bouncing RPM on coasting in low speed (LPG ) (1 Viewer)

[matus]

Hi to all,

I have just notice a strange behaviour of my LC100. In city traffic when I coast to traffic light with D (never tried this in Neutral) in low speed RPM start to bounce from approx 800 to 1100RPM. I have the feeling as if the transmission is trying to engage and disengage the gear. When I stop RPM settle, this only occurs when wheels are spinning.

This does happen mainly after the car warms up, never noticed it after the car is in traffic after longer period of time. I have noticed this once temperatures are lower in the morning, but not freezing.

Did someone experience something similar? I would like to prevent failures and avoid occasional costly repairs.

I can post video if it helps to identify the fault.

Thank you.

 

[Live to Ski]

Damn, another "miss read" & happening way too much lately:-( I read rpm but thought speed. My original answer below is waaaaay off base (maybe out of the park).

Not sure if these rigs have speedometer cables (vs electronic sensor), but in older rigs (like my 60), that bouncing is an indication of the sensor cable having dry lubricant.

 

[2001LC]

Likely a misfire of one or two coils that are going bad, but has not yet failed. First time it happen to me, felt like transmission/torque converter issue. Common time for this that does not set of your CEL, is engine warmed up and under load. Like at a stop in D with foot on brake.

The way I find this is by hooking up to tech stream, watch all cylinders, while in gear, holding brake on, raise RPM.

 

[matus]

Hi,I wanted to test it as well but my TS is only offering this data..I see no cylinders there. Or am I doing something wrong?

Thank you

 

[2001LC]

Typically when I first hook up and connect to vehicle it finds VIN. Sometimes I must select a vehicle in old models. Otherwise I don't see all data.

IIRC do a health check first. Then come back in to engine monitors or data. If you don't find keep looking through. You should see more pages.

I'll 2 to 3 pages of data here depending on years. It will have cylinders , ATF temp and much more

Notice in this short it shows year and make.

 

[matus]

HI, in mine I always have to select the model and year. It never found VIn by itself. Mine is 1998 so maybe the car does not support this communication I will try one more time..

 

[matus]

I ve tried it but without success. Do you have any other ideas how to identify intermittent misfiring coils without TS? Thank you

 

[2001LC]

Not without replacing one coil at a time with a known good one.

 

[white_lx]

Hi,I wanted to test it as well but my TS is only offering this data..I see no cylinders there.

See the little selection box 'Diagnosis' on your screen shot. Select another set of data ('All Data'?) and you should see more data.

Your fuel trims on Bank 1 and Bank 2 are very high. This could be an indication of a vacuum leak or dirty MAF. Are the numbers getting lower at higher RPM, or are they getting worse?

 

[matus]

Hi I have checked it one more time. Switched to "all data" see printscreen attached. I have more information available but it does not show each cylinder separately.

Regaring fuel trims-could it be because of the LPG?

But anyway I will have to check the car for vaccum leaks as sometimes when iding the car is running rought....

Thank you

 

[Cetus]

My 2007 and 2003 LX does the same thing. I thought this was normal. The rpm bounces up just a little bit when applying the brakes right before a stop while in drive.

 

[matus]

Hi, I have noticed that when RPM bounces and I switch it from LPG to petrol it is not that significant.. I will need to have the LPG system checked probably. Or could it be that the spark plugs are an issue? Has anyone similar experience? Thnx

 

[2001LC]

I suggest you start a new thread disclosing in heading you've LPG, or edit heading of this one. I'm no longer thinking COP (coils(s)) issue.

As for tech stream make sure to try "Health Check" as first step once proper vehicle selected and into interface.

 

[matus]

Hi to all,

this topic is still ongoing. but now it seems to be a bit worse. I did not use the car so much and was more standing parked then driving. Now I plan to use it more and also emission test is in a few months so I should dig deeper into this. I have tried to graph the performance but for me it is hard to understand if all is OK or something is wrong. I see some discrepancies in bank 1 and 2 but don't know if that is OK or not. If there is someone who can maybe check it and let me know the result would be great and very much appreciated.

I tried to upgrade techstream if the misfire monitor will not be present there but the car does not support it I think.

Thank you in advance