worf928

Folks, in the continuing quest for the answer to why my '89GT cannot out-drag a late-model Camery I've narrowed the possible culprits down to a few components one of which is the Hall sensor. It has been suggested by Mr. Speake and others that the Hall sensor is a likely cause of lack of top-end.

The LH Service Training manual indicates that if the Hall sensor is toast that the timing will be retarted by 6 degrees.

I have checked the timing with a timing light. It's around 12-14 BTDC at idle and rises to 30-35 with rising RPM. This of course calls into question whether or not the hall sensor is bad.

What should the advance be? WSM says 10+/-2 at idle and 32+/-4 at 3k rpm.

(And - before someone asks - no - I haven't 'scoped the output of the sensor as my scope died last week and the "new" one from e-bay has yet to arrive.)

For context,
- the caps, rotors, coils, and wires are new.
- The throttle switch is working as it is supposed to.
- The injectors are clean.
- I have good fuel pressure at all RPMs.
- New fuel filter.
- Both pumps are recent vinatge.
- The final stage ignition modules were swapped with the ones from my '91.
- Grounds at the engine and battery are new.
- I cleaned up the grounds at the ignition stages.
- I've had a new MAS in there before with no effect.
- LH computer is new.
- Plugs are new.
- I also ran a test pipe in place of the cats for a while with no effect either.
- Temp II sensor resistance correct at the pins and ECU harnesses.

Oh, and the car passed a stationary emissions test with good numbers (with cats of course.)

No dog food in the intake. Etc.


What's left?

Injectors not firing due to harness issues? What's the easiest way to see if all my injectors are firing correctly?



Thanks in advance for any suggestions.

John Speake

If there were problems with injectors not firing properly, then almost certainly the ignition protection realy would operate and the car will run on 4 cylinders.

As you haven't observed this, then one or both of the knock sensors, or the Hall sensor is the most likely problem.

You will need to buy one of my diagnostic testers ! Coming soon !

worf928

Even if only one injector was not firing (due perhaps to a bad harness connection?) Note that the protective circuit is not activated (or the LEDS/relay are dead - but in that case I would have had a cat fire by now...) But the LH harness is a crufty old thing with three injector connectors patched-up with electrical tape - one by the PO, and two by me as copper was showing.

Quote:

As you haven't observed this, then one or both of the knock sensors,

Knock sensors are new (forgot to mention) and properly torqued.

Quote:

or the Hall sensor is the most likely problem.

No disbelief intended - but is it possible for the Hall sensor to cause a failure mode other than retarded timing? I ask because the timing doesn't seem retarded.

Isn't the Hall sensor used to disambiguate the reference mark on the speed sensor? i.e. power stroke versus exhaust stroke?

Quote:

You will need to buy one of my diagnostic testers ! Coming soon !

Not soon enough!

In any case - I have a new Hall sensor and nothing but time on this Easter weekend. However, I don't see a way to get the hall sensor out and the new one in without removing the passenger cam cover to get access to the lower allen bolt.

This is not a problem (BTDT) - but - is there an easier way for someone with short fat fingers?

worf928

Throttle opens fully. Cable's fine.

Spark plugs are on the list of tea leaves to read...

Thanks Bern.

Old & New

Damn... no luck with the grounds?

Harness doesn't sound convincing since the problem would occur throughout the rpm range, not just in the midrange as you have described.

MAS wiring? how does it run unplugged?

Something to do with removal of intake? When did problem commence?

John Speake

Yes, u/s one injector or spark plug can be enough to trigger the system - had this on a car this weekend.

If the Hall sensor or its connections are bad, the EZK ECU can't differentiate which knock sensor outputs a signal. So to be safe, a faulty Hall signal kicks the ignition timig back 6 degrees

Good luck !

Scott M.

Dave;

I had a Hall sensor issue once on an 88 5 spd. Car would cut out under high load, progressively to the point that it would only travel under part throttle. Eventually the car wasn't able to start.

Seems as though, in my frugal nature, I reused the existing smog pump belt (that was too long) at the time of a T-belt/h20 change. When I correctly tightened the smog belt it (being the pump body) 'pinched' the wire to the hall effect sensor thus causing all my grief.

I wasted about a month tracing it down and eventually a P-car dealer took 16 hrs to find the problem. That, a new belt and ~5" of electrical tape fixed the issue.

Check for wire continuity...

Scott
93 GTS
89 GT
...

worf928

Since before I e-bayed the car as a poor(er) running specimen.
i.e. it was a known issue when I bought it.

SharkSkin

Have you run a compression check? If so, what were the numbers?

worf928

Fascinating Mr. Spock. (or is that Doc Spock?)

That is the kind of info I was looking for - other effects of hall sensor failure.

Quote:

... correctly tightened the smog belt it (being the pump body) 'pinched' the wire to the hall effect sensor thus causing all my grief.

Oy! I can see that. Also, the wire runs between the engine and p-side lift loop and can get crushed in there. Not to mention the fact that it is tight (wie ein Jungfrau) in there. Lots of ways to screw it up.

Quote:

... a P-car dealer took 16 hrs to find the problem. That, a new belt and ~5" of electrical tape fixed the issue.

I trust Jessie never saw that bill?

Quote:

Check for wire continuity...

I think I'm just going to go ahead and change it (after I finish my taxes.)

Thanks Doc.

worf928

That's good to know.

Quote:

If the Hall sensor or its connections are bad, the EZK ECU can't differentiate which knock sensor outputs a signal.

That makes sense too.

But, if the hall sensor is bad - which means the EZK doesn't know which knock sensor is ringing and it doesn't know if the crank is at TDC on the power stroke or the exhaust stroke - why the H&!! does the lump even start much less run?

Quote:

Good luck!

Thx John. The hall sensor will be the next subject of the wrench.

Hmm... maybe I can put off the tax returns until next weekend... let's see... 4/17. Nope.

ErnestSw

I don't see anywhere that you've checked the flappy valve. Is it working?

worf928

Oh. Right. I was thinking of only the FI/ignition components.

Quote:

Is it working?

Yeah. It is working. It wasn't at first due to a vacuum line that was too good at its job. But that was one meter of vacuum line and one year ago. (and one vacuum check valve ago)

worf928

The numbers are ?,?,?,?,?,?,?,?.

As in - no. I have not done a compression or leakdown test.

However, if the hall sensor is not the problem then looking at deeper problems will be the next task.

Old & New

D.-

I know tax time is here again, but maybe afterward you can take a ride down & we can stare at your engine compartment with beer-addled minds and see if we can brainstorm something.

I have a few uncorrupted brain cells left to contribute to the cause...