Plastic flex conduit for plug wires?

[the gold2]

Hello, the OEM set up on my 1992 Eldorado (4.9 liter)had installed those flexible plastic 'conduit' (having the installation access slit along the length) on certain plug wires.

I had a mechanic replace the plugs and wires with AC plugs and AC /Delco silicone sheathed wires.

But he said it did not need the extra plastic conduits (covers).

Do those plastic covers prevent possible cross talk between wires?

I'm asking because before the 'tune up' (replaced fuel filter, dist. cap and rotor and cleaned EGR valve) the idle was silk smooth with only periodic isolated blips.

After the drive home, the idle was unstable and continues to have some instability (not exaggerated unstable but not a dead-on tach needle like before).

Before taking it back for a recall look, I wanted to ask about those 'conduits'.

(I did an idle relearn and it helped some)

Thanks.

[BodybyFisher]

Well, I used them, and I believe they establish more room between the wires if nothing else

The problem is, they are not really plastic, if you buy the cheap stuff from your typical parts store it IS plastic and it melts, the OEM loom is an inert material that does NOT melt.

I make trips to the junk yard to remove it from other late model cars, as it does age and become brittle and I replace it

As far as NEW wires crosstalking, I kind of doubt it

I would make sure that he gapped the new plugs, lots of people assume that they are gapped and dont check them.

I would also make sure that all plug wires are fully seated at both ends

Did he use platinum plugs or non platinum plugs?

Did he use AC DELCO plugs? Champion/Autolite/Bosch are not recommended

[BodybyFisher]

One test you can do.

Part in a pitch dark area, start the car, let it idle, lift the hood and look at the engine, plugs, cap, etc and look for arching, any arching use the loom to stop it..

What kind of ignition wires did he use? OEM

[Texas Jim]

I will add one more thing about plug wires...

Anywhere they run side by side...make SURE they do not touch and anywhere they cross each other make sure they cross at close to a 90 degree angle.

Personally...I would want the looms back on my wires.

They were put on there for a REASON from the factory.

If they weren't needed... they wouldn't be there.

[BodybyFisher]

Ditto

[the gold2]

Hey all, thanks for the opinions.

All good quality parts. The mechanic is fussy about that and nagged his part supplier to make sure he got a particular brand etc. of quality.

And the guy knows his caddy's.

The wires are AC/Delco silicone.

The plugs are AC/Delco 100K long life plugs. No idea if they are platinum but they are probably the same OEM type.

Good to know that the 'loom' used by the factory is different than the plastic stuff you get at hardware stores...

I'll do some preliminary checks before taking it back.

A tune up is a tune up, so the idle should stay close to perfect. (car has 54K miles and old OEM AC plugs were clean and actually not too bad but wires showed a bit of arcing stains)

I'll try to update in a week or so for the sake of the archived info base.

Thanks !

[the gold2]

BODYBYFISHER, you asked about the plugs. Whether they were platinum or what.

The plugs replacement was AC/Delco 100K plugs but I'm not sure if they were iridium or platinum.

Which works best for the 4.9 liter engine (1992 Eldorado).

What was the OEM AC/Delco plug, copper, platinum, iridium?

Thanks

[BodybyFisher]

I just wanted to make sure that they were AC delco and that they were not cheap ac delcos that did not have a platinum type of tip.

I would consider that they did not gap them, and maybe they installed them out of the box

I would also check to make sure that all ignition wires are fully seated at both ends

[the gold2]

OK here is the scoop.

I brought it back to the mechanic to have the 'tune up' reviewed (since the car had silky idle before the tune and left with an unstable idle).

checked wire runs visually. Removed one plug from a front cylinder and found it to be correct 0.06 gap.

He claimed to smell a bit of fuel wisp on the plug.

Put on scope.

isolated cylinder #4 and #8 as having gap symptoms.

Pulled those plugs. At least one of them may have been at 0.05 gap. The other was correct at 0.06 gap. He replaced those two plugs anyway.

