Howdy Friends,,,,

 I believe I already brought this up but with my failing memory,,,and the fact that the issue is getting worst,,,,I come with hands open and  almost on sore knees,,,,,

 On my 2006 HHR I started to get a Check Engine light and Oreilly machine says it was the MAP sensor. Well, I ordered one and finally got it installed ,,,Boy ,,was that a frigging JOB,,,that sob weas under the air intake and wedged up under it and with my big old hands ,,I finally managed to use some long handled needle nosed pliers to get new one back in there,,,Prolly would of been easier to just remove the whole friggin intake,,,!!!!

 When I first fired it up it ran smooth as glass and as I was reaching back to pat myself,,,,the dang engine started to miss and shake same as before and the CE light came back on!!  Drove it around the block and would miss when giving it gas but would smooth out if held at constant speed,,,? When I would put engine under load (low Vacuum) it would miss like heck,,but smooth out at constant speed. Same thing at stop sign,,will mis and jerk at stop IN GEAR but smooth out at stop but in neutral or park??? Looking like it is worst at LOW vacuum AND also under load at LOW Vacuum,,,,???

 I'm wondering if there is a vacuum leak that I can't hear,,,??? The car has 256,000 tenderly used miles,,,,,,

 Any Ideas, anyone,,??

another old trick ( engine setting at idle)  is to spray starter fluid ( or other) in short bursts at various hoses and rubber gasket areas to see if it gets sucked in and changes the idle speed.

Post #'s have their PERKS 

Respect is earned, not dependent on post #...

AMEN

And you run a D19??

whats the old saying about keeping YOUR MOUTH SHUT and letting people assume your an idiot, as compared to OPENING your mouth and REMOVING ALL DOUBT ?? 

A map sensor is a vacuum sensor. Have to find what is throwing it off.

Engine compression should be 180psi. Discrepancies in the readings across the 4 cyls and you may be having a timing chain issues. 

Starting fluid is a good idea to try to find leaks around the intake gasket as Steve said.

shameless dude wrote: awww http://www....i" rel="nofollow - www....i was gonna say sumpthin...but....

 BE NICE,,!!,,,Shameless,,,!!!  It's too early to start a ruckus,,,,,,,,BY THE WAY,,,How have you and Ms Dee been? Is your Honey doing some better??

DiyDave wrote: Respect is earned, not dependent on post #...

I'll second that.

Despite all the whiz-bang technology touted, the ECM of even today's NEW machines are NOT in any way good diagnostic tools.  Without a healthy understanding of HOW the ECM determines a fault, the scanner's output is little more than a shot-in-the-dark. 

From a 'machine thinking' perspective, it can only see sensors, and can only control a few things.  It is programmed to primarily control fuel (by changing the pulse duration of injectors) and ignition (by changing the time of pulses triggering the ignition module(s).

So really, all it's doing from an 'active' sense, is marking time, and pulsing stuff.  The rest is just turning on and off other stuff like... the warning lights on the dash, the AC compressor clutch, the alternator field driver, and the radiator's electric cooling fan.

The SENSORs include MAP, they also usually have an air temperature, engine coolant temp sensor, a crankshaft position sensor, a camshaft phase sensor, a spark knock sensor, and a throttle position sensor.

Each of these sensors' data is gathered, and compared to 'data maps'... arrays of numbers corresponding to what the proper fuel and ignition outputs need to be for any given rpm and loadpoint... at any given engine coolant and ambient air temperature and pressure.

Sound simple?  It doesn't, but it actually IS.  The computer looks at the numbers for each sensor's output, and looks it up on a multidimentional 'map', then pulses injectors and fires spark plugs.

It's so simple, what could go wrong? 

Well, at 256,000 miles, just about ANYTHING can upset the apple cart.  As others noted, vacuum hoses, a PCV system leak, a bad ground... a skipped tooth on the timing belt... any ONE of those things.

The computer, however, reports an error code based on whatever SENSOR didn't match up with anything on it's data map.

