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Strange Power problem

I have a 1998 Acura RL with a strange power problem. I was driving to a friend’s house, and took the highway to get there, driving around 75-mph. Once I got off the highway, and stopped at the light, the engine began idling very low at around 500-rpm instead of the usual 850-rpm. Then when the light turned green, I stepped on the gas and it hardly moved. The fastest I could go was maybe 10 mph. So I put it in neutral and stomped on the gas to see what the engine would do, thinking I had a broken transmission. Well, the motor barely went up to 1000-rpm. So, ruling out transmission problems, now I have a motor that barely runs. It starts fine, but has no check engine light. I’m not sure what the problem could be. Could it be a broken timing belt? If so, then why does it still start? Could the timing belt have jumped the gear on the camshaft? Could it be bad gas? Or maybe a blocked off air intake, from ingesting a foreign object? I’m vaclempt and have no clue what the problem might be. Could someone point me in the right direction? Thanks.

Well, you can definitely rule-out a broken timing belt because in that case the engine would have stopped–with some very loud noises thrown in. I would also tend to doubt that the problem is the result of jumping its valve timing.

From afar, my best guess is that your throttle position sensor (TPS) is bad.
Or, possibly your Mass Airflow mechanism (MAF) might be badly gunked-up.

In any event, you need to get the car to a qualified mechanic for an accurate diagnosis and repair.

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The possibilities are myriad. It could be a failing fuel pump, a clogged cat converter (I’ve seen where the guts of the converter suddenly crumbled and blocked the out pipe), or any of a number of “engine demand” sensors gone bad.

Someone’s with the expertise and diagnostic equipment is going to need to look at this hands-on, starting with the basics.

My wild guess would probably have been the same as VDC’s, but that isn’t a diagnosis, just a wild guess.

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I did a scan of the motor, using an Actron Pocket Scanner, then looked up the trouble codes given online. Here are the trouble codes given:

  • P0420 = Catalytic Converter
  • P1201 = cyl. 1 misfire
  • P1202 = cyl. 2 misfire
  • P1203 = cyl. 3 misfire
  • P1204 = cyl. 4 misfire
  • P1205 = cyl. 5 misfire
  • P1206 = cyl. 6 misfire
  • P0401 = EGR Insufficient Flow
  • P0300 = Random Misfire

PENDING:

  • P1399 = Random Misfire
  • P0401 = EGR Insufficient Flow

So the major culprit here seems to be a bad Ignition Control Module (ICM) that bolts on the front of the motor. It could also be in combination with bad Ignition Coils, but I’ve never heard of all the coils going bad at the same time.

I also changed all of the spark plugs, and this is what I found:
the plug from cyl. #5 had copious amounts of fresh oil on the tip, and ALL of the spark plugs wells were also filled with lots of oil, too. This tells me the gasket donuts for the spark plug wells need to be changed, and the bad cylinder that seems to be why it burns oil is cyl. #5. I haven’t done a compression test yet, but before I put in the new plugs, I shone a flashlight down into each cylinder, and each piston seemed to be caked over with rough-looking carbon deposits, and were wet with “something”.

I’m also contemplating removing the intake manifold and removing the carbon deposit buildup inside the passages for the EGR. But, it just seems to me I’m gonna have to either rebuild this beast myself, or shop around for another good used motor and swop them, or what. A new long block motor will cost me $5000, but the car is only worth $3000. So this is where I’m at, wondering where I should go from here.

Let us know the results of the compression test. That’s where to start. Some of the things you’ve noticed may be normal, so don’t presume you need a new engine at this point. It’s unusual w/all those serious codes the check engine light wasn’t on. Have you checked the CEL bulb lights ok with the key in “on” but the engine not running? Given the sudden onset of the symptoms, and those codes, my first guess is an exhaust system problem, possibly the cat has broken apart & plugged up.

