Acura/Honda Ignition Specialists Enter Here

[paulo57509]

I need some help from the Honda/Acura techs on the board.

My '87 Legend (C27A; 2.7L) has developed an intermittent miss that I'm having a difficult time diagosing. The miss showed up on the drive home from work, a few blocks from the factory. The engine ran fine when I went out for lunch earlier that day. The miss is intermittent and varies in severity; it'll miss one or two beats on time and miss severely at other times. It does at times seem temperature dependent (cannot swear to this); it'll start acting up after a few minutes from a cold start. If the problem isn't ignition related, I would say it does feel similar to fuel starvation. The miss is particularly bad between 1500-2800RPM.

The car is what I would call pre-OBDI; there is a check engine light and the ECU will set trouble codes, but there is no scan tool interface. No CEL and no trouble codes have been set.

It had been a long while since the last tune-up, so I just figured I had a bad plug wire or something and just threw replacement parts at it thinking I'd catch the problem in due course. I replaced the plugs, plug wires, cap and rotor, coil (I thought this might be the problem), fuel and air filters. I left the PCV valve alone because I didn't have replacement cover seals on-hand. What I replaced had no affect on the engine miss.

I verified that there is something happening with the ignition system when I hooked up my old Heathkit scope to the engine. Intermittent "blips" can be seen on different cylinders when viewing the secondary pattern. Unfortunately the blips are too quick and the pattern is too small to really tell what is being shown. However, the blip looks similar to what happens when the coil is putting out max voltage. The scope isn't able to show a primary pattern.

This is what I have done so far:

1. Replaced the igniter. The igniter is what switches the coil primary on and off. Road test. No change.

2. Swapped the ECU for a known good ECU I had on the shelf (the ECU is what tells the ignitor to switch on and off). Road test. No change.

3. Unplugged the cam/crank position sensor. Road test. No change.

4. Unplugged TDC sensor at the distributor. Engine wouldn't start. Figured this probably isn't the problem.

5.Unplugged throttle angle sensor. Road test. No change.

6. Fuel pressure regulator isn't punctured. No fuel spews out when the vacuum line is disconnected.

7. No vacuum leaks that I can detect with a spray can of Berryman B-12.

Planned next steps:

1. Unplug the temperature sensor. Who knows? This was the cause of the idle not returning to normal a few years ago.

2. Look at the fuel system. The injectors are all happily clicking away. However, I haven't hooked up pressure gauge yet.

3. Fuel pump pick-up sock clogged?

4. Dirty throttle body?

Sorry for the long post. Any other thoughts or suggestions would be appreciated. Thanks in advance.

 

[EricF]

Check your fuel pump pressure and when was the last time the fuel filter was changed?

 

[Tosh]

I had a 90 Legend, and I had an occasional misfire that got worse for years until it became obvious what it was: distributor seal was letting oil into the distributor. New rebuilt distributor: problem gone.

(Dealer put in a new igniter free under a service campaign, although I never had problems, but this might not apply to yours.)

 

[paulo57509]

Originally Posted By: Tosh
I had a 90 Legend, and I had an occasional misfire that got worse for years until it became obvious what it was: distributor seal was letting oil into the distributor. New rebuilt distributor: problem gone.

(Dealer put in a new igniter free under a service campaign, although I never had problems, but this might not apply to yours.)


Legends are notorious for either leaking oil into the distributor or dry, rusty distributor shaft bearings.

 

[chrome]

When was the last time the valve clearances were checked? Some Honda motors have valve clearances that tighten up with mileage. Too tight clearances may cause an intermittent misfire which isn't ignition/fuel system related because the intake/exhaust valves don't fully close when they should.

 

[mechtech2]

This may not be an ignition problem.
Look to injectors or other fuel problems.

 

[paulo57509]

After careful observation, the problem appears to be temperature related. The engine runs fine after a cold start until the temp gauge gets just past the second line up from full cold. In other words, the engine runs like [censored] after it gets into closed loop.

This narrows things down a bit.

 

[mechtech2]

You should be throwing a code with an engine that really runs poorly.
Sometimes they are hidden. Have it checked. Autozone often does this for free.

 

[paulo57509]

There are no trouble codes; no scanner or coder reader is required to read fault codes. It's a pre-OBDI system so there's no interface. Trouble codes are read by counting the number of blinks of an LED through a little window on the ECU. Diganosis is performed through the use of a breakout box and special adapter harnesses.

