5 symptoms need help diagnosing, added a problem... probably culprit Options

[steveherman]

Working on a 1974 2.0 d-jet

-symptom 1- when i start it... idle is very low no where near the 1600 rpm as Brad mentions
-symptom 2- low idle...like 550 rpm
-symptom 3- when coming to a stop it almost dies
-symptom 4- stomp on gas when sitting and driving it goes blah... then takes off.
-symptom 5- as it warms up loses a little power

things to note:
-there are 20 clicks when pushing down accelerator so tps is correct
-timing and dwell were checked today and they were within spec.
-lifters just adjusted

[john rogers]

Were the timing and dwell within spec? If so then I would check the following:
- What is the fuel pressure and do all the FI parts besides the throttle switch work as per Brad's article?
- How are the valve clearances, since the engine gets worse as it gets hotter the valve adjustment could be off?
- How are the injector seals, do they leak as they can let in a bit of air that is not seen by the FI system and can get worse as the engine gets hotter.
- How old are the trigger points, do they fire equally for both sets?

[steveherman]

Were the timing and dwell within spec? If so then I would check the following:
- What is the fuel pressure and do all the FI parts besides the throttle switch work as per Brad's article?
- How are the valve clearances, since the engine gets worse as it gets hotter the valve adjustment could be off?
- How are the injector seals, do they leak as they can let in a bit of air that is not seen by the FI system and can get worse as the engine gets hotter.
- How old are the trigger points, do they fire equally for both sets?

-timing and dwell within spec
-can i get a link to brads article?
-valves just adjusted last week
-I do not THINK the injector seals are leaking
-trigger points new

[McMark]

http://members.rennlist.org/pbanders/

[brant]

are you reviving a dead car or was this one running better in the past...

usually its the last thing changed... so what have you been working on lately (ie: since it was running better)

brant

[steveherman]

are you reviving a dead car or was this one running better in the past...

usually its the last thing changed... so what have you been working on lately (ie: since it was running better)

brant

not a dead car...
wasnt really running better.
when got i it the tps wasnt working... now it is
lately a lot of work:
new cables
push rod tube seals
shift bushings

[steveherman]

so spent most of morning reading http://members.rennlist.org/pbanders/.
not really much of the troubleshooting was applicable.
seems most if not all idle probs were with hi idle
i have low idle.

[wreglesworth]

This sounds like a vacuum problem.
Check, replace and clamp your hoses.

Worked for me.

[JamesM]

Do all of your injection parts match?

Are your vacuum hoses routed properly?

Have you verified your distributor advance/retard mechanisms are working properly?

Is it hunting at idle?

When you say you have a low idle, is this with the adjustment screw opened up all the way?

If the idle screw is not having any effect I am going to guess it is something related to your distributor, check your timing at full advance and at idle and verify that your hoses are hooked up properly and the advance/retard mechanisms are working as they should.

Also be sure you have the right distributor. I cant seem to find that link right now but from what i remember the 1.7 dizzys had more mechanical advance. Using one on a 2L set properly at full advance would result in overly retarded timing at idle.

[steveherman]

ook so i also added another symptom.
i think this may be the culprit to all the other problems.
if i find and fix when starting it... idle is very low no where near the 1600 rpm as Brad mentions

[Tom]

Some one else had a similar problem in the past. Seems the AAR was stuck in the closed position. In the past it may have been sticking slightly in the open position when hot and causing a high idle, so the throttle adjust screw was adjusted to compensate. Since it is sticking in the closed position( maybe) now, the idle is too low. I would check out your AAR and see what condition it is in. Pretty simple to remove and clean and test. Easy to test on the car also. When you first start the car, remove the hose from the AAR that goes to the air cleaner - plug the end with your finger. Does the idle go down? Yes - AAR is open and should close after 3-5 min. Test again after 5 min. Is AAR closed? Idle should not change. If the AAR doesn't work like this, something is causing it to stick. Or it may be burned out. I had to replace the wire on mine as it was burned.
Tom

[ArtechnikA]

... idle is very low no where near the 1600 rpm as Brad mentions

A - Brad who ?
B - 1600 rpm is _not_ normal idle !!

Any street Porsche should idle at not more than 1000 rpm. 850 +- a few would be a nice goal, IMO, and 600 is not too low unless there's a lot of miles and low oil pressure and/or cooling is a big factor.

Where exactly did you see the reference that a T-IV should idle at 1600 ?

[Tom]

A- Brad Anders
B- when cold the idle should be @1600 with AAR open.
Tom

[914 shifter]

check your mps?

[john rogers]

You did not mention what the fuel pressure is? Should be stock or a pound high is okay too. When you checked the timing, was the vacuum line unhooked and is it hooked up to the "retard" side of the advance mechanism? On 1974 2L D-Jet models it is to pull the timing back to help with cleaner emissions and advance is all mechanical unless you have a dual ported throttle body and in that case make sure the hoses are connected correctly. As mentioned, the butterfly bypass should allow the engine to speed up at idle and you can hear the change in air flow through it when opening it up.
Finally, I would spray some carb cleaner around the injectors at their seal locations so you can be sure the seals are not leaking by.

[steveherman]

You did not mention what the fuel pressure is? Should be stock or a pound high is okay too. When you checked the timing, was the vacuum line unhooked and is it hooked up to the "retard" side of the advance mechanism? On 1974 2L D-Jet models it is to pull the timing back to help with cleaner emissions and advance is all mechanical unless you have a dual ported throttle body and in that case make sure the hoses are connected correctly. As mentioned, the butterfly bypass should allow the engine to speed up at idle and you can hear the change in air flow through it when opening it up.
Finally, I would spray some carb cleaner around the injectors at their seal locations so you can be sure the seals are not leaking by.

front was unhooked
the back was hooked up to the throttle body
is the retard side the back?

the air bypass on mine is completely closed.

[IronHillRestorations]

How are the trigger points?

[rick 918-S]

You did not mention what the fuel pressure is? Should be stock or a pound high is okay too. When you checked the timing, was the vacuum line unhooked and is it hooked up to the "retard" side of the advance mechanism? On 1974 2L D-Jet models it is to pull the timing back to help with cleaner emissions and advance is all mechanical unless you have a dual ported throttle body and in that case make sure the hoses are connected correctly. As mentioned, the butterfly bypass should allow the engine to speed up at idle and you can hear the change in air flow through it when opening it up.
Finally, I would spray some carb cleaner around the injectors at their seal locations so you can be sure the seals are not leaking by.

front was unhooked
the back was hooked up yo the throttle body
is the retard side the back?

the air bypass on mine is completely closed.

Sounds like your on track. Here is a hose diagram.

Take the AAR out and test it.

[Dr Evil]

Not sure about the dizzy hoses, some one will chime in (I don't have a manual at work), but here are a few dx tools:
1) if adjusting the idle air bypass screw has no affect then you have a vacuum leak.
2) check your spark plugg, they will tell you if you are rich or not and will tell you if it is a setting issue ( all dark or light) or a focal issue (1 or 2 off color)

[steveherman]

Sounds like your on track. Here is a hose diagram.

Take the AAR out and test it.

i just noticed a difference in diagram from PP site.



the middle hose from the decel valve is shown hooked up in different places.
on pp it goes to the air cleaner and the one rick showed it goes under throttle body.

the back hose on pp goes under the throttle body and the one rick shows it goes to the air cleaner box.

which is right?


AAR is good... heats up nicely and opens and closes