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Codes 63, 98 and idle adjustment

12K views 28 replies 5 participants last post by  miesk5 
#1 ·
Okay I'm looking for a little confirmation on my situation.

I have a '88 302 that has been throwing KOER codes of 63 and 98.

I also had a stalling at idle issue.

While looking into my stalling issue I found my idle set screw broken off leaving the butterflies fully closed at idle. Well I removed the broken set screw and replaced it with a new one. I then set the idle to 700 rpm's with the IAC unplugged. After researching I now realize I should have been setting the idle around 400 rpm's - 600 rpm's. Well after setting the idle to 700 and plugging the IAC back up (and clearing the codes) I took it for a test drive. The truck was idling high (around 1000 - 1100 rpm's). So after about 30 miles I pulled over and re-adjusted the idle down. During the first 30 miles no CEL at all. So I drove another 10 miles or so with the adjusted idle and the CEL started to flash. It flashed for a bit then just stayed on. I continued home and checked the codes and codes 63 and 98 came up again.

So after researching I have came to the conclusion (If I am grasping this correctly!) that the idle setting plays a part in how the TP sensor works/reacts. Correct? Is this why I had no CEL while the idle was set higher?

And when I adjusted the idle lower the TP sensor then was out of range throwing the code 63 and consequently code 98.

Does this all seem reasonable? If so then all I should need to do is go and reset the idle to a max of 600 rpm's with the IAC unplugged and I should be good to go. Right? Please say yes!!;) LOL!

Anyways.............let me know if I am totally of base here of if this is correct.

Thanks!:beer
 
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#2 ·
Yes there is interaction between the idle stop screw and the TPS closed throttle signal value. If you have to turn the idle screw down so far the TPS is below 0.6 VDC then there is a problem. The typical cause of a high idle RPM is a vacuum leak. I think the vacuum leak induced high idle is your root issue here. Adjusting the throttle stop screw to a value below 0.6VDC is masking the true problem.
 
#3 ·
Thank you for the response.

I may not have been clear in my previous post. I had to replace my idle stop screw due to it being sheared off. So I had to set my reset my idle stop. And the first time I adjusted the idle I had it to high (1000 - 1100 rpm's). Then I adjusted it to low and the CEL came on. So now I need to re-adjust it to the normal range.

I will definitely look for any vacuum leaks as well. I did find the two vacuum lines going into the TB intake cracked at the ends. So I just cut them down to where there was no cracks and re-attached.

Thanks again!:beer
 
#4 · (Edited)
Did you check and adjust the TPS after installing the new idle set screw and setting the idle?

Gacknar said:
1. Start engine, and run it until it has reached operating temperature.

2. Unplug the IAC, if the truck dies when you unplug the IAC then turn the idle stop screw one turn, and try to start the truck. Continue doing this step until you get the truck to idle with the IAC unplugged.

3. Now with the truck idling with the IAC unplugged adjust the idle stop screw to where the truck is idling at 400-600 rpms. I personally set all mine to 600rpm.

4. Reconnect the IAC, the idle should bump up slightly.

5. Check the voltage on the TPS
http://fordfuelinjection.com/index.php?p=30
It should be between .90 and .99 volts. If it is not, wallow out the mounting screw holes so that you can turn it to where it reads between those two numbers.

6. If you had to adjust the TPS, then unplug your IAC again and make sure the idle is where you left it.

7. If it is then your golden, if not then repeat the steps until it is

Do you have an E4OD tranny?
Where those codes KOEO or CM?
 
#5 ·
Did you check and adjust the TPS after installing the new idle set screw and setting the idle?
I haven't yet. But I plan on it. I only had Sunday off and I spent that working on getting the idle screw and intake from the pick-n-pull. But that is my next step.



Do you have an E4OD tranny?
I think it is the stock tranny but I haven't really looked into it yet.


Where those codes KOEO or CM?
Key on/Engine off was code 63. Key on/Engine on was codes 63 and 98.
 
