Multiple Problems...

[gtoman]

First Problem.
I have what feels like misfires (the engine runs real rough) starting at 2000rpm and it continues until 3000rpm. I can't tell if the misfires go away at 3k or if at that point I just can't feel/hear it anymore because of the high engine speed. Any idea what would cause this?

Second problem.
My PGM-FI light does not come on when I turn the key to "ON" and my ECU diagnostic LED does not blink at all to give me any type of code. The OBD0 computer diagnostics book I have says that means that there is a problem with the diagnostic circuit. What is that suppose to mean?

Here is what I have done to try to fix the misfires and the state of the cars health.
Car: 1986 LX-i A20A3 Hatch with the 5 speed.

New plugs, plug wires, cap, rotor button, new accel coil, valve adjustment, my timing is set to 18 degrees advance because I only run 93 octane and I get no pinging at this setting While setting the timing I used a vacuum gauge and I have right at 18 in hg at idle. The head was rebuilt only a few months ago. I did a compression test yesterday and from my highest to my lowest reading was only a 6% difference. My battery is holding at 12.6v and my oil pressure is 25psi at idle up to 52psi at around 3000 rpm. I also have installed a short ram intake that puts the filter right behind the battery. I run synthetic 15w-50 mobil 1 and have fresh 10w-40 in the tranny. That should give you guys a good idea of where I'm at...out of ideas, that's where.

My buddy said that maybe my cat is clogged up. Would that cause misfires?

Thank you in advance,
Adam

[Gt-r]

I can only answer one of your questions with certainty. A clogged cat will not cause misfires. All it will do is cause you to lose some of your horsepower. BUt misfires can indeed tear up your cat.

[2ndGenPreludeSi]

Second problem.
My PGM-FI light does not come on when I turn the key to "ON" and my ECU diagnostic LED does not blink at all to give me any type of code. The OBD0 computer diagnostics book I have says that means that there is a problem with the diagnostic circuit. What is that suppose to mean?

Thats gotta be some sorta bulb problem or somethin'. I was under the impession that if that light doesn't come on for a couple seconds w/ the key on, that the car should not run. That is actually how i was taught to check the main relay, haha. But if it was the main relay the car shouldn't even start, as it powers the ECU and the fuel pump haha

[Buzo]

First Problem.
I have what feels like misfires (the engine runs real rough) starting at 2000rpm and it continues until 3000rpm. I can't tell if the misfires go away at 3k or if at that point I just can't feel/hear it anymore because of the high engine speed. Any idea what would cause this?

This one sounds like a ignition/timing/advance problem to me.

Whatever process yo used to adjust the timing, at the end the timing must be around 15 degrees at idle with all the advance hoses normally connected.

Make sure all your spark plugs are working. If you have one timing light, connect it to one cable at the time and make sure it doesn't miss any pulse. If you see the light not giving a constant train of pulses, its the plug/wire working intermittently.

Make sure your advance actuators are not leaking vacuum.

[gtoman]

This one sounds like a ignition/timing/advance problem to me.

Whatever process yo used to adjust the timing, at the end the timing must be around 15 degrees at idle with all the advance hoses normally connected.

Make sure all your spark plugs are working. If you have one timing light, connect it to one cable at the time and make sure it doesn't miss any pulse. If you see the light not giving a constant train of pulses, its the plug/wire working intermittently.

Make sure your advance actuators are not leaking vacuum.

My process for the timing was to hook up my timing light to the #1 plug wire and my vacuum gauge to the intake manifold while leaving the advance vacuum lines plugged in like normal. I timed it at idle which I have set to about 800rpm. I thought the timing might have been the issue so later I had my wife work the gas pedal as I adjusted it and I couldn't get rid of the misses even with the dizzy at full retard...no amount of changing the timing helped. How would I check the advance actuators?

One thing I noticed is that my new plugs that have about 300miles on them are a bit sooty. There looks to be unburnt fuel carbon on the plugs and the grounding electrodes have a few spots of white as if they are the wrong heat range. They are factory spec NGK V-POWER plugs..
Any other ideas?

Adam

[POS carb]

I'm thinking dirty injectors on this one since your compression is good
they may be dripping (not closing fully)

is your vacuum reading steady or does it flick back and forth?
when you did the compression test how many compression strokes did you use to take the reading? I usually stop at 3.

Also make sure your plug gap is close to spec

[gtoman]

To POS Carb:
I ran a bottle of Techron fuel injector cleaner through the system about 400 miles ago. Also I just went out side and hooked up my vacuum gauge and it 18 in hg steady..no bouncing around. For the compression test I had my wife turn the key for 2-3 seconds with the coil wire unplugged. At lest 3-5 pulses. I think I'm in need of new injectors since I seem to have seeping from the injector body.

