Low and a bit rough idle when stopped at the traffic light on 97 LX450 (1 Viewer)

[bj70alex]

Good afternoon,
it has been a long time since i posted a question. I have a 97 LX450 with a bit over 270K on it. It was running great without any issues until I decided to replace spark plugs, distributor cap and rotor (button).
It starts right up and idles at about 1100 RPM until it warms up and then idles at 600-650. It runs fine, but it doesn't matter id the AC is on or off, when I stop at the traffic light, it drops t about 400 and needle started to fluctuate, but it doesn't stall. I cleaned the throttle plate with carburetor cleaner and it didn't help at all. Checked for vacuum leaks and didn't fins any. Any other suggestions would be greatly appreciated. Thank you

 

[lasoundguy]

I noticed my warm idle speed has dropped recently as well, so watching...I haven't checked vacuum lines yet.

 

[cahill]

did the throttle cable loosen or come out of the bracket? when was the last time the pcv valve and grommet were replaced? I changed mine out recently and the engine runs smoother. Maybe I had a small vacuum leak from the valve or grommet.

 

[bj70alex]

did the throttle cable loosen or come out of the bracket? when was the last time the pcv valve and grommet were replaced? I changed mine out recently and the engine runs smoother. Maybe I had a small vacuum leak from the valve or grommet.

No, the throttle cable never came out of the bracket. Don't remember when I replaced PCV valve and a grommet last time, probably a long time ago.. I will replace it and post the results tomorrow. Thank you

 

[cahill]

I would also check the large black air intake tube for cracks and leaks. They tend to get brittle and crack over time and create an air leak.

 

[bj70alex]

I would also check the large black air intake tube for cracks and leaks. They tend to get brittle and crack over time and create an air leak.

Will do, Thank you!

 

[letsride]

Curious if you found the problem? I had the same issue with my LX450 when I replaced the entire cooling system and distributor o-ring. It turned out my timing was off. I also know of someone who cleaned their MAF using CRC MAF sensor cleaner and ended up replacing it in his 95 Cruiser. The only other thing I can think of is the black air intake tube. A hairline crack can easily fluctuate idle.

 

[bj70alex]

Curious if you found the problem? I had the same issue with my LX450 when I replaced the entire cooling system and distributor o-ring. It turned out my timing was off. I also know of someone who cleaned their MAF using CRC MAF sensor cleaner and ended up replacing it in his 95 Cruiser. The only other thing I can think of is the black air intake tube. A hairline crack can easily fluctuate idle.

Before replacing spark plugs, distributor cap and button, I had my CEL on (EGR Valve) and never had that problem. I replaced the PCV vlave and grommet and it didn't help at all. Decided to disconnect negative battery cable for overnight and it was the same issue, but the CEL was off and it happened a few times. Now the CEL is back on and I am back to square one. I haven't replaced the black air intake tube (you mean where the MAF is located?). I will try to replace a few vacuum hoses. If replacing vacuum hoses won't help, what else could it be, ECU? But besides that issue, it starts and runs great. I am using 89 and sometimes Premium Gas. Thanks

 

[letsride]

Yes, the large diameter black intake tube that connects your throttle body to the air box...or should I say air "circle." It definitely sound like a vacuum leak. Those intake tube can have a hairline crack and that's all it takes for mine to rough idle. I couldn't find it but I replaced it with a cheap eBay tube and problem gone.

 

[fjbj40]

Check your TPS as per the manual.

You said you cleaned your TB. What may have occurred is it had a build-up of carbon and the TPS was adjusted to compensate for this. After you cleaned the TB it now closes more tightly and the TPS might need to be adjusted.

This happened to me on my 80 after I cleaned the TB and intake system.

 

[bj70alex]

Check your TPS as per the manual.

You said you cleaned your TB. What may have occurred is it had a build-up of carbon and the TPS was adjusted to compensate for this. After you cleaned the TB it now closes more tightly and the TPS might need to be adjusted.

This happened to me on my 80 after I cleaned the TB and intake system.

I believe that I found what is causing the issue. One of the catalytic converters has broken pieces inside that causing air restriction on low idle under the load. Since we don't have emissions in Florida, I am thinking of getting rid of both cats and install a straight pipe or should I buy 2 aftermarket ones since OEM is way tooooooooooo expensive.

 

[fjbj40]

Aftermarket! Check

Magnaflow Exhaust Solutions | Catalytic Converters | Performance

Magnaflow Exhaust and Magnaflow Catalytic Converters by Hottexhaust since 1992 ; now buy direct ; made in California to ISO 9001 standards ; EPA and CARB compliant as noted

www.hottexhaust.com

Running without cats crests such a stink out the tailpipe! Plus it’s polution.

 

[bj70alex]

Aftermarket! Check

Magnaflow Exhaust Solutions | Catalytic Converters | Performance

Magnaflow Exhaust and Magnaflow Catalytic Converters by Hottexhaust since 1992 ; now buy direct ; made in California to ISO 9001 standards ; EPA and CARB compliant as noted

www.hottexhaust.com

Running without cats crests such a stink out the tailpipe! Plus it’s polution.

I spoke too soon. I removed both cats and installed straight pipe and thinking it will solve the problem. It's the same thing. I really need to find out what is causing the issue with idle under load. Any suggestions? By the way, after solving the issue, I will install two new cats. Thanks.