: Engine rough running misses no power 95 Eldorado 4.6



wph101larrya
07-05-06, 10:16 PM
The current problem began with engine surging. I have replaced the EGR valve, MAP sensor, ISC motor, alternator, battery, starter, intake seals, belts, water pump and hoses during the past year. But for this particular problem the MAP sensor, and ISC motor. Things went from bad to worse when I replaced the MAP.

I have checked and double checked the vacuum lines and the PCV with no problems. I have not replaced the spark plugs, wires, ingition module or the PCM (not sure where it is in my 95 eldorado.)

The engine idles rough, has no power, will barely pull itself up the on-ramps and I don't dare try and beat the light. I can't even out drag a cement truck at the light.

I am fairly good with tools and electrical meters. Can someone give me some pointers.

I have unfortunately killed any codes trying to get the current conditions after my last repair attempt.

eldorado1
07-05-06, 10:52 PM
if it's running that bad, you should get a service engine light shortly... Once you do you can check the codes. My guess would be either a coil, or possibly the TPS sensor. More than likely a coil. It's harder for the computer to pick up on those, and you might not get a code.

Ranger
07-06-06, 12:37 AM
The current problem began with engine surging. I have replaced the EGR valve, MAP sensor, ISC motor, alternator, battery, starter, intake seals, belts, water pump and hoses during the past year. But for this particular problem the MAP sensor, and ISC motor. Things went from bad to worse when I replaced the MAP.

I have checked and double checked the vacuum lines and the PCV with no problems. I have not replaced the spark plugs, wires, ingition module or the PCM (not sure where it is in my 95 eldorado.)

The engine idles rough, has no power, will barely pull itself up the on-ramps and I don't dare try and beat the light. I can't even out drag a cement truck at the light.

I am fairly good with tools and electrical meters. Can someone give me some pointers.

I have unfortunately killed any codes trying to get the current conditions after my last repair attempt.
That says something, though I am not quite sure what. I'd consentrate there.

wph101larrya
07-06-06, 09:03 AM
I do get a check engine light P039. No other codes. I drove it this morning and the engine "seemed" to have a little more power, actually has some moments when it was hitting on all cylinders. But as soon as I try to accelerate the rough running symptoms reappear. This is all on level ground. When I must accelerate on an incline the engine loads up like an old truck, skipping and lugging.

Don't know if it makes any difference but here is the order of the repairs:
-Engine power normal, but fuel milage had declined to about 19mpg about 22mpg.
-Engine idle would not go below 1000 and varied +700 sometimes it would just jump to about 2000 like the cruse was on.
-Verified that throtle plate was closed.
-Finger over PCV killed engine instantly. (It seemed that the engine was actually sucking air from the crankcase to allow it to idle. It actually had ruptured the rubber fitting on the PCV as was pulling outside air.)

-Car off, disconnected battery ground.
-Removed ICS and replaced.
-Reconnected Battery and started engine.
-No change in idle speed and now the engine is running rough. However I drove it for a couple days to allow the computer to discover any changes and the idle speed did decline to about 600 but the roughness continued although somewhat better, actually had a stable idle with sluggish under load and some skipping.
-Next I replaced the MAP sensor.
-Started engine. Very rough idle reappeared and the engine actually seems worse overall. It will have a few minutes when you think all is well and then the next minute it will hardly go.
-I have driven it for about a week now with the new MAP and ISC the fuel milage has declined to about 17mpg and it is still a sick engine. Whatever the computer is trying to do to make it run is not really helping.

eldorado1
07-06-06, 11:35 AM
Take an ohm meter to the coil towers, one lead on each connector. (Engine not running of course) Measure the resistance of each coil, and report back the results.

Alternatively, you can try pulling injector connectors to see if you can isolate which cylinder(s) are not firing.

Ranger
07-06-06, 11:41 AM
Have you checked fuel pressure? How much do you have? How about the FPR? Have you checked it for leaks? Listen to the injectors with a stethescope and you can tell if they are actuating or not.

zonie77
07-06-06, 11:57 AM
I'm going to suggest replacing the plugs and wires. It's an 11 yr old vehicle. If they've never been replaced that's a place to start. While in there check the FPR (as Ranger suggested) instr in tech tips section.