#6 ·
DTC 63 in KOEO Throttle Position Sensor (TPS) below minimum 0.6 volts. Suspect open TP sensor, or grounded, check harness
DTC 63 in KOER TPS ckt has intermittently failed below minimum 0.6 volts

DTC 98 in KOEO/ CM Electronic pressure control driver open in EEC (E4OD).
DTC 98 in KOER Vehicle did not pass Key On Engine Off (KOEO) test; Rerun KOEO and fix whatever you find there

Hard fault present; "...Failure Mode Effects Management (FMEM) FMEM is an alternate system strategy in the PCM designed to maintain vehicle operation should one or more sensor inputs fail. When a sensor input is perceived to be out-of-limits by the PCM, an alternative strategy will be initiated. The PCM will substitute a fixed in-limit sensor value and will continue to monitor the faulty sensor input. If the faulty sensor operates within limits, the PCM will return to the normal engine running strategy. Engine Running DTC 98 or 998 will be displayed when FMEM is in effect. The Malfunction Indicator Lamp (MIL)/Message will remain on when FMEM is in effect. The MIL will come on while the engine is operating in Failure Mode Effects Management (FMEM) or Hardware Limited Operation Strategy (HLOS) modes. The light will stay on for at least 10 seconds, then stay on as long as the fault causing it is present. If the MIL flashes quickly (less than 10 seconds), the MIL circuit should be checked for concerns. Refer to «Quick Test». In FMEM mode, the PCM is receiving a sensor signal that is outside the limits set by the calibration strategy. In this mode, the PCM uses an alternate engine control strategy to maintain reasonable vehicle operation in spite of the fault. The DTC associated with this fault is stored in Keep Alive Memory (KAM). If the fault is no longer present, the light will turn off and the vehicle will return to the normal vehicle strategy. The DTC stored when the light was on is kept in Continuous Memory for the next 80 warm-up cycles (40 cycles on some applications) and then erased. This Continuous Memory DTC can be accessed by running the Key On Engine Off Self-Test..."
 
#16 ·
yo more on DTC 63 in KOEO Throttle Position Sensor (TPS) below minimum 0.6 volts
DH4 CHECK VREF CIRCUIT VOLTAGE; Key off. l TP sensor disconnected. Key on, engine off. Measure voltage between VREF circuit and SIG RTN circuit at the TP sensor vehicle harness connector. Is voltage between 4.0 and 6.0 volts?
Yes, REPLACE TP sensor. RERUN Quick Test.
No, Key off. RECONNECT all components. GO to Pinpoint Test Step C1.

C1 CHECK VEHICLE BATTERY POWER CIRCUIT; Key off. Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary. Install breakout box and connect PCM to breakout box. Key on, engine off. Measure voltage between Test Pin 37 at the breakout box and SIG RTN circuit in the Data Link Connector (DLC). Note voltage. Measure voltage across battery terminals. Note voltage. Are both voltages greater than 10.5 volts, and are both voltages within 1.0 volt of each other?
Yes, GO to C2. No Key Off, RECONNECT sensor (if applicable).
GO to B1

I don't have the B2 nor C2, yet.

BOB test pins numbersp are most often same as EEC pins numbers
 
#20 ·
yo more on DTC 63 in KOEO Throttle Position Sensor (TPS) below minimum 0.6 volts
DH4 CHECK VREF CIRCUIT VOLTAGE; Key off. l TP sensor disconnected. Key on, engine off. Measure voltage between VREF circuit and SIG RTN circuit at the TP sensor vehicle harness connector. Is voltage between 4.0 and 6.0 volts?
Yes, REPLACE TP sensor. RERUN Quick Test.
No, Key off. RECONNECT all components. GO to Pinpoint Test Step C1.
What is the VREF circuit?
 
#17 ·
yo,
EEC Wiring Diagram in 87-89 Bronco & F series (Mitchell)
Source: by equivalent (Beetlejuice) at SuperMotors.net



EEC Connector Pin Diagram & Overview
Source: by Fireguy50 (Ryan M) at fordfuelinjection.com


EEC Connector Pin Outs, Bronco & Ford Truck & Van: 4.9, 460, 5.0, 5.8; miesk5 Note, see his Connector Pin Diagram Link above)
Source: by Ryan M (Fireguy50) at http://fordfuelinjection.com/truckpinouts.html
 

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#19 ·
Thanks for all the info. miesk5! I'm going to try and trouble shoot this this weekend.

mouzer 1: Thanks for your input as well. I have considered the fact that I may have got a faulty TPS from NAPA. But I'm not sure how to tell for sure. Unfortunately I do not have a known good one to switch it out with. And I have already replaced the fuel regulator.
 
