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

[r_towle]

Set tps like this at idle.
There is only one way to set the tps.

[TheCabinetmaker]

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.

All mps' are adjustable. Chris'kit is convenient, but not totally necessary.

[BeatNavy]

Cool, I've learned something new already this morning. Time to go back to bed before it happens again.

[OU8AVW]

Here's a repost of my comments in my build thread:

So I had the local independant Porsche shop looking at my car over the last six weeks or so. They did allot of good work making the engine run properly, but they never got it right. The car would buck at various RMP. Mechanic said that the fuel pump might be to blame so I say, "replace the fuel pump." He says, "we want to make sure that's the problem." I tell him if you charge me $135 an hour to figure out that it's the issue then you might as well buy a new pump for $130 and install it. Then I'll at least have a new pump to show for it. I also tell the guy that it's probably the TPS making it buck.

I get a call a few days later that my car's "ready and running great". No fuel pump and no TPS installed. I pick up the car and guess what? It's still bucking and running like crap.... sheeplove.gif

Soooo.....

Last night I installed a new fuel pump. Car runs allot smother but still bucks

Soooo.....

This morning I installed a TPS that Rich sent me last week. You guessed it, that fucher's running like a fresh spun top. Why won't mechanics listen to people? I mean I obviously know a little bit about my car, I built the thing from scratch right?


People..... headbang.gif

[OU8AVW]

So now she's running pretty sweet. I am hiving a high idle issue. It idles at around 1600 rpm. It feels like the adjustment screw on the intake is mostly all the way in and I get no change from turning the adjuster on the computer. I checked for vacuum leaks with map gas but found nothing. I'm going to fiddle with the TPS some more.

Any other ideas?

Maybe check the timing again?

Maybe the advance is sticky? (IMG:style_emoticons/default/blink.gif)

[BeatNavy]

So now she's running pretty sweet. I am hiving a high idle issue. It idles at around 1600 rpm. It feels like the adjustment screw on the intake is mostly all the way in and I get no change from turning the adjuster on the computer. I checked for vacuum leaks with map gas but found nothing. I'm going to fiddle with the TPS some more.

Any other ideas?

Maybe check the timing again?

Maybe the advance is sticky? (IMG:style_emoticons/default/blink.gif)

It is definitely worth checking timing. Checked the AAR?

[DRPHIL914]

So now she's running pretty sweet. I am hiving a high idle issue. It idles at around 1600 rpm. It feels like the adjustment screw on the intake is mostly all the way in and I get no change from turning the adjuster on the computer. I checked for vacuum leaks with map gas but found nothing. I'm going to fiddle with the TPS some more.

Any other ideas?

Maybe check the timing again?

Maybe the advance is sticky? (IMG:style_emoticons/default/blink.gif)

this could be the alignment of your TPS still. - i ialso had the bucking issue for 5 years but once i got my repalcement TPS from Bruce stone its been like perfect ever since- except at first it was idling a bit fast, but that was cured by making 2 adjustments; one was the TPS, the other was the MPS was set too lean so making just a bit more rich helped, then reset the timing as well, and i cheated a bit here, and backed off the timing a few degrees and took it from 1000 rpm to 850 and has run perfect since!

good luck

[worn]

So now she's running pretty sweet. I am hiving a high idle issue. It idles at around 1600 rpm. It feels like the adjustment screw on the intake is mostly all the way in and I get no change from turning the adjuster on the computer. I checked for vacuum leaks with map gas but found nothing. I'm going to fiddle with the TPS some more.

Any other ideas?

Maybe check the timing again?

Maybe the advance is sticky? (IMG:style_emoticons/default/blink.gif)

High RPM is almost always a vacuum leak. There are so many hoses it is hard to find them sometimes. With your car I would suggest that you install an A/F meter and place the gauge where you can see it as you drive, rather than down low like one idiot I know personally did. The original MPS settings aren't going to be quite right and after you mess with the car it will need some adjustments. I also added a CHT sensor and found that when it is running well close to lambda = 1 at around 14 the heads are heading towards the recycling bin. Richening the mixture has cooled them and there is a sweet spot where the mixture is around 12 most of the time and a bit leaner at idle.

I know that the gauges are expensive and a pita to install. Especially the bung in the exhaust. But as you say you built it from scratch so you know your way around the block.

I have to add that I am running the resistor from the 1973 model to richen the mixture by fooling the ECU into thinking the car is still a bit cold. Sounds like you have a really nice engine there. Good luck!

[r_towle]

high idle is vacuum leak AND/OR timing.

So, remove everything from the plenum and cap it off with rubber caps available at the local hardware store plumbing isle....

Leave JUST the MPS connected to the plenum.
Its all you need.
Dont be lazy and leave the AAR on there....
Remove all of them..

Does it still do it?

Add one system (vacuum line) back at a time.


First I would quickly check timing...it may simple be that..
3500 rpms, tie off the accel on the throttl body with a piece of string, steady at 3500
Then set the timing...
vacuum line off the distributor...Dwell already set correctly.
Again, dont cheat...

Rich

[OU8AVW]

Hi ho, hi ho, off to the garage I go (IMG:style_emoticons/default/biggrin.gif)
I'll report back as soon as humanly possible.

