Where to find ranges for Map and TPS Sensor - stumbles during acceleration

Howdy all.... acceleration with a 2002 Monte Carlo LS 3400. 67,000 miles
Really piss poor accerleration in the 20 - 45 mph range... when I press on the gas pedal, it just stumbles and sits there.
No codes are being set.
Where can I locate a chart of OBDII sensor settings / ranges for this model/engine type
Map sensor is reading 13 in/hg to 29 in/hg.... will not pass 29 in/hg
TPS adjusts well
Air Flow Temp was in a 62 - 78 degree range.
O2 sensor #1 ranges from low to about .800. O2 sensor #2 seems to have a smaller range up to about .500 v.
The problem started after a visit to a service shop where they did an wheel alignment and replaced the engine bypass hose. I did an underhood inspection showed nothing except for the EGR hose being disconnected. However the EGR valve showed strong suction and engine stumbled when allowing air to flow into engine. Cleaned and checked PCV valve, checked plastic hose for cracks and leaks.. reconnected.
Engine is fine at idle.. starts up quickly, idles fine at 500- 700 rpm. While in park using throttle I can accelerate up to about 3K rpm. there is a definite stumble when rpms reach about 2500 - 3000... like something is kicking in and interfering with the engine. It's not a misfire or stumble but seems more like something controlling the engine might be dropping out and preventing the engine from continuing to accelerate
Connected a timing light to all the wire.... spark seems strong when increasing rpms, No misfires are being recorded.
However, when starting to drive... if I start slow, it moves okay however at 20 - 30 mph, under normal pedal, it just sits there.
Timing will advance up to 40 degrees, MAP will max at 29 in/hg TPS is open, rpms will move to 1500 or so, but the car will not accelerate.. Increasing the rpms suddenly and the car will accelerate rapidly, but slowly increasing the rpms, the car just sits there.
Now, by pulsating the gas pedal I can nurse the car up to 50 and it trravels well at 60 and 70 (1500 rpm or so). But it just seems it is not responding to steady acceleration.
Is there a chart showing acceptable ranges for the sensors.... I can start here.
Closed loop MAP was 13 in/hg to 29 in/hg seems maxed out at 29 Timing Advance went to as much as 40 degrees Fuel Trim short and long were adjusting. between lean and rich O2 #1 ranges between .100 and .800 O2 #2 ranges between 100 and .500 Engine Temps were within normal ranges from cool to a high of 203. Air Flow Temps were with normal All tests completed
I hate to bring it into the shop if it's something simple. And to be honest, I don't trust that shop... the car worked well when it went in for a wheel alignment. They replaced the bypass hose... and did a 30 point inspection. Left the old hose clamps and hose in the engine compartment. Found the EGR tube disconnected. So I wonder what else they screwed up.
Any other suggestions as to where the problem might be ???
Thanks in advance for your help !!
Peter
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snipped-for-privacy@nospam.net wrote:

MAP= BARO minus Vacuum. BARO minus MAP= Vacuum. MAP + Vacuum = BARO
Depending on altitude, the MAP should read around 9-10 in/hg at idle, higher if at higher altitude.
If you are below 1000ft elevation, 13 in/hg is a bit high.

It wouldn't necessarily... 29 in/hg is typical barometer pressure on earth. Again, this will vary according to weather, if a low pressure weather system is in the area, the MAP/BARO reading will be lower, if a high pressure weather system is in the area, the reading will be higher. What ever the weather report says the barometer reading is, that is what the MAP sensor should report key on engine off and when the engine is at wide open throttle.

Should start out at slightly under 1.0 volts with the throttle closed and increase to 4.5 volts at wide open throttle. The specific closed throttle reading is not important because the TPS is auto-zeroed at key on.

??? The EGR valve on this engine is 100% electronic, there are/is no vacuum to its control.

Check the fuel pressure. What does the #1 O2 sensor read at WOT under road load (not revving in park)?

Under what conditions? Idle, WOT, cruise?

