Car still looks awesome!

 

The Quattro has been running like a champ so not much to report. That and the fact that I am currently obsessed with our 911 RallyCross project means that all I have are pictures. Still; PICTURES.


250617_2280329744248_588468372_n by Team Illuminata Motorsport, on Flickr


966856_10151464810507199_1845006594_o by Team Illuminata Motorsport, on Flickr

398248_2148566850258_1728951275_1058294_1219429092 _n by Team Illuminata Motorsport, on Flickr


I have a Cars and Coffee thing tomorrow. Maybe something will break so I'll have more interesting posts next week.

Have a great weekend.

 

Here's an excellent video Winding Road Magazine's Chris Amos made of our UR Quattro.




Unfortunately I think this was about the last time the car would idle. Doesn't seem to matter if it's cold or warm, just dies, but not all at once. It takes a few seconds then it will start right up again. I can keep it running with my foot but once I let off it splutters to a halt. I think this as been coming on all year. In the spring it would die when cold if left it running a few minutes to warm up. I tweaked the throttle stop screw as a temporary fix but I think it might be time to get greasy.

I took the plugs out and cleaned them but that didn't help.

971586_3414975229676_2080066554_n by Team Illuminata Motorsport, on Flickr


539656_3414976029696_1325115924_n by Team Illuminata Motorsport, on Flickr


I took the cold idle valve off the back of the head and sprayed some brake cleaner through it. Also tested it's operation with 12V. Closed up after about a minute. Put it back on but no different.

1234855_3567257636641_965735706_n by Team Illuminata Motorsport, on Flickr


Took off the alien's head and checked the position of the air sensor plate. Seemed fine. Cleaned out what little dirt there was inside.

1377624_3584952318997_1736627655_n by Team Illuminata Motorsport, on Flickr

988317_3584952479001_1391135183_n by Team Illuminata Motorsport, on Flickr


Pulled a couple of injectors, maybe three. At least one has a bad seal. Not replaced them yet. Is it easy? Could this cause bad idle?

1382989_3584952839010_149733476_n by Team Illuminata Motorsport, on Flickr


I have been reading up on the K-Jetronic fuel injection. It seems quite straightforward but lots of vacuum hoses and other components. I'm thinking of just refurbishing the whole thing. That feels like a winter project so for now I'd just like to get it running some so I can drive it a few times before we run out of season.

Any suggestions?

 

I am familiar with the cis type fuel system that you have. I've had my share of fuel problems with old VW rabbits and Audi Fox cars. Those hardened rubber injector seals are usually a source for a poor idle, and get ruined when pulling them away from the head to make it look like it's a huge vacuum leak but usually isn't the problem to a "car won't idle at all" problem. A crack in the boots from air flow sensor to throttle body can be an issue. I've heard of them cracking on the bottom side so watch there. I don't think your engine has what is called the J boot,(you probably have one just not as large as non turbo engines) a large rubber intake part which is a source for cracked rubber on the bottom portion. I would read up on your book how to override the fuel pump relay and then test the fuel injectors for an improper fuel spray pattern. You'd need 5 jars to catch the fuel the injectors spray out.
If that looks good then your fuel system has a warm up regulator and it decides what "control pressure" should be depending on the temp of the engine, vs "system pressure" which is fixed and usually doesn't get outside of the operating range it should be within. If you had a problem with cold running and then it smoothed out and ran ok when warm I'd say you have a warm up regulator problem. But it's worth a look at running your fuel system pressure test.
I just googled "cis fuel pressure test tool" and got 4 hits off ebay, these are easy to get now. The valve on the brass portion is what you move (with engine running from cold to normal operating temps) to check the difference between system and control fuel pressures. Your repair manual should tell you how to do this test.
I suppose you could have a bad plug wire, or two. Those metal ends on the plug side and the 90 degree ones on the distrubutor cap side both thread onto the spark plug wire. They are both suppressor/resistors too. If I remember the dist cap side is 1k ohms, the spark plug side 5k ohms. They can go bad and become open, then the spark has to jump and you get a poor running engine. You can remove each wire and you should get about 6k ohms of resistance, more than that and you have a bad end on one side or the other.

 

After ordering some new (correct) spark plugs and injector seals I brought the car into the main shop and started a concerted poking around to try to figure out why it wont idle. You'd think this might have something to do with it. air temperature sensor.

1380266_3601111562968_2085144460_n by Team Illuminata Motorsport, on Flickr


I removed the throttle body and cleaned it out paying particular attention to the air bypass screw which I think allows it to idle.

