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85 D150, engine stuttering, clogged cat?
https://www.slantsix.org/forum/viewtopic.php?t=50165		 Page 1 of 2
Author:  jimbo921 [ Tue Oct 23, 2012 1:40 pm ]
Post subject:  85 D150, engine stuttering, clogged cat?
Hi all, new to this forum looks like several very knowledgeable peeps on here so here goes:

This spring I purchased what I consider one of the best trucks ever made. (Other than its just a few years too new). Its an '85 D150 short bed, slant 6 and 4 speed OD. The cab and bed are in pretty good shape especially for a native Ohio truck. However the previous owner neglected the poor 225. When I first got the truck it would barely run so here's a chronological log of what I've done to the truck so far to try and get it running right.

1.) Automatic choke housing rusted bad and not fastened to the manifold. I got this to work for now by just bending the housing a bit to fit under one of the screws.- now it starts easy

2.) Tune up, plugs, wires, cap, rotor, pcv valve.

3.) checked the initial iming, was set at 30*, I tried the factory 12* ran worse so I set it at 20* and ran it until the next step.

4.) checked timing chain by turning the engine and observing the dist, there was a good 10* slop. Replaced timing chain and re-set ignition timing to 12* at this point shes not running bad, but not perfect.

5.) replaced a very tired intake gasket, ifinally runs on all cylinders at idle but still has a stutter and low power.

6.) right after I fixed the intake, the carb sucked up all sorts of charcoal from the canister I would assume because of the now improved vacuume. - I disconnected the canister by capping the bottom suction port on the carb and leaving the fuel vent (top port on carb) open. Rebuilt the 1945 with a Napa kit. Noticed the accelerator pump was torn and was sticking badly in the top housing. I fixed the pump using a little emery cloth to bring the diameter of the plastic plunger into size. Put it back together with a new fuel filter (which was non-existant) checked fuel pressure right on the mark at 6 psi.

This is where I'm at now. The truck idles beautifully, has a good throttle response but I still have the stuttering problem under load. It has gotten worse over the summer to the point where its not really drivable now. Here's my next step, I wanted to get some feedback on this to see if im on the right track.

The truck currently has a complete working EGR system, Ive gone through it extensivly because its exactly how its acting like the EGR is stuck open. (except for the nice idle). Charcoal canister is now disconnected, and the previous owner got rid of the air pump who knows when. With that said, I am suspecting the Catalytic converters are likely plugged up causing my issues. I don't have e-check where I live so I have no problem "fixing" this issue. The only other thing I can think of is the throttle shaft seems a little bit loose, but it doesnt seem like a vacuume leak issue at this point.


Am I on the right track?
Author:  Brucehockensmith [ Tue Oct 23, 2012 2:12 pm ]
Post subject: 
Jim , I have the same truck but several "steps" down the road. I removed the lean burn ign. and went to a super six with Dutra Duals...The best running slant I drive!!! Your not too far from me in the summer...look me up next year.
Author:  Reed [ Tue Oct 23, 2012 2:36 pm ]
Post subject: 
The first thing I would do is get rid of any sort of lean-burn control on the engine. Switching to HEI ignition is very easy on your truck and will give you a HUGE improvement in economy and performance. Se how to do the conversion HERE.
Author:  jimbo921 [ Tue Oct 23, 2012 5:12 pm ]
Post subject: 
I do plan on changing out the dist to a normal one with the can on the side and magnetic pickup. The one in there now has a computer behind the battery but no mention of "lean burn" is this system still considered a lean burn?

What about my theory of the cat being clogged, am I off on this one?
Author:  jimbo921 [ Tue Oct 23, 2012 8:05 pm ]
Post subject: 
Well, I've eliminated the clogged converter theory. I guess my next step is to replace the distributer with an earlier one and throw on an orangebox. I'd do the HEI route but I have plenty of mopar ECU's laying around with pigtails.

Anyone have any other suggestions or ideas? The best way I can describe how it runs is an extreme lean condition just after part throttle. Seems to get worse the further you drive. I've triple checked the float level. and this last time I even bumped it up about .030 above the gasket. It will otherwise run perfect. Even at all throttle positions until about 2nd gear to 3rd gear, then it goes into really bad missing, If you feather the throttle it will calm down and be fine. but even that doesn't work the longer you drive it.

I'm stumped.
Author:  DadTruck [ Wed Oct 24, 2012 5:15 am ]
Post subject: 
my 83 D-150 had a continual miss at idle,, I put a timing ligt on it and at idle and at higher RPM's the timing mark on the crank damper, when viewed with the timing light would be moving forward and back, maybe an inch or so,, maybe 10 degrees,, that was with the engine PRM steady.
I removed the lean burn ( box behind the battery) initially went with a point distributor, because I had one setting on a shelf and later with a HEI,,
With either the points distributor or HEI the timing mark now is absolutely steady, advances with engine RPM..
and the miss is gone.
Author:  jimbo921 [ Wed Oct 24, 2012 5:47 am ]
Post subject: 
I did notice the mark does not seem very steady at higher rpm's when the vacuum advance should be doing its thing. No where near as steady as the MSD setup on my 440 sattelite. But again thats a nice new MSD setup.

