89 renix rough idle

I cleaned the cap and rotor tips today with a nail file, then washed the cap out with CRC brake cleaner, expecting it to dry immediately. Odor was different, not drying, so I checked the can, and seems CRC changed the red can, non-flammable Texas formula from perc only to now include trichlore.... and a petroleum distillate, that refused to air dry at 70 F , %#@&^%!$#@ nonsense!!!! Some one tell me why that would be good for brake cleaner please!!!!!

Not a happy camper!

The rough idle improved, after I dried out the cap, but was not yet right. So I started looking around the hood, pulled the vacuum line to fuel pressure regulator, and found gas leaking, diaphragm is bad.

So time for a new FPR today. I think it may be the 89 FPR still on there, unless the PO swapped it ages ago.

Seems that in the past whenever I cleaned rotor tips with a purposely broken piece of a points file, or sm. blade, the tips seem to corrode/char even faster with the protective coating thusly removed. Do you think clear nail polish, or actual clear polyurethane paint would be the proper way to re-treat the oem cap rotor tip protection against the aforementioned funkiness?

Weird deal with the formula change-up. :eyes:

Your '89 should be almost brand new by now.., right?

Actually my 87 has a lot more new stuff, work done it. The 89 only 114,000 miles on it when I grabbed it 4 years ago. It had a bad head gasket, between #4 and 5 cylinders. Got about 45,000 miles on it since then. My daughters first vehicle, the 89.

I use the brass tipped caps (no coating, and not aluminum) and the brass tipped rotor, which seems to have a black oxide coating on it when new, but the caps are bare brass. Paint will not hold up. A hard chrome or Nickel plate might work, but platinum would be the ultimate, like they use on the spark plugs now. It really only takes five minutes about once every 10-20,000 miles to knock off the high spots, carbon/oxide junk.

I found a bunch of conductive dust in my 87 cap a few weeks back, that I think was starting to track HV.....just cleaned the dust out, and knocked down the high spots on the tips, and ran great again. I think the gap widens over time from erosion and gets too large at some point. The wider gap may be increasing the wear rate as the spark gap gets wider, more than a loss of any coating or film? Thus needing to be redressed more often.

But if there is an organic film that can handle a HV, something with a very high dielectric strength, and that can handle heat, HV, probably ozone and OH free radicals, a thin film coating to stop oxide formation could be interesting. It would need to be extremely oxidation resistant.

The FPRs have gotten expensive!!! Most are wanting $80 for them. Found one at AZ for $57.

AMC/Jeep used to ship their vehicles with a dab of dielectric grease on the tip of the rotor. That caused rough running. We used to take the rotor off and give it a quick brush-off on the wire wheel. Problem solved. It seems the dielectric grease got funky somehow and inhibited conductivity between the rotor and the cap.
Won't your rotors and caps go the 30K mile interval until replacement without giving you trouble?

I have never tracked the mileage on them. But I typically only clean and reuse them once, before replacing them.

I typically use two rotors and caps to one set of plugs. The plugs seem to last forever.
I was using Ford 6 cylinder caps for awhile, half the price and better made. But that was awhile back, my local parts place had the Ford Caps hanging on a pegboard, cheep and durable. The Ford cap don't have the air vent, a plus if you occasionally get in the deep stuff.

I had continuous idle problems (miss) with my 87. I finally cured it with a set of coil wound solid core cables. Just the plug cables, my 87 didn't like the solid core, coil to cap wire. Blue Max I think, superior silicon boots seal up well.

Cleaning out the carbon dust left from the center electrode wear is always a good bet.

It is getting hard to find old school petroleum based brake cleaner anymore. Whatever they are using now eats the skin off my hands after a few days, it's either terminal herpes or I'm allergic to it.

Loc Tite (Henkel) makes a spray that seems to work. Though I use it as a sealer, plug wire boot lubricant and not inside the cap or on the rotor. Makes getting the plug cable boots off again at some future date, a whole lot easier. http://www.loctite.co.uk/cps/rde/xc...D=productfinder&redDotUID=1000000J7H8232MOUNI

8Mud said:

I typically use two rotors and caps to one set of plugs. The plugs seem to last forever.
I was using Ford 6 cylinder caps for awhile, half the price and better made. But that was awhile back, my local parts place had the Ford Caps hanging on a pegboard, cheep and durable. The Ford cap don't have the air vent, a plus if you occasionally get in the deep stuff.

