95 IP timing w/ Snap-On MT2500

[billschall]

This is rather confusing - and I used to program them miserable computers too.

Hooked up the MT2500. Can read the data:
inj timing: about 5.5 (varies btwn 4.8 - 6.5)
des timing: 5.0 - 5.5
TDCO: -0.5

Physically retarded (towards pass side) pump almost 3/16" - no change on "inj timing"

TDP's timing article says to do the des/act timing first, then do a TDCO LEARN.

AllData says that a TDCO LEARN must be done first when PCM is removed (I did) AND crank sensor replaced (I did) AND timing cover removed (I did).

Read all through the MT2500 manuals and cannot figure out how to do a TDCO LEARN with the scanner. Primary cartridge is "through 1999" with matching Troubleshooter cartridge.

The pedal/key combo apparently only works on 96+ models.

Help?

UPDATE: According to AllDAta, TDCO is within parameters @ -0.5. Des Time still = 5.5, cannot figure out how to do a Time Set w/ MT2500 to get Des Timing to 0.0

[gmctd]

Fairly certain TDCO LEARN function doesn't, on the MT2500's

And, they read and interpret the data sorta wierd, compared to a TechX.

Or to the GMTDScanTech pcware scanner, which I find to be more versatile than the Tech2.

But, I'd just leave things as-is, long as you're not getting any DTC's - not as much difference in the components as the manuals might lead you to believe.

Move the IP back to where it was, with the ESO solenoid exactly vertical, and it will be timed - that -0.5deg TDCO is oem correct on a TechX.

Most folks move the IP ~2mm to the driver's-side for the performance setting of -1.5deg TDCO - PCM will compensate for that within 50 cold-starts,
but you might want to leave it oem till you can get it on a scanner that is functional.

[JohnC]

If you changed all the stuff you say you changed and did not do TDC offset learn, the value the scanner is showing you is the old value stored inthe PCM and has nothing to do with your current situation.

[billschall]

If you changed all the stuff you say you changed and did not do TDC offset learn, the value the scanner is showing you is the old value stored inthe PCM and has nothing to do with your current situation.

I had removed & unplugged it when I hooked up the Kennedy Fast Idle switch.

Doesn't unplugging the PCM clear the codes?

[gmctd]

That clears the DTC's, but takes about 3weeks or more to clear the parameters.

JohnC is correct - so, if you set the ESO vertical, the IP will be very close to the orig stored parameters, and would not set a DTC before you can get it scanned and verified or reset.

[billschall]

That clears the DTC's, but takes about 3weeks or more to clear the parameters.

JohnC is correct - so, if you set the ESO vertical, the IP will be very close to the orig stored parameters, and would not set a DTC before you can get it scanned and verified or reset.

Done. Actually bumped it up a bit by about 1.5mm. Will monitor for codes until a scanner can be found to be used. Thanks, guys.

[gmctd]

Ok - but, be prepared to wake up some morning, 50 starts or so from now, and your 6.5 will sound like an unhappy Powerstroke for a bit, while PCM relearns the parameters.

Long as it don't set a DTC at that time, yer good to go.

You might check around, see if a local member near you has a Tech or GMTDScanTech setup.

[billschall]

Ok - but, be prepared to wake up some morning, 50 starts or so from now, and your 6.5 will sound like an unhappy Powerstroke for a bit, while PCM relearns the parameters.

Long as it don't set a DTC at that time, yer good to go.

You might check around, see if a local member near you has a Tech or GMTDScanTech setup.


Er, anybody within say, 100 miles or so, got one of these to help prevent the 50th start jitters?

(should this request be a new thread?)

[gmctd]

Most everyone reads the thread index on the main page............

[sailun]

I've plugged in my buddies MT2500 a few times lately, as I'm guessing that my timing must have deteriorated over nearly 140k miles since replacement pump at 23k.


Do these numbers show anything significant ?

Des/Act timing always track the same 12.4 once, 12.0 another time.
TDCO -1.05
Fuel rate 5.8/6.4, fluctuating, mostly right around 6.0
Inj close 1.9/2.4, fluct'g, mostly around 1.9

Go into Output Test/Time Set,

Des TIming = 0.0 Act = 3.0/3.8, fluc'g, probly avg'g 3.5

Did not try to change anything.

Vehicle was normal op temp, idling at 588.
Fuel system is all operative and less than a year old, filter 2 mos old.

Boost and Baro were both 101kpa, wastegate 69%, I think I had the WA wired during time of test. Don't know if PCM cares while idling.

