Does a bad MAP sensor have long lasting effect on vehicle?

[PeeluckyDuckee]

I have a 2001 Honda Prelude and noticed today the car seems very bogged down. The car sputters, power comes and go sporadically, but anything above 3500rpm and the car does not accelerate at all.

I know it's not the clutch slipping, as I've had that changed a year ago.

How hard is it to change out the MAP sensor on the Prelude, with my very limited knowledge of vehicles and the part is cheap enough I want to try that option and replace it myself before I bring it to the mechanic.

It'll be a day or two before I get around to it, will this have long term damage to the vehicle if I keep on driving it?

Thanks.

 

[exdeath]

Yes. MAP + MAF (if there is one) + crank/cam position sensor are the most vital inputs to the computer. If that engine doesn't have a MAF, the MAP becomes the most important sensor under the hood next to crank position.

The car is going to bog and run like shit because the fueling will be all wrong because it has no reliable indicator of air intake.

 

[natto fire]

Not really, except maybe some fouled plugs/O2 sensors.

If it is bad enough that it is switching to backup or "limp home" mode, it is basically going to run super rich to avoid detonation. The extra fuel can muck things up, but it will not cause damage that is not easily fixed (unlike detonation).

As far as changing, it is not extremely difficult, but are you sure that is the problem? Any check engine light or other problems?

 

[cardiac]

Are you getting a "CEL" -check engine light?

 

[PeeluckyDuckee]

Are you getting a "CEL" -check engine light?

Yes, the engine light came on. Does most mechanic shops have a reader where they can pull the code and find out exactly what's wrong? There's also a red circle light with an exclamation mark that came up as well.

Have an appointment on Monday to bring the car in, hope it'll last til then. At idle from gear to neutral the car wants to stall, as the RPM meter drops to near zero.

 

[manimal]

no maf on the H22 in those preludes. Id check both o2s and cam pos sensor. Has the car ever had some sludge issues? Cuz if its running like ass then vtec didnt kick in yo!


If you have been running pig rich for a while you have clogged your cats as well. SUPER common on those.

 

[A5]

Yes, the engine light came on. Does most mechanic shops have a reader where they can pull the code and find out exactly what's wrong? There's also a red circle light with an exclamation mark that came up as well.

Have an appointment on Monday to bring the car in, hope it'll last til then. At idle from gear to neutral the car wants to stall, as the RPM meter drops to near zero.

Every mechanic shop will have an OBD code reader to pull CEL codes. All the part store chains will pull your codes for free, too.

You can also buy a really cheap OBD2 reader on Amazon and do it yourself (the fancy ones will have a decoding database in them, the cheap ones just require you to write the code down and search for it online). It's a really handy thing to have around.

 

[PeeluckyDuckee]

The 5 codes they pulled indicate all 4 cyclinders are misfiring and too rich of a fuel mixture. Mechanic is not exactly sure if the catalytic convertor and both oxygen sensors are a problem. We're changing all the spark plugs and wires first to see what happens.

The mechanic took out the plugs and advised they're all bad. The wires were changed at 47000km, now the vehicle is at 225000km so we're getting the wires done as well. The distributor cap and rotor were changed mid last year. The clutch was changed not too long ago, so it's not the clutch slipping causing loss of power, I've dealt with worn out clutch and know how they feel when it is the clutch.

The guy quoted me parts plus $45 for the plugs and wires.
He also quoted me around $1000 if it comes to the oxygen sensors and catalytic convertor.

 

[NutBucket]

Converter is probably fine. Start with the plugs/wires. Then he can use his scan tools and figure out which is bad, O2 sensor or MAP.

If the plugs/wires are that old chances are replacing those will make a huge difference.

 

[PeeluckyDuckee]

The plugs he pulled were all in very bad shaped, so those and the plug wires have all been replaced, but that did not solve the problem of lack of and irratic power up to 3k and total loss of power after 3k. Applying gas at whatever throttle position it hits a ceiling at 3.5k and would not go higher in rpm.

The engine has been having ongoing issues of running rich, and I was told because of that it may have clogged up the catalytic convertor and messed up the o2 sensors. The o2 sensors regulate how much air/fuel mixture the vehicle needs? When it's clogged the system goes into "safe mode" to prevent damage?