Under what conditions? Idle, WOT, cruise?

Under what conditions? Idle, WOT, cruise?

Under what conditions? Idle, WOT, cruise?

Would need Mass AirFlow reading at idle and at wide open throttle right before the 1-2 shift.
Trace down the spark plug wires, maybe they switched one around.
The firewall side of the engine is cylinders 1-3-5 The radiator side of the engine is cylinders 2-4-6 The coils are marked unless they have been replaced.

Obviously they didn't test drive the car when they were finished...
I wonder how they knew the alignment was right?

What sort of repair shop was this?
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On Sat, 20 Feb 2010 08:05:15 -0600, aarcuda69062

Here are some answers
Using an Auto XRay Scan Tool OBDII
Here's what the engine is doing... in park... closed loop....get rpms to 3600 it starts stumbling... it reaches just below 4K rpms and something (cuts in or drops out) forcing engine rpms back down to about 3600 rpm.
While road testing when it's under load at 20 - 30 mph the acceleration stops completely... pressing on gas pedal does not increase rpm's.... speed does not increase....
here are the measurements
Outside BARO 30.14 steady    MAP key on engine off 30 at idle (600-700 rpm) about 12. WOT low RPM's 13 - 14 WOT 3600 - 4000. 24 in/hg
WOT in park - rpm's reach 3700 - 4000 and then engine stumbles and kicks back down.... starts to stumble at 3600 - 3700 will not get past 4k rpm....
Timing IDLE adv 22..... increases to 40 as I accelerate and goes to 33 % at high rpm when engine starts stumbling at WOT
O2 sensor #1 Key On Engine off .450 Engine Idle (600-700 rpm) varies from .095 to .760. WOT (stumbling) does not get above .100
02 sensor #2 Key On Engine off .015 Engine idle varies from .050 to .640. WOT does not exceed .100
Air Flow Rate sensor Key On Engine off .024 idle .74 WOT 5.0
Load 2.3 at idle 27 at WOT while parked
I didn't have an opportunity to check fuel pressure yet and couldn't road test while watching scan tool. Too much snow on the ground and traffic was kinda heavy.... however symptoms are showing up while in park. If necessary I can check under load early tomorrow morning while traffic is light.
As the engine is stumbling, the check engine light is coming on, but no codes are being set. A rescan of the system shows no trouble codes, but a pending code P0300 engine misfire, random multiple cylinders.
The work was done at a dealership.... I try really hard NOT to use them, as they are fairly overpriced and use junior techs to do a lot of the "A" work.... but figured how can you screw up an alignment.
I'm a little spoiled by doing a lot of my own work.... and enjoy the learning experience... mechanics can be fun at times, but here are some things based upon that trip, that made me think twice.
During the 30 point inspection.... it cost $75.00 to replace the engine bypass hose and the tech left the old hose and clamps in the hood well. The part is only $10 bucks and takes 5 minutes to replace. hose, 2 clamps and 10 minutes labor $75.
On their brake inspection sheet, they had all measurements marked in an 'alarming' shade of warning yellow. Made me think the pads were on their last legs. So I pulled the wheels, and discovered the pads were only 1/2 worn and good for at least another 20 - 30 K of highway driving before even considering replacement.
They replaced one outer tie rod end for a cost of $250.00....

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snipped-for-privacy@nospam.net wrote:

Idle vacuum is about 18 in/hg

Should be closer to BARO

Should be closer to BARO

Don't fixate on this symptom, it may only be the rev limiter kicking in.

I don't like this at all. AT WOT the system should be full rich, O2 voltage should be near .900mv

At some point at WOT this should get higher.

Need to know what this parameter is reported in. Is it grams per minute, pounds per minute, pounds per second?
GM reports in grams per second.

Again, how is this reported? As a percentage?

Also looking for fuel trims reported as a percentage. If available and they are more than 10-15% positive, you have a fuel starvation problem.

If the light is on, there is a code. Your tool may not be capable of retrieving it though.

