D-Jet Issues-getting close, Need a little more specific advice Options

[OU8AVW]

So I got my car back from the local Porsche shop and installed a rebuilt MPS from Bowlsby but the car is still not running right. Flat spots and intermittent dead fire misses. She starts right up, idles well and drives ok but when you get on it it has intermittent flat spots and when shes just cruising it misses once and a while. Seems like the advance is not ramping up like it should. Also, the mechanic left a vacuum line off the distributor. The line from the inboard connection on the pot is hooked up but the outside one is off. I understand that one of these is advance and one is retard.

Just need a list of crap to check (IMG:style_emoticons/default/biggrin.gif)

[76-914]

What year is it?

[914_teener]

I always liked Rich Towles way to find vacuum leaks which is what it sounds like.

BUT first check all the mechanicals.

1. Take off ALL the vacuum hoses and plug them. Check all mechanicals, valves, dizzy advance plate.

2. Plug each one back in to find the leak.


Thirdly....I would find another "mechanic".

[OU8AVW]

1974 2056. New injectors, rebuilt MPS.....

[DRPHIL914]

TPS -
mine did the same thing and i always thought it was something else but since i swapped out a new TPS assembly i got from Bruce Stone, it now accelerates smoothly with no bucking or intermittant hickup like you are describing- none, 0, zilch! i can say, like new. and i had tried a replacement board but i still had an issue until the one went in. Unfortunately - i am no fighting a different d-jet issue... (IMG:style_emoticons/default/dry.gif)

[worn]

1974 2056. New injectors, rebuilt MPS.....

Timing light? Everyone correctly goes after vacuum but I would also check wiring. Two nights ago I had the lid open and saw arcing between a spark plug wire and a vacuum hose! I kept thinking I was making a mistake and it was another spark plug wire. Didn't really want to grab the offending item so I shut it down. Sure enough: hose for the vacuum advance. Black silicone rubber. I can only think that the black is carbon black, which I suspect might conduct high voltage. Misfire went away when I moved the hose. Maybe new HT wires soon?.

At any rate I would check all the components including the wires that go to them such as the aux air, the throttle sensor, the temp sensor connections, and of course the MPS. One problem I had once was a leaking cold start valve that dribbled gas into the induction system at random. A flashlight peak through the throttle body would show wet gas in the plenum. So many piddly little things. Good luck

BTW, how does Rich look for the leaks? Propane?

[r_towle]

yup, TPS, Advance plates greased, vacuum leaks, and timing.
That may explain the flat spots on accel.

Cruise skipping typically is TPS.

Also, check the CHT both warm and cold....that contributes.

Rich

[brant]

Tommy probably knows the solution

[DRPHIL914]

1974 2056. New injectors, rebuilt MPS.....

Timing light? Everyone correctly goes after vacuum but I would also check wiring. Two nights ago I had the lid open and saw arcing between a spark plug wire and a vacuum hose! I kept thinking I was making a mistake and it was another spark plug wire. Didn't really want to grab the offending item so I shut it down. Sure enough: hose for the vacuum advance. Black silicone rubber. I can only think that the black is carbon black, which I suspect might conduct high voltage. Misfire went away when I moved the hose. Maybe new HT wires soon?.

At any rate I would check all the components including the wires that go to them such as the aux air, the throttle sensor, the temp sensor connections, and of course the MPS. One problem I had once was a leaking cold start valve that dribbled gas into the induction system at random. A flashlight peak through the throttle body would show wet gas in the plenum. So many piddly little things. Good luck

BTW, how does Rich look for the leaks? Propane?

(IMG:style_emoticons/default/agree.gif)
i believe i am suffering from this same issue(the leaky cold start valve) - WORN, can you tell me, did it have a hard time starting sometimes, like it was flooded out? if i leave the car for more than a day, it will be difficult to start, but anything from 15 minutes to half a day it fires right up... just wondering.

[r_towle]

1974 2056. New injectors, rebuilt MPS.....

Timing light? Everyone correctly goes after vacuum but I would also check wiring. Two nights ago I had the lid open and saw arcing between a spark plug wire and a vacuum hose! I kept thinking I was making a mistake and it was another spark plug wire. Didn't really want to grab the offending item so I shut it down. Sure enough: hose for the vacuum advance. Black silicone rubber. I can only think that the black is carbon black, which I suspect might conduct high voltage. Misfire went away when I moved the hose. Maybe new HT wires soon?.

