Packard Don

1985 Plymouth Voyager

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I realize that my 1985 Voyager is a bit new to post here but believe it or not, it was sold in 1984 so it is almost an antique! It also has the very rare Magic Camper option which was apparently available for only two years and I've never seen another. (Does anyone here have one?)

 

Anyway, I'm the second owner, having been around it since new because it belonged to some good friends. it has only about 74k original miles and is equiped with the 2.6L Mitsubishi engine which runs beautifully. With the new EGR valve - probably the last new one in the world - it even easily passes California's stringent smog tests.

 

The problem is, it has a bad hesitation from a stop, especially when cold, but only to a slightly lesser degree when warm. The carburetor was recently rebuilt, then when the problem persisted, removed and checked for proper flow on a testing machine but there is nothing wrong with it. The vacuum advance is also working properly yet my shop is at a loss as to what is causing the hesitation! It's so bad that if I punch the pedal even lightly enough to not crack a raw egg were one there, it will stall. I have to "pulse" the accelerator gently to get to moving. Otherwise it seems to have plenty of power. I'm no stranger to working on cars and have checked all the obvious things so what have I missed? This one, by the way, has no complicated electronics or computers to go wrong.

Any ideas?

Edited by Packard Don (see edit history)

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My parents had an '83 and it developed the same problem. A friend in the auto industry mentioned it was know problem for those vans and it was related to some sort of sensor. Unfortunately that happened 13 or 14 years ago now and I cannot recall the name of the part. Once replaced though the issue went away. That van has since been sold to neighbours down the street. Best vehicle my parents ever owned

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I've had several mid-eighties K-cars. Very fine automobiles for what they were; cheap and dependable. Does your van have a "check engine" light coming on? Have you checked the operation of the Throttle Position Sensor (TPS)? Also, verify adequate fuel pump pressure.

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The '81 Plymouth TC3/Turismo I had way back when would exhibit similar issues from time to time. Mine had the Chrysler 2.2 L engine and was a few years older in an era where they were making lots of changes before giving up on carburetors altogether and going with fuel injection, so it may have no bearing on your problem.

In my case, leaky vacuum hoses would cause that problem. The computer controlled carburetor would not adjust the mixture when the engine was cold, so a vacuum leak caused much bigger drivability issues when cold than hot where the computer adjusted the mixture based on the exhaust O2 sensor.

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All good things to check. I appreciate the great responses which is better and faster than any I've ever gotten on other forums!

 

The fuel pump is relatively new and has good pressure but I'll check it again. No, no check engine light. It was just recently "smogged" but would have been an automatic failure had the light been on. I don't know if it has a throttle position sensor but I'll check.

 

Just a bit more history, when I moved about seven years ago, it sat in storage for several years and when I brought it out finally, the transmission seems to either stay in low too long and then shifts abruptly or, worse, when I come to a stop, it stays in high. I have to remember while stopped to quickly shift to low, then back to high before the light changes. Otherwise it starts out in high but it does this only until it warms up, then it's fine after that. I thought that maybe the transaxle had gone bad, and maybe it has, but perhaps there is a shift sensor of some sort. This does not seem to be related to the hesitation problem but I thought I should mention it just in case.

 

Also, all the vacuum hoses (and belts) were replaced several years ago before the problem started and all are nice and pliable. I would welcome good photos of a California car's vacuum plumbing to be sure they are all connected to the proper places. The diagram on the firewall doesn't help much because I'm not sure what the actual components look like but it APPEARS to be plumbed correctly and the shop checked it. I did not change any sensors but I'll do that too once I find which the most likely ones are. This has no computer so the sensors simply seem to affect vacuum flow through the lines to other sensors, which I guess is like a mechanical computer of sorts.

 

One thing the mechanic suggested was a device called the vapor separator, which is mounted at the top of the engine next to the fuel pump where it is easy to reach and replace - if one were available. Parts houses have a vacuum canister available but that is not the same part. It seems, however, that the vapor separator has gone the way of the dinosaur! I have an easier time finding parts for my Packards.

Edited by Packard Don (see edit history)

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How old is the gas in the tank? Old gas could cause your problem or excessive moisture could also cause it.

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Not old because it is one of my two "daily" drivers and I usually run it to near-empty before filling up. Good question, though.

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If you have an electric fuel pump, it may be supplying adequate pressure and volume but a FAULTY FUEL PRESSURE REGULATOR may be sending most of your fuel back to the tank, and only a small amount to the carburetor. I dunno, might be worth looking at. Let us know what you find.

