1984 Dodge Ram D150, 3.7L 225

Replaced plugs, distributor cap, fuel filter (was leaking), rotor, plug wires, checked compression, set timing, Ohmed reluctors and checked gap, Valves are hydraulic, and checked for vacuum leaks with an unlit propane torch!

Truck still has the lean burn system, it only controls the spark advance (no wires to carb).

Damn thing still has a bit of a miss at idle, got a little shake to it. Runs smooth as silk with a little rpm it seems.

What the hell else can I look at without converting to an HEI setup? Might do that in the future but not yet.

I don't know jack really about carbs so haven't messed with that other than looking for vacuum leaks around the base.

The lean burn 'computer' seems to work fine as the timing advances with rpm.

Note: If it matters EGR disconnected previous to me and vacuum line to that was removed.

Check the idle mixture setting on the carb. You might need to remove the plug over the mixture screw to do this.

_________________
Casually looking for a Clifford hyperpak intake for cheap.

Thanks Reed!

Another question.......it takes quite a while before I can blip the throttle and get it down to a slow idle. What activates that idle stop solenoid (or whatever it is called)? Sure seems like the truck has to warm up quite a bit before it will activate (I am assuming a plunger pulls in letting my linkage go to a slower idle). Do I even need it? Sorry if that is a dumb question.......

THe idle stop solenoid has nothing to do with fast idle. The function of the idle stop solenoid is to increase idle when the A/C is turned on, and to prevent flooding if the throttle is closed quickly upon deceleration.

Fast idle is controlled entirely by the choke mechanism. The choke has a vacuum operated choke pulloff valve and a thermostatically controlled pulloff coil spring. When the engine is cold, the thermostatically controlled spring (which lives in the exhaust manifold) pushed the long rod that is attached to the choke flapper and closes the choke. As soon as the motor is started, the vacuum operated choke pulloff activates and opens the choke approximately 1/4 inch (this is a ballpark figure- consult your factory service manual for the exact opening for your year and emission package). As the engine warms up, thermostatically controlled spring also heats up (partly though exhaust manifold heat and partly through electric assist), pulling the rod away from the carb and slowly opening the choke the rest of the way.

What does all this have to do with your fast idle, you ask? Well, also attached to the choke flapper is a rod that is connected to the fast idle cam. When the choke flapper is closed, the rod pulls the fast idle cam into position so that (usually, depending on the year) the highest step of the fast idle cam is under the fast idle screw. As the motor warms up, the choke opens, moving the fast idle cam slowly past the fast idle screw until the fast idle cam is completely out from under the fast idle screw and the throttle is held open by the curb idle screw (or, in your case, the idle stop solenoid).

It sounds like (a) your choke is misadjusted and/or ; (b) the electric assist on the thermostatically controlled choke pulloff coil is broken or disconnected; and/or (c) the choke pulloff diaphragm is ruptured or misadjusted and not pulling the choke open on startup; and/or (d) the fast idle linkage is not adjusted properly; and/or (e) the fast idle speed is not set properly.

If I was in your position, I would spend an afternoon with a factory service manual and go over and verify the settings on all the choke related bits of the carb.

You can probably find the info you need in THIS THREAD.

Good luck!

_________________
Casually looking for a Clifford hyperpak intake for cheap.

diy_darryl:

[quote]it takes quite a while before I can blip the throttle and get it down to a slow idle.---
Sure seems like the truck has to warm up quite a bit before it will activate[/quote]

Slow warm up could be caused by partially stuck open thermostat.

I would concentrate on the choke operation first following Reed’s points. Also a good spray-down of the carburetor’s exterior, and all its moving parts with carburetor cleaner is highly recommended, and make sure all the linkage bits are free to move before doing anything.

Reed:

[quote]b) the electric assist on the thermostatically controlled choke pulloff coil is broken or disconnected;[/quote] Check its continuity. It is not uncommon for an electric choke to burn out the bimetal spring.


The nice thing about a choke is; one can look at the darn things, watch how it is operating, and make corrections and adjustments without a stinking lap top...LOL

I would suggest that you run through several cold start events after letting the engine sit over night before starting the engine, to get a feel of how the linkages, and different parts interact.

