I didn't get a chance to check out the plug but after thinking about it I'm guessing it's for the cruise control which you don't have.

 

Thanks, that makes sense. I really don't remember disconnecting it at any point and all the electrical systems seem to work. I'm pretty sure the hesitation is just a bad coincidence with removing the dash.

Next I'm going to replace the fuel filter. i haven't tried that yet because Ive been focused on electrical problems and it only has a few thousand miles on it.

 

So I looked at a few more things over the past week. The highlights are that I bought and inline spark tester to prove I have spark and I do. I also changed the fuel filter and (sadly) as expected there's no change.

Next I'll check the injectors. The 1680 secondaries were bought used this summer (August 2012) and were cleaned and flow tested. The 550 primaries are older, but all indications point to the fact that they are fine. The car idles and drives perfect under 3.5k. I don't suspect that they are an issue. The secondaries are hopefully either clogged or sticking.

At this point, if its not the injectors, I really have no idea....

 

Does the issue happen irregardless of load?

Also, do you have a PFC with commander? While driving, have someone check the sensor/switch menu when you rev the car to the problem area. See if any of the voltages go crazy, or if one of the I/O changes.

Kind of a hail mary, but you may be at the point where you need one of those

 

The issue is dependent on load. If I just rev the engine in neutral, it's fine. Also, I can rev it past 3.5 without boost while driving. It seems highly correlated to when the secondaries kick in. I'll try the sensor check with the PFC, it's worth a shot!

Here's a quick review:

1) Back in Oct 2012 I had essentially the same issue (slightly different RPMs, but it was a different tune). I checked everything at that time and, out of other options, replaced the field pump. That solved it. At this point, I'm no longer 100% sure that this was even the issue.

2) Got the car tuned (430 on a small street port at 15lbs) and she drove smooth as butter for a couple of months. Car has close to 1k on a rebuild, pulls great vacuum and idles perfectly.

3) Last month I installed all the under dash HVAC that was removed by the previous owner as well as heater lines in the engine bay. Buttoned everything up and the hesitation came back. At this point I didn't drive the car for at least 5 weeks prior.

4) Checked and rechecked the wiring, fuel and ignition. This part was actually good because I fixed many small issues (small oil leaks, coolant leaks, bad hose clamp, bad vband, rewired the FP, tucked, wrapped and tested MANY wires, bad TNS relay, replaced the fuel filter, leaking clutch line, etc.).

5) Problem still exists. My options are down to:
- Replace the secondaries: I feel they may have been stuck shut before (Oct 2012) and I jarred them with the 9V battery test. Since the injectors snapped open, I didn't retest (drive) the car, I replaced the fuel pump and that 'fixed' it. Now one of them may be re-stuck... This is my latest theory.

- Replace the fuel pump: I just can't believe that this went bad after 3 or 4 months of VERY little driving. But, it worked last time! i could just have awful luck and got a bad/weak pump...

 

Solved! Finally.... and the car drives great .

I bought 2 new 1680's with new wiring clips. I really wasn't sure if the secondaries were shot or if the wiring was shot, so I decided to tackle both.

The two highlights:

1) On BOTH injectors I had almost zero connectivity (with a voltmeter) across the injector resistor. I was shocked, and this was with them cut out with only an inch of wire on each side. I had to wiggle the wires to get the meter to read connectivity. I had soldered them in and the solder was cracked and brittle, on top of that the electrical tap had sort of melted into the cracked solder. I cleaned them up good and this time crimped them into the new clip wires. I got a clean 3 ohms and perfect connectivity. I'm confident this played a huge role, obviously.

2) I still decided to replace the injectors since this was probably the 20th time in the last two months that I had the UIM off and I was sick of being under there. Before putting the manifold back on, I tested the system for leaks (via jumping the main FP relay). Everything look perfect, but something new happened. After I pulled the key and put the UIM back on, the system maintained fuel pressure (>35psi) for over a half hour. I've checked this 10 times with the old injectors and that has never happened.


So this had nothing to do with the dash or the heater hoses... Just bad secondary injector wiring and possbily a bad injector(s) (although probably played a smaller role). What a ridiculous coincidence!

 

Glad you found the issue Matt, man what a journey for some bad fuel injectors.

Just goes to show, ruling out 'new' parts isn't always a good idea. I've been there before, trust me

 

I was reading this, not looking at dates and as soon as I saw he had the injectors flow tested then let them sit I immediately thought the injectors weren't opening. Glad to see it was solved 5 months ago. Way to bump an old thread newb.

 

Thanks rich for reminding me of those aweful couple of months :-).

Just for an update - car is down again for a bit. Just switched to a smaller turbo (BW S360) and mechanical pre-turbo WI (wannaspeed). Hope to have it tuned and back on the road in the next 4 weeks or so.

 

Matt, you should make the trip up for the Carlisi meet without the FD.... tons of awesome stuff going to be raffled off

DJ, next time I see you I'll smack you around a bit for your 'newb' comment

 

Rich, I'd love to go, but I'll be on vacation. I think this is the third year this event was held when I was on vacation .