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 graemlins/angry.gif 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 graemlins/angry.gif

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?

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??

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

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.

How about the fuel filter?

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

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! graemlins/beers.gif

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 :D

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.

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 :mad: 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. :mad:

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.........

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.

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.

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.

This just keeps getting better and better. Broke down today and went and bought the only OBDII scanner I could find for under $400...it cost $150. I wasn't very happy about that, but the repair manual says, and the the book with the code reader says, that all '96+ gm vehicles and the '94-95 lumina only with this 3.4 engine absolutely, positively, without a doubt, are OBDII. However, it doesn't fit the ALDL connector. Then there is this little note in the code reader manual that says if there is any doubt, check the emmisions sticker under the hood. Guess what...the car was built in Canada...and is OBDI :confused: :mad: So I figured I just bought a $150 scanner that won't work on anything I own as most places won't take returns on electrical tools or parts. Well, they took it back, and I got a regular cheapie OBDI scanner...and it doesn't work either. It fits the ALDL connector...but there is only 2 wires going to the 12 pin connector...and the code reader's 3 pins doesn't touch any of them graemlins/angry.gif So, at this point, even though I saved $130, I am still no farther along. I whipped up a little jumper wire to ground the only 2 pins in the ALDL connector...figured either it is going to flash the check engine light and give me the codes or it is going to fry the wiring harness and burn the car to the ground. At this point either way would be fine. Yet, it did neither...check engine light stays on with the ignition ON but the engine OFF. So, I called the shop...the guy says he can scan it with his mega fancy, titanium plated big $$$ diagnostic computer, but cant get me in until tuesday. So, in the meantime, I got a coolant temp sensor (thats what the mechanic thinks it is over the phone)...they're cheap. The book says on my particular engine and year that I have to remove the crossover pipe between the exhaust manifolds, the airbox, and the MAF sensor/intake hose. I can see that the exhaust crossover is going to be a mega PITA...the rest is easy enough. Hopefully, the coolant temp sensor (or just cleaning the contacts) will fix the trouble enough to unload this POS. But 1st, I am going to go find the group that designed this engine, and run over them repeatedly with their engineering "wonder car". tongue.gif

Much thanks for the help guys...and for listening to me whine graemlins/beers.gif

Since you have a new sensor, I'd throw it into the freezer overnight. Then see if I couldn't unlatch the sensor harness from the sensor. Next morning, plug in the frozen sensor, and start the car. It'll either run good and fast idle and idle down as the sensor thaws out or it will still run the same.

At least this would tell you something. If I had to replace the sensor, and its location is where you suggest it is, I'd probably work on the exhaust pipe with a 4 foot crowbar to make just enough room to R/R the sensor.

Those darn engineers, if it wasn't for us, you wouldn't have cupholders.......

Ok, I was ripping on engineers a bit, but it is pretty obvious that the engineers have never had to actually work on the car. There are numerous other places under the hood with easy access to a water jacket.

Everett, the new sensor is in the freezer (got some pretty strange looks from the family for it too :D ). I also got a chart of what the resistance readings across the sensor should be at different temps. I might just be able to get 1 hand in there and measure the cold resistance. I let you know how it turns out in the morning.

Good morning Travis !! Yes, I know about family looks. I used the dishwasher one time to clean VW parts, they came out spotless!! ....LOL.

Maybe a smaller hand with good instruction to remove the harness. I'll read Manday AM the results.

I'm not one of those "clean eng'rs," I do get dirty. But, I do wonder about some of those boneheads.........

Well, it isn't the coolant temp sensor. I got the old one out, and ran them both thru a series of tests. I took 3 readings on each sensor. 1 at ambient, 1 at 110* (bucket o' hot tap water), and 1 at 42* (bucket of ice water). Both read within a few hundred ohm of each other at all temps. That sounds like a lot but these things operate over a huge resistance range.

:( :( :(

Well, seems like I'd start troubleshooting for an intake leak, right after I disconnected the battery for 15 mins to dump/clear/restart the ECM to see what this would do first.. Don't they make a "Stop Leak" for intakes?

Got everything buttoned up, plus a fresh set of plugs. Didn't change 1 bit. I called the shop, guy agrees that it is probably the intake leaking since he has had to do a few of them before. So, it goes in tuesday for a full diganostics test, and most likely an intake gasket set. Unfortunately, I have to get it fixed...I couldn't get much out of it with it sounding so crappy most of the time.

Travis, Just put an intake gasket on my daughters 95 lumina (3.1) a major PITA - but... I got two quotes to do the job - one was $1300 and the other $1500. Did it myself for $36 in gaskets. I guess it was not that bad

$1300-$1500 for intake gaksets :eek: If it cost that much I would do it myself too. I wish this one was a 3.1...at least when the alternator went out the engine wouldn't have to be pulled from the car to change it. The shop said this should run between $400-$500. I just don't hardly have time to work on it...and definately don't have any more will to work on it. 3 straight hours to change the coolant sensor...most of that spent fighting with r&r of the crossover pipe.

The one piston I could see was heavily pitted, but no signs of melted aluminum on any plugs, and the car has never run hot, ever.

May have found the problem. Took it in to the shop today to have a full diagnostic run on it. Turns out the fuel pump is only putting out about 30-32 psi...nowhere near the 42-47 psi it should have at idle. Scheduled to have it changed thursday...we'll see if that fixes it.