[OU8AVW]

Following Rich's advice above I determined that:
A: the AAR was staying open causing high idle
B: the timing was set to 13 deg at 3500rpm causing a flat spot at acceleration. (IMG:style_emoticons/default/dry.gif)

I plugged the AAR and set the timing. Car ran pretty good and did not flatten out while accelerating

Now I'm worried that the shop set up my MPS with bad timing and a leaky AAR.
Now she wants to idle at 1200 rpm. Improvement but not perfection.

I'm going to fiddle with the AAR or get another one. Then start looking for a friend with an O2 sensor I can use.

[r_towle]

I removed my AAR long ago....it's not really needed.

Does the air bypass screw do anything now? Can you tune the idle with it?

[mepstein]

Tommy probably knows the solution

If it's not an LE, it's not worth fixin.

[OU8AVW]

I removed my AAR long ago....it's not really needed.

Does the air bypass screw do anything now? Can you tune the idle with it?

It's screwed pretty far in. to the point that I have to use a screw driver (I.E. remove the air cleaner) to adjust it in.
If by "now" you mean with the AAR removed, I haven't tried messing with it yet.
In chilly Maryland I don't need the AAR? Do I plug the back of the 5th injector?

[914_teener]

I removed my AAR long ago....it's not really needed.

Does the air bypass screw do anything now? Can you tune the idle with it?

It's screwed pretty far in. to the point that I have to use a screw driver (I.E. remove the air cleaner) to adjust it in.
If by "now" you mean with the AAR removed, I haven't tried messing with it yet.
In chilly Maryland I don't need the AAR? Do I plug the back of the 5th injector?

By "now" he means you have eliminated once source of a vaccum leak.

Next:

Can you adjust the idle speed with a screwdriver. Stay focused...don't worry about the AAR right now.

[r_towle]

If you cannot significantly change the idle with the air bypass screw, and almost make it die by turning it all the way in, you still have a vacuum leak.

Sources of leaks.
Head----intake manifolds
injector seals
intake runners to plenum (large rubber hoses)
anything plugged into the plenum and all rubber vacuum lines (cracks)

Throttle body gasket
Cold start injector gasket and injector itself

I figure there are more I forgot, but I take a VERY methodical approach to finding the leak....remove all (except the MPS)

If idle can now be controlled, one of those systems you removed is at fault.
If idle cannot be controlled, check intake from plenum to head.


Think of it this way.

If I put 10 holes in your house, all over the place, 1 foot square each in size....you would have a 10 square foot leak in your house.

Same thing applies here....lots of small leaks add up to a big leak.



Rich

[OU8AVW]

I had some time to mess with the FI last night. I found a vacuum leak around the throttle body to plenium gasket. Not having a new one handy I pulled the TB and cleaned the surfaces with cleaner and some sand paper. When I put it back together and started the engine it revved out of control. I reset the TPS, pulled and cleaned everything again. Same issue.
I got in it this morning and heard a click when I pushed the clutch in. The throttle cable was stuck under the clutch armature (IMG:style_emoticons/default/dry.gif)
Now the idle can be adjusted with the adjustment screw and she runs a little smoother. It wants to die when the screw is too far in.

Next I want to sort the AAR. I like how the car starts with it working.

I also bought an LM2 exaust gas analyzer. I'll double check all the vacuum stuff again and see what it's reading.

[worn]

I had some time to mess with the FI last night. I found a vacuum leak around the throttle body to plenium gasket. Not having a new one handy I pulled the TB and cleaned the surfaces with cleaner and some sand paper. When I put it back together and started the engine it revved out of control. I reset the TPS, pulled and cleaned everything again. Same issue.
I got in it this morning and heard a click when I pushed the clutch in. The throttle cable was stuck under the clutch armature (IMG:style_emoticons/default/dry.gif)
Now the idle can be adjusted with the adjustment screw and she runs a little smoother. It wants to die when the screw is too far in.

Next I want to sort the AAR. I like how the car starts with it working.

I also bought an LM2 exaust gas analyzer. I'll double check all the vacuum stuff again and see what it's reading.

Good job! That would be a hard one to find.

[BeatNavy]

When I put it back together and started the engine it revved out of control.

I did basically the same thing last night and had the same issue. I replaced the TPS board and when I put the throttle body back on and started it I got a horrific whine, almost like a turbine, and the engine would start to rev out of control. Sounds like a massive vacuum leak. Sure enough, when I put the throttle body back on I let one of the washers from the 13 mm bolts that hold it on the manifold get under the throttle body instead of on top. All better now and I think the bucking is gone.

[OU8AVW]

A quick update as I have had home projects and summer taking all my time.

I replaced the AAR with a known good unit. Now the car starts easily and warms up with no help from the throttle. Car ran pretty good. I was able to adjust the idle to 1k. Happy me. Now on hard decel the idle drops into the weeks. I hear the 2056 like a little higher idle...

I have now installed a tested good decel valve. This helped the idle drop but only until the engine is warm. I'm thinking it's rich at idle causing it to tank when the RPMs drop. A quick touch of the accelerator keeps it going.

Car accelerates great but still has a flat spot at near full throttle. I'm thinking it goes lean at full throttle. If I'm easy on the gas, RPMs climb with power and smoothness.

My assumption is the MPS was adjusted with vacuume leaks present and the guy who did it f-ed it up.

My plan is to adjust valves, change the oil (500 mile service) and the hook up the LM2 to set the MPS. I found a good thread on the Samba that I'm adding to my study list.

Samba D-Jet thread