Spastic Tach on a 1994 ManTX SHO

[GreenShoOwner]

I was pulling modestly high RPMs (Opened the pipes, smiled...) coming off of a highway stop sign, ~55mph. ...The engine stuttered, the tach when ABSOLUTELY BEZERK, I kept it in gear, and came off the gas, and waited/prayed... ...And then the car was fine. I completed my run to work without any further indication of trouble. ...I worked for several hours, then headed to the company picnic. ...Again, no trouble starting, no trouble moving out of the parking lot. ...Then, when accelerating onto the highway, the tach once again went NUTS (spastic fluctuations all accross the tach, no pattern...) and it didn't pull out of it. ...I was able to run (very, very roughly ; lurching) enough to get it back into the parking lot.

...From what the mechanic told me... ...He ran a compression test, and it checked. ...And they cannot pull codes from the EEC. ...This would sound like a textbook EEC problem to me, but... ...Usually when a circuit goes, it's just gone... ...They don't come back when you drop RPMs, etc... I really suspect the Crank sensor, and now that I know where it is, I did look at it. ...It's <gasp> still there. ...And a bit oily. I can see the EEC through the (drawer-removed) glovebox, and it looks like an easy job. ...But I don't want to shell out $300+ for a part I don't need.

Worse, the symptoms could possibly be a hole in the piston/wall, but this is the reputable 3.0L Yamaha engine, and I kind of doubt it. ...And apparently it has passed a compression test...

What do you experts say? -- I appreciate the support.

 

[GreenShoOwner]

Well... 2 days later:

Fortunately, I was able to work through it. ...The crank sensor was oily, and I suspected that there might be a problem with that. ..The little contact at the top (Well bottom I guess...) of the sensor was dirty or something. ...So I just cleaned it, and wiggled it, and now I'm BACK IN BUSINESS.

I still have a few tid-bits to clean up. I was able to pull some codes using a Velleman Oscilliscope (I didn't have a needled voltmeter.) - I'll post what I have below. ...I don't have registration, insurance nor inspection done on this rascal yet, so I won't be able to take it for a proper test drive for a bit. (But looking forward to it.)

The codes I keep getting now are - 542, 538 (possibly 539 sometimes...), 521.

I also had a 116, but I put the parking brake on, and that cleared that.

542 is fuel pump secondary circuit failure (Whatever that is?)
538 is Insufficient RPM change during KOER dynamic response test (Don't know what this one is either, I presume it's just saying the engine's sluggish?)
521 is listed as Power Steering Pressure sensor/switch did not change states during KOER. ...I'm hoping that one's just a dead sensor...

I guess that leaves:

Oil change
I have a small oil leak, don't know where.
Insurance, registration, inspection.
Small hole in radiator
Replacing the radio that got ripped off a the Ford dealership
Fixing various cosmetic things in the cab...

...AC is cool, engine is smooth, and I am happy with my 137k mi SHO. (And waiting for a good test drive.)

Anyhow, if anyone has any thoughts, please let me know.

 

[naval-avi8or]

Well... 2 days later:

Fortunately, I was able to work through it. ...The crank sensor was oily, and I suspected that there might be a problem with that. ..The little contact at the top (Well bottom I guess...) of the sensor was dirty or something. ...So I just cleaned it, and wiggled it, and now I'm BACK IN BUSINESS.

I still have a few tid-bits to clean up. I was able to pull some codes using a Velleman Oscilliscope (I didn't have a needled voltmeter.) - I'll post what I have below. ...I don't have registration, insurance nor inspection done on this rascal yet, so I won't be able to take it for a proper test drive for a bit. (But looking forward to it.)

The codes I keep getting now are - 542, 538 (possibly 539 sometimes...), 521.

I also had a 116, but I put the parking brake on, and that cleared that.

542 is fuel pump secondary circuit failure (Whatever that is?)
538 is Insufficient RPM change during KOER dynamic response test (Don't know what this one is either, I presume it's just saying the engine's sluggish?)
521 is listed as Power Steering Pressure sensor/switch did not change states during KOER. ...I'm hoping that one's just a dead sensor...

I guess that leaves:

Oil change
I have a small oil leak, don't know where.
Insurance, registration, inspection.
Small hole in radiator
Replacing the radio that got ripped off a the Ford dealership
Fixing various cosmetic things in the cab...

...AC is cool, engine is smooth, and I am happy with my 137k mi SHO. (And waiting for a good test drive.)

Anyhow, if anyone has any thoughts, please let me know.

542 = you lost ignition signal so fuel pump was shut down part of CPS failure and erratic tach signal.

538 = did not goose the throttle during the test (or did it at the wrong time).