If you can do this, and replace the “gasket donuts for the spark plug wells” yourself, for minimal cost you can see if there’s life left in it. Oh, and while the valve cover is off, be sure to check the valve clearances.

CAR REPAIR UPDATE:

  • checked for voltage at: each fuel injector, and each ignition coil. I have 12.1 volts at each cylinder.
  • checked for continuity on each ignition coil (between terminals 1&2). Only 5 showed 1.2 Ohms. Only 1 showed 0.6, so that one is a bad coil, ironically from cyl #5 - the one suspected of burning oil (based upon the fact the old plug had oil on the tip).
  • checked for continuity to ground at terminals 2 & 7 inside the connector for Ignition Control Module (ICM) - to ignition coils. A-OK.
  • checked for voltage inside the ICM - to - Ign. Coils CONNECTOR for each coil. Showed 12.1 volts for each coil. Confirms nothing wrong with wiring.
  • checked continuity for each wire from ICM - to - ECU C401 firewall connector. All showed no problems, proving nothing wrong with wiring.
  • tried starting car. It cranks, but NO START.

+++++++++++++++++++++++++++++++++

  1. I suspect the Ignition Control Module (ICM) is faulty, but I won’t know until I replace it.
  2. Need to replace Valve Cover Gaskets, (as the old ones leaked copious amounts of oil into spark plug wells, causing the old spark plugs to short out. Each of the old spark plugs shows major burn scorching all around the perimeter of their insulators. Plus, I had to use half a roll of paper towels to soak up and clean out each spark plug well, before removing old spark plugs, a huge pain in my tuckas).
  3. Need to remove EGR valve and clean with Carb cleaner.
  4. Need to remove intake manifold and clean out entire EGR passages with chisels and Carb cleaner, to clear the EGR trouble code given. (a HUGE job).
  5. Need to perform a Compression test on each cylinder, to confirm which is bad/good.

Will keep you posted on anything new.

Start with #5. It will help you figure out if the rest is worth doing.

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Commend you on the testing so far. The presence of the supply voltage to either the injectors or coils is good info but not enough to determine if parts are actually doing anything. That’s because both are controlled by the other side connection- the power electronics “ground” the other side which is what causes them to do their job. The best tool to see this happening is an oscilloscope. You could make do with a DVM but may not tell you the whole story as the ability of the power device to “go all the way to ground” has an impact on performance of the part.

The resistance measurements look to be primary side measurements. Again, good info but for an ignition coil, the secondary side is also quite important. And just measuring the static resistance will not reveal a coil that is failing under high voltage stress.

You can rule out everything except the plugs by using one of these- https://www.amazon.com/Lisle-20610-Inline-Spark-Tester/dp/B0002STSC6

It is an awesome tool to have and considering the cost, I will go out on a limb and say everybody should have one in their box. It supports the divide and conquer approach to troubleshooting. If the spark tester is lighting up, you rule out everything before it.

Same with starting fluid. If you spritz that into the intake and the engine sputters or briefly starts, you have a fuel delivery problem.

This is one of the reasons why using dielectric grease on the plug tower/inside of boot is so important. It blocks out external contaminants like this from affecting plug performance. Without it, that dirty oil can creep up the tower and cause leakage (electrical) affecting the terminal voltage at the spark plug.

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Commend you on the testing so far. The presence of the supply voltage to either the injectors or coils is good info but not enough to determine if parts are actually doing anything. That’s because both are controlled by the other side connection- the power electronics “ground” the other side which is what causes them to do their job. The best tool to see this happening is an oscilloscope. You could make do with a DVM but may not tell you the whole story as the ability of the power device to “go all the way to ground” has an impact on performance of the part.<

Thanks. I thought the control would be switching the ground, with the positive always on. And I agree with you about using an oscilloscope. I’m just gonna have to take the beast to a repair shop close by to take advantage of that - a Car Talk recommended “honest mechanic” shop, “Advanced Automotive” in Miramar FL.