(all the plugs are AC/Delco platinum 100K plugs) Again he stated that he smelled some faint fuel on plugs and made me observe a bit of darkened area around the threaded end at electrode area.

So he began to be suspicious of rich fuel burn.

He then took apart the new distributor cap and removed the original coil and swapped out a new one to see if the coil was at issue. Apparently it was not. The scope had seemed to point to a possible coil problem.

The new cap was fine.

He hooked up the scope again and monitored other categories.

He removed the vac tube from the (fuel) pressure regulator valve and we found no sign of fuel.

He did a vacuum check on the valve and found it would not hold vacuum.

Replaced the Pressure regulator valve.

Put on scope again. Agreed that scope would point to any plug gap problems so we decided not to remove the rest of the plugs to inspect gaps.

Tested ohm resistance of #4 and #8 plug wire.

#8 being the longest had more resistance but seemed to be within tolerance. (don't recall the resistance- AC/Delco 8mm silicone wires)

Ran out of time.

Idle still had a bit of instability. He mentioned dissatisfaction with the front end of the ignition graph and the definition of the final end of each cylinder's graph saying that the( reset- ? ) 'steps' could be more marked. He was saying something about the 'secondary coil' (?)

He suggested we do a fuel rail flush to clean injectors since he suspected it might be an injector that is not spraying right. (part of the previous tune up was to add a can of BG44 fuel additive/injector cleaner and a can of BG oil additive to my recently replaced engine oil)

The scope showed that on average the cylinders were balanced. He looked at other scope categories which I can't responsibly comment on.

ran out of time.

So on way home I felt the acceleration to be a bit crisper. Idle was still slightly unstable. Less pronounced.

Next day did some WOT and indeed it accelerated way better than before (I got the car in late July 2010 and slowly had services done to it. Not many miles put on. A WOT series I did month before the 'tune up', displayed a muted acceleration(pedal to the metal) response. I have not put many miles on since the 'tune up' but since I got the car, it has been freeway driving since its my weekend fun car, not City driving.

Among the things I personally did was to clean the throttle body and stack tubes and do an idle learn. That left the idle silky and steady. It was not bad before. Definitely not unstable.

So I'm hoping some more WOTS and passing some more fuel while freeway driving will perhaps dislodge hung up debris on some injector and resolve the idle issue.

Forgot, he also flowed propane gas onto the throttle body gasket while engine idled to check for gasket gaps. No TB gasket problem.

He did same to underside of EGR valve and initially it seemed to elicit an lowered idle change but this could not be repeated after 3 more such tests on the EGR underside.

He seems to suspect a possible small vac leak in the EGR valve.

BUT I had him test the EGR and solenoid and remove the EGR to clean the same day of the 'tune up'. It passed his tests and subsequently passed the Calif. SMOG test with unstable idle and all... and probably a bad pressure regulator valve at that time.

Well, that's the story for the benefit of the technical archives and for opinions of those who care to opine.

Thanks !!

What glee to feel that acceleration upon WOT !!!!

[BodybyFisher]

Thanks for the update, glad its running better, let us know how it goes

[the gold2]

Did some more research...

I have a question. Since the positive backpressure EGR valve on the 4.9 liter engine must be at higher than idle RPM to close the valve or react to vacuum, would flowing propane gas under that valve at engine idle really test for vac leaks? It would seem that in idle and the engine temp not at its highest, the EGR valve would be normally open with the air inflow (under the opposite end of the EGR vacuum line connector (nipple) and thereby allowing propane gas to enter at that normally open point (at idle speed) to possibly influence the idle speed.

Propane gas tests are a legitimate test for manifold leaks and vac leaks, throttle body gasket leaks and EGR.

Wouldn't the idle speed go faster with the introduction of propane (assuming there was a small vac leak in the EGR valve or whether in fact the propane just went into the air flow inlet) ??

