74 914 2.0 dJet slight hesitation Options

[nsargeant]

In the quest for a perfect running 914 im getting oh so close. In the past I have replaced the tps with a new one that fixed the severe bucking/hesitation. The car ran so much better after that. What I am trying to figure out now is a random hesitation/hiccup that happens mostly during steady throttle when I am cruising on a highway. If I drive 30 miles it might happen once or twice. It seems pretty minor compared to the bucking I was having with the old tps. If I recall it has had this hesitation since I have owned the car for the last 3 years. I know the distributor does have a pertronix module in it. Ive recently changed replaced a few things listed below but still have that little hiccup. What would you guys investigate next?

Replaced:
Fuel pump/filter
Installed SS lines
plugs, wires, rotor, (cap still looked new)
tps sensor

[GregAmy]

I had a similar problem last year. Suggestion was to drop a couple dabs of oil into the cotton at the top of the disty shaft, to ensure the centrifugal weights weren't stuck.

Seemed to help, but didn't totally resolve the rare burp (usually an hour away from home, causing the blood pressure and heart rate to rise...)

[nsargeant]

I had a similar problem last year. Suggestion was to drop a couple dabs of oil into the cotton at the top of the disty shaft, to ensure the centrifugal weights weren't stuck.

Seemed to help, but didn't totally resolve the rare burp (usually an hour away from home, causing the blood pressure and heart rate to rise...)

I tried that a little bit ago and the same as yours it did seem like it helped some. i don't recall there being cotton in there though (IMG:style_emoticons/default/sad.gif) . I just put a few drops down the inside of the shaft

[ctc911ctc]

I had the same problem recently:

http://www.914world.com/bbs2/index.php?sho...cking&st=20

I found that when i changed out the MPS it fixed the problem, need to re-calibrate by spare which used to be the main MPS.

In the quest for a perfect running 914 im getting oh so close. In the past I have replaced the tps with a new one that fixed the severe bucking/hesitation. The car ran so much better after that. What I am trying to figure out now is a random hesitation/hiccup that happens mostly during steady throttle when I am cruising on a highway. If I drive 30 miles it might happen once or twice. It seems pretty minor compared to the bucking I was having with the old tps. If I recall it has had this hesitation since I have owned the car for the last 3 years. I know the distributor does have a pertronix module in it. Ive recently changed replaced a few things listed below but still have that little hiccup. What would you guys investigate next?

Replaced:
Fuel pump/filter
Installed SS lines
plugs, wires, rotor, (cap still looked new)
tps sensor

[Bleyseng]

Two things to try:

1. Pull the dizzy apart and clean clean the advance weights deep inside to rid them of 50 yr old grease and the clean the advance plate.

2. Hook up a LM2 O2 setup and drive on the freeway at the speed this problem occurs. What is the AFR reading when this happens? My bet is the MPS is running at 15 to ! for your AFR and this is a Leaning out problem. Adjust the MPS to 13.7 to 1 at this "part load" operation. Reset the WOT to start at 11 to 1 .

[ctc911ctc]

Wow, I read this and thought Belgrade Maine, another teener close to me! Then I saw this is Belgrade Serbia! Wow, must be the only 914 in a 500m radius, great advice!

Two things to try:

1. Pull the dizzy apart and clean clean the advance weights deep inside to rid them of 50 yr old grease and the clean the advance plate.

2. Hook up a LM2 O2 setup and drive on the freeway at the speed this problem occurs. What is the AFR reading when this happens? My bet is the MPS is running at 15 to ! for your AFR and this is a Leaning out problem. Adjust the MPS to 13.7 to 1 at this "part load" operation. Reset the WOT to start at 11 to 1 .

(IMG:style_emoticons/default/agree.gif)

[Bleyseng]

Nah, I am back in Seattle and didn't bother to change my location. I was going back in 15 days but cancelled the trip.

[rjames]

If the MPS is stock to your car and it hasn't ever been opened up, my money is on the distributor causing the problem.

[BeatNavy]

Finding the root cause on this symptom can be tough, particularly if you don't have a wideband O2 sensor. To Bleyseng's point, it would probably show you running (or suddenly going) lean when the bucking starts. Lean meaning Air/Fuel ratio of 15 or more as he mentions.

But, it can also be ignition related (dizzy, etc.).

To break it down, the root cause can fall into one of two categories:

1. Fuel Delivery interruption, which can be caused by many things including:
a. dirty fuel filter, sock in tank, or other obstruction in lines
b. dirty or clogged injectors
c. poor ground connections on FI harness
d. bad, dirty or misaligned trigger points
e. worn TPS
f. poorly adjusted or malfunctioning MPS
g. fuel injector connections loose

etc. etc.

2. Ignition interruption
a. issues with dizzy (sticking advance), cracked rotor or cap, etc.
b. cracked or poorly connected spark plug wires

etc. etc. I'm sure I'm missing some ideas here.

