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IP or PCM issue?

My 95 is acting the exact same way. Extremely touchy throttle, can't coast or maintain hwy speed: either fueling hard with minimal throttle or no throttle quickly hold back;decel. Mine is a 5 spd so it is amplified 10x over due to no stall. Cruise has same prob; jerk, jerk, jerk on flat ground, pulls great uphill. One thing I found that helped about 50%, had 0 fuel press at cruising speed, lift pump gettting low amps. Installed underdash relay powered with key on, helped tremendously but still throttle "not as it should be" new #9 resistor fsd front bumper mounted and new boost solenoid. All stock exhaust/turbo boost set up 301,000 miles Need to scan/check fuel settings etc. Any place I can purchase a reliable scanner? Did Flash codes 12 (no codes) thanks, Mike
 
Ok. Just got done messing with the optic sensor. Moved it twice. It is only worse. Surging and rattling more than usual. I checked the fuel rate afterward and it is bouncing around from 0 to 5 mm3 with 3.75 still being the most consistent.
What I thought was wierd was that the block that is under optic sensor held down by the T40 bolt was able to move. I don't know much about the internals of the pump but I would think that the part that the T40 bolt is threaded into should not be able to wobble. When I pushed on my optic sensor to slide it it over the entire block was able to move. It isn't just flopping around but it is able to lean back and forth. Is this ok?
Thoughts??
 
That block is moved by the stepper motor to change advance. The block has to be held stationary and and the OS is moved in relation to it.
 
I don't know a lot about it, I would make sure the grounds are clean. Especially the 2 or 3 by the trans dipstick, those are for the ecm. The ecm could also be the problem or the stepper motor.
 
Ok. I have cleaned the grounds at the engine already. I will pull the PCM and check it's grounding. I will have to look in the book to see what wires to check the resistance on. Man, this is annoying!
 
Ok. The 3rd time I moved it I ended up with worse numbers than where I started but at least it ran smooth again and I know it is making a difference.

Based on what I am seeing, the fuel rate is increasing as I move towards the passenger side of the truck with the sensor. Am I doing it right?
I started out by moving it towards the drivers side because it looked, based on the pictures in the writeup, to be too far to the passenger side but that made it terrible. It would surge, rattled more, and the fuel rate at idle was hitting zero. After moving it back toward the passenger side I took it for a test drive and it did act worse than origina but I was not back as far as original yet. I plan to move it beyond where I started when I get to work on it again Friday. At least it feels like progress... :???:
 
Do you have a scan tool to look at? What is the TDC offset? If that is out of kilter, could make things rattle alot as you move OS? just one more question in a string. As you start moving things, what is the timing? My friendly neighborhood mechanic let me use Genisys for the weekend, wish I were closer!
 
I still have my friends old Genisys. He has a new one and is loaning me this one. It is good up to 2006 domestic and japanese vehicles. I am thinking of buying it from him. He wants $500.
If you get a chance, can you post what yours is running at? I will go in on Friday and scan it before I change it so I can post before and after for discussion.

You are not far from my cousin. He lives in Webster, SD. I have visited once back in late May of 2007. It was beautiful. I have been trying to get out there again ever since. I want my wife and kids to see it! Beautiful country. My wife is from Texas so she thinks it is cold here!! :rolleyes5:
 
TDC offset is -1.5, and fuel rate is 6.88. I brought the Genesys home actually, to mess with optic sensor. I had the pickup running sweet, but I thought I could get a little more, well.....more isn't always better! So I am gonna put it back. With a search, anywhere between 5mm3 and 9mm3 is ok. Stock from what I understand, is around 8 mm3. Bump is anywhere between 5mm3 and 7mm3. I hope someone will correct me if I am wrong!

Webster is norht about 2-2.5 hours. If your ever coming through, give me a holler. I like to drink coffee as much as I like to drink beer! Although I like beer so much I make my own! (though when you buy it, it takes less time!):hihi:
 
Sounds cool. So which direction did you 'bump' it to increase the fuel rate? Best I can tell, the fuel rate at idle increases as I push it to my left(passenger side of truck).

Hopefully one day I can take you up on that. I like my beer too! Havn't got into making it though. Some friends talk about making it. Easier to drink theirs. ;)
 
Drivers side to increase...

You are right, it is easier to drink theirs, but it is way more fun to make it, cause you have to drink some, to make some!
 
Had a little time this afternoon, and got my bump done. I have -1.5 TDCO, and fuel rate is fluctuating between 5.94 mm3, and 5.62 mm3. Throttle is crisp, and runs down the road beautifully! I run less boost now at cruising speed, but EGT went up some. I hope everyone had an awesome Thanksgiving!
 
Absolute WORST way for advancing timing is optic bump, can be done but as you have found isn't the easiest way to get it set correctly too far either way and PCM can't deal with the adjustment and truck runs like crap, that is a mechanical adjustment that PCM can't "see" to be able to compensate for changing conditions like changes in temperature by season.

A mechanical optic bump change to cam ring impacts the mechanical setting of the TSM so that when called for like in a cold start advance in winter the expected location within a calibrated IP the PCM is looking for is off the mark so you can get an acceptable run/start that worked in summer but is crappy come winter in some cases causing a no start condition.

TDCO via IP movement & ko/ko or scan tool learn is the way to do it properly successfully every time, contingent that your IP is healthy to begin with.

My experience has been rotate the IP to -3.6/-3.7 when in time set mode with a scan tool, vs. -3.5 base timing as recommended by GM, (as above rotate IP to driver side advances time pass side retards it) at that setting once you do TDCO learn (not same thing as time set) will result in the -1.5 to -1.95 timing advance to TDCO we like to see for improved power/performance.

Reading back to your 1st post I'm thinking armature in the fuel solenoid of the IP has gone or is going.

Need to do a 2000 rpm test.
 
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I assume the 2000rpm test is a controlled rev to 2k, hold, and slowly control back down. If so: FAIL! It is not controllable if in park or neutral. I guess this means the IP is dead?
:(
 
dka99burb said:
I assume the 2000rpm test is a controlled rev to 2k, hold, and slowly control back down. If so: FAIL! It is not controllable if in park or neutral. I guess this means the IP is dead?
:(
Click to expand...

That is true as TD said, but first get the idle fuel rate above 6mm3. An optic bump can have the same effect, ie: touchy throttle.
 
I had a New Old Stock IP installed on mine the cam ring screw came loose and optic was moving on its own accord, idling with 2-3mm fuel and running to 80 with just 20mm indicated fuel but smoking heavy black like mosqitio fogger in 1960's & 70's, they don't smoke much these days of eco friendly output. Couple be Optic setting but if this is a recent problem I'd think less optic bump & more like a fuel solenoid (IP) issue.
 
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