Well, he does have to refill the cooling system, run the engine until hot, burp the air, refill, etc. I'd be really pissed if they replaced the OE constant tension spring clamps for some generic worm drive clamps though.

Did you pull the calipers and view the entire length of the pads? IIRC, the caliper covers most of the pad and those things like to wear crooked.

I gotta raise my prices.
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On Sat, 20 Feb 2010 14:05:31 -0600, aarcuda69062

Didn't know they had one.... okay.... so I'll move onto the matter at hand... acceleration under load.

    Lb/ minute

    Percentage
I'll try to get the numbers when driving the car tomorrow morning when traffic is light and I can keep one eye on the scanner and one eye on the road.

    Will look at the trim tomorrow... they are reported as a     percentage, but will check them while driving.

    Pulled the Calipers and popped the pads. I had bought     a new set...so did a side by side comparision... new vs          existing. Pads weren't even half worn. This car doesn't     get a lot of use... and most of it is highway driving.

    I'm spoiled by doing a lot of work myself.... and don't     know if shops are higher than book. For example my girlfriend     needed brakes about two weeks ago, she wears everything down     to the metal. The quotes for front not counting new rotors     was about $350. Rear was about $380. Not counting shop     supplies and 6% sales tax.
    These quotes were based based upon whether the rotors could be     turned.     She grooved them pretty badly so they probably     would have required replacement adding a couple of hundred     to the bill
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snipped-for-privacy@nospam.net wrote:

Okay, to get grams per second; 5(LBS) X 16 X 28 / 60 = 37.33 grams per second. That would be pretty close -IF- the RPMs were around 1500 at the exact point where that airflow reading was taken.

Need road test data, revving the engine in park is meaningless.
At WOT at 5000 RPM right before the 1-2 shift or 2-3 shift. If the engine will not cooperate, take your readings at WOT at the highest RPM-highest load you can while the thing is falling on its face... Your gonna have to drive it like you stole it to get meaningful data. Engine load should be over 60% maybe higher, closer to 70%
If significantly lower, you either have an engine breathing problem (restricted intake, restricted exhaust), or the air flow sensor is not reporting correctly.
When you have some road test mass air flow numbers you can plug them into this calculator to see if the engine is breathing like it should
<http://www.autoservicetech.com/vecalculator.html
This is a ballpark calculator, it is not exact, it is but one tool to help you get an idea of what is happening.
Plug in 204 cubic inches, use the intake air temperature as reported by your scan tool and the RPM at the time the MAF reading is taken.

I don't suppose that scan tool has the capability to record does it? How about the ability to freeze the screen?

There should be long term and short term, add them together to get the total. Negatives count like regular math i.e., +15 long and a -6 short equals total trim of +9.
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On Sat, 20 Feb 2010 21:53:42 -0600, aarcuda69062
Did 3 tests.... captured data
Prior to capturing data, I grabbed data from the previous running.... Pending codes P 0301 misfire cylinder one P 0404 EGR Circuit Range Performance.
No trouble codes found..... I was unable to grab a freeze frame on one code.
    Test # 1 Driving down side street - cruising
Closed Loop
TPS        71 % Speed        16 mph RPM        2069
MAP        30 in/hg
Air Flow        3.62 Rate
Coolent        217 Temp
Load        17.6 %        
O2 1        .750
O2 2        .685
Short Term    + 3.9 % Fuel Trim
Long Term    + 1.5 % Fuel Trim
Timing        adv 46
    Test #2 .... Parking lot.... 0 to failure WOT Fuel System went into OPEN LOOP
TPS        100 % Speed         17 mph at error... it just sat there and suddenly                     accelerated. RPM        2575
MAP        30 in/hg
Air Flow        6.5 lb/min Rate
Coolent        209 Temp
Load        34.1 %
O2 1        .820
O2 2        .870
Short Term    0.0 % Fuel Trim
Long Term    + 2.7 % Fuel Trim
Timing        adv 17 '
Codes P0300 (misfire random)
    Test # 3 acelerating onto hwy from 30 mph WOT
Closed Loop Readiness Tests Completed
TPS %        100 % Speed         42 mph RPM        2776
MAP        29 in/hg Air Flow Rate    7.16 lb/min
Coolent Temp    199 F
Load         28.2 %
O2 1        .680
O2 2        .700
Short Term    - 6.3 % Fuel Trim
Long Term Fuel Trimi    + 2.3 %
Ign timing    adv 19.5 '
It seemed to respond a lot better when first running in open loop (pending operating temperature).
Is there a way to keep the system in open loop to see if any difference in operation ... (perhaps disconnect an O2 sensor). Is that an effective troubleshooting tool ??
A fuel system check and inspection ??? Cramped lines... clogged fuel filter. I did several fill-ups and added a can of injector cleaner since the problem first appeared... so it probably isn't bad gas.
EGR valve stuck open ???? - I place my hand over the pcv valve and feel plenty of vacumn.... Don't have a TECH2 tool and my scanner won't activate the EGR valve. Should the EGR system be working all the time ??? Anyway to test this ???
Map seems okay TPS seems okay oxygen sensors fore and aft seem operational
Timing advance seems to be working fine...

