The Unsolvable Miss at Idle....

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Hey, I've spent many a long hour over the last few months scouring Usenet, the Web, and my Haynes (painful, yes) manual, trying to figure out how to fix the miss I have in my V6 3.4L 1995 Camaro, now I come to you
for some help.
Let me first tell you what I've tried already:
Replaced spark plugs and wires Replaced 02 sensors Installed new intake gasket and resealed manifold Replaced IAC Cleaned throttle body
Here's the problem: The car starts up, but when it's idling at 900 RPM's, it'll violently shake/shudder and immediately drop (like a burp) like -50 to -75 RPMS from where it was idling, seemingly "catch" itself and recorrect itself back to 900 RPM's. There is a short delay between each hiccuup; but, it seems pretty consistent when in idle. From low RPM accelaration it feels sluggish.
I have had the car into a dealer, for the plugs and 02 senors, they didn't uncover any engine codes when they had it hooked up. I'm pretty sure the ECM is working, since after I put together my manifold I forget to hookup the MAF sensor and the check engine light went on. If I unplug any device, IAC comes to mind for this test, the check engine light will come on.
I was there when they hooked up a scan tool and it seemed like all the sensors were putting out "good" results. I haven't run a compression test on the engine, should that be my first move now?
Based on my most recent research, it seems like maybe my EGR is stuck open; however, in the 3.4L GM cars these are digital. Is it possible my EGR is broken and not sending an error code? Also, is it worthwhile for me to pull it off, look for the valve, and then, assuming it is dirty, try to "de-carbon" the valve and associated passageways?
Otherwise, what else should I be looking at in my car? I don't have a lot of experience hunting vacuum leaks in hoses, should I be looking for that first of all? Is the problem I have a "miss" or is just an idling problem? Got any helpful hints or candid advice? Please post or email me back at (nospam) snipped-for-privacy@ncf.edu.
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This really doesn't sound like a problem with your EGR. I was thinking MAF, but you'd only see sluggishness at WOT.
Have you checked the simple stuff like fuel filter? Air Filter? Have you run a compression check? Are you seeing any discoloration of your exhaust gases?
This sounds like a timing issue to me. It's possible your timing chain/belt (dunno what mods you've done) skipped a tooth or two.
Martin '01 Formula - MTI Air Box Lid, K&N Filter, Hurst-6, SLP Cold Air Induction & Smooth Intake Bellow Corsa Catback w/Premium Tips '83 V45 Magna
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Martin, Is there any good way to definently test if it is my timing chain? I haven't done any mods to the car so it's not like I've got I've got some fatty cams and headers and getting some surging, this car car's bone bone stock.
I haven't run a compression check yet. I'm thinking I'm gonna do that tommrow. That would be the worst case if it's a mechnical miss. I'm hoping it's roving miss due to something else. Also, there is no cloud of blue/white/black smoke from the exhaust. It sounds pretty healthy when it starts up.
So, is there a way to check out the timing chain, or do I just re-adjust it and see what happens?
Thanks, Tim-
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: > : > This really doesn't sound like a problem with your EGR. I was thinking : > MAF, but you'd only see sluggishness at WOT. : > : > Have you checked the simple stuff like fuel filter? Air Filter? Have you : > run a compression check? Are you seeing any discoloration of your exhaust : > gases? : > : > This sounds like a timing issue to me. It's possible your timing : > chain/belt (dunno what mods you've done) skipped a tooth or two. : > : > Martin : > '01 Formula - MTI Air Box Lid, K&N Filter, Hurst-6, : > SLP Cold Air Induction & Smooth Intake Bellow : > Corsa Catback w/Premium Tips : > '83 V45 Magna : : Martin, : Is there any good way to definently test if it is my timing chain? I : haven't done any mods to the car so it's not like I've got I've got : some fatty cams and headers and getting some surging, this car car's : bone bone stock. : : I haven't run a compression check yet. I'm thinking I'm gonna do that : tommrow. That would be the worst case if it's a mechnical miss. I'm : hoping it's roving miss due to something else. Also, there is no : cloud of blue/white/black smoke from the exhaust. It sounds pretty : healthy when it starts up. : : So, is there a way to check out the timing chain, or do I just : re-adjust it and see what happens? : : Thanks, : Tim-
Actually, I don't have a manual for your car, so I have no idea what the timing is. It would be folly for me to through out any numbers at you. I would have it professionally checked when it comes to timing.
Compression test is easy if you have the equip.
Martin '01 Formula - MTI Air Box Lid, K&N Filter, Hurst-6, SLP Cold Air Induction & Smooth Intake Bellow Corsa Catback w/Premium Tips '83 V45 Magna
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Before you go digging into your timing chain, check your knock sensor (senses detonation in the cylinders and adjusts timing accordingly). I had a 350 where the wire to the knock sensor came loose and it gave the same/similar symptoms you described, which would disappear with increased RPM's. No error code ever came up so I don't know if the knock sensor is monitored by the ECM. Can't hurt to check it out.
Cheers - Jonathan
--
Acta Non Verba - Deeds Not Words
Lieutenant Jonathan Race, EMS Supervisor
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snipped-for-privacy@ncf.edu (Tim Payne) wrote in message
There are two lesser problems I haven't tried to solve, maybe somehow they are related?
1)Oil burning in engine compartment. My oil sending unit, that little metal cylinder hanging off of the oil filter housing with a wire running to it, once it the car warms up it drips oil unto the exhaust header and creates some smoke. Could that be creating the miss at idle I'm experiencing?
2)Car creates cold AC but tepid (at best) heat When I first got the car, there was cold air that would come out of the bottom vents but nowhere else. It was missing a check valve for some little hoses, so I bougth a new valve hooked everything up and it dumps out lots of cold air through all vents now. However, I now notice that I can't ever get some warm air; heat cranked up all the way doesn't really produce any difference.
When I had the car in at the dealership, alongside the $2600 of other repairs, they wanted to flush the coolant system and replace the thermometer. I have flushed the coolant system, when I replaced the intake gasket, but I didn't replace the thermometer. Will a thermometer most likely fix the heat problem and could it be related to this miss in any form?
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My guess is a dying MAF. My car does this too right now, though very slight now that I have a new MAF. The other culprit was a dying fuel pump delivering about half the pressure. Together, it made for a rought ride.
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: My guess is a dying MAF. My car does this too right now, though : very slight now that I have a new MAF. The other culprit was : a dying fuel pump delivering about half the pressure. Together, : it made for a rought ride.
Ooh...ooh...fuel pump. Doh! That completely slipped my mind when I suggest checking the fuel filter.
Good catch.
Although, I still don't think it's the MAF from the behavior he described ... but ye' never can tell. Usually if the MAF is going bad, you'll notice the RPMs going up, a loss in fuel economy, and at WOT, the TC won't shift until you let up on the throttle and allow more air into the mix. That's just my experience though. It definitely COULD be the MAF, but I'd look elsewhere first.
Martin '01 Formula - MTI Air Box Lid, K&N Filter, Hurst-6, SLP Cold Air Induction & Smooth Intake Bellow Corsa Catback w/Premium Tips '83 V45 Magna
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described
notice
At what point, mileage-wise, might one want to examine the MAF (to see if it's going or not)? I haven't really looked at mine and am now at about 30K miles.
~w~
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Tim Payne wrote:

