After living with a car that runs smooth as silk at any point except when it idles for months now I think I finally got it. Car would miss noticeably at idle, trip computer showed about 13.1 to 13.4 mpg pretty consistently.

Steps I took:
1. New plugs, coil, cap, rotor, plug wires air and fuel filters. Got a euro ECM off fleabay that ignores the O2 sensor. Results - maybe 30% - 50% improvement at best.

2. checked ground strap on engine, cleaned fuel injection electrical connectors, checked and replaced all the vacuum hoses I could find/get to. Dumped several bottles of Techron into the fuel. Maybe another 10%-20% improvement. Still missed at idle though. Enough that passengers would mention.

3. Got 6 brand new fuel injectors from Rock Auto, $37 each, plus another $3 for the seal set. Did figure out the seal set does not come with new o-rings for where the little plastic cups fit into the manifold. Ordered those. Installed new injectors, cleaned throttle body (pretty dirty but not horrendous), checked side clearance for .002 gap (which it was). The old injectors were most likely original. Very bad, very dirty, half of the caps were cracked. These things were horrible. I know a re-builder that will clean, rebuild and flow match injectors but the cost for this is $35 each and they may reject any that they feel they cannot rebuild them.

Since this is not a direct injection system, I didn't think flow matching would be worth it and with new ones at $40 each with seals it was a no brainer to go with the new ones.

This made all the difference in the world. Car idles smoothly, no discernible misses, and better throttle response. Trip computer is now showing 15.2 mpg mostly surface streets with some freeway. Put 87 Octane in for first time instead of the 91 I had been using and not a ping or knock to be detected.

Very happy at this point!

I understand that many many things on these cars can create a rough idle but truthfully after finding all the things that needed doing I can tell you that my 2006 Super V8 would have flipped out way before things got to this state, set all kinds of DTCs and probably gone into restricted performance mode and had to limp home! If it even ran!

Instead, the 1985 idled a little rough.

 

Good process of elimination!


Basically, this needs to be cut and paste into every third thread on this section.


Was there any evident foreign material build up in the injector caps? I had a big issue of a rusted tank, which killed the fuel pump, yet crap still managed to get past the pump and filter and gum all the injectors up.

 

Good news.

Yep, these "old bangers" as they are often referred to will actually keep running way after the "newer banger" is dead and buried, along with your maxxed out credit card.

ENJOY.

 

Mark,
I have a maybe, a stupid question. What is the resistance of the new injectors? I'm having a few issues and recently(yesterday) tested the resistance and they were 3.6. My thought is that this is real low, but I have no data to back this theory up. if possible for you to give me this info, I would be very greatful. I have been tempted to do the same swap out, but i cleaned and tested the ones I have and everything seemed to be O.K.. Just O.K. though.
Mirek

 

Couple of pics. All (6) pretty dirty. (2) are cracked as in the detail shot here. The o-rings that go into the manifold were hard, brittle and cracked.

Here is the link to what I put in: More Information for AIRTEX / WELLS 4G1045

They do say they are on close out. At $37 each, no core charge, brand new - they worked for me!