#22 ·
VREF is an acronym for Reference Voltage (bass-akwards!). As miesk5 noted it should be in the 4-6 VDC range. My understanding is it should be +5.00 VDC +/- 5% on a good working vehicle. This is the supply voltage for many of the sensors hooked to the PCM. If this voltage is out of range it could be the root cause of a host of problems related to improper feedback to the PCM.
 
#23 ·
Thanks guys!

I checked my VREF voltage at the plug and I have 5 volts. I checked the TPS sensor readings and had a hard time getting a consistent reading. But the readings I was able to produce were below the recommended readings. So even tho the current TPS is new (NAPA part) I broke down and bought a motorcraft replacement from Rock Auto. I will be installing the new one this weekend.

After reading through the "Ultimate TPS" thread I have a few questions. I see where it references the pig tail of the TPS sensor to be facing the IAC sensor. But I also saw a few posts were members had there pig tail facing away from the IAC sensor.

Which way is correct for a '88 302?

I have been getting code 63 since I bought the truck. I had a shop change out the TPS when they did a few other things for me. When I got the truck back it was still throwing code 63. So I removed the TB and reinstalled the TPS and still code 63. Now IIRC the mechanic has the pig tail pointing away from the IAC. Could this possibly be my cause of the CEL and code 63?
 
#25 ·
yo,
via Chilton for your year
1.Disconnect the TP sensor wiring harness.

2.On 5.0L and 5.8L engines, it may be necessary to remove the throttle body. On all other engines proceed to the next step.

3.Disconnect the wiring from the sensor.

4.Matchmark the TP sensor and throttle body. Remove the 2 retaining screws and the sensor
WARNING
Slide the rotary tangs into position over the throttle shaft blade, then rotate the TP sensor CLOCKWISE only to the installed position. Failure to follow this step may result in high idle speeds for 5.0L and 5.8L engines.

5.On 5.0L and 5.8L engines, position the TP sensor so that the pigtail points toward the IAC valve.
6.Secure the TP sensor to the throttle body with the retaining screws. Tighten to 18-27 inch lbs. (2-3 Nm) on 4.9L engines or 11-16 inch lbs. (1.2-1.8 Nm) on 5.0L/5.8L engines.

7.If applicable, install the throttle body.

8.Connect the wiring.

9.Connect the negative battery cable.
 

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#26 ·
Perfect!!:clap

Thanks Miesk5! You come through again with great information. This may be the cause of my CEL and code 63 then!! :doh0715:

I will update my results when I change it out tomorrow. :beer
 
#28 ·
Update- I took the TB off and as I suspected the TSP was mounted backwards. So much for the mechanic that I had install it.:twak

So I replaced it correctly with the new motorcraft TSP. I put everything back together and fired her up. Ran great with the exception of some surging while cold. Once warmed up the surging went away.

So I took it for a few trips around town. It ran great with no CEL!

Now all I need to do is figure out the surging at start up and all will be good!

Thank again miesk5 for the great information once again!!:beer
 
#29 ·
Update- I took the TB off and as I suspected the TSP was mounted backwards. So much for the mechanic that I had install it.:twak

So I replaced it correctly with the new motorcraft TSP. I put everything back together and fired her up. Ran great with the exception of some surging while cold. Once warmed up the surging went away.

So I took it for a few trips around town. It ran great with no CEL!

Now all I need to do is figure out the surging at start up and all will be good!
---
Yo,
Great &
yw buddy!

Re; "...surging at start up.."
Get a vacuum gauge; install it at tree on intake manifold;
Run hose through clutch blank w/grommet; get hose and grommet together for proper sizing so hose is not pinched; drill as needed

Here is a good gauge and you can also use it to help control right foot for better MPG
$17.50
or get one cheaper and then mark-it up as shown in the Equs model
Vacuum Gauge Diagnosis - BEST!; Normal engine; Steady gauge 18"-20" at all speeds..." READ MUCH MORE
Source: by Craig U at classictruckshop.com


Some guesses;

a failed EGR valve can cause surging and/or knocking at part throttle

"...Surging, Rough idle, 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 retarded timing and an excessively rich fuel ratio, 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..."
Source: by aa1car.com

MAP should show a DTC; so don't buy one now.

see my site @ http://www.broncolinks.com/index.php?index=138 for MAP testing w/DVOM, O'Scope, etc.
 
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