1384214_3601111202959_1110913873_n by Team Illuminata Motorsport, on Flickr

1379411_3601110882951_514109356_n by Team Illuminata Motorsport, on Flickr

1393772_3601111042955_284031253_n by Team Illuminata Motorsport, on Flickr

I made some interesting observations:

There's a hole in the throttle plate.
The air bypass screw was fully closed
The arm that actuates the idle and full throttle micro switches was loose. Wouldn't operate the full throttle switch at all. I peened it firm with a small hammer.
Both switches appear to function as intended and are wired correctly.

I put it all back together but it didn't make any difference to the idle, even after backing out the air bypass screw a full turn


.

 

Thanks for your suggestions Jeff. I will be investigating intake leaks but I think the culprit would have to be on the low pressure side of the turbo or it would be a boost leak.

FWIW the warm up regulator looks fairly new. Last time I warmed it up fully it still wouldn't idle though.

I hadn't thought about plug wires. I should give them a good going over. Distributor cap and rotor look OK.

 

Trouble shooting after this point is tough. You found all very good things to repair. If you found the air idle screw turned all the way in to the stop, that tells me that (assuming you didn't do this) the previous owner in an effort to keep the car from idling too high, turned the idle air screw in maybe a little at a time or all at one time. This would be done to counter act an air leak. If air enters into the system after the throttle body, then you'd have a high idle and would need to turn the air screw in to bring the idle back down. You already took a look at the cold idle bypass valve though. That has a bimetal spring in it, when cold creates a controlled air leak/bypass, around the throttle body to raise the idle. As it warms up the valve inside closes up and the idle comes down. I believe, even if that valve was stuck in the warm (closed, although it's not ever fully closed if I remember correctly) it would still idle but very low and rough. The way you'd test that is if your car did idle, you'd start it cold and if it was idling at 1500 rpm you'd pinch one of the lines to the idle air valve and the idle would drop down significantly since you'd be closing off the air source around the throttle body.

The car sure sounds good on the video. I'd almost say compression test time to be sure but I don't think that's an issue. Spray test those injectors. The car probably sat for a long time, they could be in need of cleaning or new injectors. I've had many rabbits, I liked the cis system but if a car sat for a long time the diaphram in the fuel distributor head can rust through and cause fuel/running problems on that one cylinder. Poor idle, rough running issues. If one component in the cis fuel system fails, the whole system suffers. I guess the same could be said for ignition systems too, but you get the idea.

 

Do you think it's possible that the idle air screw could srew itself closed over time? It seems quite loose to turn and it's housing has been peened in an apparent attempt to stop it rotating.

 

I used to quote prices on them quite a bit back when there were more cars on the road. I bet it could back it's way out, or in. I remember them to have an o ring on it to help keep it in place and seal it too. The rubber could be too hard to both hold in place and seal it. It is 035-133-432 for 5.39 and 3 days away to order in.

In looking at the fuel drawings, I remember reading that the cold start valve could leak fuel into the intake. It shouldn't be getting a signal to operate from the temp sensor (once the engine is warmed up), if it did that injector alone puts out enough fuel for 2 injectors. So, if it's defective and leaking it's enough to cause rough running especially at idle since it would be too rich. Your plugs would foul out consistently I'd think. Also, they rarely fail, but it's something to check.

 

I had a little time yesterday so I pulled the injectors with a view to installing new seals. Here is what I found:

#1
1385836_3615180274677_1405646058_n by Team Illuminata Motorsport, on Flickr

#2
1378814_3615180474682_146302874_n by Team Illuminata Motorsport, on Flickr

#3
1394226_3615180674687_248095721_n by Team Illuminata Motorsport, on Flickr

#4
524074_3615180874692_1625075050_n by Team Illuminata Motorsport, on Flickr

#5
1393345_3615181074697_468793322_n by Team Illuminata Motorsport, on Flickr


I was surprised only #2 was really torn up though the rest look quite done. Of course the most alarming discovery was on #4 which is missing a tip! Looking at it it may have been off for some time but where is it and how long is any bodies guess. If it fell off into he intake port it can't be good right? Could it get past a valve into a cylinder. Out again and into the turbo? Pass right through without doing any harm?

I did install new seals and, perhaps foolishly started it up to see if they made a difference. I hoped it was safe based on how aged the area where the tip had been looked. It still didn't idle and I don't think it made any strange noises.

Next step?