521 = you failed to cycle steering lock to lock during test at the appropriate time.

 

[shovermont]

buying a used SHO is risky huh haha. i just got mine with 141 on it. ive done the injectors, calipers and im working on the alternator now and who knows what else will go when it goes on the road. at least you got your tach problem fixed. its weird that the CPS would make your tach jump. its strange cause does that have anything to do with the throttle? good luck with it though.

 

[naval-avi8or]

buying a used SHO is risky huh haha. i just got mine with 141 on it. ive done the injectors, calipers and im working on the alternator now and who knows what else will go when it goes on the road. at least you got your tach problem fixed. its weird that the CPS would make your tach jump. its strange cause does that have anything to do with the throttle? good luck with it though.

Tach is driven by the CPK signal produced by the CPS. Intermitant signal = jumping tach. Since he had a 542 code the car was actually stalling as the signal was dropping off and back on. If he owned an ATX vice MTX it probably would have completly stalled since the tranny is not directly connected.

 

[GreenShoOwner]

542 = you lost ignition signal so fuel pump was shut down part of CPS failure and erratic tach signal.

538 = did not goose the throttle during the test (or did it at the wrong time).

521 = you failed to cycle steering lock to lock during test at the appropriate time.

Wow! You rock! Thank you for the detailed information. ...I wasn't even thinking along those lines.

I didn't see any info on the test procedure in the Chilton manual. Is there any page I could find that would detail the proper procedure for the test?

Tach is driven by the CPK signal produced by the CPS. Intermitant signal = jumping tach. Since he had a 542 code the car was actually stalling as the signal was dropping off and back on. If he owned an ATX vice MTX it probably would have completly stalled since the tranny is not directly connected.

Absolutely right. I felt like a dirtbag, effectively performing a continuous roll-start to get it into the parking lot. What do you fly? Where did you get your degree?

 

[gas it]

Your problem is a bad cam sensor, not crank sensor. It's on the back exhaust cam above the PS pump. Black 2-3" round thing. Wires connect at the top of it.

 

[GreenShoOwner]

Your problem is a bad cam sensor, not crank sensor. It's on the back exhaust cam above the PS pump. Black 2-3" round thing. Wires connect at the top of it.

...How do you figure that?

 

[GreenShoOwner]

Found some information on the actual procedures here:

http://www.corral.net/tech/maintenance/eecivtest-koeokoer.html#koeo

Key On Engine Running (KOER) Testing Procedures
After you have corrected any problems in the KOEO test you are now ready to perform the KOER EEC-IV test. This test checks all sensors and engine functions while they are in their normal operating states. This test requires up to three inputs from the driver during the test. The first input requires that the brake pedal be depressed, the second requires that the steering wheel be turned at least one-half turn and then released. Finally on cars equipped with an E40D automatic transmission, the Overdrive Cancel Switch (OCS) must be deactivated, then reactivated.

As with the KOEO test, the KOER test will output codes twice during its display cycle. The EEC will display codes in the following order:

1. Engine Running I.D. Pulse - this pulse is used to identify the type of engine. The EEC-IV will pulse half the number of cylinders. For example, on a 5.0 Liter Mustang the EEC-IV will pulse four times, on a 2.3 Liter Mustang it will pulse two times.
2. Pause of 6 to 20 seconds
3. Dynamic Response Test - this is a single pulse that indicates that you should briefly move the throttle to Wide Open Throttle (WOT). This test checks to verify the functinality of the Throttle Position (TP), Mass Air Flow (MAF), and Manifold Air Pressure (MAP) sensors.
4. Pause of 4 to 15 seconds during this time Fast Codes will be displayed.
5. KOER codes - any codes generated during the KOER test. If everything checks out OK, you should receive a code 11. These codes will be repeated twice.
6. KOER codes- if you press the throttle to WOT briefly the EEC-IV will begin a cylinder balance test. When the test has completed its first cycle it will display result codes. The test will continue to cycle at twice the threshold of the previous test until the engine is shut off.

The following instructions will walk you through the procedures for performing the EEC-IV Key On Engine Off test.

