Hi all,

Having some problems with my 86. It's hard to start and idles really rough. Doing alot of "seeking" for an idle speed. Once it's warmed up it's a little better but while driving it kinda cuts out and stumbles pretty badly when you try to accelerate. The only code it is giving me is a 44 - oxygen sensor lean error.

Here's what I've done so far:
New spark plugs, wires, distributor cap and rotor
New fuel filter
Checked injectors all were around 18 ohms except for the cold start injector which was only 6 ohms. a search tells me that the regular injectors are okay but I'm not sure about the cold start.

Since it isn't throwing me much in the way of diagnostic codes, any help would be appreciated. I freely admit that this has me kinda stumped.

Paul

 

just because the inj Ohms OK does not mean they are good.
That means the coil in the inj is ok. The inj nozzel can still be clogged or worn out. Spray is everything...

fuel pressure? at key ON ...then at idle>?

does it maintain that pressure driving?

Fuel is the only problem that doesn;t have a code. If the 44 code shows lean, that can be from the inj not spraying well.
Run some high quality inj cleaner thru, or even a pt of marvel mystery oil in 1/4 tank of good gas. See if that makes a difference. Usually at this age they need and should get new injectors..

 

Try checking (Ohm) the injectors when the engine is hot. If they're original injectors I can guaranty you've got a couple that are bad.

 

Thanks for the replies. I bought the car used about 8 years ago, so I assume they are the original injectors. From what I read, it sounds like they should read somewhere over 11 ohms hot, is that right? What about the cold start? Cold it was only reading 6 ohms. Which leads me to believe it is failing for sure.

I usually added a bottle of injector cleaner about once a month but I'll try a heavy duty cleaner and see if it helps. I hadn't checked the pressure at the rail yet but I'll try to pickup a gauge and see what it reads.

If I do need to replace the injectors, who has the best quality and price for a set of all 9?

Thanks!

Paul

 

does it die at idle? if so it could be the IAC.

I have an '86 and replaced the fuel filter, rand some Techron cleaner thru and then the injectors with stock ones from Jon at FIC.

very different running car. the best money I ever spent.
Good Luck!

John

 

don;t worry about the C S injector. Its only involved for 8 seconds and even then, its almost unnecessary in most climates.

Buying new injectors...without a doubt,...FIC. Call Jon. His "kit" comes with all the o-rings (and you need to change them ALL or die in a car-b-que) all the gaskets for runners, plenum and TB, and 8 Bosch-III injectors that are flow matched and tested. Approx $250. Best deal in town. Do a search here for some opinions of FIC. Do a YouTube search for "fuel injector change" to see a C4 get new inj...and some good FIC video thats educational besides entertaining.

fuel pressure...there is not any place in this system that matters other than that schrader valve. FP anyplace else doesn;t mean much. That valve IS the pressure the inlet side of the injectors will see, and that rail pretension tells you how the pump is doing and IF the inj are holding.

Fuel system fun facts:
For reference:
key ON no cranking 40 psi
key on cranking: steady drop from 40 psi about 2 at a time until it fires
eng idle 38 psi
eng revved: drop as low as 30 as the engine rpm goes UP....but immediate recovery and full recovery when engine hits a steady rpm, no matter if its 600 or 6000. That tells you if the pump is keeping up or not. When rpm go up the pressure should go down for an instant...until the pump catches up.
d/c the vac hose to the fuel reg and pressure should rise a few lbs. Should drop back to 38-40ish idle when vac hose is re-attached. Once charged the system should hold pressure for hours...Shut eng off,. should hold 40. 2 hrs later it should still be in 30s. A good system will have over 20 as much as 8 hrs later. Or more...thats what the 2 second prime is all about...recharging the fuel pretension so the engine can fire but NOT flood.

While idling and observing the gauge...Any flickering of the gauge needle is telling you that the filter or sock is clogged. A needle thats slow to recover after the eng is revved says tired pump. Gauge needle should be solid and move smoothly, not erratic or tics.


If you;re going to do a filter, run the engine with the pump unplugged and fuse removed. Since there are several ways for power to get to the pump, I prefer to simply unplug the pump at the tank and be sure...run engine till it dies so you have used as much of the gas in the line as possible. This keeps you from wearing it. You've already done a filter so you have some understanding of this...

If you do injectors...trick is to use vasoline for o-rings, be clean, and have your tools assembled on hand when you start. Test each phase for leaks during reassembly.
It takes a fair collection of 1/4 drive torx wobbles and extensions to pull runner bolts. Pulling the dist makes some things easier. Have new vac hose there to replace any that is now accessable. Many folks toss the torx and replace with allens.

IMO...you;re headed one of those 2 places...either in the tank, or most likely under the hood. BTW...driving it up on ramps and getting that front end UP as much as possible will make your spine much easier to live with in the days following the inj swap..

fuel system cleaner...get the top shelf kind. $20 a bottle. Techron at least. MM oil will free sticky inj and help for a while. These inj were never designed for alcohols..so when they;re gone they're gone for good. FIC does not even bother rebuilding these. You'll see the pile of C4 fuel injectors if you watch his videos..

Good luck and have fun!

 

Check for vacuum leaks while you are looking around.

 

Thanks for all the replies! Good information here. Guess I've got alot of work to do this weekend.....

Paul

 

Remember,

money spent on the proper test and maint tools will save you that cost again each yr.
Test, check, confirm. Its too easy to throw parts at a C4 and still NOT get it fixed.
The BEST investment that you will ever make is in a set of FSM for your yr model. That, a fuel pressure test gauge, DVM, spark tester, mechanics stetiscope, vac tester and ramps.

At some point in the future you;ll be needing a box, full set of allens and torx bits,. lots of extensions and wobble joints for sockets and a dental mirror and a little person. Any little person will do but really little ones seem to work better for brake booster link pins, a/c programmers and blend door actuators... It's hard to find a good one this time of year. They're all under contract till after Dec 26....