While the engine is stone cold, remove air cleaner, manually rotate throttle to “wide openâ€￾ while observing how all the linkages move on the opposite side of the carburetor. Once the choke is set (snaped fully closed), a second partial throttle opening say 50% should open the choke plate to about 75%, and when throttle is released close back up leaving a 1/4th inch gap**, all the while the high idle cam stays in position. Now the carburetor is set as if the engine has just started.

To reset the choke as if it were the first start of the day, with your finger flip the high idle cam back to its warm engine position and just crank the throttle full wide open once again, and the choke should snap closed. You will need to cycle through this cold start sequence several times before your eye catches all that goes on to get a feel for its operation.

You may find that the high idle cam is lazy and or slow to move into position (needs more cleaning), or the choke plate won’t snap closed or closes too tightly and wont pull off to that 1/4th inch gap** (adjust length of heat riser rod, and or back off electric choke coil to lean direction) check the instructions for proper adjustment.

Check for worn rods & pivot points that cause hang-ups in the linkage movement. They can be disassembled, dress lightly at the wear points with a fine file to relive binding.

You can test any of the rubber diaphragms by sucking on them using a length of vacuum hose. If they won’t hold while sucking, replace it.

**1/4th inch gap is a guess, your carburetor may have a different gap setting. Once you establish the correct gap, use a drill bit of the correct diameter to gage the opening.

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

A stuck thermostat has nothing or extremely little to do with how fast the thermostatically controlled choke pulloff opens. The thermostatically controlled choke pulloff spring gets the majority of its heat from heat radiated from the exhaust manifold to which it is bolted. Coolant doesn't flow through the exhaust manifold, and the small amount of cooling effect the coolant has on the temperature of the exhaust manifold is negligible at best. A stuck thermostat won't make your choke stay closed longer.

To check if the electric choke assist is hooked up and working, put the key in "run" and get a test light. See if the light lights up when you connect it to the choke wire and to the terminal on the inside of the thermostatically controlled spring housing.

_________________
Casually looking for a Clifford hyperpak intake for cheap.

Fine print department:

[quote]Sure seems like the truck has to warm up quite a bit before it will activate[/quote]

Author was not clear as to “truck warming upâ€￾. I took it to indicate the temperature gage was slow moving. Cold engine, open choke, can make for possible rough running. I did recommend to concentrate on carburetor first.

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Truck warms up to temp pretty quick so staying cold not an issue.
I'll dig into the carb as suggested.
FSM seems hard to locate.

If it helps at all my 87 D-150 did the exact same thing and wouldn't kick the throttle down until the temp gage started coming up. It never gave me any problems, it was just annoying when you drove it cold.

I hooked up a manual choke because I replaced the carb ( 70's holley 1920) and put in a vacuum distributor to get away from the lean-burn, (it still powers the coil and distributor) and it misses at idle still. So the computer has to be the cause of the miss, low voltage at idle or something.

_________________
Get out your aluminum magnets!

THere's no reason why you can't keep the automatic choke, but if you like the manual choke then you are set.

When you remove the lean burn system, you must disconnect it completely from the ignition and carburetion system. I would recommend you go all the way and switch to an HEI system. Leaving it halfway hooked up to the distributor will cause problems.

Even when brand new the lean-burn systems were notorious for poor idle quality, stalling, poor fuel economy, and poor performance. Darryl might still have his idle miss problem if everything else is fine but he still has the lean burn computer hooked up.

_________________
Casually looking for a Clifford hyperpak intake for cheap.

I am currently going to school, so the truck only moves when my parents need to move it or haul something. I just haven't got around to getting the parts. Plus I am a little weary on splicing into the the electrical . . .

_________________
Get out your aluminum magnets!

Seriously, the swap to HEI is about as simple as you can get. You use the existing (-) coil wire, the existing (+) feed for the computer, and then the wires to the non-lean-burn distributor. In fact, you can even use the (+) feed to the coil to power the HEI. All you need are the right size crimp-on ring terminals, the harness to hook up to the new distributor, and a crimping tool. Easy-peasy.