To Buzo:
I just put my timing light on each wire and the pulses from them all look pretty inconsistent. Does this mean my dizzy is dieing since its on all four wires? I hope not as these dizzys are expensive but at this point I just want it fixed so I'd be happy if the fix was that easy.

Thanks guys,
Adam

[Dr_Snooz]

the grounding electrodes have a few spots of white

I ran a bottle of Techron fuel injector cleaner through the system about 400 miles ago.

My Bimmer did something similar after I ran a couple bottles of Techron through it. The spark plugs got white spots and I failed a smog test. Replaced the plugs and all was well.

You probably want to look into your bad ECU too.

[Buzo]

To Buzo:
I just put my timing light on each wire and the pulses from them all look pretty inconsistent. Does this mean my dizzy is dieing since its on all four wires? I hope not as these dizzys are expensive but at this point I just want it fixed so I'd be happy if the fix was that easy.

Thanks guys,
Adam

At least you know where the problem is, good plugs/wires should give constant trend of pulses, always.

But don't worry, it might be only because the plugs are getting too much fuel during the start ups you are doing while chasing the failure.

Remove your plugs and clean them. I use my dremel with the little wheel made of small wires (Don't know how it is called in english!) But you can use anything that works for you. polish them until all the carbon deposits are removed and the metal brights again.

Re-install them and re-test. It should work OK now, but if they come back to the same inconsistency, then the problem is still there and the fouled plugs are a consequence and not the cause.

Did you measure the timing with all the hoses connected? What was the value?

[gtoman]

To Dr._Snooz: So, no PGM-FI light and no led blinks means the ECU is bad for sure? Tomorrow I'm going to change the plugs and see if that helps since it's the least costly attempt.

To Buzo: Yes, I meant the timing with all the hoses connected. The timing mark on the flywheel lines up with the timing mark on the block and my timing light says 18 degrees BTDC. I have tried lowering it back to 15 but like I said, that didn't help.

To all: I hope the plugs fix it cause if not I think I'll be stuck looking at the dizzy and the ECU as the problems... I have no idea how to test these electric parts.. How ever I can work a voltage meter and am willing to learn so.. I will repost tomorrow to let you all know if the plugs worked.

Thanks again,
Adam

[Oldblueaccord]

Could try and unhook a sensor and see if the ECU does code out. Unhook some thing easy like the intake temp sensor. Its possible the ECU light on the dash is just bad since the car does run.

The dizzy advance runs around 2500 rpm so if you right at 55 mph in 5th you will get some surging etc as it pulses in and out. If its out right missing there then the plates inside the dizzy might be worn so bad there causing it. Pull the cap and the cover and look in there.


wp

[gtoman]

So I bought new plugs and the first thing I did when I got home was finish installing my a/f ratio gauge.. After I got home from a test drive I noticed that sitting in my garage the car stopped the missing prob completely. This lead to some experimenting and I found that it only does it when the car is warming up and still in "open loop" mode. Once it's up to temp and I drive for a while I can stop and bring my rpms up slowly to test it and I get no missing. Each time I let the engine cool completely and then test it while cold, it misses until it's warmed up. This I can live with but I still wonder why it does this. While warming up my a/f ratio gauge is pegged all the way rich and I can watch the ratio come down as the engine warms up. Could the missing be a result of the overly Rich "open loop" mode?

I did put the new plugs in anyway (NGK V-Power) but it didn't change anything.

Thanks for the ideas guys,
Adam

[Buzo]

Congrats for your experimenting. I believe these cars are set too rich during warm up, at least the carbed ones are. So at soon as something go wrong with the settings, they start acting up due to the too rich mix. And the proof is the people here experimenting the problem of hard re-starts after a quick stop.

So yes, I believe your missing pulses are due to the rich mix at startup. But if you have that great fuel economy, just leave it as it is.

How about the original problem you had? Are the misfires and running rough fixed now?

[POS carb]

how long has it been since you got new o2 sensors? They are cheap for these cars!

[gtoman]

To Buzo: I would't say fixed cause it still misses when cold but now I understand that it only happens when the engine is cold so I don't really mind because I let all my cars warm up some before driving. My gas mileage was 29.4mpg on my last tank and that was driving hard most of my commute.

To POS carb: I have not replaced the 02 sensor yet. I know it's cheap and I plan to do it soon because I want to relocate the 02 sensor down into the collector so it reads from all four cylinders. Right now my sensor and A/F ratio gauge are only reading from cyl #4.