Replaced Both Coils. Problems Still The Same.

[thenewmexican]

My 91 LS400 blows black smoke out the tail pipes, AND, The RPM's will not get above 2K before the engine stutters, then drops down to about 700 RPM.

Replaced both coils with new ones. Still the same problems.

Any pointers are greatly appreciated.

[Alexander the o.k.]

When did it start doing this? After maintenance/oil change/ PS flush? Does it do this at start up, or when hot?

Have you pulled engine codes yet?

http://www.lexls.com/tutorials/intro/codereading.html

Post them here.

You have an obd1 so all you need is a paperclip, and a pencil.

Could be a combo of things. Try checking the infamous trunk hinge wire harness.

Open the trunk. On the left side you will see a wire harness on the left hinge. After repeated openings and closings the wires inside that harness become fatigued and frayed. Then they start shorting out. Then sputtering, stalling, and everything you describe. This is a design flaw and lexus knows it.

If this describes your problem, then remove the plastic bracket on the left hinge, strip down the harness, untwist all the wires, re-connect, then re-tape.

Make sure to leave off the hinge bracket that ensures tension on the harness. Just let the whole mess swing free and loose.

In my case, problem solved, and no spending thousands of dollars in diagnostics, parts, and tech snafus.

Best of all, it's free. Takes about 30 minutes.

[python]

this guy has posted many things wrong with his car and im sure hes leaving info out..this is why i havent responded, he needs to make one post and tell us everything in order to get this sorted out

[thenewmexican]

this guy has posted many things wrong with his car and im sure hes leaving info out..this is why i havent responded, he needs to make one post and tell us everything in order to get this sorted out

Sorry. Didn't mean to offend anyone.

I have ironed out most of the problems.

My LS400 Idles purflectly. However.

It is still blowing black smoke, and I still can't rev above 2K RPM.

My next replacement part of the TPS. I have a BMW, and I remember it doing the same thing.

Replaced the TPS. And the problem went away.

I'm also going to clean the throttle body and see if that helps.

Thanks again.

[python]

not offended bro, its just u have so many threads started all over this forum that its hard to follow exactly what u r trying to accomplish, make one lenghty post, state everything that is wrong and dont leave any info out, then people can help, usually by pecking away at it...hope this helps u for future problems

[thenewmexican]

not offended bro, its just u have so many threads started all over this forum that its hard to follow exactly what u r trying to accomplish, make one lenghty post, state everything that is wrong and dont leave any info out, then people can help, usually by pecking away at it...hope this helps u for future problems

Thanks for the reply.

I understand about the numerous posts. I will try to get everything into one long post as you suggest.

Ok.

What I have left to solve is. The black smoke coming from the tail pipe, and the inability for the engine to rev above 2K rpm.

The car starts and idles perfectly at 700RPM. Purrs like a cat. However, when I try to rev the engine, the RPM's get to 2K,

then convulses, going between 0RPM and 2KRPM. After which black smoke coming out of the tail pipe becomes very noticeable.

And. The idle becomes a little rough.

I sure would appreciate any input.

Thanks Python.

[thenewmexican]

Someone. Anyone.

PYTHON.

HELP !!! :(

[93ls400walt]

The post of mind bending rough running with one poster stating that his prob. was solved with a new fuel pump. This may be a fuel starving issue that you have. As for the black smoke I'm not sure how that would factor in to the lack of fuel. But I think it's worth looking into.

[thenewmexican]

The post of mind bending rough running with one poster stating that his prob. was solved with a new fuel pump. This may be a fuel starving issue that you have. As for the black smoke I'm not sure how that would factor in to the lack of fuel. But I think it's worth looking into.

Thanks for the reply.

I replaced the throttle position sensor.

Problem still exists. Can't get above 2K RPM before the engine drops down to about 700RPM, and the black smoke is still blowing.

I'm not sure what this could be now. Maybe the ECU ??

[smooth1]

Are you throwing any cels? How much black smoke are we talking about?

Problem still exists. Can't get above 2K RPM before the engine drops down to about 700RPM, and the black smoke is still blowing.

It sounds like the motor is in limp mode, it's a protection system programmed into the ECU that says something could be very wrong that can or may damage the motor. Have you had the car scanned? Do you have an ODBII scanner?

