1973 2.0 D-Jet Hesitation Stumble 2500-3300 RPM Options

[gonzo54]

I had this problem shortly after I purchased my car in 2019 and I solved it with a new 2.0 914 Rubber TPS Circuit Board.

Fall 2022 I rebuild the motor to a 2056 with a mild Webcam 73 (D Jet compatable) and The Hesitation Is Back. So far I have accomplished the following using PB Anders articles and with the help of Bob D @bob164 who has logged numerous hours on this project.

-Checked the resistance of the entire engine wiring harness repairing and improving resistance on several connections. Checked all grounds. No Hesitation Fix

-Smoke tested the intake which found a leak at the Cold Start Valve, fixed. I still have a minor leak at the Throttle Body shaft and #1,2 Intake Manifold (replaced gasket and added sealant - needs resurfacing) No Hesitation Fix

-Fuel Injectors were sent to Mr Injector for cleaning and flow test during the rebuild.

-The Dizzy was disassembled-Trigger Points cleaned, Weights cleaned and lubed, Vacuum advance checked. No Fix, so I bought a 123 Blue Tooth Dizzy after reading about Trigger Points possibly being the problem. No Hesitation Fix

-The CHT sensor is within the paramaters of PB Anders data.

-The MPS checked out and did hold vacuum withing the leakdown parameters but it decided to quit holding vacuum so we rebuild it with a Tangerine Racing Kit and PB Anders data. No Hesitation Fix

-The ECU 0 280 000 037 that came with the car was replaced with ECU 0 0280 000 044. I've read that ECU's rarely fail. No Hesitation Fix

-TPS: All of the 914 World threads regaring this problem takes me back to the TPS and TPS Circuit. I now own 2 complete TPS's 0 280 120 032 and 4 circuit boards. I've tried all combinations including the 914 Rubber TPS Circuit Board and the Throttle Switch has always been set up per Ralph Ricks Instructions. I still have the Hesitation. When I disconnect the harness plug to the TPS The Hesitation Does Not Occur! The car has a little lag with the TPS harness unpluged but accelerates through all RPM's with out a problem. This test continues to lead me back to a bad or dirty TPS Board. I have cleaned and sprayed the boards and sweep fingers with electronic cleaner numerous times, perhaps the gold plated contact fingers are too warn but a continuity test as the fingers run over the track appears good. I have rechecked the TPS harness wires to the ECU and they check good.

I do not want to continue buying parts that may not fix this problem, so at this point I'm Stumped! Should I buy another Board or complete TPS or go in another direction? This is a great group with a wealth of information what do you think?

Thanks in advance,

[emerygt350]

Can you borrow a tps from a known working car? Have them put your tps on their car, see if it starts to stumble.

And just to be clear, is this at cruise or while you are accelerating? Are you wot or is this as you are actively moving the gas pedal?

[Dlee6205]

"And just to be clear, is this at cruise or while you are accelerating? Are you wot or is this as you are actively moving the gas pedal?"

- (IMG:style_emoticons/default/agree.gif) This would be helpful information to have.

What parameters have you changed to compensate for the increased displacement? Bumped fuel pressure? Modified MPS?

[gonzo54]

Can you borrow a tps from a known working car? Have them put your tps on their car, see if it starts to stumble.

And just to be clear, is this at cruise or while you are accelerating? Are you wot or is this as you are actively moving the gas pedal?

I would like to borrow a good working TPS but that hasn't worked out so far.

Yes, this happens while cruising and accelerating. It varies from approximately 2500-3300 RPM. It does not happen if I stomp on it WOT.

[gonzo54]

"And just to be clear, is this at cruise or while you are accelerating? Are you wot or is this as you are actively moving the gas pedal?"

- (IMG:style_emoticons/default/agree.gif) This would be helpful information to have.

What parameters have you changed to compensate for the increased displacement? Bumped fuel pressure? Modified MPS?

