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Discussion Starter #1
Hello,
after restoring the engine on my 89 302 bronco (first post here) I am now facing and engine light.
The engine light shows after running about 15m when I push a little on the engine. There no visible side-effects, the car seems to run normal.

I read about the code (EGR circuit failure), but before I start spamming with questions, shooting into all directions & buying new parts - and to properly request your advice and learn from it :), I did some homework. here's what I have done so far:

So in the KOEO I read code 84 (followed by pause, 1, then 41 and 33)
In KOER I read 41 then 33.
I've installed a vacuum gauge - videos bellow - and I seem to see a normal 20 on idle, not dropping too much when I rev;
When I run it, I goes below 5 when I really accelerate (not sure this is normal). I haven't seen much difference before and after the engine light goes on.
One thing to note is the car seems to be (still) heating a bit - mostly if I push it in highway for long - I replaced water pump, new fan clutch. Also attached an image just to understand if this is normal or not. Photo also below.

Any advice for next steps?

vacuum accelerating running

vacuum reving parked

temperature 20m run pushing it a bit
165208
 

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My bronco runs same temp although mine is a 95 351 new rad new water pump hoses and thermostat. That temp doesn't worry me that much although I watch it like a hawk.

Egr failure could cause higher combustion temps.

Sent from my SM-N960U using Tapatalk
 

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Yo Ruddy,
"When engine is rapidly accelerated (dotted needle), needle will drop to a low (not to zero) reading. When throttle is suddenly released, the needle will snap back up to a higher than normal figure."

Ford's PCED/EVTM pin-point testing revolves around the ford break out box (BOB) settings, such as;
"...DTC 84: CHECK RESISTANCE OF EVR SOLENOID indicates a failure in the EGR Vacuum Regulator (EVR) solenoid circuit/Damaged EVR solenoid; Open harness, Shorted harness, Damaged Powertrain Control Module (PCM). ;
Install breakout box, leave PCM disconnected. Measure resistance between Test Pin 33 at the breakout box and EVR circuit at the EVR solenoid vehicle harness connector. Is resistance less than 5.0 ohms?
No - SERVICE open circuit. REMOVE breakout box. RECONNECT all components.RERUN Quick Test.
Yes - GO to DN13.
DN13 CHECK EVR CIRCUIT FOR SHORT TO POWER OR GROUND. Key off. EVR solenoid disconnected.
Breakout box installed, PCM disconnected. Measure resistance between Test Pin 33 and Test Pins 37 and 57 at the breakout box. Measure resistance between Test Pin 33 and Test Pin 40, 46 and 60 at the breakout box.
Is each resistance greater than 10,000 ohms?
No - SERVICE short circuit. REMOVE breakout box. RECONNECT all components. RERUN Quick Test. If DTC is repeated, REPLACE EVR solenoid.
Yes -REPLACE PCM. REMOVE breakout box. RECONNECT EVR solenoid. RERUN Quick Test.."
Source: by Ford via miesk5 at FSB
as I mentioned in another thread here; In place of the breakout box, go to the EEC pin instead; for instance - Measure resistance between Test Pin 33 and Test Pin 40, 46 and 60 at the breakout box. Substiture EEC for :breakout box"
EEC IV Connector Pin Diagram

by Ryan M (Fireguy50)

EEC IV Connector Pin LEGEND, Bronco & Ford Truck & Van: 4.9, 460, 5.0, 5.8;
Source: by Ryan M (Fireguy50) at Ford Fuel Injection
****

In front of the TAB/ TAD Solenoids is the EGR Vacuum Regulator (EVR); also called EGR Vacuum Solenoid
It is a "normally closed" solenoid, which means that when it is de-energized, the position of the disc allows for maximum venting to the atmosphere (resulting in negligible vacuum flow to the EGR valve)
EVR LOCATION PIC

by SeattleFSB (Seattle FSB

The most common problem with the EVR is for its vacuum line to crack. Simply slip rubber vacuum line over the break.
Static Resistance Values:
TAB/TAD: 50-100 ohms
EVR: 30-70 ohms
Injector: 11-18 ohms
Coil: 0.3-1.0 ohms between primary terminals
Coil: 8-11.5 K ohms between output & either primary
Coil: >12K ohms beteen any terminal & E-core
..."
○▪○

