors changed at 130K miles
Spark Plugs at 151K miles which is current mileage.

I've seen some posts similar to this. So many possibilities.
I tried to think what I may have done. Don't think I cross threaded any plugs.

Possible issues:
1. I haven't checked the rear driver side plug wire because I couldn't get to it yet. Gotta lift the car. But it should be fine. I double checked it the first time I put the wire back on. When I can jack the car up again I will recheck wire connection.
2. Didn't have dielectric grease handy, but had plumbers grease so used that on the plug.
3. When I was trying to pull the wire from the Left rear spark plug I was reaching down there with a wrapped plier and I think when I was pulling on the plug wire I was actually pulling on the knock sensor wire. A cloth was covering the plug and sensor wire so I can't say for sure but I think the first time I was pulling on the sensor. So maybe something is up with the sensor. I think it's the knock sensor. And on the driver side the plug on that sensor just spins around.
That doesn't seem normal.

Sad to say that I tried to do this simple job and made things worse. At least before this swap the engine ran good but had poor gas mileage (14 mpg). But that's kind of normal for these cars. Now it's idle is not so great.

So any leads on those 3 possible issues. Or any more thoughts.
My back is pretty wrecked lately so I may have to opt to go to a shop. So anyone in the San Diego area, near Poway, have a good Impala expert, please send me their info. I am also willing to drive.

I used to drive all the way North to George Bates' in Upland, CA to get the car worked on but he no longer has that business. I don't suppose Angel who took over from George is still running it now. However, I don't know about driving that far with the engine acting up as it is.

Thanks
 

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Get a scan tool and check the engine coolant temps. If the signal is bad from the sensor, they'll run poorly as they warm up.

A simple check is to pull the connector off at the sensors (there are two) and see if it looks nice and clean/new inside or if it's all corroded and ugly in there. If it's ugly - replace the sensor AND the connector/terminals. It needs to be done anyway, and might fix your problem.
 

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Discussion Starter #3
So those sensors near the back of the block are Coolant sensors? I'm just getting back into working on this car and don't have the manuals to show where/what everything is.

OK I'll check that. I have a simple scan tool.
Thanks
 

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Discussion Starter #5
With the exception of that example where I tried with the covered plier I used my hands. But yes they were tough to get off. I suppose pulling wires to see which cylinder is misfiring is the next step. Getting my hands in there on a hot manifold was tried yesterday. Not fun. Guess I'll be quick and turn off engine while I pull the wire then restart.
It doesn't miss until it warms up...fun?!
 

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Discussion Starter #6
At least it appears I only have to deal with the Passenger side (4 plugs)
 

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Like I said, dangerous.
I missed the part in your original post that it ran fine during warm up.

I read it as missing after the terror ride.

Some cases, poor secondary spark components, high tension leads, plugs , will be OK during richer open loop but not once you go closed.
You could unplug injectors to check suspect cylinders but you might be up setting more marginal wiring.
Maybe take my ideas as ideas not advice.
So different if someone was actually there.
They might look and point out you did something silly like broke a vacuum tube and you have a lean closed loop misfire.
 

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Discussion Starter #8
Roger that.

I was looking at tubing this afternoon. Tried a bit of starter fluid to see if I'd find a leak.
That's why looking if good mech in San Diego that knows these cars.
Looks like the start of a fun project. Hope not too long. Or $$

I saw post for George Bates automotive but it's under new manager. Not sure they still have experts.
 

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You need a laptop and one of these cables. Then use EEHack to see what's going on. No other way with a car this old and OBD1. Guys in my town continue to be amazed at how easily one can diagnose the '94-95 cars with this setup.

Low gas in the tank is no friend to these cars. Make sure you have plenty of gas in the tank.

You're saying it runs fine when cold but has an intermittent misfire at hot idle that goes away when you drive it? Try starting the car and turning on the headlights and AC and see if the stumble goes away. If so, you may have bad fuel injectors that aren't functioning reliably at low pulsewidths. The stock fuel injectors do not hold up well long term. I sell much newer replacements with all the tuning data needed for half the cost of new ones. That solved the problem on the '96 SS I'm restoring.
 

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Discussion Starter #10
I have a cable that used to work with an old PC laptop. But that laptop doesn't function anymore. I will see if there is an adapter for the computer because my apple or modern PC probably doesn't have that old pin connector.
I went out there this afternoon with the scanner and realized the connection is wrong. Been so long since I've done any work on the car I need to be re-acquainted with everything.

I will try to get that set up soonest.

Thanks.
 

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Discussion Starter #11
I started the car up this afternoon after going over the plug wires again.
I started the car and it seemed like it had a little rough idle. I drove down the street and it sounds/feels rough.

I went to the exhaust and the Driver side was rhythmic.The Passenger side had a noticeable larger feeling PUFF from the exhaust. When it ran normally it had the same pressure of puff but when it ran rough the pressure seemed to produce a larger puff of gas out of the exhaust.
I did not disconnect the wire from plugs to see if I can locate the specific cylinder, if there is one. But it wasn't only one large puff. It would be a few then settle down then repeat.
 
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