You need to start methodically eliminating these off your list (you've already replaced a bunch of parts, so a lot of this list should already be checked). If you had the O2 sensor you could probably eliminate either fuel or ignition (if it goes lean, it's something on the fuel side, if not, something on the ignition side). In any event, I would check all your grounds and other FI connections to make sure they are secure.

I know it's annoying. Good luck!

[gonzo54]

I'm having the same problem with my 73 2.0 Djet. Happens around the same RPM or 55 MPH 5th gear. I've done a number of things suggested but have not replaced the TPS. MPS has not been adjusted-still sealed. Where can I purchase a replacement TPS and how hard is it to replace and calibrate?

-Rick Seal Beach

[Bleyseng]

Take the black cover off the TPS and look at the traces. Are they worn to a deep groove or dirty? You can use 0000 steelwool very lightly to buff the traces. Use the TPS adjustment procedure with a volt/ohm meter to set them. Article was on Pelican Parts by Mike .

[BeatNavy]

I'm having the same problem with my 73 2.0 Djet. Happens around the same RPM or 55 MPH 5th gear. I've done a number of things suggested but have not replaced the TPS. MPS has not been adjusted-still sealed. Where can I purchase a replacement TPS and how hard is it to replace and calibrate?

-Rick Seal Beach

It's pretty easy to replace if you can use a hand drill and rivet tool.

Kit is available here: https://900designs-container.zoeysite.com/2...on-sensor-board

Calibration procedure here (requires ohmmeter): https://www.pelicanparts.com/techarticles/9...alibrate_20.jpg

You can test by unplugging the TPS connector. Car won't accelerate as well, but you can see if you're still having hiccups.

[nsargeant]

I replaced my tps last year so I would be less inclined to think it’s that. Got mine at 914 rubber. I noticed that my MPS didn’t have the epoxy on the back so somebody might have done some adjusting before me. I think I might put the distributor and give the advance unit a cleaning. I could understand sticking weights. Perhaps it might the sporadic ness of it. Short of testing the vacuum on the mps, anything else with it might be above my ability. Do I need to dismantle the whole distributor to clean it? Should I file and clean the trigger points while I have it apart?

[Bleyseng]

Yes, carefully disassemble the dizzy as its pretty easy just take pics as you go so you know where to put stuff back. Clean clean the advance weights! I use a small brass brush to clean off the Gunk and brake cleaner. Leave the trigger points alone other than a dap of grease on the block.

[bob164]

Rick, I have taken mine apart and cleaned it, not too tough. I can help you clean yours to see if it solves your problem. I'm in Seal Beach also. PM if you want some help.
Bob

[nsargeant]

so im getting into cleaning the distributor and the vacuum advance plate is definitely a little gunky so it is currently soaking in solvent. I pulled the trigger points and noticed what seems like a slight oil film on the whole plate as if someone put to much oil in it.

https://i224.photobucket.com/albums/dd47/ns...zpsjw9hkdqf.jpg


Can I spray this whole plate off with electronic cleaner to get the oil off of everything?



I also had residual oil in the bottom of the distributor housing. Is this normal?

https://i224.photobucket.com/albums/dd47/ns...zpsf4abotar.jpg

I also noticed after running part numbers that my dist is out of a 73 914 model # 0 231 174 007 if that makes any difference

thanks for all of the help and I apologise if the pics dont work

nathan

[Bleyseng]

yes, clean off the trigger points. Oil at the bottom of the dizzy means the O rings on the outside body is old.Change it.

[nsargeant]

So I went through the distributor and cleaned everything, it needed it, but I still have the hesitation. I'm certain my vacuum advance is working better now though. When i did the test drive i noticed the hesitation a couple times at steady throttle just as I was going up a hill as well. I dont know if I had picked up on that before. you pick up more when you turn the radio off. It also did it at no incline as well. It seemed to be more prevalent when it encountered more of a load at steady throttle though. Another thing I noticed was the throttle transitions weren't always smooth. For instance if i coasted down to 60 and then back up to 70 repeatedly. I have replaced the tps last year but I can look into that again. I will look into the grounds for the fuel injection harness next and then check vacuum and resistance on the mps.

nathan

[DRPHIL914]

So I went through the distributor and cleaned everything, it needed it, but I still have the hesitation. I'm certain my vacuum advance is working better now though. When i did the test drive i noticed the hesitation a couple times at steady throttle just as I was going up a hill as well. I dont know if I had picked up on that before. you pick up more when you turn the radio off. It also did it at no incline as well. It seemed to be more prevalent when it encountered more of a load at steady throttle though. Another thing I noticed was the throttle transitions weren't always smooth. For instance if i coasted down to 60 and then back up to 70 repeatedly. I have replaced the tps last year but I can look into that again. I will look into the grounds for the fuel injection harness next and then check vacuum and resistance on the mps.