To help testing on all codes; use these by Ryan

EEC IV Connector Pin Depiction Pic by Ryan M
& EEC IV PIN LEGEND @ Ford Fuel Injection
°°

33 KOER & CM EGR valve opening not detected.
KOEO & KOER EVP circuit above the closed limit of 0.67 volts.
DTC 33 is triggered when the EVP sensor is not closing;
Testing & Operation; "...The EGR Valve Position (EVP) sensor monitors the position of the EGR valve pintle. The EVP sensor converts the mechanical movement of the pintle into an electrical voltage signal which is relayed to the PCM. The EVP sensor is a linear potentiometer in which resistance varies with the EGR valve pintle movement.
Voltage is fed to the EVP by the signal return circuit. As the EGR is opened the EVP directs more voltage to the EEC and less down the voltage reference circuit. The EVP sensor provides the PCM with information on EGR flow and EGR system failures. The EVP should read between 0.24 and 0.67 volts at idle with a closed EGR valve..."
EGR Valve Position (EVP) Sensor Testing & Replacement by Seattle FSB
EGR Valve Test; "...these procedures are based around a typical OBD II Ford system but the overall principals should hold on most vehicle lines. Engine running, so be careful and use proper care! Find the EGR valve and disconnect the vacuum line going to the top of the valve. There should be no vacuum there at this time. If there is then check for proper EVR (EGR vacuum regulator) operation and vacuum line routing. Repair and continue testing. Hook up your hand vacuum pump to the EGR valve and slowly apply a vacuum. If the EGR valve is functioning then the engine should begin to run poorly and stumble. If you apply full vacuum and notice no RPM change or can’t pull a vacuum at all, then check for a faulty diaphragm in the valve or a restriction of the EGR tube, exhaust or intake manifold EGR ports. I have run across many concerns where the EGR passages in the intake manifolds become plugged with carbon and prevent EGR flow, so try to keep this in mind during testing. Repair and continue testing..."

Damaged EVP sensor pull vac hose off @ EVP - I pull em off and use the straw sucking test; one finger over one end; and... ya get the idea?
•Corroded or dirty connector
•Damaged EGR valve
•Faulty Vacuum system
•Broken wire in harness
•Grounded harness
•Damaged EEC IV

Try my vac leak test @ https://www.fullsizebronco.com/forum/21-noobie-bronco-tech-questions-flame-free-zone/206824-help-dtc-codes-idle.html?highlight=Vacuum+Leak+Test;+idling
post #11

34 CM EVP circuit above the closed limit of 0.67 volts.
DTC 34 - EGR voltage above closed limit
...in Key On Engine Off (KOEO) or Engine Running (KOER) Self-Tests; indicates that the EGR valve may not be fully seated in the closed position; or the EVP sensor voltage is greater than the closed limit voltage of 0.67 volt. Because of the preload on the installed EVP sensor, it is very difficult to determine whether the EGR valve is seated or the EVP sensor is in contact with the EGR valve stem.
•Faulty Vacuum system - See my Vacuum leak test in post #11 incl some jowens HVAC Control Panel pics/info @ Help with dtc codes and idle
One way to do a quick check is to grab a vacuum gauge. Some parts stores will loan you a gauge with refundable deposit.
The vacuum gauge should read between 15 and 22 in-Hg depending upon the engine condition and the altitude at which the test is performed. SUBTRACT ONE INCH FROM THE SPECIFIED READING FOR EVERY 1,000 FEET OF ELEVATION ABOVE SEA LEVEL.
The reading should be quite steady. .
When engine is rapidly accelerated (dotted needle), needle will drop to a low (not to zero) reading. When throttle is suddenly released, the needle will snap back up to a higher than normal figure.
When vacuum leaks are indicated, search out and correct the condition. Excess air leaking into the system will upset the fuel mixture and cause conditions such as rough idle, missing on acceleration, or burned valves. If the leak exists in an accessory unit, such as the power brake, the unit will not function correctly. Or Air Conditioning when in MAX mode may switch to Defrost.
•Damaged EVP sensor
•Corroded or dirty connector
•Damaged EGR valve
•Broken wire in harness
•Grounded harness
•Damaged EEC IV
- Failed sensor, carbon between EGR pintle valve and seat holding the valve off its seat.
Remove the EGR valve and clean it with carbon remover and a brush if necessary
Prior to re-installing see if you can blow air through the flange side of the EGR by mouth.

