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Won't Rev Over 2000rpm


Liammr2
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Bad things happened yesterday :-(

Started the car (96 ls400) and it was happily running at approx 1200 rpm - which is where it idles until warm. Was just sitting idling waiting for the missus to put on her seat belt. Heard a noise in the engine, and some burning smell. Now the car runs, but won't rev over approx 2000rpm.

If I do anthing other than feather the throttle then the tach needle will drop to 0 rpm and the engine will bog down - but doesn't stop. Any ideas what I might be in for?

Not a good time for it to break - someone sideswiped off the drivers door mirror when we were in NJ at xmas - and that is $560 just for the part :-(

Cheers, Liam

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Can you describe the burning smell? Does it smell like rubber, oil, or wiring? :unsure:

Does the exhaust have any unusual smells?

Yep, the exhaust was where the burning smell was. It has 2 collapsed cats :-(. So getting after market cats, and Lexus O2 sensors. That explains the not reving and burning smell. The mechanic isn't sure why the tach drops back to 0 when the engine goes over 2000rpm. But that behaviour started the same time the cats died - so I am hoping that it's just the electrics getting confused and it will behave once the cats are fixed.

You don't want to know how much it is costing :-(

Thanks for the pointer.

Cheers, Liam

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Out of curiosity, who is your mechanic?

Johnson & Johnson Imports on Mechanical Bvld, Garner

They've worked on my '96 Lexus and my wife's '99 Avalon - and we've been happy with the work to date. Place is owned and staffed by ex BMW mechanics.

Cheers, Liam

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A few years ago I had a 84 Dodge Ram Van with a 6 banger that experienced a similar problem. It had a carburetor and was not fuel injected. The blocked catalytic converter would build up back pressure over time and the only way to fix it was to spray carburetor cleaner in it until it would free up the unburnt deposits. The shop actually did this a number of times and I paid for a tune up each time. They never told me what they were doing until it blew the exhaust manifold off the motor and one of his workers spilled the beans. They were supposedly tuning up the motor each time. I had forgotten about it until you mentioned the collapsed catalytic converter. It had the exact same symptoms where the engine would lose power and bog down when you applied more fuel.

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Bad things happened yesterday :-(

Started the car (96 ls400) and it was happily running at approx 1200 rpm - which is where it idles until warm. Was just sitting idling waiting for the missus to put on her seat belt. Heard a noise in the engine, and some burning smell. Now the car runs, but won't rev over approx 2000rpm.

If I do anthing other than feather the throttle then the tach needle will drop to 0 rpm and the engine will bog down - but doesn't stop. Any ideas what I might be in for?

Not a good time for it to break - someone sideswiped off the drivers door mirror when we were in NJ at xmas - and that is $560 just for the part :-(

Cheers, Liam

Liam,

This happened to me last week. It was rather disconcerting and worrisome but it was an easy fix. Symptoms were exactly as yours. Came on right away, same limits on RPM, same exhaust smell, almost smooth idle and almost smooth in revving. THE CAR WAS RUNNING ON 4 CYLINDERS! One of the two ignition coils had failed. Replacement coil was $42 at Advance Auto. Other parts in the ignition chain may also be the culprit such as the igniter module and the distributor pickup coil. It may be what you have. Check the spark coming out of a plug wire on each of the two ignition coils. Mine had one side dead with no spark at all.

PS: Two collapsed cats??? Yes, that would give you a problem if they were but I have never heard of this in a Lexus. Are you sure? I say this because a friend of mine thought of blocked cats first also. (because the exhaust flow was greatly reduced due to firing on only four cylinders). Luckily, I stayed with ignition troubleshooting first. Mechanically, Lexus cats are very rigid and not prone to collapse or becoming blocked. I looked internally at mine at 175K miles. They look fine from a flow standpoint.

Elvis

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Liam,

This happened to me last week. It was rather disconcerting and worrisome but it was an easy fix. Symptoms were exactly as yours. Came on right away, same limits on RPM, same exhaust smell, almost smooth idle and almost smooth in revving. THE CAR WAS RUNNING ON 4 CYLINDERS! One of the two ignition coils had failed. Replacement coil was $42 at Advance Auto. Other parts in the ignition chain may also be the culprit such as the igniter module and the distributor pickup coil. It may be what you have. Check the spark coming out of a plug wire on each of the two ignition coils. Mine had one side dead with no spark at all.

PS: Two collapsed cats??? Yes, that would give you a problem if they were but I have never heard of this in a Lexus. Are you sure? I say this because a friend of mine thought of blocked cats first also. (because the exhaust flow was greatly reduced due to firing on only four cylinders). Luckily, I stayed with ignition troubleshooting first. Mechanically, Lexus cats are very rigid and not prone to collapse or becoming blocked. I looked internally at mine at 175K miles. They look fine from a flow standpoint.

