I am experiencing a really odd intermittent miss with my '85. About a month ago, I drove across town, stopped at a store about 6 blocks from the house. Went back out and cranked it up, it acted like the timing was way out and was missing unbelievably bad. Nursed it to the house, bucking and jumping. Went out the next day, cranked it up and its running fine. Two weeks ago in bumper to bumper traffic it started to miss a bit but cleared up when I got out of the traffic jam. Last week it started a steady miss, not horrible but chugging along running like crap. Ran like that a day and a half and cleared up and running fine. Any suggestions on where to start looking? I am thinking maybe coil or ICM going south or the grounds for them? I hate intermittent problems!!

The only diagnosis I have managed so far is put the Auto Xray on it and it shows no codes and I checked the timing and its dead on 6*.

Other info from the Auto Xray:
IAC KOEO: 122 beats KOEO 22 beats
TPS: .54v
O2: 444mv
Knock Sensor: 118 counts
MAF: 2798 gr/sec
Injector Pulse: 1.8ms
It does indicate the car is running rich.

I am not sure what is right or wrong, school me please.

Any help would be greatly appreciated!

 

Are you running a crappy type of gas?

You have knock counts, which means the computer is picking up spark knock, which may cause those symptoms.

I would try running some octane booster first and see if it goes away, if it goes away then you know which direction to go in.

Also, check your fuel pressure while it is doing it. Report back with your results.

 

Thanks Daniel, that was another thing I thought of was fuel. First thing I did was put some fresh in just in case the premium I bought was ethanol dead and no improvement. This weekend I will see about a FPG. Typically incoming fuel issues dont throw codes right?

 

The codes that I could see appearing would be 42, 43, and 44.

But, check the operation of your EGR valve. See if it is stuck in one position. You should be able to push the diaphragm up and down. This may explain the intermittent problem now that I think about it.

Remember to only do this when the engine is cold.

 

A miss is almost always caused by ignition problems.

Usually a wire will go bad internally. When I had a miss I found it by looking at the plug wires in a dark garage. #6 was arcing to the oil dipstick tube. When I went to pull the boot off the plug it came off the end of the wire. The internal conductor was eaten up by the spark jumping the gap where it broke.

The weird thing was the engine ran fine when it was cold but started to miss when it warmed up. Apparently the spark is stronger when the ignition system is cold.

 

Sounds, like a weak, fuel pump?...

Check the fuel pressure.

 

I would put a fuel pressure gauge on the window and drive around. If you lose pressure and the car acts up, then you can zero in on the fuel system. If the pressure is good, then go for the ignition system or other as needed. At least it will give you basic direction.

You got to catch something while it happening and spark is difficult to check when you are on the road.

 

Thanks for the input guys. I am now leaning more towards fueling issues. The car has tried to act up twice in the last two days but I "cleared its throat" by punching it. I will "borrow" a fuel pressure gauge this weekend from AZ and tape it to the windshield for a bit and see what is up.

After that I will go with Cliff and ohm out my wires and check for carbon steaks on the cap. They are about 4 years old now so I dont rule them out yet.

And Daniel, my '85 doesnt have an EGR so that isnt it.

I will post up what I find. Thanks again fellers!

 

If it doesn't have EGR, did you make sure to remove it from the tune? The computer takes away fuel during EGR cycles. If you didn't remove it from the tune, the computer will still make the mixture lean.

 

Ive never done anything to the ECM and I doubt the PO did either. When I got the car part of the EGR piping was still on the exhaust system so I think that wouldnt necessarily indicate a deliberate removal. Reprogramming is not something in my skill set. The fact that it doesnt throw any EGR related code would suggest that something has been done I would think. The fan comes on at 208* so maybe that was done from the ECM and not a sensor change. I dont know. I probly need to find someone local who has the software and find out for sure. Thanks for the ideas.

 

If the computer does not have a different chip set up than stock, then it probably hasn't been taken out of the tune.

This is straight out of All Data. So if you don't let the car cruise at half throttle for 4 minutes, I guess something else may be possible.

I would fix the EGR before you take any other steps though.

Here you go:

CODE 32, EGR SYSTEM FAILURE

Code 32 means that the EGR diagnostic switch was closed during start-up or that the switch was not detected closed under the following conditions.
a. Coolant temperature greater than 80°C (176°F).
b. EGR duty cycle commanded by the ECM is greater than 27%.
c. TPS less than wide open throttle (WOT), but not at idle.
d. Codes 21, 22, 33, or 34 not present.
e. All conditions above must be met for about 4 minutes.
If the switch is detected closed during start-up, or if the switch is detected open when the above conditions are met, the "Check Engine" light will remain "ON" unless the switch changes state.
The EGR vacuum control uses an ECM controlled solenoid valve signal. The ECM will turn the EGR "ON" and "OFF" (Duty Cycle) by grounding CKT 435. The duty cycle is calculated by the ECM based on information from the coolant and mass air flow sensor and engine RPM's. There should be (NO EGR) when in Park or Neutral, TPS input below a specified value or TPS indicating Wide Open Throttle (WOT).
With the ignition "ON", engine stopped, the EGR solenoid is de-energized, and by grounding the diagnostic terminal the solenoid is energized.
1. This test will determine if the ECM set the code due to CKT 935 being grounded on start up. If the code does not repeat but the customer complained of a check engine light after start up then this circuit should be checked carefully for an intermittent grounded condition.
2. If Code 32 repeated, then disconnect the EGR temperature switch and try to reset the code. This will determine if the ECM, wiring or temperature switch is at fault.
3. This test will check for a possible open in CKT 935. The ECM supplies 9-12 volts to CKT 935.
4. By grounding the diagnostic terminal, the EGR solenoid should close and allow vacuum to be applied and the vacuum should hold.
5. This test will determine if the electrical control part of the system is at fault or if the connector or solenoid are at fault.
6. By plugging the EGR valve side ungrounding the diagnostic terminal, the solenoid valve should open and allow vacuum to bleed off through the vent.
7. With the engine not running and vacuum is applied to the valve, the valve should move to the fully open position.
8. Due to this engine using a negative back pressure valve, the valve should close when the engine is cranked over.

 

Sticky injector is my first thought. Punching it moves the coil faster and could free it up. Failing injector coils can also degrade with heat -- creating temporary/intermittent symptoms.

 

again, check the ohms on your injectors before buying anything.
Had the EXACT same symptoms with my old 89.


Edit; check them when the motor is good and hot

 

Injectors, uh huh, uh huh. It crossed my mind that maybe the 9th injector stuck when it happened the first time because it was running so badly. I will ohm them this weekend. I need to go ahead and get rid of the old injectors anyway. It will be another week but FIC will probly be getting a call for some Bosch IIIs.

 

Just keep in mind that checking the ohm's for the injectors will only show you a weak, shorted, or open coil. It will not show you a stuck closed, stuck open, partially blocked, or leaking injector. It's a good starting place but does not in any way rule out injectors.

 

The first thing I would do is replace the Fuel Filter, and go from there if that doesn't cure it.

 

Its first on the list after all the free things like checking the injectors, plug wires and fuel pressure.

 

I only suggested a fuel pressure test as an initial starting point. Not having a pressure tester causes you the guess, dance around and prolong getting it repaired. For an tool that costs $15-$35, it's worth having. Not a tool that used every day but invaluable if you want to maintain your car. Maybe you can even help a friend one day.

In regard to the car being an 85 and given the symptoms, I think bad fuel injectors are a strong possibility. We all have read numerous posts on these vintage cars needing fuel injectors.

 

Wait, How Are You Viewing Knock Counts With An 85 Computer?

 

Wow I cant believe I have been chasing the miss for a year. It has been a real challenge because this car is a daily driver so I havent been able to just leave it until fixed. Throw in a lot of lack of money and I have been nursing it along making it to work every day and buying parts along the way.

My miss was not a single item but a multitude of issues. I am going to go thru the saga of fixing the car which will provide a partial list of things to look at in case someone happens to come across this thread.

1) First I diagnosed with the FSM that the pick up coil went bad. It should have no resistance and after checking mine it did. Pick up coils are not that plentiful for our cars even in a bigger city like JAX. I installed the pick up and the car ran great!.......for two days. Then slowly it deteriorated back to where it was. Called a buddy and asked him about it and he told me the ignition coil was bad and putting too much voltage to the pick up (or something like that). Bought a new pick up coil and found out it was not milled properly and the star wheel points were striking the corresponding distributor points. No other pick ups available in JAX except with a whole rebuilt distributor from NAPA. I also bought the new ignition coil. Car runs good for two days.

2) Convinced that the ignition system was still to blame, I replaced my high dollar Taylor distributor cap and rotor that was about 4 years old. The car finally really improves but not there yet.

3) next was a new set of Accel Spiral core wires. Closer but still not right.

4) Now that the firing system is new, that leaves the fuel system. I replaced the fuel filter while I was under the car fixing the OD coolant lines that had rubbed a hole into each other. No real improvement but a necessary maintenance item.

5) The car FINALLY throws a code 54, low voltage to fuel pump. I work on resoldering the FP relay wiring and get some improvement and the code 54 goes away.

6) Still feeling like the car isnt getting fuel as needed and not having a fuel pressure gauge, I throw a fuel pump at it. Acts like it is fixed for about 15 minutes.

7) I finally give in and buy some rebuilt Bosch III injectors and after discovering a wire I believe came from my deleted EGR grounding against the head where I pinched it under the valve cover and plugging the EST wire back in, I believe its finally fixed!

We shall see. I will be happy if this time next week its still running well.