I guess my next step is to remove the lean burn. Do I have to change the Holley 1945 to do this conversion?

I was thinking about this one from Summit as I dont see a 1920 listed:
http://www.summitracing.com/parts/HLY-64-3117/
Author:  DadTruck [ Wed Oct 24, 2012 7:01 am ]
Post subject: 
PM Slant Six Dan for carbs / info
Author:  Reed [ Wed Oct 24, 2012 9:00 am ]
Post subject: 
Whether or not you have to change the carb depends on whether or not the carb is computer controlled. Lean burn systems came in three flavors- ignition control only, carb control only, or both carb and ignition controlled. Depending on the original market and application for your truck, you could have any one of those systems. If your system does not have a computer controlled carburetor, then you can just swap the ignition out with HEI or standard Mopar electronic ignition.
Author:  jimbo921 [ Wed Oct 24, 2012 9:18 am ]
Post subject: 
Thats interesting, I assume mine is ignition only, The only vacuum hose going to the lean burn is to the advance transducer. the emmisions sticker on mine looks just like this one: Image

how do I tell what I have?
Author:  xjarhead [ Sat Oct 27, 2012 2:13 pm ]
Post subject: 
Quote:
Well, I've eliminated the clogged converter theory. I guess my next step is to replace the distributer with an earlier one and throw on an orangebox. I'd do the HEI route but I have plenty of mopar ECU's laying around with pigtails.

Anyone have any other suggestions or ideas? The best way I can describe how it runs is an extreme lean condition just after part throttle. Seems to get worse the further you drive. I've triple checked the float level. and this last time I even bumped it up about .030 above the gasket. It will otherwise run perfect. Even at all throttle positions until about 2nd gear to 3rd gear, then it goes into really bad missing, If you feather the throttle it will calm down and be fine. but even that doesn't work the longer you drive it.
I'm stumped.
Here is a link to the HEI converison i did on my 86. http://slantsix.org/forum/viewtopic.php ... highlight= I plulled guts out of the computer and mounted HEI in there. All wiring to hookup module was taken from the 2 connectors for the computer. I used single pickup electronic distributor, and 1973 Holley 1920 carb. It starts much better than computer ever did. Also do the electric choke conversion too. If you have any questions let me know.

Dave
Author:  Reed [ Sat Oct 27, 2012 3:44 pm ]
Post subject: 
Quote:
how do I tell what I have?
You see the box on the vacuum diagram labeled "ESA"? That stands for "Electronic Spark Advance," A.K.A. "lena burn computer. To tell if your carb is computer controlled, look for any wires going into the float bowl of the carb. Don't get confused by the wires going to the idle stop solenoid (if your carb has one). You are looking for wires passing into the actual body of the carburetor. If you don't have wires going into the body of the carb, then your carb is not computer controlled and the ESA is only for the ignition.

You likely will be able to switch to HEI by replacing only the ignition system. HOWEVER!!!!! Some (not all) carburetors used with lean burn systems did not have a vacuum port without vacuum at idle. This means that the carb will not work with a standard vacuum advance electronic ignition distributor. Check the ports on your carb for vacuum at idle before you decide you won't have to change carbs.
Author:  jimbo921 [ Sat Oct 27, 2012 7:02 pm ]
Post subject: 
Luckily my carb is not electronically controlled. It also has the proper port for my advance. I got my distributor from summit and will be wiring it up tomorrow. Unfortunately I have to take it apart and straighten out the pickup coil bracket and set the gap. It was interfering with the rotor out of the box! Gotta really check anything you buy that's"remanufactured" these days. I'll post the progress with pics soon.
Author:  jimbo921 [ Sat Oct 27, 2012 7:02 pm ]
Post subject: 
Btw Dave I really like the way you did you hei conversion. I already had a Mopar ecu, about 30 ballast resistors and 10 coils laying around the shop so I'm gonna go with the ma Mopar ignition I'm familiar with.
Author:  jimbo921 [ Mon Oct 29, 2012 7:03 am ]
Post subject: 
Well I did the ignition upgrade to a Mopar ECU an in doing so I found the actual cause of the problem. The old distributor was caked full of rust and I'm sure not making a good reference signal as a result:

Image

Here's a pick of the setup I put together. I made a separate harness for it so I simply hooked it into the existing harness using the coil + as my "run" and jumped over to the start relay for "start". Then just put shrink tube over the old connections and tucked them up into the loom.

Image

I also wanted to make a note, guys be very wary of the cheep "reman" distributor from Summit. I don't mean to flame Summit as I've used them for well over a decade and I've never really had any quality issues to date. In this case however, the distributor looks to have been damaged in shipping. It did have a warning on the box that stated "this item has been carefully inspected and repackaged" which tells me they likely had a pallet come in damaged. Al well in good, but apparently the people "carefully inspecting" didn't know what to look for. The pickup was bent pretty badly, I opted just to ditch it and put in one I have laying around from a big block distributor.

Image


Anyway, thanks all for your help!
OL red is running perfectly now and sounds great with my custom 2-1/4" exhaust I made trying to get to the bottom of this issue.

Image
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