I had continuous idle problems (miss) with my 87. I finally cured it with a set of coil wound solid core cables. Just the plug cables, my 87 didn't like the solid core, coil to cap wire. Blue Max I think, superior silicon boots seal up well.

Cleaning out the carbon dust left from the center electrode wear is always a good bet.

It is getting hard to find old school petroleum based brake cleaner anymore. Whatever they are using now eats the skin off my hands after a few days, it's either terminal herpes or I'm allergic to it.

Loc Tite (Henkel) makes a spray that seems to work. Though I use it as a sealer, plug wire boot lubricant and not inside the cap or on the rotor. Makes getting the plug cable boots off again at some future date, a whole lot easier. http://www.loctite.co.uk/cps/rde/xc...D=productfinder&redDotUID=1000000J7H8232MOUNI

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Solid "what?" cores? Ours are some kind of conductive carbon fiber secondary wires to the plugs.

I went out and looked today, I used straight solid core wires, pretty much straight braided copper with no suppression properties. Worked for me and didn't mess with my sound system (likely luck). Except I used a new regular carbon core, coil to cap wire after trying a solid core coil to cap wire and picking up a significant miss.

Old Man said he used coil wound copper core, that does have (spark noise) suppression. And got about the same results.

In effect, low resistance spark plug cables seem to work better. I don't know exactly why the higher resistance carbon core cables may cause a miss. My guess is the stock ignition coil is basically a hotter (higher voltage or cleaner sharper spark) and the resistance in the carbon core wires can cause some sort of interference. Or maybe even the extra resistance in the carbon core wires causes an occasional odd or wrong path to ground for the high voltage spark. Much like carbon dust can do inside the distributor cap.

I didn't have to buy the wires, I had a bunch of left overs from my race truck days. I stuck them in there to see what would happen, both my 87 and my 88 thump nicely and never miss a beat.

Back in the day, a Dodge with a hotter ignition coil needed a bigger diameter distributor cap or the spark tended to jump occasionally from the cylinder that was supposed to fire to an adjacent electrode on the cap. They said it was because the high voltage took the easier path to ground and that may be to an adjacent cylinder electrode in the cap. They said ( I sure don't know the validity of the statement) this was because a plug under compression actually has more resistance at the gap than a plug not under compression, who knows? They made kits for the Dodge so you could install a larger diameter cap on the standard base. I've seen carbon/flash trails from one lug in the distributor cap to an adjacent lug on my Dodges, it happens with high output coils. A lower resistance spark plug cable may be the difference between the spark finding an odd/wrong path and the right path to the spark plug that is supposed to be firing. Just a hypothesis that may or may not be valid.

But lower resistance solid core or coil wound solid core plug wires just seem to work better in my Renix. I've ohm tested many carbon core plug wires. The way to test them is the ohm meter on each end with a clean solid connection (end) then flex the wire like a snake crawling and watch your ohm meter closely. A significant number of times I've found high resistance in the carbon core especially when the cable is flexed some. More common in older cables.

You might want to take a look at the connectors between the coil and ignition module. Coils are relatively high ampere. The connectors between the coil and the module can get that blue color from overheating, anneal and relax. Soft connections in a relatively high ampere circuit can cause voltage/amperage loss. The loose connections radiate heat (watts) and/or have reduced contact area and may not be passing enough juice to do the job efficiently. BTDT

Nothing quit like the sound of a well tuned Renix, maybe idling a tad low and going thump, thumo, thump and never missing a beat.

Something like this may work better for you, the next time you need spark plug cables. http://www.summitracing.com/parts/TAY-74648/ Though I can't recommend this specific wire, never tried them.