Oh - forgot to mention - this died as well.
EGR relay and valve died. This in turn stressed the MAF until it failed. Oh - there was a lot of gunk in the EGR passages - make sure you get it out or get the tech to. The relay was salvaged by a little TLC and cleaning, but the valve was toast along with the MAF.
Almost lost my cat. as well due to unburnt fuel from the bad timing and stalling.
Fix? $220.
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: Tim Payne wrote: : : >>Based on my most recent research, it seems like maybe my EGR is stuck : >>open; however, in the 3.4L GM cars these are digital. Is it possible : >>my EGR is broken and not sending an error code? Also, is it : >>worthwhile for me to pull it off, look for the valve, and then, : >>assuming it is dirty, try to "de-carbon" the valve and associated : >>passageways? : : Oh - forgot to mention - this died as well. : : EGR relay and valve died. This in turn stressed the MAF until it : failed. Oh - there was a lot of gunk in the EGR passages - make sure : you get it out or get the tech to. The relay was salvaged by a little : TLC and cleaning, but the valve was toast along with the MAF. : : Almost lost my cat. as well due to unburnt fuel from the bad timing : and stalling. : : Fix? $220.
Is there a PCV in this model?
Martin '01 Formula - MTI Air Box Lid, K&N Filter, Hurst-6, SLP Cold Air Induction & Smooth Intake Bellow Corsa Catback w/Premium Tips '83 V45 Magna
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GLK9MM wrote:

