Uh oh, this can't be good... - Team Camaro Tech
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post #1 of 25 (permalink) Old Aug 31st, 03, 10:53 PM Thread Starter
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My daily driver '95 Lumina (3.4 DOHC) has over the last few weeks really began to idle badly when the engine is cold. It got really, really bad over the last few days since we have had all this rain. When leaving work at 0800 it is the worst. The car will start right up, then rev to about 2500, then drop down to about 500 (it normally idles at about 950 rpms), back and forth until I just take off down the road. Once it warms up it runs fine. I had trouble with this last winter but it cleared before I ever found the problem. Now, it is back with a vengence. Today, I was standing behind the car and it sounded like it had a burnt exhaust valve...you could hear a "pfft" in the exhaust. After changing the oil in it today, I decided to yank the plugs to see what they looked like. The plugs have about 12k miles on them. Every single one of them was caked in this white ash stuff, and all where quite white. The ring around the base of the threads was black but not sooty or crusty. The electrodes were quite worn down where they kept firing thru the ash deposits. Even the ground strap and porcelin are covered with this stuff. I scraped all the plugs off and cleaned them the best I could. Now, the engine starts normally (no radically fluctuating idle), the exhaust has that nice throaty sound like it did when I bought it, and it runs much smoother. Where did all this white ash come from? Some kind of additive in our fuel?

Now for the bad part. Plug #1 has just a faint green tint on the ground strap [img]graemlins/angry.gif[/img] There was no sign of water/antifreeze in the oil...heck, I haven't had to add water to the resevoir since I can remember when. No bubbles blowing in the radiator either. I can't help but think this thing is going to need head gaskets within the next 6 months [img]graemlins/angry.gif[/img]
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post #2 of 25 (permalink) Old Sep 1st, 03, 05:42 AM Thread Starter
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Well, I only thought yesterdays plug cleaning helped the cold idle problem. It rained all night, and temps got down in the mid 60's. Left work this morning, car immediately revved to 3K, dropped to a very rough 500 rpms, then died...twice. This is with no touching of the gas pedal. Got it started the 3rd time...still rough but a little better, and drove it home. Where should I go from here? It seems to be mostly temperature related. Maybe a coolant temp sensor?
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post #3 of 25 (permalink) Old Sep 1st, 03, 06:16 AM
 
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Travis,

Have you read up on what a going bad O2 sensor might do? Aren't some of them hot ones that don't work right unless they are preheated with a built-in electric preheat coil so they sense earlier after engine light-off??

Just asking b/c I really have no idea??????

pdq67

PS., as for the white deposits, NO idea???

Have you added a bottle or two of Seafoam Gasoline Treatment or ran some Marvel Mystery Oil in your gas to help purge combustion chamber deposits??



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post #4 of 25 (permalink) Old Sep 1st, 03, 09:43 PM
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my guess is idle control solenoid. they keep the idle in check during warm up, or when ac is on, etc. this is especially noticable during cold starts, where you will actually have to control the idle, or keep it running with the throttle. once warm it runs (fairly) normal. sounds like what you describe. try taking it off and cleaning it, this sometimes works, or you may have to replace it. also, if there is a coolant leak in a cylinder, generally it will show up as a very clean plug, green is likely from a fuel additive or something. good luck

Sean

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post #5 of 25 (permalink) Old Sep 2nd, 03, 12:45 AM Thread Starter
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68, I hope you are right about the plug thing. However, I have replaced cracked heads before with green plugs...although this was just a very faint tint on one plug. Where do I find this idle control solenoid? Is this the idle air control I have heard of before, that is located on or around the throttle body and sometimes get grunge and dirt built up in them? I'll check into that...hope your right.
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post #6 of 25 (permalink) Old Sep 2nd, 03, 02:49 AM
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How about the fuel filter?
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post #7 of 25 (permalink) Old Sep 2nd, 03, 12:27 PM
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travis, yes, it should be attached to the throttle body, and will likey be sort of cylinder shaped. i havn't worked on one of those cars, but most all of the "newer" injected cars have them, as far as i know. it really sounds like the problem to me, i just fixed this very thing on my wifes grand cherokee in fact, i was able to just remove it, clean it up and its worked for a couple of months now. they have a tendancy to get gummed up with carbon, and stick. i have seen it on other cars as well, they all kind of acted the same, won't idle cold, run ok once warmed up. i hope thats your problem too, fixing your driver is always a PIA. should be a fairly cheap part even if you have to replace it, also. good luck

