J30 Will Not Idle Long

[GerryO]

Garaged (cold, damp coastal environment) my J30t well over a year ago, and had been starting and running it every couple of weeks for brief periods without any problems, and then the battery went dead. Several months later I replaced the battery and the car starts fine.

It won't idle normally/properly and for long, as eventually the engine dies as it warms up, unless I keep feathering the throttle. It revs pretty good, but it seems better when the engine is colder.

There aren't any codes, though it appeared MAF voltage was low, but cleaning and then replacing the MAF with a $40 ebay special made zero difference. Plugs, EGR, injectors, fuel filter, plenum pull and clean-up, O2 sensors, timing belt and numerous other items have less than 10K miles and 5 years on them. Dielectric grease applied to almost all connectors, and no signs of corrosion or leaks of any type.

Bad gas? Maybe I'll try a fuel additive, a new air filter and adjusting the TPS to up the idle speed, in hopes of making it more driveable.

Other ideas? Thanks!

[ImStricken06]

id get a normal AIT, and MAF sensor. the cheap fake stuff on ebay can easily be worse than what you had.

[chiken7]

what a bummer!
after all that lovin care and still having problems.
sorry to hear that; when was the last time you filled up?

[GerryO]

what a bummer!
after all that lovin care and still having problems.
sorry to hear that; when was the last time you filled up?

Well over a year ago.

[chiken7]

ooop there it is, hit mae.
you know what to do: please drain and replace.

[jdurrty]

Yep, unless you put in an additive like sta-bil, the gas starts breaking down and is only good for about 3 months or so.

[fourdrinie]

I agree...either drain the gas tank...or fill it up with new gas...depending on how much is in the tank.

[GerryO]

Have been reading the FSM about pulling the tank (at least four o-rings can't be re-used) and will start investigating what to do with possibly 15 gallons of bad gasoline, plus I'll need a few gallons of good stuff for rinsing and refilling, and maybe a new fuel filter too.

[yodawill2000]

Hey GerryO !!
Long time no see.
I wounder if putting a bottle of Stabil and a bottle of Redline SL1 would let you burn through the bad gas ?
I would imagine that sitting that long the ethenol caused the water and Gas to seperate.
Stabil will mix them up and redline will clean out the gunk.

[fourdrinie]

Can't you siphon a good portion of it out?

[GerryO]

Hey GerryO !!
Long time no see.
I wounder if putting a bottle of Stabil and a bottle of Redline SL1 would let you burn through the bad gas ?
I would imagine that sitting that long the ethenol caused the water and Gas to seperate.
Stabil will mix them up and redline will clean out the gunk.

Hey Yoda! I've been lurking about and not driving the J30. You are still an inspiration to us all. Have read a number of things about not running old fuel, treated or not, but who knows how much of what is in the tank, as there are also slight signs of some stuff growing on outer surfaces of fuel related hoses under the hood.

I suspect higher octane fuels have more additives that tend to break down and provide some nutrients, as I've similarly parked my F150 that runs on regular on the street for a longer period of time and it doesn't have a similar problem, though the climate is also drier.

[GerryO]

Can't you siphon a good portion of it out?

Good idea, as the J30 fuel tank does sit relatively high in the car. I'll probably do that at least to reduce the total weight of the fuel tank plus the gas. I tend to do things the hard way and really want to remove what's sitting at the very bottom and possibly coated walls of the tank, if I do end up pulling it.

[GerryO]

Yesterday afternoon I added a bottle of STP Octane Booster and a bottle of Gumout Fuel System Cleaner to the approximately 3/4 full gas tank, and started the engine just a few minutes later. As per "usual" as of later the cold engine would idle at lower than normal rpms, that dropped as it warmed and eventually stalled. I kept it running by keeping my foot on the gas.

Next I fully removed the idle adjustment screw. It looked reasonably clean and dry, but I wiped it down anyhow and squirted some WD40 on it before re-installing it, backed almost completely out. Upon restarting the still warm engine, it idled, a little fast though and it seemed like the car would be streetable.

This afternoon I drove the car for about 30 minutes, before parking it in the driveway to adjust the idle. After running the idle adjustment screw in to the point that rpms dropped to about 900 when in Park, I revved the engine a couple of times and then took my foot off the pedal; engine rpms dropped and it stalled. I backed the idle adjustment screw out some more, restarted the engine and watched the idle speed in Park, Drive and Reverse; it cycled; steady for a while, dropping about 100 rpms, while the engine stumbled a bit, before returning and holding steady where it had been, and then dropping again, etc. I backed the idle adjustment screw out a bit further and the cycling is now gone.

The idle adjustment screw is now backed out quite a bit further than I'd positioned it four or five years ago and the idle speed is a bit higher, but we are able to drive the car again!

[fourdrinie]

Sounds good..would still top it off with some high end gas, ie Chevron

[Mkiisupra]

I would put the idle screw back where its supposed to be. I dont know why people get the idea that the idle screw is something they should be messing with. You should clean out your iacv, that is what controls the idle speed between cold and hot starting.

[GerryO]

Chevron is the only gas that I've used, since I fixed a long list of other things four or five years ago.

I have a spare IAC/AAC/Air Regulator unit that I've been cleaning up for swap, as it's the one thing that I didn't remove when I had the plenum out, plus for other reasons I still may want to replace the currently deleted length of metal tubing that indirectly heats the Air Regulator. My parts and tools are now miles apart, and time is in very short supply. The engine started easily, cold or hot. It just wouldn't idle after it warmed up. Now it does and the car runs great.

[swimshark]

have you thought of doing a fuel pressure test and make sure your pump is functioning properly?

as for tank removal, you will remove the back wall of the trunk and then take the seat back of the rear seat out of the car and there is a metal panel that is removable and gives access to the tank as well.

[GerryO]

Thank you for the photo. Now that I can get under the hood again when the engine is running, I'll also be snooping around for vacuum leaks and checking the fuel pressure regulator, and I still need to run out what's left of that possibly bad gas.

[GerryO]

Just removed and replaced several accessible, suspect and hardened vacuum hoses with thick wall silicone, and was able to turn the idle adjustment screw in some more. Believe the real problem was a vacuum leak and the chief suspect is the short hose connected directly to the EGR, as it shows few cracks and is in the highest temperature location.

Lately have been disconnecting the battery when the car will sit for weeks at a time, so I don't know when the ECM will have an opportunity to learn and save all of the "normal" settings.

[fourdrinie]

What size did u get and from where?

[GerryO]

What size did u get and from where?

I found some length and size kit information on another site and ordered several feet of three different sizes, but so far I've only used a foot or so of this:

http://www.siliconeintakes.com/product_ ... a51001e977

when replacing lengths not involving any plastic OD clips, as the thick wall hose OD size is larger than original. If you find something better, please let me know.