MAP Sensor

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Deep

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Been trouble shooting my emissions system....following componets have been replaced:

1. Throttle Position Sensor

2. Oxygen Sensor

3. Idle Control Valve

4. EGR Valve

5. EGR Position Sensor

6. Distributor Cap and Rotor

7. Spark Plugs

8. Air cleaner

9. PCV Valve

10. MAP Sensor

11. Fuel filter

12. Divertor Valve

13. All vacuum lines have been replaced and rechecked for leaks...NONE

14. Engine timing checked and within specs.

Tonight while working on my bronco, I unplugged the MAP Sensor and started mt truck; for the first time in a month, it idled without surging and sounded top notch. When I plugged the MAP Sensor back in and started the engine again, the engine returned to surging and acting up.........could I have possibley received a bad MAP Sensor???? I have disconnected the battery after replacing componets, thus allowing the system to reset. What am I missing....what direction do you suggest????? Ready to have my bronco back on the road, I restored it and love it, but I am completely frustrated.

Would appreciate any help or suggestions.

Thanks.

 

Seabronc

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I guess that Deep stands for Deep Pockets ;) /emoticons/[email protected] 2x" width="20" height="20" /> . Sure you could have gotten a bad part, take it back to the parts place you got it from. You sure spent a lot of money looking for your problem.

Good luck,

:)>-

 

miesk5

96 Bronco 5.0
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YO!

Agree with Seabronc on this... Try to buy electrical/emission parts from NAPA or Advance Auto; many Wells parts have the Ford pn stamped or etched into them.

The MAP sensor is a tricky device, itdepends on construction quality since vacuum and voltage are measured; here is a test;

Testing w/DVOM & Overview :...The most accurate way to test this sensor is to measure output using a DVOM (digital volt-ohm meter). In this case the meter must have a frequency measuring ability..."

Source: by kemparts.com

Also, ck timing, throttle body (carbon build-up (etc.)) & tb ports where the IAC (your #3. Idle Control Valve) connects...carbon/sludge builds up there too.

btw, in one of your older posts, you mentioned that you did or were about to do a DTC scan; did you do it yet? if not do it now, both KOEO & KOER....

Self Test for Diagnostic Trouble Codes (DTCs) by BroncoJoe

 
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Deep

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YO!Agree with Seabronc on this... Try to buy electrical/emission parts from NAPA or Advance Auto; many Wells parts have the Ford pn stamped or etched into them.

The MAP sensor is a tricky device, itdepends on construction quality since vacuum and voltage are measured; here is a test;

Testing w/DVOM & Overview :...The most accurate way to test this sensor is to measure output using a DVOM (digital volt-ohm meter). In this case the meter must have a frequency measuring ability..."

Source: by kemparts.com

Also, ck timing, throttle body (carbon build-up (etc.)) & tb ports where the IAC (your #3. Idle Control Valve) connects...carbon/sludge builds up there too.

btw, in one of your older posts, you mentioned that you did or were about to do a DTC scan; did you do it yet? if not do it now, both KOEO & KOER....

Self Test for Diagnostic Trouble Codes (DTCs) by BroncoJoe

A lot of sound advice, thank you. I tested my map sensor with a multimeter and all numbers were "textbook". Timing is good and I cleaned the throttle body with a good carb cleaner to the point it is spotless. Ports for the IAC and EGR valve have received special attention and are extra clean. I did in fact perform the scan and I got a code 34 EGR Valve Position (EVP). I replaced the EVP sensor that mounts on top of the EGR valve initially, so I suppose there is a possibility that the sensor is bad........today I unplugged my map sensor and drove my bronco for over 50 miles without any problems. When I plugged the map sensor back in the idle problems and surging resumed to how it was before I unplugged. I did notice with the map sensor unplugged that the idle was higher....I am definitely open to thoughts and suggestions...............

 

miesk5

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yo;

34 EGR Valve Position sensor signal voltage out of range. Faulty Vacuum system, Connection at the EVP sensor is bad, the EGR sensor is faulty, or the EGR valve is not seating properly (sticking); clogged exhaust or cat. converter; Test EGR valve

MAP sensor test- did you use a vacuum pump to go thru the full range?

Read this;\

"...MAP SENSOR DRIVABILITY SYMPTOMS

Anything that interferes with the MAP sensor's ability to monitor the pressure differential may upset the fuel mixture and ignition timing. This includes a problem with the MAP sensor itself, grounds or opens in the sensor wiring circuit, and/or vacuum leaks in the intake manifold (airflow sensor systems) or hose that connects the sensor to the engine.

Have seen a few intake man. leaks...

Typical driveability symptoms that may be MAP related include:

* Surging.

* Rough idle.

* A rich fuel condition, which may cause spark plug fouling.

* Detonation due to too much spark advance and a lean fuel ratio.

* Loss of power and/or fuel economy due to ******** timing and an excessively rich fuel ratio.

A vacuum leak will reduce intake vacuum and cause the MAP sensor to indicate a higher than normal load on the engine. The computer will try to compensate by richening the fuel mixture and retarding timing -- which hurts fuel economy, performance and emissions.

MAP SENSOR CHECKS

First, make sure engine manifold vacuum is within specifications at idle. If vacuum is unusually low, there may be a vacuum leak (leaky hose connection, intake manifold or throttle body gasket, power brake booster, etc.), an exhaust restriction (clogged converter), or an EGR leak (EGR valve not closing at idle). (CODE 34)

A low intake vacuum reading or excessive backpressure in the exhaust system can trick the MAP sensor into indicating there's a load on the engine. This may result in a rich fuel condition. (SURGING)

A restriction in the air intake (such as a plugged air filter), on the other hand, may produce higher than normal vacuum readings. This would result in a load low indication from the MAP sensor and possibly a lean fuel condition.

Next, check the sensor's vacuum hose for kinks or leaks. Then use a hand-held vacuum pump to check the sensor itself for leaks. The sensor should hold vacuum. Any leakage calls for replacement.

An outright failure of the MAP sensor, loss of the sensor signal due to a wiring problem, or a sensor signal that is outside the normal voltage or frequency range will usually set a diagnostic trouble code (DTC) and turn on the Check Engine light..."

by aa1car

--

so, let's look for a vacuum leak now.

the Code 34 can also be caused

a problem in the EGRC or EGRV vacuum solenoids (did you find a source for those?)

by EGR Vacuum Regulator (EVR)

& Differential Pressure Feedback (DPFE) but this is used only in 95 CALIF models and all 96's; so ignore that.

The systems with the PFE sensor were used as early as 1986 on some Tempo, Taurus, Bronco and Ranger models. The style with the DFPE sensor started in 1991 with the 4.6L Town Car and are still being used today on many Ford/Lincoln/ Mercury vehicles.

So look thru my bronco site for the testing of the EVR, EVP, etc.

Common to all is manifold vacuum.... test for vac leaks again... find a shop w/a "Smoke Machine"

or diy w/carb spray on a COLD ENGINE..do ALL hoses and fitting again as well as around intake manifold

buy a vac gauge.. best all-around low cost tool for a DIYer

 
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