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Discussion Starter #1 (Edited)
Hi, I have noticed the car recently starting to give subtle signs of impending issues.

2005 Impala LS 3.8

3 or 4 days ago, I noticed the gauges went haywire for a few seconds as I was pulling out of a parking lot after work. Returned to working fine.

yesterday, I noticed the idle rpm is sometimes a little higher than normal (1100 rpm). I noticed this only because during coast at low speeds, I felt the car was pushing me faster than usual (that's how I noticed it at first).

This morning I started the car in my garage and the headlights and gauge lights were slowly flickering normal intensity to low intensity and back and forth for about 15 seconds. During this, the idle was acting a little erratically, slowly climbing to around 1600 rpm or so before slowly dropping back to 1100 (again higher than usual idle rpm).


Any obvious wires touching hot parts to look for first? What can I check?

There is no CEL at the moment. and no messages in the message center.

Any ideas? I googled a bit but didn't find anything. The BCM wouldn't control idle would it? Are there any notorious ground points on this vehicle that would need cleaning?
 

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Hi, I have noticed the car recently starting to give subtle signs of impending issues.

2005 Impala LS 3.8

<snip>

Any ideas? I googled a bit but didn't find anything. The BCM wouldn't control idle would it? Are there any notorious ground points on this vehicle that would need cleaning?
I think you're onto it with the grounds. I would start at the battery, and follow the cables on both sides and trace them out. You probably have a couple (or more) corroded connections that are causing voltage drops in the paths resulting in the erratic behavior.

Along with that, you might also pull the battery and alternator and have them tested at an auto parts store. A bad cell in the battery or a failing voltage regulator in the alternator can cause fluctuating voltage levels that result in erratic behavior.

HTH.

Doug

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Remove and clean the battery terminal cable connectors, and clean the battery terminals (using a terminal cleaner brush tool - inexpensive at any auto part’s store). I know some 7th generation models came with side terminal batteries - if so, still remove the cable connectors and clean them with battery corrosion cleaner and a toothbrush. Ensure the connectors are snug when you replace them (don’t over tighten, as the side posts can twist out of the battery).

It is also possible that your battery is failing - but I’d clean the connections first.
 

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but I’d clean the connections first.
Would try this first, and clean all connections you can. Failing or poor connections can cause all kinds of screwy behavior. Perfect example, just in the past 2 weeks after heavy rains here had issues with our durango. It had given some screwy stuff the week prior with a no bus message displaying in the odo and the gauges and speedometer all stopping, but ran fine other than the air blowing hot all of a sudden. Disconnecting and reconnecting the negative battery terminal seemed to resolve the no bus issue. More recently had a no start issue which had me dc'ing the pcm connections and reconnecting after dc'ing the neg battery terminal did not resolve that issue. After reconnecting the pcm connection started up and has run fine with no issue. Point is, connection points are not too difficult to check before throwing money at problems, sometimes glitches happen for whatever reason. Still possible in our case we have a failing pcm on its way out, but unless we have more issues in the near future with it, not gonna replace it just yet.
 

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Discussion Starter #6
Sorry guys, I thought 2005 was 8th gen, but I guess it's actually 7th gen??? Guess google was totally wrong on that one.

I checked two chassis grounds that I could find, not conclusive but I will search for wiring diagrams and if I cannot find good ones, I will ask for their recommendations in terms of where to source quality wiring diagrams.

I also did find a wire that was spliced into one of the wires that goes to the coils, so maybe that's it maybe not.

Anyway, please excuse my mistake.
 

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Discussion Starter #7
I tried to re-create this post in the 7th gen forum. If you wouldn't mind, could a moderator move this to the 7th gen forum?



-begin post-
A short while after posting this the original thread, the left headlight went out. Not sure if coincidence or related.

Found a great YouTube instructional - "The Trainer #47 : What measuring Voltage on the Ground side means". It makes a lot of sense. Easy in theory, not so easy when diagrams aren't easy to find.

Looking at the mess that is the engine bay, it's hard to know where to start. I'd like to know each ground location on this vehicle so I can loosen/clean/tighten
 

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Discussion Starter #8
more info. I pulled out the bad headlight and tried it on the other side, it still wouldn't light. Went to remove it and upon touching it, it lit up. So it guess the connector terminals may have just been slightly corroded. no dilithium grease on it. Put it back in the drivers side and it works fine now

So, it was coincidence and the bulb is still good. I'm pleasantly surprised at how easy it is to remove the headlight assembly to access the bulbs!!!!

found a 3rd ground location near the drivers side headlight. loosened/cleaned. 3 down how many more to go? I think I'll try driving her again today, see what happens.
 

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Discussion Starter #9
ah ok, just got a CEL on the dash just before trying to take it out for a drive - P0171 - lean condition.

Will continue looking into this further and report back
 

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Discussion Starter #10 (Edited)
wow, I stumbled onto another thread where someone had a p0171 and someone mentioned to test for suction or pressure through the oil cap hole (which would mean bad LIM gaskets), and sure enough I have suction through the oil cap hole.....

I have already replaced the LIM gaskets once before, maybe 5 years ago. I guess it went bad again???!!! it was an aftermarket aluminum body with embedded rubber/polymer.

ugh ugh ugh. My 96 chevy 1500 pickup also started pissing coolant on Thursday through the back of the water pump. Why do they always develop problems at the SAME TIME!!!!!!!
 

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ugh ugh ugh. My 96 chevy also started pissing coolant on Thursday through the back of the water pump. Why do they always develop problems at the SAME TIME!!!!!!!
I've done the LIM gaskets on the 3.8 (1999 Lumina). It's not too bad, maybe a tad easier than the 3.4, but look out for the plastic fuel lines going to the intake.

Can't say how easy the water pump is on the 96, but my instinct is that will be easier, so do that first. You'll then have one trustworthy car, as well as some positive momentum to carry over to the LIM job.

HTH.

Doug

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Discussion Starter #12
Solved the problem of sucking air through the oil fill tube. Had massive leak. It was the PCV. apparently my pcv kit didn't come with new bottom o ring for the pcv when I did the LIM gaskets. what's puzzling is how in the hell that car didn't have vacuum issues for the 5 years that I've been driving it without the O-ring!

Anyway, ordered the acdelco pcv kit, put it in. Dramatically reduced vacuum through the oil fill tube, but there was still a tiny bit left. Ordered a new seal for the MAP sensor. Problem SOLVED!

Total cost: roughly $20 and a couple hours chasing a phantom electrical problem
 
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