Intermittent Weird Issue, I've tried everything...

[91 TSi GP]

Ok first of I wasnt sure what category to classify this in so I went with Bolt on. I am having some wild issues with my 1G that I cant troubleshoot and am about at my wits end. Bear with me while I write a book to explain the issues I'm having.

2 weeks again I was driving though town and my car suddenly started feeling like I was running out of fuel. I got to a parking lot got it idleing smooth again and managed to make it to BP. I put $20 in it and was convinced I was low on gas (gas gauge doesnt work). Pulled out of BP and started doing to same thing all over again not even a mile later. It's hard to explain.. feels like it was starving for fuel and/ or only running on a few cylinders. When it would do this my wideband would go dead lean also. It ended up completely dieing on me and I coasted into a parking lot. It wouldnt start back up on me at all. I was convinced now that my fuel pump was shot.
I got home and took the line off my fuel rail and turned it over and I had fuel coming out so eliminated the fuel pump idea. I then looked at the gauge on my cheap regulator and saw it was showing 0 fuel pressure. I went to Summit and bought a Aeromotive Regulator, came home installed it set base fuel pressure to 37psi and tried to start it still nothing.
After looking around a little more found that my MPI fuse was blown and I wasnt getting any spark. Replaced the fuse and it fired right up.
Everything should be good now right? Nope it was still running like it was before it died on me a few days earlier. But it is intermittent. One time i'll start it and it will be idleing fine, the next time its running like crap (like its on 2cyl or out of time).
I took my MPI relay out and tested it, came back good. Switched out the spark plugs. Swapped the Power Transistor with a known good one. I had a coil pack laying around from a '90. I know the plugs are different so i combined the 2 using the coils and bracket from the '90 and the wires and plug from my '91. Would this cause an issue?
Checked my base timing, dead on. Checked my ignition timing, 5 BTDC. I had my ecu repaired about 7 weeks ago now by Steve and everything was fixed properly so I dont think that would be the issue. Compression test came back good, and I have tons of spark on all 4 cyl (i can produce 2" lightning bolts off the valve cover). I also did a fuel pump rewire.

So now I am stumped after doing everything above with still no results. It will start fine, and one time its idleing fine the next time its running with the description I said before. If it starts and its idleing good and I go to take it for a test drive.. usually by the end of the driveway its running horrible again like its only on 2 cyl and/ or the timing is way off. If you have any idea's please fill me in because I am stumped now. thanks

91 Tsi
60 Trim, 255lph, 680's, 3" GM MAF, MAFT, SAFC, Rewired pump, etc...

Quick Recap on Everything thus far...
Fuel Pump - Ok
Regulator - Ok
ECU - rebuilt 7 weeks ago
MPI Relay - Ok
CAS - Ok
Power Transistor - Ok
Coil Pack - Ok
Rewired Fuel Pump - Ok
Timing - Ok
Plug/ Wires - Ok
Compression - Ok
_______________________________________________________________
Resolved!!
After undoing all the main harness wiring everything tested fine! I retaped everything back up re-ran all wires and took it for a drive and it was STILL MESSING UP!!! WTF right, so I get home and shake the same part of the harness again, sure enough it comes and goes (2 cyl running). So I spy a few wires going to a random plug down by the subframe, i grabbed them and give them a shake and walahh there is my problem.
It was to dark to see anything so I quit for the night and the next day it was on! My injector resistor box was never nowhere to be found since ive had the car, but the previous owner relocated a few things so i never bothered looking for it. I got under the car to trace that plug and walahh there was my injector resistor box just hanging there on my exhaust and the metal casing around it was smashed causing it to ground out. I fished it out of there remounted it on the firewall and everything was perfect

 

[gofer]

Make sure the SAFC wiring is making a good connection the ECU, if its not getting a good signal from the MAF wierd things start to happen especially if its a GM.

CAS - Ok

How can you be certain? I had a similiar issue and started inspecting connectors for a bad connection. I found a hairline crack in my CAS connector causing it to drop two cylinders randomly.

I see you have ECMLink V3, post a log...

 

[91 TSi GP]

Make sure the SAFC wiring is making a good connection the ECU, if its not getting a good signal from the MAF wierd things start to happen especially if its a GM.


How can you be certain? I had a similiar issue and started inspecting connectors for a bad connection. I found a hairline crack in my CAS connector causing it to drop two cylinders randomly.

I see you have ECMLink V3, post a log...