nathan

hey there I've been contemplating this as I read your post, and thought i'd share a few thoughts since I have had this issue with my d-jet as well for ever.
here is what I have done with no elimination of the issue-
after rebuilding and calibrating an MPS , 2 actually , I switched out the TPS board and it did improve after that but still get a bucking some times at light cruising like at about 2800-3k rpm , never at idle and never on hard acceleration. I also have a 123igintion distributor installed last year, and I have no vac leaks, injectors are tested as perfect , ess new everything except the rebuilt MPS from a few years back and the TPS board was a Dave Sprinkle one I put in probably 5 years ago.

with all that I am leaning toward either the TPS circuit not being right OR the MPS.

here is one other bit of information that is interesting, I also have observed that my A/F meter does jump when this happens, so the mix is suddenly changing for what ever reason . I think it drops, like suddenly rich for a spit second, which kind of rules out a short or ground issue because if that were the case it would go lean right?
all my grounds are rechecked and my ignition harness and other wiring for FI and motor are all less than 5 years old so ess new.

anyone have a thought on this? id like to test another MPS, and I am thinking about sending this one out to be rechecked and calibrated by Jeff B. It has new diaphragm etc in it by Chris Foley and was set by them when the car was up there 2 years ago for rust repair, and my other one I had to adjust because it was set to factory spec but was WAY lean according to my A/F but also plugs and temps confirmed too lean.
- also wondering if decel valve is part of issue because I seem to remember not having this issue before I installed the d-cell last year, and I did this when I reinstalled the motor and put in the 123ignition distributor, as I was told this would protect the MPS from getting back pressure and killing the MPS.

any ideas from others?

t\what I am saying is while you should check all this stuff, I dotn think the actual problem for you or me is the distributor or a vac leak. yes eliminate those as issues, but we have something else going on that causes this on the D-jet and its been discussed many times on other threads but I don't remember anyone every getting to the bottom of it.

Phil

[ctc911ctc]

Having been through this exact thing recently, reach to Chris and follow his advice. If your MPS can hold VACUUM (not pressure, ask me why I say this.....) then you can make a small adjustment that will clear this stammering.

My bets are MPS,

So I went through the distributor and cleaned everything, it needed it, but I still have the hesitation. I'm certain my vacuum advance is working better now though. When i did the test drive i noticed the hesitation a couple times at steady throttle just as I was going up a hill as well. I dont know if I had picked up on that before. you pick up more when you turn the radio off. It also did it at no incline as well. It seemed to be more prevalent when it encountered more of a load at steady throttle though. Another thing I noticed was the throttle transitions weren't always smooth. For instance if i coasted down to 60 and then back up to 70 repeatedly. I have replaced the tps last year but I can look into that again. I will look into the grounds for the fuel injection harness next and then check vacuum and resistance on the mps.

nathan

hey there I've been contemplating this as I read your post, and thought i'd share a few thoughts since I have had this issue with my d-jet as well for ever.
here is what I have done with no elimination of the issue-
after rebuilding and calibrating an MPS , 2 actually , I switched out the TPS board and it did improve after that but still get a bucking some times at light cruising like at about 2800-3k rpm , never at idle and never on hard acceleration. I also have a 123igintion distributor installed last year, and I have no vac leaks, injectors are tested as perfect , ess new everything except the rebuilt MPS from a few years back and the TPS board was a Dave Sprinkle one I put in probably 5 years ago.

with all that I am leaning toward either the TPS circuit not being right OR the MPS.

here is one other bit of information that is interesting, I also have observed that my A/F meter does jump when this happens, so the mix is suddenly changing for what ever reason . I think it drops, like suddenly rich for a spit second, which kind of rules out a short or ground issue because if that were the case it would go lean right?
all my grounds are rechecked and my ignition harness and other wiring for FI and motor are all less than 5 years old so ess new.

anyone have a thought on this? id like to test another MPS, and I am thinking about sending this one out to be rechecked and calibrated by Jeff B. It has new diaphragm etc in it by Chris Foley and was set by them when the car was up there 2 years ago for rust repair, and my other one I had to adjust because it was set to factory spec but was WAY lean according to my A/F but also plugs and temps confirmed too lean.
- also wondering if decel valve is part of issue because I seem to remember not having this issue before I installed the d-cell last year, and I did this when I reinstalled the motor and put in the 123ignition distributor, as I was told this would protect the MPS from getting back pressure and killing the MPS.

any ideas from others?

t\what I am saying is while you should check all this stuff, I dotn think the actual problem for you or me is the distributor or a vac leak. yes eliminate those as issues, but we have something else going on that causes this on the D-jet and its been discussed many times on other threads but I don't remember anyone every getting to the bottom of it.

Phil