The fuel pressure is set at 29 PSI and the MPS has been set with a LCR Meter back to the original settings.

[windforfun]

Are any of the TPS parts loose? Like the drive shaft that moves the TPS? Have you aligned the TPS properly?

(IMG:style_emoticons/default/confused24.gif) (IMG:style_emoticons/default/confused24.gif) (IMG:style_emoticons/default/confused24.gif)

[gonzo54]

Are any of the TPS parts loose? Like the drive shaft that moves the TPS? Have you aligned the TPS properly?

(IMG:style_emoticons/default/confused24.gif) (IMG:style_emoticons/default/confused24.gif) (IMG:style_emoticons/default/confused24.gif)

Both TPS's appear servicable and I have done a continuity test from the Pins through the pressure contact, through the board and through the drag switch. However there could be a problem with the sliding contacts that I can't pick up with my OHM meter. Yes the TPS has been aligned per Ralph Ricks Instructions.

Thanks

[iankarr]

I assume you tried adjusting the advance curve on the 123, increasing it around the flat spot?

[JeffBowlsby]

Delete

[gonzo54]

I assume you tried adjusting the advance curve on the 123, increasing it around the flat spot?

Hi Ian, I'm still in the learning curve for the 123 Dizzy and have not adjusted it in the flat spot. I had the same problem with the stock Dizzy but willing to try different curves for the 123. I have attached my curve, I'm not using the vacuum advance. So what would you recommend?

Thanks

[emerygt350]

Lean miss? Nothing doesn't work like setting a mps by LCR. Except maybe prayer.

Do you have an AFR gauge?

[gonzo54]

Lean miss? Nothing doesn't work like setting a mps by LCR. Except maybe prayer.

Do you have an AFR gauge?

No I don't have a AFR gauge but will probably weld in a bung and tune the MPS in the future. I did try a 1.7 MPS I own and had the same hesitation.

[JeffBowlsby]

For your 73 2.0L to run correctly you really need to use matching parts as they are not identical. Recommend reinstalling the correct 037 ECU for your car.

If you need a backup 037 ECU I have one and would trade your 044 for it.

[DRPHIL914]

Are any of the TPS parts loose? Like the drive shaft that moves the TPS? Have you aligned the TPS properly?

(IMG:style_emoticons/default/confused24.gif) (IMG:style_emoticons/default/confused24.gif) (IMG:style_emoticons/default/confused24.gif)

Both TPS's appear servicable and I have done a continuity test from the Pins through the pressure contact, through the board and through the drag switch. However there could be a problem with the sliding contacts that I can't pick up with my OHM meter. Yes the TPS has been aligned per Ralph Ricks Instructions.

Thanks

@gonzo54
having had this same issue with my 75 2.0 d-jet and i had it for a really long time until i pulled the TPS and cleaned the circuit board, my contacts had some corrosion or oxidation , i have seen some with wear patterns too, but- i used an pencil eraser and that eliminated that bucking and hesitation.
you can simply un plug it and see if that gets rid of the bad bucking if it does you know thats where the problem lies.
new circuit boards are also available, Dave Sprinkle makes them and i think 914rubber carries them.

Phil

[dr914@autoatlanta.com]

to test the throttle position sensor, just disconnect it and see if the 3200 rpm stumble sudden cutout stops. If so it is the device, if not it is something else like grounds

I had this problem shortly after I purchased my car in 2019 and I solved it with a new 2.0 914 Rubber TPS Circuit Board.

Fall 2022 I rebuild the motor to a 2056 with a mild Webcam 73 (D Jet compatable) and The Hesitation Is Back. So far I have accomplished the following using PB Anders articles and with the help of Bob D @bob164 who has logged numerous hours on this project.