[eatingupblacktop]

Smooth is right. You should check for any codes that might be stored. Here's info on how to read OBD1:

http://www.lexls.com/tutorials/intro/codereading.html

[93ls400walt]

Ya, I was wondering about any codes also. Also sounds like the black smoke is just a side effect of the engine rpm issue. Are you in gear and driving or in park/neutral when the rpm drops? The black smoke would indicate to me that you are getting a rich mixture of fuel or a lack of air to burn the fuel. Is your throttle cable properly adjusted, is the throttle plate opening as it should? I don't recall if you did any thing with the injectors maybe they can leak excessive fuel into the cylinders.

Just trying to brain storm

[eatingupblacktop]

As Python suggested and Walt mentions, it would be helpfull to list everything you've done in addition to what you think has yet to be solved.

[thenewmexican]

As Python suggested and Walt mentions, it would be helpfull to list everything you've done in addition to what you think has yet to be solved.

Thanks for the reply.

What I have done:

1) Replaced both coils.

2) Replaced Plug wires,dist cap, plugs and rotors. Both sides.

3) Replaced TPS.

4) Replaced PCV

5) Replaced the MAF

6) Thoroughly cleaned the throttle body.

The drop in the RPM occurs when parked/idle, and I attempt to rev the engine.

While driving I can't get to speeds above 20mi per hour.

I'm receiving error codes 24, and 31. Which points to the MAF. But. I replaced the MAF with a known good one.

The throttle cable looks to be properly adjusted. I know for sure that the throttle plate is opening. Plenty of air is being

sucked in.

I have not had the injectors checked yet. I might do this tomorrow.

I have not yet had the car scanned. The only place to have that done is the Lexus dealership. And. It's very far from where I live.

I don't have an OBDII scanner. But. I believe this is an OBDI device on the car.

Thanks again everyone.

[thenewmexican]

An Update.

I disconnected the battery to reset the ECU. When I reconnected the battery. The black smoke stopped coming from the tail pipes.

Also. The engine check light, and TRAK OFF liight were no longer visible on the instrument cluster.

I then went to drive. The vehicle stuttered, then died. When I restarted the vehicle. The CEL and TRAK OFF liight were visible again,

and. The black smoke resumed coming from the tail pipes.

Any pointers are greatly appreciated.

Thanks again.

[smooth1]

Are you sure you put the coils back on the right way? You do know there is a firing order and each coil fires to a specific piston right? You didn't change any of those did you?

[thenewmexican]

Thanks for the reply.

However. I don't understand what you're saying. How can a coil fire to a specific piston. If it were true that a coil fires to a specific piston.

Wouldn't there need to be eight separate coils ??

My understanding of this engine thus far. Is that there are two identical sets of ignition components(coils,plugs,dist cap,rotors). A given set of ignition components are used by each of the four cylinders respectively.

But. To answer your question. I replaced both coils. I installed them in exactly the same way that I removed each one.

Thanks again.

[smooth1]

Thanks for the reply.

However. I don't understand what you're saying. How can a coil fire to a specific piston. If it were true that a coil fires to a specific piston.

Wouldn't there need to be eight separate coils ??

My understanding of this engine thus far. Is that there are two identical sets of ignition components(coils,plugs,dist cap,rotors). A given set of ignition components are used by each of the four cylinders respectively.

But. To answer your question. I replaced both coils. I installed them in exactly the same way that I removed each one.

Thanks again.

What I am talking about is when you replaced the coils, you put the wires back in there original sequence correct? You didn't take the wire from cylinder 1, and re route it to cylinder 2 or anything like that right? Your aware there is a firing order, and you have to route the wires from the dist. cap to the correct cylinder right? I don't know what you know and what you don't. I also don't have your motor in front of me to look at what you have done and if you have done it correctly or not. Your having a misfire issue. The first thing I would do is make sure you have spark at each spark plug. If you do, then I would check the timing. Make sure the belt didn't jump timing. If the timing is within spec, and you have spark then I would move on to the fuel injectors. Make sure they are working and inspect the seals. Then check the fuel pump. Then go back over all your sensors, knock sensor, and 02's, your sure the MAF is installed right? along with the IAT? All the vacuume hoses are on right and working? You said you replaced the TPS? Why did you replace the coils, TPS and and MAF and clean the throttle body in the first place?