(the idle speed control motor was not disconnected by the mechanic during this test and the only non-replicable elicited reaction was a sudden short dip in idle speed)(I retested the EGR with propane twice today with no change in idle speed. Once upon first starting the vehicle and then again after returning from a log drive.)

Anyway here is the Technical Service Bulletin for my car and others, 1990-1992.

#T-92-88: INTERMITTENT ROUGH IDLE DIAG. SERVICE PROCEDURE INFORMATION - (Apr 15, 1992)

SUBJECT: ROUGH IDLE

MODELS AFFECTED: 1990-1992 DE VILLES, FLEETWOODS, ELDORADOS, SEVILLES

Some 1990-1992 DeVilles, Fleetwoods, Eldorados, and Sevilles may experience an intermittent rough idle condition.

To determine the cause of this condition use the following procedure:

1. Compare to another vehicle of the same year and model. If the roughness is similar, the vehicle should be considered normal and no further work should be performed.

2. Check engine grounds to make sure they are clean and tight.

3. Using on-board PCM parameters check coolant temperature and MAT sensors key on cold to verify they are within three degrees of each other. Verify that MAP and BARO match key on and are correct for your altitude.

4. Check MAP during the condition. At a warm idle with the A/C and other accessory loads off, in park or neutral, it should read between 30 and 40 kpa. A higher reading may be caused by a vacuum leak or a faulty sensor.

5. Loosen the powertrain mounting nuts, brake torque the engine in drive and reverse, and check for gaps between the mounts and engine indicating uneven weight distribution of the engine. This may cause an engine vibration. Shim up any mounts that are not evenly loaded with the others.

6. Check ignition secondary pattern on a scope. If any cylinders indicate erratic spark lines, refer to Section-6E-C4 of the appropriate Service Information Manual and repair as necessary.

Cheers ! Regarding point #1, anybody else's 1992 4.9 liter engine seem to operate 'normally' with a sublime rough idle (misfire)??? Cheers again !

[BodybyFisher]

Not sure what you are getting at with the EGR and propane, but I do not believe the EGR is your idle problem. I had a 91, and the EGR caused light pedal detonation on mine, and I replaced it, and all detonation was gone. If you put you finger under that EGR and open it, the idle will stumble. If you think the EGR is hanging open even slightly, pull the EGR off and clean it good, and use a new gasket. I used to soak the valve end in carb cleaner and clean the pindle with a 22 caliber brush bent to get into the seat.

We have seen many 92s have problem with intermittant roughness, loss of power etc

We have seen many have issues with grounds, check the ground near the starter, remove and clean it

We have seen many 92s have PCM problems, a search of our archives may turn up interesting threads, but I would check the grounds near the PCM and 'tap test' the PCM to see in you can induce a stumble by tapping it. The PCM has been a source of problems on the 92

The rough idle started when you did a tune up, and that you didnt have a rough idle before the tune up, are you sure? Why was the tune up done? How is it that your mechanic is so good, that he installed the plugs WITHOUT checking the gaps?

If in fact this rough idle started after the tune up, I would check the ignition wire routing, and make sure they do not run parallel to any injector feeds. I would look at the engine in the pitch dark to see if there is any arching. I would check all vacuum hoses for cracks. I would consider replacing the ignition module, I would check the distributor for a bad bushing at either end. I would look at the quality of the ignition parts that were used, ie, rotor, cap

While this may seem odd, I would also clean the battery connections and have the battery load tested. My 91 did something very odd, the battery had a bad cell, I could jump it to start it, but once I tried to drive it, as soon as I pushed the gas pedal to move, it stalled, as the battery could not deliver enough current to supply the ignition system adequate current. As soon as I replaced the battery the problem went away. A strong battery and charging system is required.

[the gold2]

BodybyFisher, thank you very much for these very salient insights.

Regarding:

EGR, the same mechanic cleaned the EGR and checked the solenoid and EGR to make sure they worked. (I requested it in order to pass the NOx smog at another shop, it later passed, misfire and all).

