jreifler

To narrow a question with 100 equally legitimate answers - the misfire presented immediately after I replaced my fuel lines and injectors. The car ran brilliantly immediately prior to me f*cking with it.

For context - I am totally under-qualified to have done this job. I have never done any substantial engine, fuel, or electrical work on any car. But I owed it to my childhood dream car to teach myself how it really works. So here we are.

Theories eliminated: Everything OTHER than (i) vacuum; (ii) fuel lines; (iii) injectors; (iv) fouled plugs on 5/6 (wait for it); (v) sensors; and (vi) other **** I'm sure I'm missing.

Why? Because that's all I touched. Before this, my very skilled, air-cooled mechanic was responsible for how perfectly the car ran.

In order:

Vacuum - I could have screwed this up anywhere that I removed a seal, but I very thoroughly checked and re-checked everything. But still . . . ?
Lines - Installed a full Griffith's unit. Don't see this as a likely source of weakness, as it was fairly straightforward once the manifold was out of the car. Light anti-seize on all fittings, all tightened properly.
Injectors - Tried AmberGramps's Bosch -715 idea. What I bought were either new or refurbished, so this shouldn't be the issue. BUT, I did feel a little unsure on installation. Never felt a solid "click" that assured me that the injectors were seated fully in the rail and the manifold.
Plugs - Yeah, I crossed wires 5 and 6 on initial install. On first start, loud, popping backfires at idle. Plus rough idle generally. Stared and thought about it, and knew that I was unsure of this step while I was doing it. Now I know that the lines are actually numbered. Swapped them proper, but not until it backfired dramatically for 2 minutes at idle. Fingers crossed that this is the answer.
Sensors - Carefully removed everything and reinstalled as I found them. However, I did soak the entire throttle body (and whatever the sensor attached is called) in mineral spirits. Mechanic endorsed this re: not an issue for the sensor.

Went for a drive after the initial plug wire fiasco was sorted, and the car eventually settled in and drove decently, but with a much higher idle than normal (injectors?). It ran incredibly for a few miles. Dramatic improvement in throttle response and acceleration, but then a persistent misfire under acceleration and at idle. However, it's not constantly there. Granted, I only drove it for 45 minutes after the job, but there were stoplight to stoplight jaunts under WOT, and it pulled brilliantly all the way through 3rd. Next jaunt, consistent misfiring under acceleration, regardless of force.

Whatcha got?

Amber Gramps

Was this with the 715's?

Any chance you are just working out the air bubbles in the fuel rails?

If your injectors were not in proper you'd have fuel everywhere so it ain't that.

Oh, duh.....went back and read your entire post.

Did you wash the car?

jreifler

With the 715s. I would think that a 30 minute drive would work out air bubbles, but maybe not. Good to know re: injectors. That's eliminated. I'll admit that initially miss tightening on the venturi line clamps, but I double checked everything after that. Did not wash the car.

Amber Gramps

What is a Venturi line clamp?

jreifler

As I understand it, it's the line off the left (driver's side) that provides brake boost vacuum. Connects on the left side to the manifold, and also has a hard line into the throttle body intake

jreifler

Amber Gramps

Change out your DME relay just to rule that out.

Did you happen to unplug the crank position sensors? Maybe swapped them....

Still sounds like a heat related vacuum issue.

Any chance there was crud in your fuel rails that is clogging up your injectors? Not likely. Almost want you to put the stock injectors back in and see if that changes things.

Wait.....won't turn over/won't crank....or won't fire and run?

jreifler

der Mond

Check that the wires are firmly tightened at the connection at the upper left intake manifold.

jreifler

Doug - It shouldn't have had this effect, but I am going to put the old injectors back in. Talked with Steve Wong yesterday, and he said his program very well might not take into account all of the changes associated with the new injectors. Rattled off a laundry list of things I hadn't thought of that could be affected by the swap. I can't think of anything else that would do it. I've triple checked every vacuum line and electrical connection.

Amber Gramps

I would absolutely listen to Steve Wong and swap the stock injectors back in. I run a Multi-board chip and it has no issues with the injectors. A couple other guys run the injectors but I don't know who's chips they run. This is why I try to only do one mod at a time.

SARGEPUG

Might be unrelated, but did you check your air meter?! I went through a long nightmare ruling everything out to solve my stalling / idling issue. Here's the thread if it helps....

https://rennlist.com/forums/911-foru...startup-3.html