-Checked the resistance of the entire engine wiring harness repairing and improving resistance on several connections. Checked all grounds. No Hesitation Fix

-Smoke tested the intake which found a leak at the Cold Start Valve, fixed. I still have a minor leak at the Throttle Body shaft and #1,2 Intake Manifold (replaced gasket and added sealant - needs resurfacing) No Hesitation Fix

-Fuel Injectors were sent to Mr Injector for cleaning and flow test during the rebuild.

-The Dizzy was disassembled-Trigger Points cleaned, Weights cleaned and lubed, Vacuum advance checked. No Fix, so I bought a 123 Blue Tooth Dizzy after reading about Trigger Points possibly being the problem. No Hesitation Fix

-The CHT sensor is within the paramaters of PB Anders data.

-The MPS checked out and did hold vacuum withing the leakdown parameters but it decided to quit holding vacuum so we rebuild it with a Tangerine Racing Kit and PB Anders data. No Hesitation Fix

-The ECU 0 280 000 037 that came with the car was replaced with ECU 0 0280 000 044. I've read that ECU's rarely fail. No Hesitation Fix

-TPS: All of the 914 World threads regaring this problem takes me back to the TPS and TPS Circuit. I now own 2 complete TPS's 0 280 120 032 and 4 circuit boards. I've tried all combinations including the 914 Rubber TPS Circuit Board and the Throttle Switch has always been set up per Ralph Ricks Instructions. I still have the Hesitation. When I disconnect the harness plug to the TPS The Hesitation Does Not Occur! The car has a little lag with the TPS harness unpluged but accelerates through all RPM's with out a problem. This test continues to lead me back to a bad or dirty TPS Board. I have cleaned and sprayed the boards and sweep fingers with electronic cleaner numerous times, perhaps the gold plated contact fingers are too warn but a continuity test as the fingers run over the track appears good. I have rechecked the TPS harness wires to the ECU and they check good.

I do not want to continue buying parts that may not fix this problem, so at this point I'm Stumped! Should I buy another Board or complete TPS or go in another direction? This is a great group with a wealth of information what do you think?

Thanks in advance,

[914_teener]

Follow Jeff's advice with the ECU, also you could try to up your fuel pressure a bit. Easy to do and then check it with a wide band.

As for the 123 you don't mention if it is a switched version for D-jet or not?

If it is switched then get a matched ECU first and then use the correct setting for your engine.

The cam you have will idle a little higher then stock but....use the vacuum port on the dizzy and make sure you have ported vacuum. Ported vacuum is on the atmosphere side of the TB. Do not use manifold vacuum on the dizzy.

The symptoms you describe sound like part load advance which is what the vacuum advance is for.

That's a great cam and if the set up is right should run like a Hurricane Hilary.

Good Luck

[gonzo54]

For your 73 2.0L to run correctly you really need to use matching parts as they are not identical. Recommend reinstalling the correct 037 ECU for your car.

If you need a backup 037 ECU I have one and would trade your 044 for it.

Thanks Jeff, I will put the 037 ECU back in. I've run it with a ballast resistor and without and do not see any difference. TPS?

[gonzo54]

to test the throttle position sensor, just disconnect it and see if the 3200 rpm stumble sudden cutout stops. If so it is the device, if not it is something else like grounds

I had this problem shortly after I purchased my car in 2019 and I solved it with a new 2.0 914 Rubber TPS Circuit Board.

Fall 2022 I rebuild the motor to a 2056 with a mild Webcam 73 (D Jet compatable) and The Hesitation Is Back. So far I have accomplished the following using PB Anders articles and with the help of Bob D @bob164 who has logged numerous hours on this project.

-Checked the resistance of the entire engine wiring harness repairing and improving resistance on several connections. Checked all grounds. No Hesitation Fix

-Smoke tested the intake which found a leak at the Cold Start Valve, fixed. I still have a minor leak at the Throttle Body shaft and #1,2 Intake Manifold (replaced gasket and added sealant - needs resurfacing) No Hesitation Fix

-Fuel Injectors were sent to Mr Injector for cleaning and flow test during the rebuild.