Sean

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post #8 of 25 (permalink) Old Sep 2nd, 03, 12:45 PM Thread Starter
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Well, I yanked the IAC solenoid...it had a pretty heavy buildup on it. Cleaned it up, blasted out the air passages, and verified that the resistance across the 4 pins on the solenoid was within spec. Guess I'll know in the morning whether that fixes it or not. Thanks for the help! [img]graemlins/beers.gif[/img]
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post #9 of 25 (permalink) Old Sep 2nd, 03, 01:28 PM
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That same device can make your idle go up and down repeatedly then stall out the engine if it's messed up. Cleaning is normally all it needs. It normally goes into the up and down idle after doing a quick tap or punch of the throttle. Then it goes up and down with out you touching anything. Makes life interesting sitting there listening and watching asking your car if it's going to be a B---- and die when all you have to do to snap it out of it is to add some throttle
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post #10 of 25 (permalink) Old Sep 2nd, 03, 04:33 PM
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Travis,
The 3.4 DOHC engines have a know problem with vacuum leaks from the intake manifold. They cause exactly the problem you are decribing. One of my customers just finished doing intake gaskets on his wife's Olds Cutlass for the same exact problem. Hope you get lucky and its the IAC or EGR, but intake would be next.

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post #11 of 25 (permalink) Old Sep 2nd, 03, 05:11 PM Thread Starter
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Unfortunately Bill, that is what I was afraid of. When I had a timing belt put on the car (about 10K ago) the guy had commented on how lean the plugs looked. He had also tried to re-use the old egr gasket because nobody in town had one. The gasket split and caused a vaccuum leak...and it acted just like it is now. A new egr gasket cleared that issue up...for a while.

I was going to go pick up acode reader for the car to help troubleshoot it. Found out that '95's with the 3.4 engine need the '96+ obdII scanner...so instead of a $20 code reader I need a $120 reader If it acts up again in the morning, I think I am just going to run up to the shop and have them scan it.

And then when I get that problem fixed Ithink I am going to sell it.
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post #12 of 25 (permalink) Old Sep 3rd, 03, 06:42 AM
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Yep, there's a TSB out on these engines, 3.1 & 3.4, for leaking of a/freeze intake manifold gaskets. I would suspect a faulty OBD coolant sensor. When it was cold, I'd unplug the connector from same sensor and plug into the wire harness, a 10-12K resistor. This would resemble a cold start-up, meaning alittle more fuel and IAC would open up alittle to "fast idle" till warm.

A good way to check out the IAC if working after clean-up, would be to select DEF or A/C, and see if engine rpm remained the same. Check that EGR valve gasket, if not the valve itself for leakage. I would still suspect a faulty coolant sensor or wire harness to the PCM. Coolant sensor should ohm out to 8-12K when cold, 200 ohms or less when operating temp.

Good Luck, yea, spend the money for a diagnostic..........With OBD II, as I understand, memory cannot be cleared until the problem(s) are fixed and the PCM clears itself. I could be mistaken.........

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post #13 of 25 (permalink) Old Sep 3rd, 03, 02:54 PM Thread Starter
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Well Everett, that would mean that my IAC is working fine then. It always drops a few rpm when you kick on the A/C then kicks right back up to the proper rpms. I knew it couldn't be that easy. The coolant temp sensor is buried under the throttle body and intake...per the book you have to remove the intake to get to it. I might be able to get to the harness plug for it...where would I get this 10k-12k resistor?

How bad is replacing an intake gasket on these things? I assume it would be quite a PITA since everything else on this car is damn near impossible to work on.

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post #14 of 25 (permalink) Old Sep 4th, 03, 01:53 AM
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One can go to Radio Shack or an electronics supply store and get one, R/S would sell it in an assortment, any 1/4 to 1/2 watt size resistor would work in the 10-12K, up to 18K range.

Know of a TV repair buddy? Yep, the connector is in a precarious place. It may just be corroded contacts in the connector and sensor itself. While at R/S, get a can of Tuner cleaner and use it to clean those contacts on both sides. Wear safety glasses, just like using Brakleen, goes everywhere!

Green plugs are signs of antifreeze entering the combustion chamber. Depending on how much coolant being added per miles/week, I believe would determine the severity of repair needed. I have a friend with an Acura Legend using a quart of coolant (3000 miles) a month doing just fine. Maybe a lower pressure radiator cap might be an experiment to do, providing the car doesn't bubble (boil) after shutting down the engine and allowing it to heat soak.

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post #15 of 25 (permalink) Old Sep 4th, 03, 03:20 AM
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Travis,
I agree with BillK. The 3.4 engine is known for intake gasket leaks which cause the same symptoms that you are describing. Try spraying some carb cleaner down the intake valley next time you cold start the vehicle. If the intake is leaking the idle will change.
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