Yes, my next step is to check grounds. The service manual points to some ground points including the 'distributor ground'. Is this latter ground inside the distributor under the rotor or outside the distributor body?

I'll check for the other grounds also.

Tune up: Initially the service request was to test and clean the EGR valve due to NOx Fail Smog test but the mechanic recommended the tune up 'full 9 yards' because the plug wires were factory original (45K miles).

Prior to tune up, Idle was smooth with only a single 'blip' periodically. Definitely no misfires, no sublime tremors felt through steering wheel, or tach needle 'hunting'. It was hard to tell the engine was on !

However, my records show that at least one month before the tune up, the injector pressure regulator valve may have been already bad because my WOT definitely did not have crisp acceleration take off that is now has, presumably due to the new regulator valve. At that earlier time, I figured that the muted WOT may have been the effect of the 'Emissions programming', being a naive new owner to this car.

The plugs, wires, cap, rotor are good quality. Next time, the mechanic may have to remove the remaining spark plugs to verify the gaps.

My battery is brand new, bought last August 2010 (Kirkland, made by Interstate- fresh production date) but I'll also check the battery cables and the plug wire routing relative to injector feeds.

I'll research the PCM and do a 'tap' test.

Your insights are very welcome and helpful !

Thank you.

[BodybyFisher]

Here is a nice diagram showing the 1992 Seville grounds, this should be similar for the Eldo. Kirkland is a good battery. Check the battery connections and grounds. Try a bottle of Techron and even try a bottle of Magic Mystery Oil in your crankcase, in case you have a hanging up valve

[the gold2]

BodybyFisher, Thank you very much for that diagram.

Here is the update,

I did the TPS parameters test (ED01)and it is fine in all respects.

Also did the tap test and no erratic values were elicited.

Grounds look good. Battery cables also.

No DTC codes.

Seems like it was running a bit better during the test.

I'm thinking it may just be a bit of hung up debri on an injector at this point.

I'll keep an eye on it.

I may swap out the EGR solenoid just for the heck of it.

Bought a new (delco) one on sale....

Thank you again for the support. All your points were verified in the service manual especially the weak battery as a probable problem source. It always help to get direction. i.e. you know your stuff !!!!

[BodybyFisher]

Thanks!

If you think its your injectors, try a bottle of Techron, read the directions and use it with the proper amount of gas in your tank

Let us know how it turns out

[KHE]

The failed NOx test was most likely due to restricted EGR feed tubes in the throttle body - remove the air intake and hold the throttle open with your hand. There will be two 1/2" diameter tubes visible. They should not be choked off with carbon. If they are, rod them out with a small screwdriver.

The injectors used in the 4.9 engine tend to develop shorts in the windings with age and miles. It is possible the #4 and #8 injectors have developed shorts on your car. Possibly, the fuel injector cleaner exaggerated the problem. If it gets worse, look at replacing the injectors on the problem cylinders. You must use the OEM injectors so the flow rates are matched unlkess you replace all of the injectors which would be expensive.

[the gold2]

Thanks to both of you.

KHE, I did clean the stack tubes and throttle body last October or early November and afterward the idle was silk smooth. It passed the SMOG re-test.

Yesterday I did a few WOT. And an idle learn. Both first time since the new (fuel) pressure regulator valve.

The idle is variable. The mis-fire (and minor tach needle 'hunting')seems a bit less pronounced than before the latest review by the mechanic but it appeared that upon garaging at the end of the drive, with engine coolant temp. then at about 203F (outside environment temp about 62F)the idle with trans in park, was smoother and the tach needle steady.

I'll update after a few more tests.

The injector theory sound plausible, car has 45K original miles only.

Thanks.

[BodybyFisher]

You can test each injector with an ohm meter. We can probably dig up what the normal resistance should be. But test and record the resistance, a shorted injector would stick out.

The mileage of 45K is not pertinent

[the gold2]

OK I'll try the resistance test in the near future.

Last week I replaced the EGR solenoid and the PCV valve for the heck of it.

No big difference. Nuances on the positive side may just be subjective or coincidental.