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Maybe sticking/lazy IAC valve. Good luck.
Rodan. _________________________________________________________________________
Howdy all.... acceleration with a 2002 Monte Carlo LS 3400. 67,000 miles
Really piss poor accerleration in the 20 - 45 mph range... when I press on the gas pedal, it just stumbles and sits there.
No codes are being set.
Where can I locate a chart of OBDII sensor settings / ranges for this model/engine type
Map sensor is reading 13 in/hg to 29 in/hg.... will not pass 29 in/hg
TPS adjusts well
Air Flow Temp was in a 62 - 78 degree range.
O2 sensor #1 ranges from low to about .800. O2 sensor #2 seems to have a smaller range up to about .500 v.
The problem started after a visit to a service shop where they did an wheel alignment and replaced the engine bypass hose. I did an underhood inspection showed nothing except for the EGR hose being disconnected. However the EGR valve showed strong suction and engine stumbled when allowing air to flow into engine. Cleaned and checked PCV valve, checked plastic hose for cracks and leaks.. reconnected.
Engine is fine at idle.. starts up quickly, idles fine at 500- 700 rpm. While in park using throttle I can accelerate up to about 3K rpm. there is a definite stumble when rpms reach about 2500 - 3000... like something is kicking in and interfering with the engine. It's not a misfire or stumble but seems more like something controlling the engine might be dropping out and preventing the engine from continuing to accelerate
Connected a timing light to all the wire.... spark seems strong when increasing rpms, No misfires are being recorded.
However, when starting to drive... if I start slow, it moves okay however at 20 - 30 mph, under normal pedal, it just sits there.
Timing will advance up to 40 degrees, MAP will max at 29 in/hg TPS is open, rpms will move to 1500 or so, but the car will not accelerate.. Increasing the rpms suddenly and the car will accelerate rapidly, but slowly increasing the rpms, the car just sits there.
Now, by pulsating the gas pedal I can nurse the car up to 50 and it trravels well at 60 and 70 (1500 rpm or so). But it just seems it is not responding to steady acceleration.
Is there a chart showing acceptable ranges for the sensors.... I can start here.
Closed loop MAP was 13 in/hg to 29 in/hg seems maxed out at 29 Timing Advance went to as much as 40 degrees Fuel Trim short and long were adjusting. between lean and rich O2 #1 ranges between .100 and .800 O2 #2 ranges between 100 and .500 Engine Temps were within normal ranges from cool to a high of 203. Air Flow Temps were with normal All tests completed
I hate to bring it into the shop if it's something simple. And to be honest, I don't trust that shop... the car worked well when it went in for a wheel alignment. They replaced the bypass hose... and did a 30 point inspection. Left the old hose clamps and hose in the engine compartment. Found the EGR tube disconnected. So I wonder what else they screwed up.
Any other suggestions as to where the problem might be ???
Thanks in advance for your help !!
Peter
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Thanks... I'll test it out..
wrote:

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I've not seen any technical specification information available for the various sensors like you would find for ANY other electronic products. All you can find on the internet or elsewhere is a part number! This seems to be the case with all auto parts.
They do provide testing information for the various sensors in vehicle factory service manual sets. These can be 4 books and a total of 2000 pages. Lots of information. (Order from dealer or helminc.com)
The information in the service manual sets is just enough information to determine if a sensor is working or not and should be replaced. Not much more beyond that. And they also give a description of operation which explains how the various sensors and systems work.
If you do a bit of digging, you can sometimes find data points for sensors like a coolant temperature sensor might have 3 different temperatures given and the resistance readings you should get at those temperatures. And you can take that data and stick it in an Excel spread sheet and fill in the numbers in-between.
But other times it is frustrating because everything is "dumbed down" and geared toward the non-technical crowd. Like they might not give a specific operating temperature range the engine coolant thermostat should operate at in degrees F., rather they say to use a "heat sensing stick" and never mention any acceptable temperature range.
But in general these books are good enough to determine if a sensor is doing what it should or not.
As vehicles get to be more technologically sophisticated, they are going to need more intelligent persons to troubleshoot difficult problems. And these people are going to want to see electrical specifications for the various components. Like this for a non-automotive part... http://www.senscomp.com/specs/600%20instrument%20spec.pdf
All the rest of the electronic world provides this basic information!
Sometimes there are very strange problems or intermittent problems which occur. And these turn out to be a design problem. And a highly skilled technician can track these problems down if ALL the specifications are provided. He must first fully understand how the system should work and what specification parts are used, then do some advanced testing to find the problem. And then can send an intelligent letter to the factory engineering department detailing the specific problem.
My pet peeve is they keep the internal workings of engine computers secret. Then you don't understand how it works. How it should work. For example in some cases there is a "limp home mode" if a certain diagnostic code is set. There is little or no information about this in the factory service manuals. It would be nice to have a little chart / table showing various codes and if there is an associated "limp home mode" when the code is set. And what specifically happens when this occurs.
"Splain how it operates!" Need input!
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I seem to recall a class action lawsuit involving the association of inedependent shops against a few major manufacturers. Seems the independents are claiming anti trust against the manufacturers in regard to information which the manufacturers claim is proprietory thus given dealerships a competitive advantage for 'the type of vehicle which they are servicing'. So if you have a GM, you are being forced into a GM dealership, Toyoyo, a Toyoyo shop.... etc. This severely restricts the amount of options available to the consumer.
Many, many years ago...(my background was in electronics and clinical engineerign).... it was fairly easy to chip chase discrete components and circuitry with a medium amount of general troubleshooting knowledge and the data books published by companies such as Motorola and National Semiconductor.
Unfotunately, our screwed up government forced a lot of corporations to turn over their information to help the Asiatic companies grow.... resulting in the electronics industry moving from the US to overseas (this government policy started back about 1960's trying to help our enemies from WWII recover from their devestating losses because they waged an agressive war against us. (Nothing beats a really LONG memory in a time when political correctness and social engineering is trying to rewrite the truth about history.
So today.... no service manuals here in the US and the stuff is becoming increasingly complex. Not a problem with the low end consumer stuff, but is a major problem with clinical and laboratory equipment.
Looks like cars might be headed the same way.
Anyway... didn't want to rant and rave... we all have pet peeves.
But you're right... the factory service manuals are pretty good.... I just don't have one for the monte carlo just yet... Helms is a reliable source.
Because auto manufacturers probably don't develop their own sensors, but purchase them on the open market... it might be feasible that one could track down the spec's from the manufacturer of such equipment.
On Sat, 20 Feb 2010 10:44:28 -0800, "Bill"

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