There is one, or something like it on every car. It recirculates exhaust into the engine again when it is cold to help it get warmed up faster.
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: > : Tim Payne wrote: : > : : > : >>Based on my most recent research, it seems like maybe my EGR is stuck : > : >>open; however, in the 3.4L GM cars these are digital. Is it possible : > : >>my EGR is broken and not sending an error code? Also, is it : > : >>worthwhile for me to pull it off, look for the valve, and then, : > : >>assuming it is dirty, try to "de-carbon" the valve and associated : > : >>passageways? : > : : > : Oh - forgot to mention - this died as well. : > : : > : EGR relay and valve died. This in turn stressed the MAF until it : > : failed. Oh - there was a lot of gunk in the EGR passages - make sure : > : you get it out or get the tech to. The relay was salvaged by a little : > : TLC and cleaning, but the valve was toast along with the MAF. : > : : > : Almost lost my cat. as well due to unburnt fuel from the bad timing : > : and stalling. : > : : > : Fix? $220. : > : > : > Is there a PCV in this model? : : There is one, or something like it on every car. It recirculates exhaust : into the engine again when it is cold to help it get warmed up faster.
Wrong-o! Not only doesn't every car have a PCV, not ever car has an EGR...which you just described.
Which is why I asked the question in the first place. Don't answer questions you don't understand.
Martin '01 Formula - MTI Air Box Lid, K&N Filter, Hurst-6, SLP Cold Air Induction & Smooth Intake Bellow Corsa Catback w/Premium Tips '83 V45 Magna
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GLK9MM wrote:

Well, as far as I know, every GM 3100,3400 and 3800 series engine has one, which is what the O.P. is having a problem with.
Sheesh. You need to chill out. Newsgroup. Not real life.
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: GLK9MM wrote: : : > : > Wrong-o! Not only doesn't every car have a PCV, not ever car has an : > EGR...which you just described. : > : > Which is why I asked the question in the first place. Don't answer : > questions you don't understand. : : Well, as far as I know, every GM 3100,3400 and 3800 series engine has one, : which is what the O.P. is having a problem with. : : Sheesh. You need to chill out. Newsgroup. Not real life.
Well, not only was your original answer wrong, but it came across as snotty. (Maybe just my own internal voice.)
<shrug>
Sorry.
But, like I said, I'm not as familiar with this powerplant as I should be so I'm just shooting at the hip on this one.
If it does turn out to be the MAF like Joe and a couple others have guessed, then it's a relatively easy and inexpensive fix. (Hell of a lot easier than timing, that's for sure.)
Martin '01 Formula - MTI Air Box Lid, K&N Filter, Hurst-6, SLP Cold Air Induction & Smooth Intake Bellow Corsa Catback w/Premium Tips '83 V45 Magna
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: : GLK9MM wrote: : : : : > : : > Wrong-o! Not only doesn't every car have a PCV, not ever car has an : : > EGR...which you just described. : : > : : > Which is why I asked the question in the first place. Don't answer : : > questions you don't understand. : : : : Well, as far as I know, every GM 3100,3400 and 3800 series engine has : one, : : which is what the O.P. is having a problem with. : : : : Sheesh. You need to chill out. Newsgroup. Not real life. : : : Well, not only was your original answer wrong, but it came across as : snotty. (Maybe just my own internal voice.) : : <shrug> : : Sorry. : : But, like I said, I'm not as familiar with this powerplant as I should be : so I'm just shooting at the hip on this one. : : If it does turn out to be the MAF like Joe and a couple others have : guessed, then it's a relatively easy and inexpensive fix. (Hell of a lot : easier than timing, that's for sure.)
Well...that's not entirely true either. Timing can be pretty easy if ye' know what you're doing. < 1hr. Parts can be a bitch though.
Martin '01 Formula - MTI Air Box Lid, K&N Filter, Hurst-6, SLP Cold Air Induction & Smooth Intake Bellow Corsa Catback w/Premium Tips '83 V45 Magna
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GLK9MM wrote:

Got that right. Holy hell. $50-$80 a pop for these little components if you want the OEM ones. Adds up real fast.
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If you had your car at a dealer for $2600 of repiars and they couldnt fix a stupid miss I'd say you have an extremely shitty mechanic.
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Rommel wrote:

I agree. the EGR valve and MAF are the firt things that any competant mechanic should check, then the timing chain, then the camshaft sensor.
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They wanted to charge me $2600 for a few repairs... like $1000 for the intake gasket! Needless to say, it didn't quite happen....
Also, I have replaced the PCV valve. The cheap $2 valve was one of the first things tried.
I did pull off the EGR today and I noticed some drops of watery condensation in it. Other then that it didn't look like there was any sort of EGR part to clean. But I'm going to look into it tommorow again.
I don't know about the MAF, since it's not sending any engine codes... but you never know.
The fuel pump or fuel pump regulator seems possible based on some other posts I've read. The best bet may be to bring the car into somebody and have them diagnosis it.... any other ideas?
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