[UGARAM]

So my 88 318 177000 R/C puts these codes out.
Any ideas on what this could mean or how to fix it? When the check engine light comes on, it bothers me. Also, I cannot get any power when climbing hill, which I do in North GA. I don't mind the gas money to put into the beast, but I want more umph up deez hills.
Thanks,
UGARAM

 

[TaZMaNiaK]

Don't worry about code 12, it just means the battery was disconnected at some point in the last 100 key-ons.

CODE 13 (CEL ON)--MAP Sensor Pneumatic Circuit problem --No variation in MAP sensor signal is detected during engine running. No difference is recognized between engine run MAP reading and the stored barometric pressure reading.

Check to make sure the MAP sensor vacuum hose isn't cracked or disconnected, then pull the hose off with the engine running and feel for vacuum. If there is none, the port in the throttle body is clogged. If you have vacuum, replace the MAP sensor. It is on the passenger side of the throttle body with a 3 pin connector and a short hose between it and the TB. This will definitely cause a lack of power, because it tells the computer what kind of load the engine is under.

Matt {peace}

 

[MudFlap]

On my 88 the MAP sensor is located on the firewall to the right of the engine, so you might look there, too.

 

[UGARAM]

Anyones,
Should I just change out my Map Sensor. What would that do? Auto parts guy says is easy. Thanks for that, but will it solve my code thirteen problem. Let's hope so. Also, in changing rear brake pads what tools do I need? Where should I jack my Beast Charger - location undercarriage?

On my 88 the MAP sensor is located on the firewall to the right of the engine, so you might look there, too.

 

[Guest]

This thread had me thinking. I checked my Haynes book.

Its possible that the problem may not be caused by the MAP sensor. If code 12 and 13 is being shown it may be a fluctation in voltage output. SMEC/PCM receives information from MAP as a voltage signal. MAP failure should come up as a code 13 or 14 and trigger 'Check Engine' light. Code 12 should not. Check your alternator, battery and regulator as a suggestion.

Hey TaZMaNiak question? My '91 acts up when it is hot and humid weather. I believe the fuel mixture becomes so lean that it down shifts, stalls and back fires. You mentioned a 'stored barometric pressure reading'. Can that be adjusted or corrected for extreme weather?

 

[TaZMaNiaK]

This thread had me thinking. I checked my Haynes book.

Its possible that the problem may not be caused by the MAP sensor. If code 12 and 13 is being shown it may be a fluctation in voltage output. SMEC/PCM receives information from MAP as a voltage signal. MAP failure should come up as a code 13 or 14 and trigger 'Check Engine' light. Code 12 should not. Check your alternator, battery and regulator as a suggestion.

Hey TaZMaNiak question? My '91 acts up when it is hot and humid weather. I believe the fuel mixture becomes so lean that it down shifts, stalls and back fires. You mentioned a 'stored barometric pressure reading'. Can that be adjusted or corrected for extreme weather?

Code 12 is nothing.. It just means the battery has been disconnected recently. He said the check engine light was on also.. Code 13 and 14 are both MAP codes, 13 means the computer is getting an unchanging output from the sensor (meaning the problem is in the vacuum side), and 14 means it isn't getting an output at all (electrical side). The "stored pressure reading" is the "limp-home" default reading that the computer uses just to make the engine run when there's no "real-time" sensor input.. It can't be changed because it's only used during a malfunction of the sensor.

As far as your problem goes, I'm not real sure... I'm still learning the whole computer-engine thing.. I've always had carbed engines.. If it's an environmentally-related problem, first thing I would check would be the air temp sensor.. Are you getting codes? Also, does it downshift because it stalls? There's no electronic or vacuum control on Torqueflites, so any shifting is through engine speed and throttle position.

UGARAM.. Did you check to see if you had vacuum to the sensor? If you don't, changing it won't help.... The MAP sensor tells the computer to adjust the fuel delivery and timing based on load on the engine. The computer isn't getting a reading off the MAP, so it doesn't know whether you are climbing a hill or sitting still. Correct the problem (clogged/broken hose or the sensor itself) and you should gain a considerable amonut of power.

Matt {peace}

 

[big10]

This thread had me thinking. I checked my Haynes book.

Its possible that the problem may not be caused by the MAP sensor. If code 12 and 13 is being shown it may be a fluctation in voltage output. SMEC/PCM receives information from MAP as a voltage signal. MAP failure should come up as a code 13 or 14 and trigger 'Check Engine' light. Code 12 should not. Check your alternator, battery and regulator as a suggestion.

Hey TaZMaNiak question? My '91 acts up when it is hot and humid weather. I believe the fuel mixture becomes so lean that it down shifts, stalls and back fires. You mentioned a 'stored barometric pressure reading'. Can that be adjusted or corrected for extreme weather?

