82 Vanagon hunting cold idle ~ FIXED

[Lanval]

When I start the engine in the morning, the idle starts at 800 (normal) and then proceeds to cycle between very low rpms (sometimes engine dies) all the way back to 800.

This goes on until the head temps read about 280+ and then it smooths out and idles fine.

I couldn't find any obvious air leaks (checked the S-boot going into the AFM fairly carefully) and tried using carb cleaner to ferret out the problem and couldn't find any air leaks that way.

Idle is at 7 deg BTDC as it should be when checked this morning.

Wondering about fuel pressure, possibly, and need to check the points.

Suggestions? I have video, but not sure how to post it.

Need to smog this puppy in a couple of weeks, so I suppose I need to figure this out.

Here's the video:
http://www.youtube.com/watch?v=lCl_FH2XjRg

Best,

Lanval

[Amskeptic]

When I start the engine in the morning, the idle starts at 800 (normal) and then proceeds to cycle between very low rpms (sometimes engine dies) all the way back to 800.

Acute onset or gradual? Pull the vacuum hose off the fuel pressure regulator and plug it before starting cold engine. Symptoms go away?
Colin

[Lanval]

Colin,

Onset is acute (i.e. immediate) and continues until the engine reaches normal operating temps.

I'll try your suggestion in the morning, and report back.

Best,

Michael L

PS ~ The fuel pump is whining like a whipped puppy when powered, and I've never been too happy about the new fuel filter setup.

I do have a shiny-new used fuel pump from the junkyard as a backup.

ML

[Lanval]

Colin,

Yep, removed the line from the regulator (that is, the little metal canister is open, and the vacuum line coming off the little metal canister was plugged.)

The rubber on the end of the line was splitting, so I snipped off about 1/4 in to find new rubber. The new rubber looked OK, so I put it back on the regulator; same problem emerged.

Best,

Mike

[Gypsie]

Sorry to butt in

Colin,

Yep, removed the line from the regulator (that is, the little metal canister is open, and the vacuum line coming off the little metal canister was plugged.)

The symptom went away set up thusly?

The rubber on the end of the line was splitting, so I snipped off about 1/4 in to find new rubber. The new rubber looked OK, so I put it back on the regulator; same problem emerged.

after the problem went away with the previous set up it came back when reattached?

Any changes in vacuum routing lately? Vac Advance and fuel Pressure reg.

7deg not 7.5?

How is high rpm timing?

whining fuel pump may indicate some sort of blockage? any rusty hunks found in fuel filters of late?

This could be a combo of one, several or all above elements.

Whatever you do, don't pull it apart 'nless your ready to get a new case.
Jes pokin' fun at myself.

[Lanval]

Sorry to butt in

Colin,

Yep, removed the line from the regulator (that is, the little metal canister is open, and the vacuum line coming off the little metal canister was plugged.)

The symptom went away set up thusly?

Yes ~ Canister is open to the air, vacuum hose is plugged, problem resolves. Replace vacuum hose on canister, problem resumes (even after cutting away potentially leaky split hose ends).

The rubber on the end of the line was splitting, so I snipped off about 1/4 in to find new rubber. The new rubber looked OK, so I put it back on the regulator; same problem emerged.

after the problem went away with the previous set up it came back when reattached?

Any changes in vacuum routing lately? Vac Advance and fuel Pressure reg.

No

7deg not 7.5?

I eyeballed it. Could be 7.25 deg; it's pretty close. And the problem emerged without any changes to the system, so there weren't any adjustments leading up to the change.

How is high rpm timing?

I'll have to check to make sure it's advancing correctly.

whining fuel pump may indicate some sort of blockage? any rusty hunks found in fuel filters of late?

Fuel pump is suspect. I had a problem over Christmas with no-starts. At that time, I could hear that the pump wasn't running. I suspected overheating due to straining from the filter. Replaced filter with the newer version (for my 82 it takes a small square filter between the tank and pump; originally, this filter was 12mm on both sides; the replacment they sell now is 7mm on input, 12mm on output, requiring me to jury rig a fuel line fix for the input side)[/quote]

This could be a combo of one, several or all above elements.

Totally agree that two issues could be in play. Dealing with the more obvious (cold idle issue) before the less obvious (fuel pressure issue).

Whatever you do, don't pull it apart 'nless your ready to get a new case.
Jes pokin' fun at myself.

[Lanval]

As an addendum, I assume the fix for the FPR is a new one?

Finances are tight, so I don't want to buy one if I don't have to.... also, is the FPR something I can pull off another (more common) vehicle at the junkyard?