I just hope it has nothing to do with the manual transmission itself.

Left it with ZR Auto in Calgary for further diagnosis, as my usual mechanic cannot seem to resolve the issue. The spark plug and wires needed changing anyhow, so it's not all time wasted. But this problem is frustrating to say the least.

 

[A5]

I just hope it has nothing to do with the manual transmission itself.

I'd rather have transmission problems (manuals aren't as expensive to replace/rebuild as automatics) than the major engine issues it sounds like you have.

O2/MAP/Catalytic Converter will run you a pretty penny if it all needs to be replaced.

 

[NutBucket]

Eh, one can also just buy a JDM motor for $1200 and call it a day if its that serious

My opinion is if the O2 is bad the engine would run rich with a default fuel table. So assuming there isn't a physical issue like a melted/clogged cat its probably a bad sensor on the input side causing the car to run in limp mode....or maybe a wiring issue.

 

[A5]

Eh, one can also just buy a JDM motor for $1200 and call it a day if its that serious

My opinion is if the O2 is bad the engine would run rich with a default fuel table. So assuming there isn't a physical issue like a melted/clogged cat its probably a bad sensor on the input side causing the car to run in limp mode....or maybe a wiring issue.

Well yeah, but I tend to always go straight to worst-case scenarios

 

[PeeluckyDuckee]

TPS reads fine. Pressure check on cyclinders shows 35% on cyclinder 3, 15-20% on other cyclinders. Blue smoke coming from exhaust. Mechanic is going to check the valves and see what's going on there.

A5, if there are 02 and catalytic convertor issues, would it show up in the CEL code pulls?

 

[DaTT]

o2 sensors would throw a code, but not the catalytic convertor. Only way you would get a "code" from the cat is if there was an o2 sensor after it monitoring its output.

 

[PeeluckyDuckee]

o2 sensors would throw a code, but not the catalytic convertor. Only way you would get a "code" from the cat is if there was an o2 sensor after it monitoring its output.

There's an 02 pre and post cat, and I was told both sensors are fine. So you're saying perhaps it's the cat that's clogged? The mechanic advised that if it was a clogged cat, the cat's temperature would drop noticeably after running the car for 10-20 minutes, but he only noticed a 15* degree drop in difference?

 

[NutBucket]

Clogged cat wouldn't allow enough air to pass through which would cause the car to stall out/run rough. A coworker had a cat "melt" in his Saturn and it had some odd stalling issues. Its a simple physical inspection for that one..

I don't quite understand your bit about the "pressure check" for the cylinders. A compression test would yield results in PSI or kpa.

 

[PeeluckyDuckee]

Clogged cat wouldn't allow enough air to pass through which would cause the car to stall out/run rough. A coworker had a cat "melt" in his Saturn and it had some odd stalling issues. Its a simple physical inspection for that one..

I don't quite understand your bit about the "pressure check" for the cylinders. A compression test would yield results in PSI or kpa.

My bad, compression test, all other cylinders were 180ish, while cyclinder 3 is 130. At idle the car's RPM drops to near zero and the car feels like it would stall but it doesn't, every time.

 

[NutBucket]

That's not a good sign. Maybe the JDM motor route isn't so bad after all

 

[PeeluckyDuckee]

I recall the previous mechanic saying it threw a generic 1399 code, I did some googling and found out it relates to the TPS sensor as a possible cause of its hesitation, loss of power, and misfiring at low RPMs.

At cold start, the initlal drive would seem normal until about a minute later when everything comes back and the check engine light comes back on.

 

[PeeluckyDuckee]

Things known thus far:
- 02 sensor readings come back normal
- cat temperature readings are normal
- still misfires after spark plug and wires changed
- p1399 TPS error code still exists after plug and wire changes
- compression test indicates cyclinder 3 is lower at 130 vs 180 for others
- valves are noisy (as per the mechanic, myself I can't hear it)

What I plan to do is take the vehicle back to my usual mechanic who changed my timing belt a few weeks ago and have him double check his work (if timing belt is not centred TDC is that a cause for concern?), change out the TPS sensor (it's a relatively inexpensive job I'm told), adjust the valves (never adjusted since I got the car and it's at 225,000KM now), take out the cat and test for back pressure, and see if any more recurring/new codes comes up.