And it tells you where it 'fell off' the map, either based on either whatever 'bad SENSOR SIGNAL' it read FIRST.... or whichever was the LAST sensor read before 'falling off' the data map.

It is MOST likely, that whatever problem you're having, is related to age and mile wear.  If you were in a less-arid environment, you'd have corrosion as a most likely.

Whatever you do, don't assume that the COMPUTER is actually smart enough to know what is REALLY wrong, because it isn't.  A really good scanner will likely give you a better translation of codes, and let you reset them, and retest, possibly see the ORDER of codes, but never assume the actual code is little more than a 'clue'.  Regular test tools (vacuum gauge, spray-stuff, and a well-tuned hearing-aid for vacuum leaks, compression tester for cyl seal health), a good volt-ohmmeter, and a good service and diagnostic manual on the car is what you really need.

in Joes case, the "code says its a MAP sensor" does not mean to replace the MAP sensor... You need to have the actual CODE... which will give you 3-4 different "possible" causes... There are several CODES that will list MAP SENSOR as a possible problem.

 Well, ordinarily, I would not have responded to a post such as this, but since you directed it to me, I shall attempt to enlighten you. First of all, Neither I nor anybody else on here prolly think to consider post counts as to whether to respond to a particular post or not. While you may or may not realize it, your responses always come across like a finger nail on a chalk board, then you get upset and resort to name calling because you never seem to get the response you were looking for. In every group, there is ALWAYS someone (S) that thinks they have done it all and know more than all others.  Since you joined up, you have made every effort to be that person. I don't think you realize it but with all the questions you are always posting,,,I seriously doubt that you are a "Know iT aLL" type person. Try to "Chill" and accept that someone quite possibly,,,does know more than you do! OR,,,,OR,,they really do not know, so they refer to a search engine so YOU can look for your answer. Nothing wrong with that.

 I myself do ask questions but I also respect that those that do respond quite possibly do not know so they refer me to a search engine ,,,which I do not mind and would never think to BAD MOUTH any responses because they may honestly not know. ,,,,Ya see how easy that is,,,??

 Chit,,,I'm havin one of those "Can't Sleep" nites,,,Soo,,,I'll burn off a little energy and fill ya'll in,,,

 Great News,,,, Fixer and Dave's (2) and Steve,,,,,let me see who else,,,, I went to Oreillys and asked the dude for a printout of their tester and it gave me the code plus all the "possibles" in a percentage formatt and after plugging in all of ya'lls suggestions,, I whip out my can of carb cleaner (much cheeper that starting fluid) Ole Shameless will be so proud of me,,,,,

 I sprayed the intake manifold and didn't find any leakers but,,,,BUT,,in all that rukus,,,I could tell there was a hose that was leaking and finally narrowed it to a 3/8" "S" shaped hose coming from the valve cover to the big 3" rubber elbow that had a small split right at the clamp area and the engine would rev up when I shot some juice at it,,,,,!!!! I Go to Oreillys and they wanted $28 for that frigging S shaped hose bout 6" long, so I get a regulaR 3/8" vacuum hose bout 6" long and it fit like a glove and,,,,and,,that old HHR is now running like new..!!  What was weird is when I first drove it after replacing the hose, the tranny shift points were very high and very hard.  I stopped and started several times til it finally started to shift a lot smoother,,,Wonder what happened?? OH,,and the CEL went off by itself bout halfway home,,,YEA,,,!!!

 Many Thanks to all Ya'll,,,,ps,,,I'm fresh out of Black Label as ole Shameless done took all I had with him on his last visit,,,,,,,

Woohoo!  Nice work Joe!

I'm bettin' something like that happened to our old Montana Soccer Shuttle.  "You need a new mass air flow sensor" would "fix" it for 50-100 miles, "You need a crank position sensor" would fix it for a 100 miless, "need a new this, must be that".....We ended up scrapping the van out as the issue was never found.  The symptoms were exactly as you described in your first post.

 Well,,,YOU GUYS are the ones that solved this one for me and soon as I can catch the Black Label on sale again,,,I'll throw a "Get Together" and celebrate,,,,!!