_________________
Casually looking for a Clifford hyperpak intake for cheap.

Information correction rant department:

Reed:
[quote]Even when brand new the lean-burn systems were notorious for poor idle quality, stalling, poor fuel economy, and poor performance.[/quote]

We purchased new in March of 1976, a cat free Lean Burn 1976 Cordoba with 400 4V, the first engine line to be so equipped, and it never gave any problem. The computer & its related sensors always worked. It idled very well, got great gas millage on the highway, 19.5 on several trips to Chicago from Boston & back. We had that car for 86,000 miles most of which were driven in eastern Massachusetts.

The one time the car quit was due to the ballast resistor crapping the bed while on route to a wedding one fine Sunday morning. In those days nothing in New England was open on Sunday, but a replacement resistor was located in time…

One had to blow out these early lean burn cars if they were driven in town a lot, as they had extremely high rear axial ratios, and once in third gear lugged around hardly coming off idle. In fact, when our car was on high idle it would cruse down the road at just under 30 mph until kicked down. If one kept the combustion chamber cleaned out with frequent frisky driving, these engines worked great.

Most of the Chrysler dealer service departments, and I worked at one for a bit in the eighties, were slow to get up to speed on computerization of engine management, mom & pop service stations were even slower, and this is why some people had problems with lean burn. The systems were hacked will-nilly by mechanics with no clue as to how they worked.

The moto of the day was “it’s the computerâ€￾, when ninety nine times out of a hundred a bad sensor or ground was at fault, or the engine was so carboned up it hardly could run. Also in 76, catalytic converters arrived, and were immediately blamed for any drivability problems; more black magic for the technician to deal with you might say…

Fast forward thirty years, all I hear is; rip the Lean Burn out, its crap, and every one of these discussions illustrate that the lean burn system has been compromised, and partly circumvented. When were they hacked during the vehicles life time, who knows, some were hacked as soon as the warrantee was up.

I will concede that after thirty years the components in the computer have most likely degraded, and probably don’t work, but that doesn’t mean the system was a bad design to begin with. From what I have read there are no replacement electronics for these units available, so now these engines have to be retro fitted with antique ignition systems & no engine management.

Too bad, as Chrysler was one of the first to strap electronics to an engine in order to achieve better performance & emission control. A mid step to fuel injection one might say, which was tried on the 1981 – 1983 Imperials in the form of an electronic carburetor.

That Imperial fuel injection system sent service department personnel to the rubber room. Most of those guys out back were just not equipped to deal with electronics, and fuel injection in those days. Cadillac experienced the same problem servicing their ‘75 and up Seville’s injection systems as well.

There was quite a lag time before trade schools could train up enough technicians to service all brands of “advancedâ€￾ engine controls in those days.

My $0.02.

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Information correction rant correction department-

WJAJR-

You got lucky. I have read many reports from original owners and period vehicle reviews where brand new lean-burn equipped vehicles didn't run right coming off the dealer lot.

for example:

original owner mentions lean burn idle problems

And besides, who cares how well it worked 30 years ago? The pertinent issue is how does it work now, and how do you fix any problems it has. There are no cheaply available replacement parts, and there have been too many documented cases of vehicles getting better performance, economy, and emissions after the lean burn system has been removed and replaced to make keeping the lean burn system worthwhile.

I have owned or worked on three vehicles originally equipped with some form of lean burn system- a 1983 Dodge van, a 1984 Chrysler Fifth Avenue, and a 1986 Dodge van. All vehicles ran smoother, had more power, got better gas mileage, and ran as clean if not cleaner with the lean burn systems replaced than with the lean burn systems in place. I still say lean-burn, especially computer controlled carbureted lean burn, isn't worth keeping or messing with. I happy you had a good experience with the earliest form of lean burn computer control. However, don't assume that your one experience means that all lean-burn equipped cars worked great except for the poor dumb mechanic who couldn't figure it out.

_________________
Casually looking for a Clifford hyperpak intake for cheap.

I forgot- I also had a 78 LeBaron, 90k original miles. It had the Spark Control Computer system. I went around and around with the lean burn trying to get it to run right, never replaced it. It always had idle problems and didn't get the greatest gas mileage. I sold the car before I replaced it. Everything else on that car was cherry (it was a true little old lady car).

_________________
Casually looking for a Clifford hyperpak intake for cheap.