It's a moot point now. The car was stolen out of the park-and-ride lot sometime yesterday. It's probably in Stockton someplace in little pieces by now.

 

[paulo57509]

Originally Posted By: paulo57509
It's a moot point now. The car was stolen out of the park-and-ride lot sometime yesterday. It's probably in Stockton someplace in little pieces by now.


The Tracy Police Department left me a v-mail message on the cell phone over the weekend.

The car was found in Denver, CO. From what the Denver Sheriff's Department told me, the car seems to be in one piece without damage (I figure the ignition has to be bashed). They don't know if it runs; no key and the battery is dead.

Now I have to figure out a way to get it back to CA.

 

[eljefino]

 

[PandaBear]

At least you found it in one piece. Not too bad out of a bad situation.

 

[jmac]

I have this exact engine in an Accord. Mine was doing the same thing and I replaced plugs, wires, cap and rotor and still was happening. So it was either bad igniter or coil, both fairly common with age, replaced with a Honda coil and all is good.


Oh, I see you replaced the coil, mmmm, does yours have an EGR valve?

 

[paulo57509]

Originally Posted By: jmac
I have this exact engine in an Accord. Mine was doing the same thing and I replaced plugs, wires, cap and rotor and still was happening. So it was either bad igniter or coil, both fairly common with age, replaced with a Honda coil and all is good.


Oh, I see you replaced the coil, mmmm, does yours have an EGR valve?


Yes, it has an EGR valve. I was getting an intermittent Code 12 (EGR). The diaphram in the EGR had a small puncture. Replaced the vale and the code was gone.

 

[Tosh]

Originally Posted By: paulo57509
Now I have to figure out a way to get it back to CA.

What does your insurance co say about it?

 

[paulo57509]

Originally Posted By: Tosh
Originally Posted By: paulo57509
Now I have to figure out a way to get it back to CA.

What does your insurance co say about it?


Vehicle was only covered for liability.

 

[paulo57509]

Just posting to close the loop on this one.

I wasn't holding out much hope that it would do anything, but this afternoon I used this:

Along with this:

And the miss has gone away. I'm not going to say it's gone for good, but it OK for now.

 

[paulo57509]

The injector cleaning didn't do anything permanent. I got a decent price on a set of six new injectors so in they went = FAIL.

However, when I looked through the holes the injectors squirt through, the injector cleaning did clean up the portion of the manifold where the injector spray pattern hits.

Continuing to think fuel because the ignition had already been addressed with no resolution, I installed a new fuel pump last weekend. It still had good pressure, but ?? regarding volume. It was the original pump with +400k miles on it, so I figured I might as well kill at least one bird with one stone. FAIL as far as the engine miss goes.

Last night I figured I'd hook up the engine scope again and take another look at the ignition. No. 5 firing line looked kind of funky. I swapped plug wires with No. 6 and the funkiness remained with No. 5.

I pulled No. 5 plug this morning and found this:

I must have broken the plug during installation. This would explain why I saw no difference after servicing the ignition system way back when. I still don't know what the original cause was, but the engine miss under load is gone and it's running like a champ again.

Lessons learned:

1. It doesn't hurt to double check your work.
2. Don't be lazy and get the engine scope out of the cabinet.
3. Use care when installing spark plugs, STUPID.

 

[mechtech2]

That plug may have been dropped in the box before you ever saw it, or simply made with a fault.
Good eye to find this, and good deductions.

I can't see why the injector cleaning fixed this missfire, though. Maybe perceived hope?

 

[paulo57509]

Originally Posted By: mechtech2
That plug may have been dropped in the box before you ever saw it, or simply made with a fault.
Good eye to find this, and good deductions.

I can't see why the injector cleaning fixed this missfire, though. Maybe perceived hope?


I have to credit the old Heathkit scope I picked up on ebay 10 or so years ago. I had to dig out my old text books, etc. to refresh my memory on how to read scope patterns. I don't own any cars that I can hook it up too; everything is electronic ignition. But I was able to get it to show a secondary pattern on the Legend after looking at the car schematic for a few minutes.

The injector cleaning fixed it for a few hours. I didn't have much hope that it would do anything, but it wasn't difficult to unplug the fuel pump and attach the cleaner canister to the service port at the fuel filter. It was a shot in the dark.

I was also wondering if the plug was defective out of the box.

It only took a year to figure this one out.

At least I have a somewhat rebuilt fuel system (new injectors and pump). I should be good for another 400k miles.