Elvis

Liam,

I'm inclined to agree with Elvis. It's very unlikely that two cats would go at the same time. More likely ignition or fuel related. Before buying expensive converters, I would make sure your efi is operating properly. That includes your filter/pump/regulator/injectors. If you find the injectors need cleaning, you can add injector cleaner to your fuel tank and if they're not too bad, it should clean them up. If your doing that, then your throttle body could probably use some cleaning as well. The other direction I would go is to check the spark/voltage at your ignition coils. Bad coils usually smell burnt. If that's ok, then check your plug/ignition cables. Another easy check is for vacuum leaks.

I hope you find your problems in one of those areas. Replacing yor mirror is bad enough without having to get cats as well.

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This happened to me last week. It was rather disconcerting and worrisome but it was an easy fix. Symptoms were exactly as yours. Came on right away, same limits on RPM, same exhaust smell, almost smooth idle and almost smooth in revving. THE CAR WAS RUNNING ON 4 CYLINDERS! One of the two ignition coils had failed. Replacement coil was $42 at Advance Auto. Other parts in the ignition chain may also be the culprit such as the igniter module and the distributor pickup coil. It may be what you have. Check the spark coming out of a plug wire on each of the two ignition coils. Mine had one side dead with no spark at all.

PS: Two collapsed cats??? Yes, that would give you a problem if they were but I have never heard of this in a Lexus. Are you sure? I say this because a friend of mine thought of blocked cats first also. (because the exhaust flow was greatly reduced due to firing on only four cylinders). Luckily, I stayed with ignition troubleshooting first. Mechanically, Lexus cats are very rigid and not prone to collapse or becoming blocked. I looked internally at mine at 175K miles. They look fine from a flow standpoint.

Elvis

Liam,

I'm inclined to agree with Elvis. It's very unlikely that two cats would go at the same time. More likely ignition or fuel related. Before buying expensive converters, I would make sure your efi is operating properly. That includes your filter/pump/regulator/injectors. If you find the injectors need cleaning, you can add injector cleaner to your fuel tank and if they're not too bad, it should clean them up. If your doing that, then your throttle body could probably use some cleaning as well. The other direction I would go is to check the spark/voltage at your ignition coils. Bad coils usually smell burnt. If that's ok, then check your plug/ignition cables. Another easy check is for vacuum leaks.

I hope you find your problems in one of those areas. Replacing yor mirror is bad enough without having to get cats as well.

PS - If your problem is fuel related, I would use premium grade fuel only from a top tier supplier if you don't already.

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This happened to me last week. It was rather disconcerting and worrisome but it was an easy fix. Symptoms were exactly as yours. Came on right away, same limits on RPM, same exhaust smell, almost smooth idle and almost smooth in revving. THE CAR WAS RUNNING ON 4 CYLINDERS! One of the two ignition coils had failed. Replacement coil was $42 at Advance Auto. Other parts in the ignition chain may also be the culprit such as the igniter module and the distributor pickup coil. It may be what you have. Check the spark coming out of a plug wire on each of the two ignition coils. Mine had one side dead with no spark at all.

PS: Two collapsed cats??? Yes, that would give you a problem if they were but I have never heard of this in a Lexus. Are you sure? I say this because a friend of mine thought of blocked cats first also. (because the exhaust flow was greatly reduced due to firing on only four cylinders). Luckily, I stayed with ignition troubleshooting first. Mechanically, Lexus cats are very rigid and not prone to collapse or becoming blocked. I looked internally at mine at 175K miles. They look fine from a flow standpoint.

Elvis

Liam,

I'm inclined to agree with Elvis. It's very unlikely that two cats would go at the same time. More likely ignition or fuel related. Before buying expensive converters, I would make sure your efi is operating properly. That includes your filter/pump/regulator/injectors. If you find the injectors need cleaning, you can add injector cleaner to your fuel tank and if they're not too bad, it should clean them up. If your doing that, then your throttle body could probably use some cleaning as well. The other direction I would go is to check the spark/voltage at your ignition coils. Bad coils usually smell burnt. If that's ok, then check your plug/ignition cables. Another easy check is for vacuum leaks.

I hope you find your problems in one of those areas. Replacing yor mirror is bad enough without having to get cats as well.

PS - If your problem is fuel related, I would use premium grade fuel only from a top tier supplier if you don't already.

Thanks for all the info! I don't know for sure about the cats - but I'll be seeing them when I pick up the car. I had the ignition all done by the same firme not long ago - so if something like a coil failed then it failed in the last 2 or 3 thou miles. I do always use premium.

Cheers, Liam

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Thanks for all the info! I don't know for sure about the cats - but I'll be seeing them when I pick up the car. I had the ignition all done by the same firme not long ago - so if something like a coil failed then it failed in the last 2 or 3 thou miles. I do always use premium.

