1998 3.3l low drive idle and cutting out

[Kyleblaqk]

Hello!

 

So I've just picked up a 1998 R50 with the 3.3 litre engine and automatic gearbox. Once the car is warm it idles a little rough, it's fairly stable in P but in any of the drive gears the revs drop and fluctuate between 450 and 600. When flicking between D and R when adjusting to park, for example, the revs are so low it cuts out. And when it's cut out, it cranks for a while before it wants to start again!

 

I made a little video (link below) of it idling and switching between P and D, where you can witness the revs drop. I also pan to a multimeter just so you have more metrics to reference.

 

https://youtu.be/ZjUrRVaSO3U?si=VibdLH7aSFLK_wNC

 

On the road it feels smooth, it's only when it's stopped at lights for example where I feel like it's verging on cutting out at any moment. I'm also scared to come across any form of incline, as I very much doubt the idle is strong enough to hold itself on a hill of any sort

 

I've cleaned the throttle body as per some forums suggestions and it wasn't so dirty anyway.

 

One thing to note is that it does have an LPG system fitted. Though I'm told it won't even kick in until it exceeds 1300rpm or there abouts. And I have the system turned off as there's no gas in there anyway. Perhaps putting gas in might help? Seems unlikely, but I might do it just to be safe.

 

If anyone has any suggestions for diagnosis then that would be super!

 

Thank you all in advance

[Slartibartfast]

My '93 behaved very similarly when the connector for the MAF was worn out. It ran fine most of the time, but now and then it would surge at idle, or forget how to idle entirely, especially once it warmed up (high idle when cold masked the problem). Screwing around with the MAF connector always cleared it up, for a while. I finally got tired of messing with it, and replaced the connector, and it hasn't done it since.

 

I don't know that I've heard of an R50 doing that, but that's the first thing I'd check. (Also check for OBDII codes, on the off chance the computer has some idea of what's wrong. Mine didn't, but yours should be smarter than mine.)

 

I have zero experience with LPG (apart from cooking hamburgers!), so I'm no help there. Though, yeah, if it only kicks in over 1300 rpm, I doubt it's related, unless something is very wrong with it.

[IanS]

Kyle,

 

I had something similar that took me way too long to chase down.

 

My 99 Pathy would behave wonderfully when cold, then after about 30 mins, I would stop at a stoplight, in Drive, even with A/C on and the idle would fluctuate and then drop to 500ish and stay there, feeling like it was idling weirdly, like it wasn't smooth and it was going to die soon. I got a few check engine lights for Misfire in Multiple Cylinders, Running too Rich or too Lean, and after quite a while I got a Cat code. 

 

Finally, after replacing the MAF sensor and cleaning it multiple times, checking for evap system leaks, turning the distributor a bit to increase idle, cleaning the intake manifold multiple times, checking the IACV, messing with fuel pump and whatever other random things I could come up with I decided to check the O2 sensors. Unplugged the upstream ones and went on a drive. No change in the bad idle.

 

A few new O2 sensors later, no idle issues. 

 

I'm curious to know if you have the same issue.