A bad MAP sensor or one that isn't getting enough vacuum will result in a stalled engine when the AC compressor cycles and the computer doesn't recognize the additional load. But this should happen no matter what the air temperature is if you have the AC on or heater in defrost. It's not a bad idea to pull the MAP vacuum hose off and check for vacuum and also spray some carb and throttle body cleaner into the hose. This will set code 13 so remember to clear the codes afterwards.

 

[UGARAM]

Alright,
Found the Map sensor and connecting hose. Pulled off hose, engine started to smell like gas, put thumb on hose, there was pressure and slight crack where attaches to nipple of sensor. Ready to replace hose but no idea where it goes in to under air filter which is in the way. Will put on new wires and distributor cap tommorrow, but similary they are partially blocked by air filter and such. Any ideas?
UGARAM

This thread had me thinking. I checked my Haynes book.

Its possible that the problem may not be caused by the MAP sensor. If code 12 and 13 is being shown it may be a fluctation in voltage output. SMEC/PCM receives information from MAP as a voltage signal. MAP failure should come up as a code 13 or 14 and trigger 'Check Engine' light. Code 12 should not. Check your alternator, battery and regulator as a suggestion.

Hey TaZMaNiak question? My '91 acts up when it is hot and humid weather. I believe the fuel mixture becomes so lean that it down shifts, stalls and back fires. You mentioned a 'stored barometric pressure reading'. Can that be adjusted or corrected for extreme weather?

A bad MAP sensor or one that isn't getting enough vacuum will result in a stalled engine when the AC compressor cycles and the computer doesn't recognize the additional load. But this should happen no matter what the air temperature is if you have the AC on or heater in defrost. It's not a bad idea to pull the MAP vacuum hose off and check for vacuum and also spray some carb and throttle body cleaner into the hose. This will set code 13 so remember to clear the codes afterwards.

 

[UGARAM]

Alright,
Found the Map sensor and connecting hose, which had small crack in it at nipple of sensor. Will attempt to connect hose tommorrow, along with distributor, but is quite difficult with air filter in the way. Any ideas on movement around or through filter? Also, where do I attach the MAP sensor hose under the air filter. All quite difficult.
UGARAM

This thread had me thinking. I checked my Haynes book.

Its possible that the problem may not be caused by the MAP sensor. If code 12 and 13 is being shown it may be a fluctation in voltage output. SMEC/PCM receives information from MAP as a voltage signal. MAP failure should come up as a code 13 or 14 and trigger 'Check Engine' light. Code 12 should not. Check your alternator, battery and regulator as a suggestion.

Hey TaZMaNiak question? My '91 acts up when it is hot and humid weather. I believe the fuel mixture becomes so lean that it down shifts, stalls and back fires. You mentioned a 'stored barometric pressure reading'. Can that be adjusted or corrected for extreme weather?

A bad MAP sensor or one that isn't getting enough vacuum will result in a stalled engine when the AC compressor cycles and the computer doesn't recognize the additional load. But this should happen no matter what the air temperature is if you have the AC on or heater in defrost. It's not a bad idea to pull the MAP vacuum hose off and check for vacuum and also spray some carb and throttle body cleaner into the hose. This will set code 13 so remember to clear the codes afterwards.

 

[TaZMaNiaK]

Remove the air cleaner.....
Pull the crankcase breather out of the valve cover, and pull the intake hose off the ram air inlet. Lift the cleaner housing up and disconnect the small hose from underneath (don't forget to put it back on when you're done tho)
The MAP goes to the first (left) nipple on the front of the throttle body. Also, if you say you're getting vacuum at the MAP end of the hose, the problem is in the sensor itself. Replace it and the hose at this point.

Matt {peace}

 

[UGARAM]

TAZ,
So, say I replace the Map Sensor and the hose is in ok condition, can I put some carb cleaner directly into that hose from the MAP Sensor?
Also, if I replace the map sensor and the code thirteen still comes up, what does that mean?
All thanks,
UGARAM

Remove the air cleaner.....
Pull the crankcase breather out of the valve cover, and pull the intake hose off the ram air inlet. Lift the cleaner housing up and disconnect the small hose from underneath (don't forget to put it back on when you're done tho)
The MAP goes to the first (left) nipple on the front of the throttle body. Also, if you say you're getting vacuum at the MAP end of the hose, the problem is in the sensor itself. Replace it and the hose at this point.

Matt {peace}

 

[CLRracer]

if u replace the map sensor, disconnect the battery to reset the codes. if the code still shows up, u have not solved the problem.

Duane

 

[TaZMaNiaK]

Yeah, you have to clear the codes after you fix the problem. Carb cleaner is fine down that hose (actually it's good for it).. If you still get code 13 after resetting the computer and replacing the hose and sensor (and you have good vacuum att he hose), I don't know what to tell you.. It can't be a broken wire or bad connection because that would set code 14. 13 is only for the vacuum side of that sensor. Let us know..

Matt {peace}

 

[Chump]

Yeah, you have to clear the codes after you fix the problem. Carb cleaner is fine down that hose (actually it's good for it).. If you still get code 13 after resetting the computer and replacing the hose and sensor (and you have good vacuum att he hose), I don't know what to tell you.. It can't be a broken wire or bad connection because that would set code 14. 13 is only for the vacuum side of that sensor. Let us know..

