Initial Timing Questions + rough idle

[ab_slack]

87 Bronco II, 2.9L

I have to questions about setting the initial timing

1) When I pull the shorting bar off to remove the electronic advance, is there still anything that will affect the advance or can I be certain that all advance is removed and that adjusting for 10deg will be the correct initial timing? In other words, could a problem someplace else, like in the vacuum system mess it up? If there are other things, what do I need to watch out for?

2) I believe I am using the correct reference mark. I can clearly make out the markings on the pulley and the 10deg mark is highlighted. It is the referenced marks I have some doubt about. Below is a picture. In the picture I believe the pointy indicator at A is the correct mark, but I am puzzled by the purpose of B. Can anyone confirm I am understanding this correctly?

My reason for digging into this starts with a rough idle with a significant number of misses. This causes the B2 to fail emissisions. I found there was no EGR solenoid. Putting one in made little difference but seemed to help low end power slightly.

I went to check the initial timing out of concern that it may have been set incorrectly. With the engine warm and the shorting bar removed, the RPM dropped from around 800 to 500 and I found the 10deg mark was falling about midway between the pointer (A) and that circular item (B). I adjusted it till 10 deg aligned with the pointer (A). When I put the shorting bar back on the timing advanced to where the pointer was now at 27deg. From what I read this is about what it should have done.

After making this adjustment, the idle remained about the same however the number of misses seemed to be reduced slightly. In neutral if I gave some throttle, the engine seemed to be “quieter” if that makes any sense. It seemed smoother (less vibration?) if that is possible. When driving however, power seemed to be a bit less above 2500 RPM. There was also some hesitation in the 1500 to 2000 RPM range which I had only noticed a hint of before. Lastly, there seemed to be an odor to the exhaust that I hadn’t noticed either. In the emissions test, the NOx and CO were not a problem and this got me wondering. It is possible the odor was a remnant of all the off tuning that occurred while adjusting.

I am hoping to get the initial timing good so I have one solid footing to start digging into some other suspected areas like the vacuum system. Getting these questions I have answered would help. If there are any other suggestions I would appreciate it.

Thanks,

Andrea

 

[slc10844]

Use the pointer to set the timing. The round tab is for some types of diagnostic equipment that have a timing probe. The probe gets inserted into the ring which holds it in place. You set the timing correctly.

 

[adsm08]

If NOx was not a problem then installing the EGR solenoid has done nothing, and I assure you THAT had NO effect on your low end power since the EGR system is only engaged at high ground speed and a steady cruise.

As stated before, you did set the timing correctly. It is fully electronic advance, no vacuum, nothing but the computer.

If your NOx and CO were correct on the initial test I'm going to assume that your HC was an issue, which is fairly predictable given the misfires.

Given the hesitation, the stumble, and etc I would recommend replacement, or at least inspection, of the spark plugs and the wires. I'll bet you have at least one cylinder that has a bad plug.

Finally, if you want a hair more power out of it, hit the timing for another 2 degrees once you get it through emissions. More timing will help HC levels, but can screw with your NOx.

 

[ab_slack]

Thank you for the feedback. Glad to know I got that bit right.

I also did a EGR diagnostic after the original post and realized from the details that the valve was defaulting closed and thus the EGR solenoid was irrelevent.

The shop I had it at insisted they couldn't get idle running smooth at idle and didn't know what that missing item was in the vacuum system. From what I found out, how far off initial timing was and what you said here about only electronic advance it is clear they don't know this engine.

They should have put new plugs in it, but I am gonna have to check. I was already starting to think about getting a new set of wires, distributor cap and rotor.

I also believe the check engine lamp is either burned out or pulled. It doesn't come on when I turn on the ignition during the time when several light temporarily. I thought it did. So it is possible it is indicating and there might be some codes that are useful.

I think I will try the wires and check/replace the plugs if they aren't new as the next step.

Thank you both for the confirmation and help.

 

[Psychopete]

There's no provision for a CEL in 86-87 model years.

 

[ab_slack]

There's no provision for a CEL in 86-87 model years.

CEL, Check Engine Lamp I am guessing. Okay, good to know tho that seems odd just those two years.

 

[Psychopete]

First years for multi port fuel injected 2.9L. 86-87 years are the only 2.9Ls that were equipped with EGR systems (you can swap to a later computer to properly disable it). Just hate to see you try and solve a non-existent problem.

 

[ab_slack]

Replaced, the cap, rotor and wires. The cap was very dirty inside as well as the rotor. Plugs should have been new, maybe 300 miles on them, but I pulled one to check anyway. It looked at it seem some heat, but there wasn't major discoloration of the insulator on the inside nor evidence of erosion and gap was right on. So I figure the are good so left them in.

The result was some more improvement on top of what I got from the timing adjustment. At higher idle 950rpm and up there were little to no detectible misses. At 800rpm to 850rpm I there were some, a bit more than I cared for. Sometimes a couple quickly and then none for several seconds. It seemed worth trying emissions again though I been very sensitive to any miss. This time it passed. I don't know how close to the limits it was as they didn't give a report this time. Previously the unburned HC were 3x the limit, but idle was much rougher then.

I'm thinking there is no point sweating the occasional miss at low idle. Beyond that it actually idles quite smoothly.

Again thanks for the help.

 

[armadillon]

Thanks for letting us know =) Very cool to hear