I have a problem and thank you all in advance for any help. My ’96 X300 VDP (120,000 miles) has extremely poor quality idle-very lumpy with stalling. A short time ago I replaced the round gray plastic breather in the crankcase ventilation hose (my car had the TCB installed for sticking throttle). Until this replacement the car ran perfectly, since the replacement the idle quality has gradually deteriorated from a minor roughness to being virtually un-driveable. The car runs well under load. I’ve cleaned the EGR valvle and the valve moves freely, I disconnected the crankcase vent hose from the cam cover with no change. I also cleaned the throttle body and the idle air valve with no change. I would say that the car is air starved when at idle -it runs well under throttle. When the car stalls it will throw a P1775 (trans fault) code which is easily erased with my Actron code reader. Did I disturb something while changing the breather? Is there a way to test the operation of the idle air valve? The crankcase vent system appears to be straight forward and fairly simple in design, so I must have missed something or disturbed something somewhere.
Thank you,
Roger

 

That's how mine has behaved when I have a coil problem

<shrug>

Not sayin' that's your problem but it's worth investigating.

Cheers
DD

 

Thanks Doug, I'll check the coils - I have a tester. The thing that throws me is everything was fine until after I changed that breather. It's not throwing any codes other than that P1775...

 

Doug is probably right on the money about the coils, but there are a few other things to check.

Check the hoses on both sides of the oil/vapor separator [gray thing] closely. They are prone to splits that are very hard to see, yet make for a good sized air leak. Also, make sure the restricter is still properly in the elbow section to the cam cover.

The P1775 does only indicate the engine stalled. Anytime the TCM sees road speed and no input [engine] speed, it signals the ECM to log P1775 and turn on the Check Engine light. There is probably a P0726 in the TCM to go with it that you are not able to read. Clear the P1775 and move on.

Good luck!

 

When I put everything back together the restrictor was in place in the upper hose.
Junior is stopping by tonight and I think we are going to spend some time with it before dinner. In anticipation of the need I'm also going to order a couple of coils from Rockauto, afterall the ones in the car are 16 years old with 120,000 miles on them.

 

Cool. Just for grins, after dark go take the cover off the ignition coils and let the car idle, try it both in and out of gear. Look down at the coils and see if you see any kind of light show down in the epoxy of the coils. Sometime these coils break down and cause really random misfires that manifest in different ways. Sometimes it runs rough, sometimes it stalls and sometimes it even makes the instruments go haywire. If you see any flashing going on in any coil, that one is junk. Weird, I know, but easy to check and can remove any doubt about a failed coil.

Good luck!

 

You know Steve, it's not as wierd as you think. "Back in the day", (I'm a child of the '60s...) that was the same rule when your car ran like s**t. Open the hood (bonnet) and if the spark plug wires looked like a light show they were crap, needed to be replaced and once they were your car ran like a dream again. As much as things change... I expect bad coils, ordered a couple off Rockauto and I will attempt the light show tomorrow night...

 

Did you order the Beck Arnely coils? I've had multiple failures with them in less than 12 months.

Cheers
DD

 

Absolutely! In the last month I've had to replace 3 recently installed aftermarket ignition coils, in two cars. Don't know who made 'em or where they came from; but they were basically new and they were junk.

Cheers,

 

Yeah I bought Beck Arnley. If I had planned this better I would have gotten the Wells... I'll get the car going and replace all 6 with Wells. $150.00 a pop though, jeeziz...!

 

You can spend even more than $150 each if you have a mind to. I think the bona-fide orignals are more like $200 each. Ouch.

I took a gamble.....and lost!


Cheers
DD

 

To be sure and it's only my opinion and I'm of the opinion that there is a bit of gouging going on here...

In getting my VDP up and running again I will revisit the crankase ventilation breather and hoses to be sure everyting is properly connected, installed and so forth. Then I'll get into the ignition and troubleshoot. The gradual worsening of the idle quality is what points to an ignition problem. So, I will replace all 6 coils with el-cheapos for now, replace the crank position sensor and then I'll begin laying in a supply of "quality" coils. Twelve coil packs six for the VDP and six for my XJS - about $1,800.00.
Ouch!
Kinda makes me think about gettin' an "old" XJS and throwing in a jazzed up XK motor with carbs...

And then again; my VDP and XJS are paid for and only cost me money for gas, insurance and repairs. Speaking of repairs I need to begin planning on replacing the diff. pinion seal in my XJS...

 

Well...replaced all six coils last night and a slight improvement but I still have the problem. Car only throws a code when it stalls. I did by a Craftsman scan tool and will go as far as I can with it.

It's beginning to look more like fuel pump and pressure regulator - 16 years and 120K miles.

 

I just went back and re-read your first post......you say all this began with the replacement of the gray oil separator in the breather system. Is that ABSOLUTELY ALL that was done at that time?? Nothing else??

Are you sure the throttle butterfly or its adjustment was not disturbed??

 

"Is that ABSOLUTELY ALL that was done at that time?? Nothing else??"

Yes. I replaced that breather and that is the exact moment all this started, which is why I have found it so puzzling. The degradation of the idle has been gradual from where it was barely noticeable to where the car idles very rough and will stall. I haven't had the time over the past few weeks to properly diagnose the problem either.

 

I'm back... I've been screwin' around with this for 3 weeks now; '96 VandenPlas, 120K miles. Poor idle quality, stalls on stop and is not throwing a DTC. I have replaced, coils, fuel pump and crankshaft position sensor and checked for vacuum leaks and not found any. I'm going to go through my workshop manuals in the a.m. EGR, IACV, TPS, Fuel pressure regulator. I checked the FPR by pinching off the vacuum hose with no change. Motor is in good shape and is well maintained; what am I missing?

Thank you all,
Roger