funxman

I need some direction here. My 86.5 idles fine and pulls hard at WOT over 3500 rpms. But say 1500 to 3500 rps or so it lugs and feels like half the motor is dead, once in a while i'll get a little backfire under the hood. New plugs, compression between 162-170 on both banks, checked ohms and lightning tested wires, caps and rotors near new, coil resistance is good on both sides. Replaced the TB and ALL gears two years ago. I've been looking through the posts here like mad lately and see a lot of different things. Im overwhelmed with possibilities... just need someone with some expertise to tell me I will survive this and where to go next. I'm plenty mechanical, just need to know where to mechanize.. Much appreciation in advance to everyone on here.
Robert

SeanR

I'd start by going through the vacuum system and ensuring that that is nice and sealed up.

Landseer

I'd also pull the wires and look inside each of the two coils for corrosion if you haven't already.]

Also, weird, but make sure both cam covers are seated well and aligned with the motor. Had one slightly crooked on an 85 and it allowed the rotor to cut grooves in the cap.

Mrmerlin

inspect the plug wires where they connect to the plugs see if one or more of the wells have oil in them

Ron_H

I have symptoms similar to those described when cold and at light throttle just starting off...........when it is raining(high humidity). Engine warms and it goes away. Raise the revs and it goes away with a jerk as if something was not connected and suddenly connected. No rain = no problem. I'll check the suggestions posted too.

Landseer

On Jadz928's S4 he had those symptons. We discovered one coil end packed with white corrosion.

On my 85, it was bad grounds at the back top of the motor, hard to access, under the fuel lines under the air filter.
That is where important stuff is grounded, i.e. MAF, LH, O2 sensor to name a few. In my case, the wires were corroded in the solder joint leading into the ring terminal, under the insulation!!!

funxman

The originally posted symptom are mostly when weather is cold as well. Ron, that "jerking" as you described is a big problem with mine in cold or hot conditions. Especially when accelerating after gear change...and randomly cruising through town.. Im gonna check those engine grounds next then go through the vacuum lines - again. Thanks. R

Landseer

The temperature and humidity and car temperature seemed to have unpredictable and non-repeating interactions with my ground issue.

Never knew if it would start, and if it did if it would keep running, and if it did, whether it would act completely normal or die under load or stutter like the driveline was binding.

John Speake

Have you set idle CO and speed as per the WSM ? That is also a good check of MAF ageing. If you can't get up to the correct idle CO reading of 0.6% +/- 0.2% then the MAF is due for replacement.

A weak MAF could also give hesistation in the mid range.

funxman

I adjusted the maf using the ohm meter discussed on other threads. I have no idea how to check "correct idle CO reading of 0.6% +/- 0.2%" I went from 345, to 300 and it smoothed out a lot, but mid range power seem to drop. Down to 270 and power started to pick up again with slight hesitations. I pulled each plug wire while running and found a cylinder not keeping up with the rest. Compression and all ignition components are good so I pulled the injectors over the weekend. The weak cylinder had an oddball injector evident of a previous replacement or something. And the rest looked pretty cruddy. I ordered matched set of the 24# ford blue tops. I am sensing progress...

Thanks Robert