 Seriously tho,, I had always just relied on the tester fellow at Oreillys to tell me something but after listening to ya'll  describe how the codes lead you to the different possibilities causing the issues,,,I asked the dude if I could get a Printout for what the tester was noting. The guy kinda balked and said he would have to get permission from the Mgr,,so I say "Lets go ask!! The Mgr was kinda hesitant ,,so I asked her if she KNEW a Shameless from Nebraska,,and she says   CHIT don't send HIM in here,,,,!!!

 I reminded her that I spend a lot of money in her store and she told the dude,"Print him a copy" Chit,, that copy has a lot of info, and lets you see what the percentages of probabilities it could be affecting the codes. What I really liked is that the dude had told me it "MAY" be the fuel pump ($286),,,BUT that one was way down on the frigging list of possibilities,,,,they would of prolly had me buy a fuel pump and then do like they did to TBone and just keep selling you parts til you either scrap the car or replace every part on the car,,,,!!!

 SO,,,while I have shut down my shade treeing on other people's cars,,I STILL have to maintain mine and the 3 boys that live some close.,,,!  I'ma gonna buy me a good one like they got at Oreillys ($138)  that I can download and PRINT to my desk top. I really like that you can (almost) take the guess work out of them friggin ECM's

 Don't the ECM's have a small internal battery that will power itself to where you could check some parts at a wrecking yard to make sure it is still serviceable???

Not really...  and I wouldn't be inclined to get sensors and actuators from a wrecking yard unless I knew-for-certain that the donor was extremely-low-mile and certainly NOT there because of the component.

The sensor that suffers the most wear, is the throttle position sensor... and it wears most in the right-off idle position, and at the position where it tends to sit at highway speeds.  Like the steering worm on a tractor, the TPS spends most of it's time working in one vicinity, while the rest goes mostly unused.

The MAP sensor is usually a peizoelectric device, air pressure causes a sandwich of dissimilar metals and a thin sheet of mica to flex, generating a slight voltage... a good shock in either pressure or physical (whack with a hammer, or long drop onto concrete floor) can cause them to go bad... but over time, the dissimilar sandwich will delaminate, and the thin mica sheet can fracture, then they become erratic.

Crankshaft and phase sensors come in several flavors, one of them is a 'hall effect' device, it's a transistor that, rather than responding to a signal voltage to amplify, it responds to a magnetic field.  Hall-effect devices can fail from being 'oversaturated' with magnetism, or frozen, or shocked, or bit with static electricity.  Another type is 'reluctance', which is a magnetic core with wire coil around it, just like the pickup on your Fender Telecaster... tooth comes by the polepiece, you get voltage swing at the output.  Just like on the guitar, the coils can fail from vibration over time, so they're usually potted in some sort of epoxy, that after a dozen years, slowly shrinks, and cracks, and you end up with the shrinking epoxy ripping the wires in two.

The Exhaust Oxygen Sensor (O2) is a chemical-balance device, it has two dissimilar metals spaced close together, and once at proper temperature, exhaust gasses passing by will generate a voltage based on the amount of oxygen present in the gasses.  In order for it to work properly, it's gotta stay CLEAN, as oil and carbon fouling will cause problems getting a good reading.  They're most likely to foul bad on cold startup, because a cold engine is belching out condensates and excess fuel until the combustion chamber temp comes up, and then they're a bit skunky 'till the crankcase oil temp gets to normal, as that oil is also holding condensation products.  To help make the O2 sensor last longer, there's a heating element in 'em, it forces the tip temperature up, so that it will help 'burn off' crud that's coming by.  Sometimes the heater works better than others, but as an engine gets older, and more blowby travels from the crankcase into the PCV system, there's more unburned crud coming down the tailpipe.  Most of the time, a new O2 sensor won't last too long, as the main problem is a plugged up Positive Crankcase Ventilation system.

There's a whole lot to know... and I'm not the guy that knows it all.

 Well when do we get the report of how good it worked  as weed killer or  was it fertilizer.  Or was it just to over run the stockholder with the homeless following that wonderful aroma.

Sorry Joe, back under my rock I go.