Cheers, Liam

Sorry to update myself, but just another couple of points I remembered. There was a definite noise that happened to the car just before it started playing up - it's reasonable that the noise could have been something going bang in the exhaust somewhere. The burning smell we were getting was coming off the cats - as was smoke. So I suspect that even if there is a contributing ignition issue that the cats aren't in the best shape of their lives. Car is at approx 162k, and there is no replacement of exhaust things in the Lexus service history (Lexus serviced it up to 2004).

Again, thank you for all the info - great info in this forum!

Cheers, Liam

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OK. Just talked to DougtheMechanic. I told him about the ignition coil issue that was mentioned,.

Rather than rip off the exhaust and maybe have that not be the issue (he said there was 6psi back pressure and that was more than there should be (I think he said 6 anyway)) he pulled the O2 sensors and tested with the hole in the exhaust. He said that if it was back pressure then pulling the O2 sensors should make a noticable difference and get back some of the power.

Well, it had no effect at all. So he checked out the coils and they are good. Now he is working through other things that could be the issue, starting with the MAF sensor. He also has a call out to their Tech info people to see if there is something known that he should be looking at.

Any other ideas people have I'll pass them on.

Cheers, Liam

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OK. Just talked to DougtheMechanic. I told him about the ignition coil issue that was mentioned,.

Rather than rip off the exhaust and maybe have that not be the issue (he said there was 6psi back pressure and that was more than there should be (I think he said 6 anyway)) he pulled the O2 sensors and tested with the hole in the exhaust. He said that if it was back pressure then pulling the O2 sensors should make a noticable difference and get back some of the power.

Well, it had no effect at all. So he checked out the coils and they are good. Now he is working through other things that could be the issue, starting with the MAF sensor. He also has a call out to their Tech info people to see if there is something known that he should be looking at.

Any other ideas people have I'll pass them on.

Cheers, Liam

This is getting to be quite the adventure. You never did describe the smell. Was it like burning rubber, oil, or rotten eggs?

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Liam,

Here's some possibilities:

Make sure Doug verified he is actually getting a good spark at plugs that originate from each distributor/igniter/coil circuit. I say this because my coil passed the resistance test in the shop manual but would not produce a spark.

Other possibilities are:

1. Timing belt jumped a few teeth (has the timing belt been changed once? Think you said you have over 150K miles) Doug can verify this easily with a timing light. Hope he knows Lexus. The LS400 uses # 6 to time, not #1 like a lot of cars. Lexus belts are good belts. I changed mine at 90K and it looked new. Still, its an easy test with a timing light.

2. Low fuel pressure (fuel pump or blocked filter).

3. Bad or disconnected Mass Air Flow sensor.

4. Some sort of huge air leak between the MAF and the Throttle body. Should be able to see something that big. Large crack in the bellows or a major vacuum hose off.

5. Something blocking the air flow going in. Can't imaging what this would be.

Good luck and let us know what it is.

Elvis

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Liam,

Here's some possibilities:

Make sure Doug verified he is actually getting a good spark at plugs that originate from each distributor/igniter/coil circuit. I say this because my coil passed the resistance test in the shop manual but would not produce a spark.

Other possibilities are:

1. Timing belt jumped a few teeth (has the timing belt been changed once? Think you said you have over 150K miles) Doug can verify this easily with a timing light. Hope he knows Lexus. The LS400 uses # 6 to time, not #1 like a lot of cars. Lexus belts are good belts. I changed mine at 90K and it looked new. Still, its an easy test with a timing light.

2. Low fuel pressure (fuel pump or blocked filter).

3. Bad or disconnected Mass Air Flow sensor.

4. Some sort of huge air leak between the MAF and the Throttle body. Should be able to see something that big. Large crack in the bellows or a major vacuum hose off.

5. Something blocking the air flow going in. Can't imaging what this would be.

Good luck and let us know what it is.

Elvis

Looks like it might be fixed! Thank you for the pointer Elvis.

It was one of the ignitors, which is also why the tach went funny. The tach gets it's signal off only one of the ignitors - and that one was dying under load. Doug says it's still under powered, and that's probably the backpressure in the exhaust system (6 psi instead of 2 psi) but he says that I am probably back to where I was when the ignitor went west. I'll drive it this afternoon and have a better idea.

Cat/back pressure-wise - I'll get them swapped out, and probably get the o2 sensors done at the same time but I'll collect the parts for that and supply them to the shop. I think I can cut the cost pf parts to 1/2 of what they were able to find (which was 1/2 of the Lexus parts!).

Cheers, Liam

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Liam,

Here's some possibilities:

Make sure Doug verified he is actually getting a good spark at plugs that originate from each distributor/igniter/coil circuit. I say this because my coil passed the resistance test in the shop manual but would not produce a spark.