Before changing plugs take the plug wires off one at a time while running. Check which cyls are dead. Record this info. Loosen them first and use insulated pliers to lift them off so you don't get shocked.

eldorado1
07-06-06, 12:06 PM
Unplugging the injectors is safer

wph101larrya
07-07-06, 10:16 AM
Thanks to everyone for the help! 136k+ miles (11years) and it has a bunch of tired parts that all seemed to cascade fail.

Reminds me of a certain space vehicle...

I had previously replaced plugs and wires at 100k miles. So from my experience not to mention the fact that just about everything else had already been replaced in the ignition system (and I happened upon my favorite auto mechanic at the gas pump) a coil was bad which affects two cylinders.

Anyway, I replaced the ICM which made a HUGE difference. Then I could zero in on the engine missfire. With the brake set and the engine idling in Drive (puts a small strain on the engine) I began pulling plug wires. When I pulled one that didn't change the engine speed I knew I had the offending coil. A quick dash to the autoparts house and its running smooth as silk!

Note: I did check the bad coil with my ohm meter and the secondary was open.

Now if i could just figure out how to get it to idle below 1000 rpm.

Ranger
07-07-06, 11:25 AM
Thanks to everyone for the help! 136k+ miles (11years) and it has a bunch of tired parts that all seemed to cascade fail.

Reminds me of a certain space vehicle...

I had previously replaced plugs and wires at 100k miles. So from my experience not to mention the fact that just about everything else had already been replaced in the ignition system (and I happened upon my favorite auto mechanic at the gas pump) a coil was bad which affects two cylinders.

Anyway, I replaced the ICM which made a HUGE difference. Then I could zero in on the engine missfire. With the brake set and the engine idling in Drive (puts a small strain on the engine) I began pulling plug wires. When I pulled one that didn't change the engine speed I knew I had the offending coil. A quick dash to the autoparts house and its running smooth as silk!

Note: I did check the bad coil with my ohm meter and the secondary was open.

Now if i could just figure out how to get it to idle below 1000 rpm.
Start by cleaning the TB. The bore may be carboned up and preventing the throttle plate from closing completely. Not uncommon on a car with that milage.

eldorado1
07-07-06, 11:51 AM
More than likely a coil.

Damn I'm [a] good [guesser]. :cool2:

:thumbsup:

wph101larrya
07-07-06, 09:09 PM
Cleaned the throttle body. The ISC motor is holding the throttle open. I had the main air intake off so that I could see the throttle plate. For some reason ISC decided to retract and it slowed down to a normal idle speed. I drove it around town for about 20 minutes everything normal.

When I came back later and cranked the engine it again would not idle and the ISC is holding the throttle open. This is a new ISC and some signal is telling it to hold the engine throttle open. The adjustment screw is fully in (bottomed out in the ISC.)

Somewhere I read that from the dash panel that I could override the PCM but it had no effect.

So here we are. I have no clue why the PCM or whatever is commanding the ISC to hold the throttle open. I have to give it this much, AC on or off, in or out of gear the ISC hold the idle dead on 1k rpm.

It is not surging or racing away.

parts68
07-07-06, 09:12 PM
If you dont have TPS signal thats low enough(normally .65-.80V)
then the ISC wont adjust right.

Read your TPS at idle and see what its putting out.
You may then have to do a TPS and ISC relearn.

Ranger
07-07-06, 09:18 PM
Did you adjust the ISC motor properly after instalation?

wph101larrya
07-07-06, 10:12 PM
First how do I read the TPS signal (what PCM code is it)

And obviously I have not properly adjusted the ICS. I don't have any instructions. I am trying to search for a procedure. I have found several that tell me to override the p03 in PCM but it has no effect.

Another indicates that PCM output 07 should cycle the ICS in mine it does nothing.

So mine is either intermittent or there is some other problem.

Ranger
07-07-06, 10:56 PM
Start with the proper adjustment.With the engine at idle, press on the ISC plunger. It should retract. When it is fully retracted, unplug it. Idle should drop to about 450 or even die. Now adjust the plunger to a .030 gap with the throttle lever. Plug it back in and see if that solves your problem.

You'll find all the DTC definitions here.
http://myweb.accessus.net/~090/dtcobd1.html