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It has a mechanical pump that mounts near the carburetor at the top of the engine. The old one suddenly developed a leak a few years ago so it was replaced. I'm not sure that there is an actual pressure regulator since it's a mechanical pump but it is certainly something more to check.

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I finally was able to get and use a fuel pressure test gauge and according to the factory shop manual, the pressure should be between 4.5psi and 6psi. Directly from the fuel pump, it is running at a rock-steady 6 lbs (a hair over, actually) ragardless of engine speed but measuring out of the vapor separator which is between the pump and the carburetor inlet, it is all over the place with the average at about 6psi at idle. Reved up, it steadies out at 6psi. It's not totally clear what the vapor separator does so maybe this is normal.

 

As far as I can tell, this 2.6L Mitsubishi engine with Mikuni carburetor does not have a throttle position valve as such but it does have an integral sub-EGR valve that is connected to the throttle linkage. It also has an engine speed sensor and solenoid valve that seems to regulate what the manual calls the CAV ("Coasting Air Valve") system. This system seems to be only for low engine speeds but, if defective, it's not clear what it would do at higher speeds.

 

Do these things give any clues as to what to start replacing first?

Edited by Packard Don
Corrected a typo. (see edit history)

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Still trying to resolve this problem but now the power brake booster has gone out with the replacement arriving later today. Won't know until the new one is installed but perhaps the old had a vacuum leak. Had the transmission serviced for now but it really needs a rebuild (lots of metal shavings around the magnetic drain) but will save that for a later date as I already have many times the value into it!

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On 10/22/2014 at 7:28 PM, Packard Don said:

I realize that my 1985 Voyager is a bit new to post here but believe it or not, it was sold in 1984 so it is almost an antique! It also has the very rare Magic Camper option which was apparently available for only two years and I've never seen another. (Does anyone here have one?)

Anyway, I'm the second owner, having been around it since new because it belonged to some good friends. it has only about 74k original miles and is equiped with the 2.6L Mitsubishi engine which runs beautifully. With the new EGR valve - probably the last new one in the world - it even easily passes California's stringent smog tests.

The problem is, it has a bad hesitation from a stop, especially when cold, but only to a slightly lesser degree when warm. The carburetor was recently rebuilt, then when the problem persisted, removed and checked for proper flow on a testing machine but there is nothing wrong with it. The vacuum advance is also working properly yet my shop is at a loss as to what is causing the hesitation! It's so bad that if I punch the pedal even lightly enough to not crack a raw egg were one there, it will stall. I have to "pulse" the accelerator gently to get to moving. Otherwise it seems to have plenty of power. I'm no stranger to working on cars and have checked all the obvious things so what have I missed? This one, by the way, has no complicated electronics or computers to go wrong.

Any ideas?

Yes I have a 1985 Voyager with the fold down bed in the rear. In the photo, it was the display vehicle used at the 'American Patriot Award' Ceremony for Lee A. Iacocca, as he considered the MiniVan to be his greatest contribution to the automotive industry, not the Mustang which was just a re-skinned '64 Falcon Sprint.

F5380E38-DCB3-4A15-9A2F-599238606B97.jpeg

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By the way, I use to be a Tech at a Chrysler Dealer, I rebuilt all the Mikuni carburetors on those 2.6L engines.

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Nice color combination and better than my red with a gray interior.  Do you still own it and is the Magic Camper decal intact in the rear window?  I allowed mine to fade away without documenting it so now I having no pattern to use in making a new one.

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If my brain is remembering correctly, the early 80's Chrysler 4 cyl engines in California all had stumbling problems when new. The fix at the time was simply a new and different carb spacer between the intake and the carb. When the carb was replaced the spacer may have been left off, worth a check.

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This one has the Mitsubishi 2.6L engine with the Mikuni carburetor so I’ll have to research about a spacer.  Not sure if that problem applies to it or not but worth looking into!

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The real problem is within (inside) the carburetor. I could explain it better verbally than here in the forum.

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On 2/7/2020 at 12:34 AM, Packard Don said:

Do you still own it and is the Magic Camper decal intact in the rear window?  I allowed mine to fade away without documenting it so now I having no pattern to use in making a new one.

No, it didn't have the sticker when I bought it with 126,000+ miles in the odometer.  Long story there as well.  Now sporting the 3.0L MMC engine.