EGR Valve Position (EVP) Sensor Testing @ Ford Fuel Injection » EGR Valve Position sensor (EVP)
by Ryan M

31 CM EVP circuit has intermittently failed below minimum voltage of 0.24 volts.
EVP - EVP signal is/was out of range - EVP
EVR - (O, R, M) EVP signal is/was low - EVR
URL="http://web.archive.org/web/20110704111747/http://www.tomco-inc.com/Tech_Tips/ttt32.pdf"]EVR Testing, Ford; "....check the filter on the solenoid (Fig. 4, EVR filter shown). If this is clogged it will inhibit the venting of the solenoid; "...EVR Solenoids should be 20 to 70 ohms (100 to 135 ohms for 7.5L engines). A functional test can be performed on most applications by using a Scan Tool. Enter the Output State check and cycle the accelerator pedal. This will turn all the solenoids on and off. Using a DVOM monitor the voltage at the EGR solenoid(s). They should toggle from a high voltage to a low voltage. Typically this is stated in the manuals and scan tools as above 10.5 volts to below 2 volts. If the voltage does not toggle make sure that you have system voltage on the power side of the connector. If system voltage is present and the voltage does not cycle to the low side check the connector and wiring to the PCM. If the wiring and connector are okay the problem may be in the pin at the PCM or the driver in the computer itself..." READ MUCH MORE by Tomco.[/URL]
¤
DTC 41 CM HEGO sensor circuit indicates system lean (right side).
KOER No HEGO switching detected always lean (right side).
DTC 41, 42, 85 OR THREE DIGIT CODES 171, 172, 173, 179, 181, 182, 183 & 565 are received , Check for proper HEGO Ground; in Catalytic Converter Diagnosis TSB 91-12-11 for 86-91 Bronco, F Series, & Econoline
by Ford via Stephen
O2 Sensor Ground Location in an 89: "...it's not near the sensor. It sticks out of the loom of the wiring harness that traverses the back of the engine. You can find it by putting your hand around the loom and following it across the back of the engine. You can also use a mirror. I had to lay on top of the core support to reach mine. Trust me it's there. It serves only as a PCM ground for the O2 sensor. It isnt hooked to the sensor, it comes out of the PCM..."
Source: by j. r. Nice (J. R. N)



DTC 33
 

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Discussion Starter #4
@cheapthrill - thanks for the temp tip - bit more comfortable knowing it's "normal", but would prefer to keep in the 'R' letter. maybe all problems are related as you say!

@miesk5 thank you so much. Lots of digging now on my side. Don't have a breakout box, so I'll need to convert some of the instructions to test straight from the components. Also need a vacuum tester to apply vacuum.
Looks like something not flying somewhere between the EGR - EVR. So I'll start there by testing those two and the vacuum hose between them.
I'll post soon, Thanks
 

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Yo Ruddy,
YW!
I forgot to mention, in place of the break-out box, go to the EEC IV harness connector pin instead; for instance - Measure resistance between Test Pin 33 and Test Pin 40, 46 and 60 at the breakout box. Substitute EEC IV pin number for "break out box".
 

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Discussion Starter #6
thanks @miesk5
found this to guide me. Is it accurate? it's from a Mustang forum here, but it looks quite the same
165309
 

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Discussion Starter #8
It seems I found the culprit. The EVP resistance is not within 30-70ohms range. It's about 0.1 ohm. Maybe that's why the pcm is complaining. It also looks dusty and rusty.
Will replace and update soon.

I also tested the egr electronically and mechanically (looks like it was stuck for a long time so there a pop sound first time I applied vacuum to it, but after it moves up and down ok), the wires from pcm harness to components, and the vacuum tubes between egr and evp. All good.

Images from the evp bellow
 

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Yo ruddy,
WTG!
ONE LAST CHECK to POSSIBLY save $, onspect EVP connector for corrosion, loose, bent or damaged terminals.
 

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Discussion Starter #10
Actually the evp harness is broken, so I'll order one new together with the new evp :) but if given there is no resistance betwee Evp terminals, cleaning those would only make it worse I guess :p.

Thank you for all the help @miesk5 , I'll post soon when I replace it.

(Now I'm also replacing a noisy speedometer cable - found some weird VDO box near the gearbox - I'll create a separate post on that)
 
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