-The Dizzy was disassembled-Trigger Points cleaned, Weights cleaned and lubed, Vacuum advance checked. No Fix, so I bought a 123 Blue Tooth Dizzy after reading about Trigger Points possibly being the problem. No Hesitation Fix

-The CHT sensor is within the paramaters of PB Anders data.

-The MPS checked out and did hold vacuum withing the leakdown parameters but it decided to quit holding vacuum so we rebuild it with a Tangerine Racing Kit and PB Anders data. No Hesitation Fix

-The ECU 0 280 000 037 that came with the car was replaced with ECU 0 0280 000 044. I've read that ECU's rarely fail. No Hesitation Fix

-TPS: All of the 914 World threads regaring this problem takes me back to the TPS and TPS Circuit. I now own 2 complete TPS's 0 280 120 032 and 4 circuit boards. I've tried all combinations including the 914 Rubber TPS Circuit Board and the Throttle Switch has always been set up per Ralph Ricks Instructions. I still have the Hesitation. When I disconnect the harness plug to the TPS The Hesitation Does Not Occur! The car has a little lag with the TPS harness unpluged but accelerates through all RPM's with out a problem. This test continues to lead me back to a bad or dirty TPS Board. I have cleaned and sprayed the boards and sweep fingers with electronic cleaner numerous times, perhaps the gold plated contact fingers are too warn but a continuity test as the fingers run over the track appears good. I have rechecked the TPS harness wires to the ECU and they check good.

I do not want to continue buying parts that may not fix this problem, so at this point I'm Stumped! Should I buy another Board or complete TPS or go in another direction? This is a great group with a wealth of information what do you think?

Thanks in advance,

Hi George, I did disconnect the TPS harness:" When I disconnect the harness plug to the TPS The Hesitation Does Not Occur! The car has a little lag with the TPS harness unpluged but accelerates through all RPM's with out a problem"

Thanks,

[gonzo54]

Follow Jeff's advice with the ECU, also you could try to up your fuel pressure a bit. Easy to do and then check it with a wide band.

As for the 123 you don't mention if it is a switched version for D-jet or not?

If it is switched then get a matched ECU first and then use the correct setting for your engine.

The cam you have will idle a little higher then stock but....use the vacuum port on the dizzy and make sure you have ported vacuum. Ported vacuum is on the atmosphere side of the TB. Do not use manifold vacuum on the dizzy.

The symptoms you describe sound like part load advance which is what the vacuum advance is for.

That's a great cam and if the set up is right should run like a Hurricane Hilary.

Good Luck

I have the Bluetooth 123 Dizzy. Can you send me some curve numbers for the centrifugal curve and the vacuum advance (MAP)? And by ported vacuum you mean the hose above the throttle plate?

But why do I have the same hesitation with my stock Dizzy 039 905 205A? It's been disassembled, cleaned, checked and Petronix

Thanks

[DRPHIL914]

Follow Jeff's advice with the ECU, also you could try to up your fuel pressure a bit. Easy to do and then check it with a wide band.

As for the 123 you don't mention if it is a switched version for D-jet or not?

If it is switched then get a matched ECU first and then use the correct setting for your engine.

The cam you have will idle a little higher then stock but....use the vacuum port on the dizzy and make sure you have ported vacuum. Ported vacuum is on the atmosphere side of the TB. Do not use manifold vacuum on the dizzy.

The symptoms you describe sound like part load advance which is what the vacuum advance is for.

That's a great cam and if the set up is right should run like a Hurricane Hilary.

Good Luck

I have the Bluetooth 123 Dizzy. Can you send me some curve numbers for the centrifugal curve and the vacuum advance (MAP)? And by ported vacuum you mean the hose above the throttle plate?

But why do I have the same hesitation with my stock Dizzy 039 905 205A? It's been disassembled, cleaned, checked and Petronix

Thanks

- because its the TPS not the distributor........