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I would love to hear more but speaking verbally, unless you happen to be local, is not possible as I’m virtually deaf and do not hear well on a telephone. After the carburetor was rebuilt and the problem started, the shop even took it back out and checked it on a machine that showed proper flow and no vacuum leaks. The emissions system’s plumbing had gotten hoses mixed up around that same time which was my own doing so it added layer of complexity to the issue.

 

Having said that, I found that the brakes have been dragging, ruining the transmission so that it needs to be rebuilt so that might be a major contributor to the problem. The brakes had been replaced but the shop apparently did not check the lines and hoses so, even with only a few hundred miles on them, the rotors were blue.

Edited by Packard Don (see edit history)

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56 minutes ago, Packard Don said:

I would love to hear more but speaking verbally, unless you happen to be local, is not possible

OK, I'll try to tell the story in short form, remember that I am speaking of the Mikuni Carb before someone else fiddled with it.

The problem I have found is that the low speed jetting is very 'tiny' and is easily restricted. We had nearly new cars, be they the 'K' body LeBaron or the Voyager with the 2.6L

The carburetors were bench tested at the factory that manufactured them. They used some sort of liquid which left a 'whitish film' on the inside of the float bowl.

When the carburetors were installed on the engines in Japan, on the finished engines, and shipped to Chrysler assembly points here in the US, this was the first time gasoline was introduced and the vehicles driven off to the dealers. The gasoline loosened this 'whitish film' and it collected at the bottom of the float bowl and was sucked up into the jets.

We had a constant flow of these vehicles, so equipped, into the dealership for the annoying stumble or hesitation on initial acceleration from a stop and even while driving in slow traffic.

I merely removed what we'll call the air horn so the float bowl was exposed. I used normal carb cleaner spray to clean the bowl and the jets and passages. I let the stuff soak a while and then vigorously blew it out and often gave it another shot of cleaner followed with more air. I also removed the anti-tamper plug at the idle mixture screw and adjusted the mixture when the carb was together and the engine running again. The plug was reinserted. This was done with an exhaust analyzer attached in the tail pipe so it would still pass CA exhaust emission tests.

I cannot tell you what is wrong with your Mikuni all these years after. I can only tell you that the tech has to make absolutely sure it is not internally restricted and that everything else is correct. I suspect that you have a sub-EGR valve in the base of your carb and that it is properly adjusted?  

More if you require it.

 

Hemi...

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On 9/15/2017 at 1:14 PM, Packard Don said:

Still trying to resolve this problem but now the power brake booster has gone out with the replacement arriving later today. Won't know until the new one is installed but perhaps the old had a vacuum leak.

Here is another situation with the 2.6L engines and power brakes on any 'K' car or minivan. The vacuum hose that supplies the brake booster is tapped into the intake manifold near the #4 cylinder intake port. IF THERE IS A DEFINITE ENGINE MISS WITH THE BRAKE PEDAL APPLIED, there is an internal leak at the booster causing the #4 cylinder to lean out to the point of misfiring. This condition has not been found to affect the low speed hesitation though.2D54715F-B910-4656-A2D1-7800EF15E9FF_1_101_a.thumb.jpeg.e9bcb022dcba9e038033d5ce06bd9157.jpeg

This is how my 85 Voyager looks today at 264,405 miles. Best thing was replacing the 2.6L engine with a 3.0L and 3 speed automatic transaxle at 126,xxx miles when the camshaft in the 2.6 snapped in two. It is a reasonably simple swap since the 87 body is exactly the same, so it fit in as though it was made for it. That solved the entire 2.6L problem and performance is so much better. I used it to tow cars cross-country, one trip from North Carolina to my shop in California.

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Thank you for all the great information! Don’t believe that there is a vacuum leak at the booster’s connection to the manifold but all the other things are possibilities. Another is that the emission system is mis-plumbed or has a bad device in it as it seems to have components not on, or different than, those on the firewall tag, which itself is different than the manual!  I’ve got it all connected as best as I could with no good guide to follow. You also mentioned the a secondary EGR adjustment but I’m but sure what or where that’s done. The main EGR that was on it when I got it was physically broken and it took a long time to find a new replacement and a lot of money to buy it as it was apparently the last new one in existence!

 

I live in California but the van at my Oregon shop 550 miles away and I’ll be heading up there in a few weeks. Although it’s not my current project, I do want to work on the brakes to see why I cannot pressure-bleed the left rear and that may involve disconnecting the line to the rear from the master. Do you happen to know which line feeds the back axel?

 

Don

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3 hours ago, Packard Don said:

Do you happen to know which line feeds the back axel?

The forward line from the master cylinder feeds the rear brakes.

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