1. Make sure you have a paper and pencil ready so that you can write down any codes output by the KOEO test.
2. With your reader disconnected from the EEC-IV diagnostic port, start and run the engine at 2,000 RPM for two minutes. This will bring the Heated Exhaust Gas Oxygen sensor to its normal operating temperature.
3. Shut the engine off and wait 10 seconds, then connect your reader.
4. Connect your reader, and start the car. Don't depress the throttle unless you receive a Dynamic Response Code.
5. Your reader will flash your Engine ID Code, if you have a 5.0 Liter Mustang this will be four flashes. Immediately after you see the Engine ID Code depress the brake pedal, turn the steering wheel at least 1/2 turn, and for E4OD Automatic Transmission cars cycle the Overdrive Cancel Switch.
6. After a pause of 6 to 20 seconds you may receive a Dynamic Response Code. This will be a single pulse on your reader that indicates the EEC-IV is requesting a WOT input from you. If you detect this code, briefly depress the throttle to WOT. Failure to do so will generate an error code.
7. After a pause of about 4 to 15 seconds, and if everything checks out OK, you should receive a code "11." If not, the EEC-IV will display any errors it has received, they will be displayed twice. Record these code numbers.
8. Check your code readings here and correct any problems, then re-run the KOER test before continuing on.
9. Once you have completed the KOER test you may shut off the ignition or continue on with the Cylinder Balance test.

...Looks like I have more work to do.

 

[SHOtime2511]

Your problem is a bad cam sensor, not crank sensor. It's on the back exhaust cam above the PS pump. Black 2-3" round thing. Wires connect at the top of it.

X2
classic CID failure.

 

[GreenShoOwner]

X2
classic CID failure.

OK -- ...I'm really surprised though. ...I adjusted the Crank sensor, and now everything seems (SEEMS?) to be fine. Is the only solution to this problem replacing the part, or is there some cleaning, etc. that can be done?

Also, if I had the results of an "EEC-IV Cylinder Balance test", what would that get me? Could I do anything worthwhile with it, or would it just serve to add one more thing I can't fix?

 

[naval-avi8or]

The motor will run with a cam sensor failure but will not run with a crank sensor signal failure. 542 was a loss of crank sensor signal which shut off the secondary fuel pump circuit.


I currently fly F-18A/B/C/D Hornet(s) aka legacy hornets.

 

[gas it]

The motor will run with a cam sensor failure but will not run with a crank sensor signal failure. 542 was a loss of crank sensor signal which shut off the secondary fuel pump circuit.


I currently fly F-18A/B/C/D Hornet(s) aka legacy hornets.

I would ignore the 542 code. His car was running but bucking and missing. That's a cam sensor failure. I've experienced both crank and cam failures on more than one SHO. Plus the cam sensor is a piece of cake to replace compared to a crank one.

The cylinder balance test will tell which cylinder is not running correctly, like a clogged injector, low compression or a misfire. Won't really help with sensor problems.

 

[GreenShoOwner]

So far, it seems that just cleaning up the Crank Sensor did it. ...I will definitely keep this information in mind if this kicks up again. Thanks!

My uncle was a AH-1W pilot for the Marines. ...He was able to fly a (in a?) Hornet once, and apparently he really loved it. I have alot of respect for what you guys do. My grandfather was also a navy aviator, a TBF-1 Avenger Pilot. (He didn't actually see combat during WWII. ...Just as well. He was 19, and his two crewmen were 17! -- And they loved knocking out the torpedo-bombers.)

 

[Dubpander]

I would have to agree with the cam sensor. I had a similar experience. Whenever the car warmed up she would act up, then if I turned it off, she wouldn't start back up til later. Finally the tach started jumping, so replaced the cid and problem solved.

 

[GreenShoOwner]

OK - Noone laugh.

The wire I adjusted was some sort of lower oilpressure switch (mostly guessing again). ...Not the CPS. ...Don't ask what's wrong with me. I went through the 60K Front step-by-step instructions, and that's clearly not the CPS.

...Which brings me to my next point. The CIS needs replacement, and I'd be happy for someone around Mexia or south of Dallas to perform the Front 60K on my 1994 MTX SHO. I'll post another topic soon I think. PM me if you want to do it, with a price estimate. -- Thanks!

 

[gas it]

OK - Noone laugh.

The wire I adjusted was some sort of lower oilpressure switch (mostly guessing again). ...Not the CPS. ...Don't ask what's wrong with me. I went through the 60K Front step-by-step instructions, and that's clearly not the CPS.

...Which brings me to my next point. The CIS needs replacement, and I'd be happy for someone around Mexia or south of Dallas to perform the Front 60K on my 1994 MTX SHO. I'll post another topic soon I think. PM me if you want to do it, with a price estimate. -- Thanks!

Take your car to Tony in Dallas at North Texas Performance, he'll do your 60k right.

 

[GreenShoOwner]

Thanks gas-it

 

[GreenShoOwner]

Hey, I decided I'd make time to get this done today, and... ...I have been unable to find a phone number! Would you mind helping me just a little bit more?

Thanks again!

 

[GreenShoOwner]

Got it -> 214-724-3246