I want to approach this from a cost perspective, from lowest to highest. This has been a nightmare for me, for someone who knows nothing about cars, relying on the expertise of the mechanics yet they haven't been able to narrow down or resolve the issues surrounding my car. Very frustrating to say the least.

Any other helpful comments/suggestions are much appreciated!

 

[phucheneh]

There's a lot to reply to here...I'm gonna start at the top.

First, maybe make a recording of the car running. Spoken or written descriptions, especially by people who don't either do this for a living or as a major hobby, can often be misleading and hard to diagnose by. This is not any kind of insult- just pointing out that it's pretty important with drivability stuff to...be able to drive the car. So give us the best representation you can.

It sounds like you're describing a heavily misfiring engine. This will sometimes smooth out at high RPM, but it also may simply continue to compound itself until the engine resists even increasing RPM anymore.

What happens under steady acceleration while driving? Are you limited to a certain RPM or speed? How about when you rev the engine in neutral? Less labored? Does it rev higher?

As far as the MAP, it is very unlikely to be the main issue (or an issue at all). For it to cause damage, you generally need either an open or shorted circuit/sensor, which can cause the car to run either extremely rich (the unburned fuel is what raises converter temps and causes the catalyst to melt) or extremely lean (this causes preignition/detonation/spark knock). Generally, this will set a diagnostic code.

Now, a case in which the MAP reads a normal 'in range' pressure reading, but one that is not correct, can cause issues without setting a MAP DTC. The engine will run rich or lean, but to a much lesser degree, and eventually set a fuel trim code (probably).

More in a moment...

 

[phucheneh]

The 5 codes they pulled indicate all 4 cyclinders are misfiring and too rich of a fuel mixture. Mechanic is not exactly sure if the catalytic convertor and both oxygen sensors are a problem. We're changing all the spark plugs and wires first to see what happens.

The mechanic took out the plugs and advised they're all bad. The wires were changed at 47000km, now the vehicle is at 225000km so we're getting the wires done as well. The distributor cap and rotor were changed mid last year. The clutch was changed not too long ago, so it's not the clutch slipping causing loss of power, I've dealt with worn out clutch and know how they feel when it is the clutch.

The guy quoted me parts plus $45 for the plugs and wires.
He also quoted me around $1000 if it comes to the oxygen sensors and catalytic convertor.

So you have: P0301, P0302, P0303, P0304, and....a fuel trim code. Multiple options for fuel trim DTC's. It would help to know the specific one. People often interpret these codes backwards. Someone telling you 'too rich' can be interpreted multiple ways:

The long term fuel trim has hit the upper limit. (a number over 100%; usually it sets the code after a 15-25% deviation. I don't remember if there's an OBD2 standard amount). This would mean the engine is actually running LEAN. The feedback from the O2's was continually informing the ECM of a lean condition. In response, it was altering the fueling strategy to richen it back up. The fuel trim is supposed to change during normal operation, but within a certain range. When it gets to a certain maximum, as mentioned, the ECM says 'fuck it, something's wrong, I'm not giving you any more extra fuel' and turns the CEL/MIL on.

Now, the opposite of that is that the O2 sensor signal is being interpreted as 'too much fuel,' and the the LTFT start to drop below 100%, again, eventually setting a code when a limit is reach and the ECM no longer wants to continue to lean out the fuel trim.

Now here's the kicker: A misfiring (misfire means proper combustion is not occurring) engine spits unburned oxygen AND unburned fuel into the exhaust. The O2 sensors monitor OXYGEN levels, not fuel. And there is only one sensor per bank of cylinders...so one misfiring cylinder, which dumps unburned fuel and oxygen into the exhaust, will actually indicate a lean condition to the computer (ECM), while harming the converter with the large quantity of hydrocarbons that it is not designed to deal with.

And now another problem- you must define 'bad spark plugs.' I interpret a 'bad plus' as one that is physically damaged. This is usually a result of detonation inside the cylinder. A fouled plug, however, indicates something completely different. Fouled with gas usually means there is no spark occuring. Fouled with oil means...well, there's oil in the cylinder. This can come from a few different places.