And just measuring the static resistance will not reveal a coil that is failing under high voltage stress.

I agree with you, which is why I am hesitating on doing any more backyard “testing”, seeing that I’ll need that oscilloscope to do it. I was also considering doing the “check for spark out of the spark plug with each coil” by using a short rubber hose on the end of the coil tube, sticking the plug in the hose and grounding the plug with jumper cables, and then have a friend try to start the car. But all that will do is confirm there’s a spark.

I can still do the starting fluid test though.

This car stopped working for a reason. I’ve GOT to find out what that reason is, and then fix it.

Thanks for your help, TwinTurbo.

True, but if a spark test shows a problem, you can defer other testing until you’ve got the spark problem solved. It may be the only problem is the spark function. It doesn’t matter what other problems you may or may not have, the car won’t run well without a proper spark to all plugs. When you’ve got a problem like that which could have multiples causes, a long list of possibilities, you’d got to somehow narrow down that list. Easy peasy tests like spark tests are one way to do that.

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True, but if a spark test shows a problem, you can defer other testing until you’ve got the spark problem solved. It may be the only problem is the spark function. It doesn’t matter what other problems you may or may not have, the car won’t run well without a proper spark to all plugs. When you’ve got a problem like that which could have multiples causes, a long list of possibilities, you’d got to somehow narrow down that list. Easy peasy tests like spark tests are one way to do that.

~ CYLINDER COMPRESSION TEST ~
in DRY state.

  • CYL. #1: 120 psi
  • CYL. #2: 150 psi
  • CYL. #3: 170 psi
  • CYL. #4: 122 psi
  • CYL. #5: 200 psi
  • CYL. #6: 160 psi

ALSO, I did the spark test with an ign. coil & new spark plug, grounded with jumper cables.
Result: NO SPARK with ALL coils at all coil connections.

BUT, when I took out the new spark plugs to do the compression test, I smelled fuel on all of them. This tells me I have fuel delivery, but NO SPARK.

I guess you’re on to something, Sparky.

To get a spark: the engine must be turning (which is, since it is cranking ok), the crank position sensor must be sensing, and passing that signal along to the ECM, which then should be firing the spark plugs, via the ignition module and coils. Suggest you start by checking the connections at the crank position sensor. The two 120 psi compression readings are a little concerning, but unlikely to be the cause for the no-start.

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Thanks George, I’ll do that… tomorrow. (I live in Florida, and it’s raining.) :cowboy_hat_face:
By the way, Scotty Kilmer on Youtube suggested the same thing. And the repair manual says to check the Ignition Control Module (ICM), aka “igniter”, how(?)… by replacing it. You’d think an Acura repair manual would say different, like how to test the gizmo. But Noooooooooooo. Just replace it. (stupid morons).

The ICM receives a logic (on/off) signal from the ECM to fire a spark plug. This triggers a circuit in the ICM which triggers a transistor controlling the current to the primary circuit (low voltage) coil to switch. That transistor might be located in the coil ass’y rather than the ICM. The effect of the rapid current change in the coil primary is a high voltage in the coil secondary. To do al that the ICM must have

  1. power and ground inputs
  2. a trigger input
  3. primary coil outputs

A diy’er could test for the power and ground inputs presumably. You’d need an o’scope or perhaps a proper scan tool to test 2 and 3. And access to the wiring schematics of course.

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Is it possible … that the reason why the compression ratios vary so much is because the heads are warped?

Yes, that’s possible. If the two cylinders with the low readings are adjacent, could be a head gasket problem too. And it’s pretty easy for a diy’er to get incorrect compression readings.

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I think this is right (EDIT: Front is to the left):

Picture 2

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the front of the car is as pictured here at this link.

Engine Bay for 98 Acura RL 3.5L V6

The front is at cylinders 1 & 4.

I’m also looking into the possibility that the Immobilizer is causing the no-start, in which case I’ll need to install one of those “immobilizer Bypass” gizmos. Opinions?