At any rate I would check all the components including the wires that go to them such as the aux air, the throttle sensor, the temp sensor connections, and of course the MPS. One problem I had once was a leaking cold start valve that dribbled gas into the induction system at random. A flashlight peak through the throttle body would show wet gas in the plenum. So many piddly little things. Good luck

BTW, how does Rich look for the leaks? Propane?

(IMG:style_emoticons/default/agree.gif)
i believe i am suffering from this same issue(the leaky cold start valve) - WORN, can you tell me, did it have a hard time starting sometimes, like it was flooded out? if i leave the car for more than a day, it will be difficult to start, but anything from 15 minutes to half a day it fires right up... just wondering.

Check your fuel pressure.
That may be a leaky injector, and you need to check all five.
Typical of a leaky cold start injector to relieve all the fuel pressure, drip raw ful into the plenum and make it hard to start.

I always turn the key to run three or four times before I crank it when the car has sat for a long period of time.

Rich

[DRPHIL914]

Rich,
fuel pressure in line gauge says its at 30. stock setting should be 28, correct? would that be enough to cause this?

[BeatNavy]

Mike, I'm assuming you don't have an O2 sensor & A/F Gauge installed, right? I gathered that the O2 sensor and an adjustable MPS might be pretty important for getting the 2056 to run optimally. Having said that, based on my limited experience I agree with most of the other suggestions (TPS, advance/retard function, etc.), but the sensor can help you troubleshoot.

[worn]

[quote name='r_towle' date='Mar 16 2015, 10:13 AM' post='2160821'] right up... just wondering.
[/quote]

Check your fuel pressure.
That may be a leaky injector, and you need to check all five.
Typical of a leaky cold start injector to relieve all the fuel pressure, drip raw ful into the plenum and make it hard to start.

I always turn the key to run three or four times before I crank it when the car has sat for a long period of time.

Rich
[/quote]

Yeah, i turn the key and listen to the fuel cycling through.
Sometimes if it is quiet i will listen to the injectors click as i slowly press the pedal to the floor. Quick checks that tell you that so,e parts are alive.
The sure sign of cold start leak is gas showing up in the plenum. My car will hold normal fuel pressure for more than half an hour with the engine turned off. If you have a leaking injector that pressure will slowly be dissipated as the fuel leaks wherever.

[OU8AVW]

I'm thinking TPS is one issue. I'm not opposed to getting another one.
I hooked up the outboard (retard) vacume line on the distibutor. Car ran a little better but idles quite high. I could hear vacuum. Removal and plugging of the line corrected idle and stopped the leak sound. I'm thinking a bad vacuum pot too. Flat spots feel like a lack of advance and they are intermittent.

[r_towle]

Remove the advance vacuum line and plug it.
Drive it.

Also, remove the distributor cap and rotor.
Hook up the advance vacuum line to the little can on the distributor.
Remove the DECEL line so the port is open.
Take the other end of the advance line and suck on it, see if you can move th advance plates.
If yes, when you let off do they SNAP back to no advance???
Rich

[914_teener]

Tommy probably knows the solution

(IMG:style_emoticons/default/laugh.gif)



Do what Rich says..........


AND find a new mechanic.

[OU8AVW]

Remove the advance vacuum line and plug it.
Drive it.

Also, remove the distributor cap and rotor.
Hook up the advance vacuum line to the little can on the distributor.
Remove the DECEL line so the port is open.
Take the other end of the advance line and suck on it, see if you can move th advance plates.
If yes, when you let off do they SNAP back to no advance???
Rich

Ok, sucking on the advance moves the plate and it pops back nicely. I'll plug it and drive it. And report back.
I cleaned the TPS. It looks pretty iffy. Cleaning it did help the surging about 50% but caused a low idle. (IMG:style_emoticons/default/headbang.gif)

[OU8AVW]

So Jeff set up the MPS for a 2.0. Now we need to set it up for my 2056. Question is, do I take it back to the same guys?

[BeatNavy]

Is your MPS adjustable (does it have the adjuster kit from Tangerine installed)? I'd install an O2 sensor and AFR gauge and tune it myself. But that's just me.

[914_teener]

So Jeff set up the MPS for a 2.0. Now we need to set it up for my 2056. Question is, do I take it back to the same guys?

So what happened when you drove it?