The absolutely worst oxygen sensor in the world will not cause an engine to run terrible. Worst case, it will slightly over- or under-fuel, possibly to the point of setting a fuel trim code. The way your car has been running (and having DTC's), your oxygen sensor is being ignored by the engine computer. The engine is simply running in 'open loop,' meaning it is not taking O2 feedback into account. If everything else is working properly, open loop simply means worse gas mileage due to slightly less efficient combustion. It does not cause massive running problems.

And yes, and engine can run with a relatively 'stopped up' converter. It does not cause misfiring. It is more likely to cause labored (but somewhat smooth) engine operation, along with poor gas mileage and excessive oil consumption (which exacerbates the converter issue).

 

[phucheneh]

The plugs he pulled were all in very bad shaped, so those and the plug wires have all been replaced, but that did not solve the problem of lack of and irratic power up to 3k and total loss of power after 3k. Applying gas at whatever throttle position it hits a ceiling at 3.5k and would not go higher in rpm.

The engine has been having ongoing issues of running rich, and I was told because of that it may have clogged up the catalytic convertor and messed up the o2 sensors. The o2 sensors regulate how much air/fuel mixture the vehicle needs? When it's clogged the system goes into "safe mode" to prevent damage?

I just hope it has nothing to do with the manual transmission itself.

Left it with ZR Auto in Calgary for further diagnosis, as my usual mechanic cannot seem to resolve the issue. The spark plug and wires needed changing anyhow, so it's not all time wasted. But this problem is frustrating to say the least.

Okay, get a new mechanic. This guy does not properly grasp engine performance issues.

First, he should know the difference between old, worn plugs, and plugs that are damaged. Damaged plugs are like that for a reason...the plugs themselves are not committing seppuku.

Second, I'm guessing your understand of O2 function is from said mechanic. O2 sensors don't regulate shit- they merely provide feedback to the engine computer. And you only have one O2 for that. The other does nothing but monitor the operation of the catalytic converter.

O2's do not really 'clog'. They can become fouled up with various crap, which decreases their sensitivity. This will result in inaccurate feedback, and yes, if it gets bad enough, the ECM will start to ignore the O2 signal. This is open loop. It does not hurt your car to run in open loop- in fact, properly running cars do it every time they are started cold.

Open loop means the metering of fuel is primarily by-

A mass airflow sensor, which reads the quantity of air flowing into the engine. It is placed between the throttle body and air filter. Not all engines have one, especially older EFI cars. I want to say that the Honda 4cyl in your car does not have one.

MAP then becomes the next most important for purpose of measuring airflow. It simply senses pressure inside the intake manifold. But it cannot be used as independently as a MAF. Calculations for the amount of air flowing into the engine are made using this and other sensor data.

Like the IAT (intake air temperature), ECT (engine coolant temperature), and TPS (throttle position sensor).

There is a lot of math going on, and the ECM (in open loop) is simply fueling based on preprogrammed logic regarding the amount of air flowing into the engine. Plus engine RPM, calculated load...it's somewhat complex stuff. But basic troubleshooting, which it sounds like is all you need...really not that hard.

edit: am I done yet? Ballsacks. I wish I wasn't a perfectionist and could just throw some random guess out there.

 

[phucheneh]

TPS reads fine. Pressure check on cyclinders shows 35% on cyclinder 3, 15-20% on other cyclinders. Blue smoke coming from exhaust. Mechanic is going to check the valves and see what's going on there.

A5, if there are 02 and catalytic convertor issues, would it show up in the CEL code pulls?

If he's using percentages, this is a leakdown test. Your engine mildly worn the hell out, and the third cylinder has a major problem.

Bad cats don't cause codes, unless the parameters are met to set a catalyst efficient code.

Random guess on diagnosis- engine was running like shit. Possibly having random misfires on all cylinders due to a worn out distributor cap or something similarly simple. Excess fuel caused the 'honeycomb' of catalyst material inside the converter to begin to melt. Excessive exhaust backpressure caused a blown headgasket.