A plug under compression would have a denser mass across the spark gap, so if that mass is a poor conductor, the resistance would increase. If the mass is a good conductor it would reduce resistance. Temperature would be higher under compression, which would typically increase resistance in a copper conductor, but it in gas, I think it may be a lot more complex. Especially if the gas is a semiconductor, that switches to a conductor, or ionizes at some critical pressure and temperature. The other nearby cylinder (next in line in the cap) should be cooler, and at a lower pressure. I forget how a spark works in a vacuum, versus a gas.

New FPR did the trick this time. The GP Sorenson (new one from AZ) had a smaller vacuum hose nipple than the OEM Renix FPR. About 1/8" instead of 1/4" OD (APX). I had to scrounge the spare stuff for a fix.

Well the 87 got jealous of the attention the 89 was getting. Did not like the 89 getting new parts, so it started complaining, LOL.

I posted a few weeks ago that I fixed the rough running (shimi-shake) I was getting when the TC was locked up (87) which preceded a sudden death at idle at a stop light and no restart by a week or so, fixed by cleaning the rotor and cap. Well it was running smooth as glass (even with a low 550 rpm idle the last day, another new symptom perhaps?), when I stopped to fill up with gas last night.

Then back to a no restart after fill up. I checked the TPS, the IAT, the CTS, voltages all perfect, the ground(s) resistance all great, refreshed the connectors contacts, pulled four spark plugs for inspection and cleaned some black smut off the white insulators, cleaned the cap and rotor again (not that they really needed it yet), checked the FPR for any leak, checked that I had fuel, tried restarting at WOT early on, but the plugs were dry when I pulled them later, I refreshed the ICM input wire connectors, stood on my head a few times while I cranked it again, LOL, begged and pleaded with it, , LOL, checked for vacuum leaks, and at some point I tried it again (after the plug inspection) and got a back fire, that tossed the vacuum line loose that goes to the air filter and valve cover, and so I left it loose and cranked it, in case the IAC valve was stuck....anyway, I finally got it to run (I think I had the vacuum hose loose), running rough, reattached the vacuum hose, got it back home, and today I changed the cap and rotor and installed new plugs. Three of the old plugs had excessive gaps from age....

I started it before and after changing the plugs, cap and rotor. Don't recall any real difference before or after replacing the cap, rotor and plugs, so I did a multi wire wiggle test, even the C-101, and finally got some noticeable change pulling and pushing on one injector wire connection (while it ran), so I repeated the action until the engine smoothed out and stopped missing. But now it is back to odd idle speeds. I had a high idle early in the tests today, 2000 rpm once, then about 1000 rpm once, (I forget at what point it was) but now the last 3-4 restarts it seems to want to idle about 550 rpm, unless I turn on the AC or shift into drive or reverse. In Drive with the AC on the idle runs up to almost 700 rpm. But idling in park, with all loads like AC off, it is dropping to 525 to 550 rpm. It has never in the last 2-3 years idled that low, and only once did in the last 7 years, when I had the O2 sensor connectors connected backwards, and it idled at 250 rpm.

So the IAC seems to be working, as it raises the idle speed when I turn on the AC or shift into gear, but does not reach 750 rpm in drive, or 800 rpm in drive with AC running like it use to do) I get about 100 to 150 rpm rise to 650 to 700.

Is it possible that Renix is smart enough to lower the parked idle to 550 rpm when the engine is finally running smooth enough to run at 550 rpm with out running rough? It was running smoother tonight than it ever ran (after I replaced the last batch of parts, and got the injector connection working again on the one injector).

This one really has me scatching my head. I know I still need to consider data degradation through the C-101, but this C-101 has never given me any grief (that I know of), in 7 years now.

Oh, and the CPS is working great. It passed all my tests too.

Oh, and I ohmed the old plug wires (they are not that old), and they gave me about 4000 ohms per foot, so they seem to still be OK too (I checked 4 of them as I recall, and the primary as well). I did buy a new Bosch wire set today, the MAG versions, that as I understand it are the ones 8Mud was (is) using, they have a solid copper wire coil plus a carbon core IIRC what I read yesterday. They ohmed out at about 550 ohms per foot. The coil (versus straight wire) kills the electronic and radio interference, with less resistance than just carbon cores, giving a hotter spark, per the Bosch sales pitch, and per Wiki...., but I have not installed them yet!!