Matt {peace}

Taz...don't take the codes to heart. Just because it says a vacuum problem does not mean that it is a true vacuum problem. Here's the scoop..the SMEC only sees electrical signals, it does not have any way to actually monitor vacuum. So what the computer is telling you is that the symptoms appear to be vacuum related by the way it's reading the electrical feedback from the sensor. MAP sensor signals have also been known to change from bad vacuum hoses or contaminated hoses. Always replace the hose and I dont recommend using any sort of cleaner in the hose as this can contaminate the MAP. During periods of acceleration and deceleration your vacuum continuously changes and this can actually force dirt and liquids back into the MAP when the throttle closes abruptly and vacuum changes. There are a number of Service Bulletins out about some of these types of problems and one which is really bizarre is when moisture gets trapped in the vacuum hose/MAP and freezes during cold weather...this can block the hose or freeze the MAP and give no starts, hard starts and poor performance until it warms up. Computer codes and CEL lights are only designed to get you somewhere in the area of the fail, after that you have to examine the entire circuit from sensor to SMEC which includes high resistence in connectors, this can skew the signal to the SMEC also.
Try replacing the hose and check the vacuum reading at the source on the manifold. After you replace the hose clear the codes and see if 13 comes back. You could change the MAP also but they run about $60. Good luck.

 

[TaZMaNiaK]

{blush} {blush} See? I told you I was learning... Learn something new every day... But carb cleaner evaporates so fast, I didn't think it would be a problem to spray some in....

Matt {peace}

 

[big10]

{blush} {blush} See? I told you I was learning... Learn something new every day... But carb cleaner evaporates so fast, I didn't think it would be a problem to spray some in....

Matt {peace}

It would seem very unlikely since it evaporates so fast and is burned and out the tailpipe by the time you put the hose back on

 

[Chump]

Remember..."LAW of CONSERVATION of MATTER-states that matter cannot be created nor destroyed, but only changed in form."? You are right about evaporation but remnants of the chemical still remain. There is no real need to put any liquid cleaner in the port..just take it apart and clean it? Why take a chance? Also if sprayed into the hose, the rubber may deteriorate. If moisture can cause a problem than so can a chemical? Was just a small point to bring up for the best reliability. Peace Brothers!

 

[UGARAM]

Dudes,
Tanks for the info, although it has lead me back to a great mech. So, I replaced the Map Sensor. Upon ignition, the Code 13 would immediatly come up and then the beast would shiver and die. IF I put it in to gear instantaneous death. At least I know that the Map is good to go, eh.
Any news will assist, and I will do the same.
Thanks,
UGARAM

Remember..."LAW of CONSERVATION of MATTER-states that matter cannot be created nor destroyed, but only changed in form."? You are right about evaporation but remnants of the chemical still remain. There is no real need to put any liquid cleaner in the port..just take it apart and clean it? Why take a chance? Also if sprayed into the hose, the rubber may deteriorate. If moisture can cause a problem than so can a chemical? Was just a small point to bring up for the best reliability. Peace Brothers!

 

[Guest]

Hey TaZMaNiak question? My '91 acts up when it is hot and humid weather. I believe the fuel mixture becomes so lean that it down shifts, stalls and back fires. You mentioned a 'stored barometric pressure reading'. Can that be adjusted or corrected for extreme weather?

As far as your problem goes, I'm not real sure... I'm still learning the whole computer-engine thing.. I've always had carbed engines.. If it's an environmentally-related problem, first thing I would check would be the air temp sensor.. Are you getting codes? Also, does it downshift because it stalls? There's no electronic or vacuum control on Torqueflites, so any shifting is through engine speed and throttle position.

Matt {peace}

UGARAM--Some codes can only be reset by computer. So just re-hooking up the battery will not reset this code.
I have had my rig to alot of mechanics. The one I have now is pretty good. Where do you live?
The MAP has been replaced and the problem remains?
My theory on voltage fluctuations has not been ruled out? But vacuum leaks have not been ruled out either right?

On my rig's problem--It has been long standing. I notice changes as soon as the atmospheric humidity rises above 50%. I will be driving along and the trany will suddenly downshift. With increased load, like up a hill, it will take longer to up shift back. It continues to do this with increased downshift upshift frequency until it stalls (as heat increases). It is sometimes difficult to re-start. Then increases in stalling. I will give up and it will backfire after I shut it off. I'm sure the problem lies with the throttle kicker. I've had it replaced twice with no change. Rig runs sound in the winter and in low humidity weather. No problem when it rains. The codes are almost always the same 31-35-37. I have chalked it up to a design flaw. But I am open to trying anything to get around this.
I thought my tranny was vacuum 1 to 3 and electrical 3 to 4? That's why it only downshifts to 3rd and not lower, then back to 4th when its acting up?