The replaced items were probably good.

I tried to coax a reaction from the EGR valve by passing propane under it again. No reaction.

That aside, I have had four episodes of hot-start odd behavior.

(normally my pleasure drives are a two engine start event)

I'm hoping this might point to something in particular.

Basically, upon the third engine start within a day's vehicle use: ie.

Initial cold start is immediate and no abnormal symptoms. (By the time it gets to 180F coolant temp, the idle hits around 650. It starts at around 1000 drops to around 800 then drops to around 650.)

After a small or long period of time parked, the second engine start (hot start) is normal and immediate.

Park the car and shut off engine.

After a short (10 minute) or medium 30 minute (so far) period, the third hot-start (coolant temp around 185 to 195F)

will be immediate but the idle and tach bounces from 650 to around 1100 for about 5 secs. (one-one thousand, two-one thous. etc.) and then normalizes.

But just a while ago, the third hot start bounced the idle for over 50 seconds, this time spanning from just under 500 to around 1000 RPM.

This time the dips were close to stall but it did not stall out, it just resumed an upward swing.

I shut engine off. Checked to make sure PCV valve was fitted. It was fine.

Started engine again and the idle bounced again btw. 650 and 1000 for only about 5 secs. and normalized.

It seems like this episode reflects the sensors a bit confounded until it settles.

But it seems a coincidence, at this point in time, that this behavior has onset after the third hot-start during a driving sequence.

At all times the car starts up immediately , even before the fuel pressure valve was replaced.

I checked the DTC codes yesterday and no problem codes.

So, I'm just relating this new behavior which , unfortunately, coincidentally started after the 'tune up' and the simultaneous introduction of the BG44 fuel additive.

I'll look into the injector resistance values in the near future.

Thank you.

p.s. making lemonade of lemons. The 'crash course' into the car at least is healthy !

[BodybyFisher]

Was the EGR an OEM unit or an aftermarket unit?

[johnnyjaws]

could of cracked a plug putting them in

[the gold2]

Hello, the EGR valve is the original OEM one. Positive type, of course.

The next time I take it back to the mechanic, I will have him check the rest of the plugs' gaps. We ran out of time last time.

Third time is a charm!

[the gold2]

Hello here is the update,

last Saturday I took it back to the mechanic and he removed all the plugs and checked the gaps. They were all 0.06 (previous visit found one at 0.05) Also checked the integrity of the plugs.

He used the propane again to check for possible TB gasket leaks etc.

He suggested I keep running it hard and also possibly it had an EGR pintle leak i.e. not sitting closed all the way.

(well he had removed, cleaned and tested the EGR valve about 2 months ago)

So today I ran the DTC diagnosis for the EGR valve.

PCM override, ES02, PCM data ED11

raised RPM to 2000, depress warmer button to turn off EGR solenoid and expect RPM to drop by 100 or greater if all OK.

Idle actually went up about 75 to 100 RPM after several tests.

So the book algorithm dictates EGR valve removal and inspection. (my TB and tubes are clean)

That is next on the agenda before I fork out and buy a new EGR valve.

I have not had time to test the resistance of the injectors but I doubt that is the problem.

The unstable idle occurred right after the tune up and EGR valve cleaning.

It idled bad when I arrived home from the shop 2 months ago, a 25 minute drive.

Before that shop work, it idled smooth even with a -then-unnoticed bad fuel pressure valve!

[the gold2]

Update, I can rule out the EGR valve and solenoid, TPS sensor, O2 sensors and Coolant temp sensor.

I still have no relevant DTC codes but I ran the on dash test for the MAP sensor codes.

I do not have a shorted MAP but I'm half way through the test tree , up to the start of step 3, for an Open MAP test... so far it reads 101 kPa which is not within the 107 to 109 kPa normal -'no fault' range. I'm thinking it could be a wire problem or ground problem, although there is no DTC code.

Vac lines are OK.

Have not listened to injectors yet.

Slow going.