Best,

ML

[Gypsie]

Hal will probly have a nice recommendation for an alternate FPR. I have been looking for an adjustable one. Is yours adjustable?

I wouldn't jump there quite yet though. Have you tested F pressure?

You could do a 'flow test' by disconnecting the fuel tank return line and manually kick in the pump (Bentley speaks to time and volume specs for this test). This may tell you if there is anything interfering with fuel supply.

Do the same test pre and post FPR for a comparison.

I had a fuel starvation issue that was a result of stuff in the tank outlet port. Long wire cleared it.

To which port is the FPR vac line connected, the intake plenum or the throttle body?

Check you FPR action with a spare piece of fuel line with mouth suction. As I recall the diaphram will not let air pass. Does the fuel pump change tone when vacuum is applied?

Just suggesting tests that don't require purchasing anything as yet.

[Lanval]

Totally appreciate it. Best to narrow it down if I can; easier if I had the IAC Maverick here, gotta man up and do it myself.

Thanks,

ML

[Amskeptic]

Totally appreciate it. Best to narrow it down if I can; easier if I had the IAC Maverick here, gotta man up and do it myself.

Thanks,

ML

The test I asked for was not an indictment of the fuel pressure regulator, it was a quick enrichment of the mixture to see if your hunting was a lean-caused hunt or a rich caused hunt. I am of the mind that you have a lean condition.
I asked if the symptoms over days/weeks/moths came up suddenly or did they gradually develop. If you have thoroughly checked out all vacuum leak sources (to the extent, even, of blocking off each vacuum hose connection to remove that "branch" entirely to see if symptoms go away, i.e. taking off the brake booster wye and blocking the intake manifold nipple will at least tell you if that circuit is good, and if not you might have to track it all the way to the booster itself), then move on to temp sensors I and II.
Colin

(p.s. crap in the fuel system or a failing pump or a cheesy filter are not going to give you cold-idle specific symptoms, I promise you)

[Lanval]

For the gradual/quick question: it was quick ~ one day I started the engine, and it was hunting big time, and died once. I'd say something gave way, since: 1) it happened "all of a sudden" and 2) it hasn't changed in a couple of weeks.

I'll go back to the vacuum lines and start checking.

I used a straw on the FPR, and got a taste of fuel vapor. The straw didn't fit over the nipple though, so the connection was a bit suspect.

I'll try a more secure fitting apparatus and try again.

Thanks,

ML

[Amskeptic]

The straw didn't fit over the nipple though, so the connection was a bit suspect.

As any infant could have told you . . . .
All of a sudden, yes I would look for a hose that split or chafed.

My booster hose trickily and craftily split along the top immediately at the front tin, the split would only open when hose was bent into installed position. As it straightened when I took it off to look, it closed up subtly.
I am not familiar with Vanagon S-boots, but they need to be taken off carefully and cleaned before a worthwhile inspection can take place. They split at the pleats.

[Lanval]

I'll check things a little more carefully. I did an inspection today that wasn't conclusive, but it wasn't precise enough either probably.

Here's what I found ~ no obvious cracks or splits on any of the rubber I could see. I removed some of them to look closer.

Some of the air hoses are wrapped in cloth/string making it difficult to check them. These also seem to be the older ones ~ i.e. the hose connected to the FPR, which was split at the ends.

Here's what I did discover: Carb cleaner sprayed at the FPR fixes the idle. Spraying the area where the hose connects (in the front, in the engine bay) gives the most effect. Continuous spray = continuous idle.

Does this narrow it down to that hose or the FPR or connector hose, or does that merely tell us that we're lean again?

Also, the FPR location makes a lot of straining noise when the fuel pump is on. It's quite loud. If you want to see a video, let me know.

I'll check the S-boot (since they are notorious) in the dark with a flashlight.



Best,

ML

[vdubyah73]

you found a vacuum leak! New hose is cheaper than a new FPR so start there.

[Lanval]

Dagnabit. Replaced the hose, still runs crappy. Working all day tomorrow, will check on Wednesday for continued vacuum problem. Assuming it's there, I'll be heading over to the junkyard on the lookout for Bosch FPRs. I can see the number on mine, bet the vanagon isn't the only place it was used. First stop, other VWs (don't ask me about the straight, rust-free 16v Scirocco I saw there last time. Effing nearly cried...) and then onto the Volvos.

That doesn't resolve, there's a Kragen and a NAPA on the way home...

Money is so bad right now. I wish someone had told me two things when I started graduate school:
1) there are far, FAR more English Ph.D.s than jobs for them
2) Student loans *sound* like a good idea, but in fact are very, VERY bad.

Thanks guys,

ML