I will certaintly check the CAS connector.. the safc wiring is all good, just rechecked that yesterday and i DID have V3. Had to sell due to needing quick cash for closing on my house

 

[gofer]

I will certaintly check the CAS connector.. the safc wiring is all good, just rechecked that yesterday and i DID have V3. Had to sell due to needing quick cash for closing on my house

ECMLink is not only a GREAT tuning tool, its great at diagnosing no starts and stupid intermittent DSM hiccups too! Sucks you had to sell it... I'd also check the MAF, can you pull up a Hz reading on the SAFC? Its been so long since I've used mine I'm not sure? If so at idle it should be around 35 to 50 Hz.

 

[jmartinez1228]

I'm throwing this out of left field but make sure the plugs for the injectors are making a good secure connection. i had a similar issue where my car would fall on its face when I would hit the gas and it happened after i upgraded the injectors. Turns out i broke one of the retaining clips and the plug was just barely making a connection to the injector enough to keep it running at idle but would come loose under load.

 

[91 TSi GP]

Ok quick update, I had only about a half hour to mess with it tonight. It started up perfect, sat there and idled great for about 5 min reving it up and everything. I decided to venture to the road and almost immediatly it started running like crap again. I got back to the garage and it was idleing perfect for another 10 min and I couldn't get it to mess up. I drove it around the yard and started running like crap. By the time I got to the garage it smoothed out and idles good for another 5 min. I got annoyed and shut it off and went in the house....

If it was from a connector not making a good connection and coming loose while under load wouldnt it happen when I free rev?

 

[gofer]

If it was from a connector not making a good connection and coming loose while under load wouldnt it happen when I free rev?

Not necessarily. When the car starts to run like ass hit the brakes and pop the hood, wiggle your MAF and CAS connections and see if the idle changes just by wiggling them. If nothing changes you might have a sticky injector, pull the injector plugs off one at a time... If they're all working like they should the cars idle should get worse when you unplug them. You also mentioned combining the '90 coil pack with the '91, if you had to splice any wires together I'd start wiggly those while its running like ass and see if it changes as you move them since you might just have a bad connection.

 

[91 TSi GP]

Not necessarily. When the car starts to run like ass hit the brakes and pop the hood, wiggle your MAF and CAS connections and see if the idle changes just by wiggling them. If nothing changes you might have a sticky injector, pull the injector plugs off one at a time... If they're all working like they should the cars idle should get worse when you unplug them. You also mentioned combining the '90 coil pack with the '91, if you had to splice any wires together I'd start wiggly those while its running like ass and see if it changes as you move them since you might just have a bad connection.

Ok I will do this tonight, I have plenty of parking lots around my house so hopefully i can get it to act up real good and coast into a parking lot and wiggle them. When it was idleing good last night i pulled the injector plugs and #1 made the car die, #2,3, and 4 made it run crappy (similiar if not identical to the way it runs when its bucking). And no I didnt have to splice any wires. Just unbolted the wires from the 91 and bolted to the 90

 

[gofer]

If you can get it to act up and find that pulling the injector plugs didn't change the rough idle I'd pull out a multimeter and test your injector resistor box located on the firewall, its a silver rectangle if you aren't sure what it looks like. The wires coming from the box to its connector are typically exposed a bit so if you measure good resistance at all the pins try moving the connector around and see if theres a break in the wire somewhere which could cause a intermittent connection...

 

[91 TSi GP]

Thanks for that, ill check tonight.

 

[GsxEcutioner]

fuel filter?

 

[boostforfun]

Also, check your voltage at the back of the alternator and at the battery.. low volts caused similar problems in my 90

 

[91 TSi GP]

Mark this as resolved please.

 

[DSMnoobsause]

what fixed it? im having the same problem

 

[gofer]

If you can get it to act up and find that pulling the injector plugs didn't change the rough idle I'd pull out a multimeter and test your injector resistor box located on the firewall, its a silver rectangle if you aren't sure what it looks like. The wires coming from the box to its connector are typically exposed a bit so if you measure good resistance at all the pins try moving the connector around and see if theres a break in the wire somewhere which could cause a intermittent connection...

Read the bottom of his original post.

Resolved!!
After undoing all the main harness wiring everything tested fine! I retaped everything back up re-ran all wires and took it for a drive and it was STILL MESSING UP!!! right, so I get home and shake the same part of the harness again, sure enough it comes and goes (2 cyl running). So I spy a few wires going to a random plug down by the subframe, i grabbed them and give them a shake and walahh there is my problem.
It was to dark to see anything so I quit for the night and the next day it was on! My injector resistor box was never nowhere to be found since ive had the car, but the previous owner relocated a few things so i never bothered looking for it. I got under the car to trace that plug and walahh there was my injector resistor box just hanging there on my exhaust and the metal casing around it was smashed causing it to ground out. I fished it out of there remounted it on the firewall and everything was perfect!

 

[DSMnoobsause]

for some reason i didn't see it. thank you