Have you ever refreshed the C101?

cruiser54 said:

Have you ever refreshed the C101?

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Yes, but it did not help at the time.

Try it again and tweak the female receptacles a bit tighter. Can't hurt.

Did you test the MAP and it's connection?

I think you are barking up the wrong tree. The question is, if the Renix ECU has correct CPS data, why would it deliberately idle at a low idle. And since the idle is extremely smooth, the ECU must be getting the right CPS data, and most the hardware must be working right!!!

The TPS is giving the ECU the right data, at the TPS. I may try disconnecting the O2 sensor, to see if it defaults to 750 rpm.

The only programming conflict I am aware of (based on experience) is the O2 closed loop tries to control fuel ratio, which seems to override idle speed, TPS, vacuum issues and so forth. But I also know from experience that the IAT sensor data seems to affect idle speed (when there is no O2 sensor data available, as I had a randmon high idle issue cased by a bad IAT sensor a few years back. But my current question I guess, is do I even have a problem if Renix has dropped the parked idle speed to 550 rpm? I prefer it at 750 rpm, so I may adjust the throttle positon on the throttle body again, now that it seems to want to idle slower, over riding the IAC minimum air flow?

I did wiggle the hell out of the C-101 and it's wires, with no changes!!! But I did find one fuel injector connection that was giving the rough idle, which is gone for now (I may need to order and replace the fuel injector connectors for the harness, but I don't they are involved in the new lower idle).

I got two different temperature and voltage reading data sets on the CTS and IAT sensors that looked normal (not way off). Disconnecting the TPS while the idle was high, before I replaced the plugs, rotor and cap, dropped the idle back down, but the TPS is less than a year old, and I had .806 V at idle at the TPS. Disconnecting the map sensor killed the engine immediately. Also, once I got the engine running ultra smooth, I tested the engine decel and accelleration with rapid swings, and got excellent response, meaning the CPS, TPS, EGR, and MAP sensors and ECU are working normally under rapidly changing parameters!!!!

So I am starting to wonder about the O2 sensor, and what is truely normal for a fully functioning normal (LOL) Renix. I am wondering now if the O2 sensor is biased suddenly. Disconnecting during a test may me tell me more. I will also check the voltages on it.

I started it up this morning (cold overnight, about 40 F low, the 87), and ran it for about 10-15 minutes at idle, then tested the P, D, R and A/C on idle speeds.

After warm up I got 550 rpm in P, no A/C

and 650 to 700 RPM in D, R with A/C on. Most of the idle speed increase is from turning on the A/C, about 100 rpm increase.

Until recently, the last 3 years or so now, it has idled at about 900 RPM in P, and 750 rpm in D, R with or with out the A/C on.

Black boxes are such fun to debug!!!!! LOL.

It's smooth now but idle is lower?

cruiser54 said:

It's smooth now but idle is lower?

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Exactly. It use to have a slight miss, and idle higher, for years.

Ecomike said:

Exactly. It use to have a slight miss, and idle higher, for years.

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As to why, I don't know. Have you ever set your idle speed using the bypass screw on the driver's side of the throttle body?

cruiser54 said:

As to why, I don't know. Have you ever set your idle speed using the bypass screw on the driver's side of the throttle body?

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Not sure. I think it still the anti tamper cover on it, but I need to check. I have adjusted the idle stop/ear a few times over the years on both in a pinch, but this 87 was stable for a good 3+ years at the current throttle settings.

I think my problem is a Renix algorithm error in the program that has trouble properly regulating idle when it gets a certain set of odd input data. I fixed a random high idle. and hot engine no start that drove me nuts for nearly 6-12 months (got progressively worse), that was bad IAT sensor that gave good data cold, but bad data hot.

One would think the programmers would have been smart enough to compensate for that, but at the time I think my O2 sensor was also bad (or bypassed?) (IIRC).

I am starting to wonder if the recent no start might have been a B+ relay failure to reset the IAC on a hot engine...., but I did try multiple resets, time outs, and pulled and reseated the relays, with no improvement on the recent 2 no restarts.

I will check the O2 sensor this weekend and see if there are any issues there.