Any insights ?

Someone came in with a nice '92 pickup, with only 60k miles on it. Still had the plastic 6.5 cover on it. That motor sure sounded a whole lot better than mine did. Sounded alive, instead of dull and a little ticky.

[gmctd]

Idling at ~180degF Des\Meas should be around +8.5deg - they're tracking so that's a good sign

TDCO looks ok, could be -1.5deg or so, would give crisper idle, much crisper at -1.94deg

I like to see Injector Pulse width around 1.84ms, but the MT2500 doesn't always jive with the TechX stuff.

Else looks ok

Your '97 - OBD2 - has TDCO LEARN routine using the IGN switch and the APP pedal

[Robyn]

My 94 always sounds like a stroke when fired cold.
I had the injectors set to the top the spec for POP pressure.
No codes and runs fine.

Sounds reeeeeeeeeeeeeeeeeeeealy loud when its very cold and the sucker has not been plugged in.
I reinstalled the IP exactly where it came from when I replaced it after the rebuild.
New crank sensor, Ummmm everything else was as it came from Ma general..
Never have scanned it.

[gmctd]

If the crisp start is due to some IP advance, then your hi-pops should be more functional than at oem timing - they effectively delay injection timing as the IP builds up the higher pressure required to 'pop' the valve.

Iirc, the lower end is ~1725psi and the upper end is ~2225psi.

The PCM doesn't know this, and cannot compensate, so you should dial-in a little advance when they are installed.

One symptom is occasional low idle rpm, but seldom results in Cylinder Balance DTC - reason: unknown.

When the hi-pops are used with the DB2 and the fuel has been turned up, the increased fuel is effective from idle to full-out, so idle is more stabe in those systems.

Probably wouldn't hurt to get it scanned, see what ya got, eh?

[sailun]

gmctd, after re-reading your TDC Offset exposed a coupla times, I gotta ask you..............

Timing chain wear retards cam and IP timing, so I would want to advance the pump, right?

I would be advancing my pump roughly 2 MM to make up the 5 degrees from + 3.5 to +8.5 ?

And this advance would also reduce my desired and actual timing from the 12's down to the 7's or 8's ?

Does it make any sense for me to attempt to change my base timing from +3.5 to +8.5, or some intermediate figure, given that @162k miles, my timing chain musta stretched a bit, and I'm still on my original injectors ?

Or wait until I do timing chain, someday ?

Sounds like the -1.94 TDCO, is a bit too harsh, and somewhere around -1.5 is more reasonable.

Looking for MPG and longevity, not 2-3 HP at redline.

Channel Locks OK to use, or should I find/make an IP spanner somewhere ?
("Bueller ?, .....Bueller ?")

Source for an IP spanner, or plans to make one, would be great.

[gmctd]

Actually, PCM does a routine to compare current OPS\CPS offset value to previous value, then compensates for any difference due to timingset wear - a scanner is not needed for that, nor will you notice when it occurs.

From your recent scan - depending on Engine Coolant Temp, Intake Air Temp and ambient temp, PCM could have been calling for +12deg advance, which it does at each start.

Desired Inj timing is the value the PCM is demanding, Measured is the value read from actual position of the Optic Sensor

All things being equal, I would have expected Des\Meas inj timing to be around +8.5deg at idle.

Next scan, look for ECT to be ~180deg, IAT to be ~80deg, Fuel Temp to be around ~100deg - Des\Meas inj timing should begin around +12deg or higher, depending on ambients, dropping down to around +8.5deg as all engine temps normalize to those values.

Difficult to say on resetting the timing - but, if you advance the IP and don't like it, you can always put it back.

Just mark it first, for reference - 1mm = ~2.5deg, so very little movement is required

Your scanner gives you all the options usually requiring trips to see Mr Goodwrench.

Having fresh injectors, timing chainset, and Inj Pump will restore all the oem power, and advancing the timing will give it that extra kick.

I wouldn't suggest channel-locks for the job, nor using the ESO solenoid - the Stanadyne IP adjusting spanner is available from snapon and matco and otc, maybe your local pawnshop.

[sailun]

Thanks, GM.

I'll make sure everything is very good and warm, the next time I get a chance to scan it. Not doing anything before good numbers.

When I turn the key off, motor shakes and dies hard, a few extra turns, ya know ? Something like injectors still passing fuel ? ESO not cutting off fuel, fast enough ? Or normal for older motor ?

[gmctd]

'97 is ten years old - so that's probably normal for wintertime