Other possibilities are:

1. Timing belt jumped a few teeth (has the timing belt been changed once? Think you said you have over 150K miles) Doug can verify this easily with a timing light. Hope he knows Lexus. The LS400 uses # 6 to time, not #1 like a lot of cars. Lexus belts are good belts. I changed mine at 90K and it looked new. Still, its an easy test with a timing light.

2. Low fuel pressure (fuel pump or blocked filter).

3. Bad or disconnected Mass Air Flow sensor.

4. Some sort of huge air leak between the MAF and the Throttle body. Should be able to see something that big. Large crack in the bellows or a major vacuum hose off.

5. Something blocking the air flow going in. Can't imaging what this would be.

Good luck and let us know what it is.

Elvis

Looks like it might be fixed! Thank you for the pointer Elvis.

It was one of the ignitors, which is also why the tach went funny. The tach gets it's signal off only one of the ignitors - and that one was dying under load. Doug says it's still under powered, and that's probably the backpressure in the exhaust system (6 psi instead of 2 psi) but he says that I am probably back to where I was when the ignitor went west. I'll drive it this afternoon and have a better idea.

Cat/back pressure-wise - I'll get them swapped out, and probably get the o2 sensors done at the same time but I'll collect the parts for that and supply them to the shop. I think I can cut the cost pf parts to 1/2 of what they were able to find (which was 1/2 of the Lexus parts!).

Cheers, Liam

it is possible that you have a chunk of carbon stuck in the cats, I believe it happened to Blake918's 95' once, and if I recall, he revved it pretty hard until whatever it was blew through and out. Usually the smell of trouble from your cats is gasoline based, and they'll get so hot they'll actually glow red. It takes a lot to kill the cats on the LS400, and for both of them to go at the same time, just didn't make sense. Are you using oem parts?

It might be time to do some seafoam work on the intake, and clean out that throttle body. Sounds like your car is having a little touble breathing clean air.

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Cheers to you Liam. Sounds like they got it.

Elvis

PS: It would be worth it to pull the EFI/ECM fuse for 10 seconds with the car off then put the fuse back in. Start the car and let the computer automatically revise its fuel map now that you are firing on all 8. Expect a few minutes of it getting the right solution to fuel/air ratios. This will erase the biased map it had from running on 4 cylinders. Then go out and get up to speed for 30 miles or so to get the Cats up to temp and clean them out.

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  • 4 weeks later...

I had the same thing happen to my 90 ls400. I am still baffled. My story is a little different. I finished putting a new timing belt, plugs, valve cover gaskets, power steering idle valve, distributor caps, oil crankcase seal, oil pan gasket, and new timing belt tensioner on the car. It took a long time for the car to start probably because the intense cleaning of the throttle body etc. Now when I start the car it starts fine but wont go above 2000 rpm and shudders really bad. I take it on test drives with the pedal floored and it just wont go. When I get back i see smoke and the catalytic converter is glowing red. I followed the advice for the ignition coil and replaced it but same results. One more thing, I pulled the spark plugs wires of on the drivers side while it was running and no spark. there is spark on the passenger side. that tells me that it is running on four cylinders. I need help on figuring this out.

thanks,

Lance

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I had the same thing happen to my 90 ls400. I am still baffled. My story is a little different. I finished putting a new timing belt, plugs, valve cover gaskets, power steering idle valve, distributor caps, oil crankcase seal, oil pan gasket, and new timing belt tensioner on the car. It took a long time for the car to start probably because the intense cleaning of the throttle body etc. Now when I start the car it starts fine but wont go above 2000 rpm and shudders really bad. I take it on test drives with the pedal floored and it just wont go. When I get back i see smoke and the catalytic converter is glowing red. I followed the advice for the ignition coil and replaced it but same results. One more thing, I pulled the spark plugs wires of on the drivers side while it was running and no spark. there is spark on the passenger side. that tells me that it is running on four cylinders. I need help on figuring this out.

thanks,

Lance

Hi Lance

What doug explained to me is that the V8, ignition-wise, is effectively two four cylinder engines. Each bank has one of everything, coil, caps, ignitors etc. It happily 'runs' as a four, but can't rev out with only one bank firing. So what you need to do is to check out each ignition component for the side you aren't getting a spark for.

Cheers, Liam

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  • 2 weeks later...

Liam is right, you probably lost one component in the chain. You can swap ignitor connectors and ignition coils since they are the same on both sets of four cylinders. See if you can get the other bank to have spark. One ignitor cable is slightly different. It has an extra wire to drive the tach but you can swap it to isolate the bad part. You could also have a cable problem going to the pick-up coil in that side's distributor. I did. My fan belt ate through it when I didn't tie-wrap it.

Congratulations on doing a lot of work. It will pay off. Let us know what it was.

Elvis

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