72 Tii Sputtering- After Warmed Up

[Ncbimma]

I'm hoping you all can help point me in the proper direction to assist my problem. I've searched and search to find the different scenarios I am experiencing but cannot find a solution yet.

 

Car starts up with little struggle from sitting for a day or two- once fuel is pumped in after a few seconds and a couple turns at the ignition, the car cranks and idles just fine. It runs from then on just great, great power when stabbing the accelerator and throttle is very responsive on blips.

 

My problem arises around 15-20 mins later almost like once the car is warmed. At a stand still the car will begin to sputter a bit and as time goes on, get progressively worse. It will then run OK with deep throttle but once you let off the sputtering returns and you have to feather in the throttle at a stand still to keep the idle going which will stabilize but is at a much slower rate now. A minute after that, the car will act like there's not lot of power and a rapid sputter will occur in the higher gears on throttle and run only slightly better in 1st-2nd gear. Then maybe 30 secs later the car acts like there's not enough power to propel it forward in any gear on throttle and sputters heavily almost til it dies ....you can recover it with throttle feathering and it will have a slow sickly sounding idle. The red light on the dash will faintly come on at this time.

 

My question is, where should I attack here?

• I've replaced the cold start valve, voltage regulator (yellow tape), thermo time switch
• I've checked the intake runners, one was poorly seated with a slight vac sound- I fixed it but the problem persists

 

My thoughts- something to do with once car is warmed up?

• Zeitschalter- thermo time relay?
• Bad fuel pump?
• Bad Alternator?

 

(Stock engine with K-fish) 

 

Any thoughts are appreciated- I'm a pretty big '02 newb and not very smart on car electrical/fuel systems 

Edited July 6, 2017 by Ncbimma

[dlacey]

Sounds like it's too lean, the car runs fine while in enriched warmup phase but once warm the base mixture is too lean. Since kugels are very reliable then an air leak into the manifold due to a failed gasket or hose is most likely. You may be able to confirm it's mixture by identifying the 'verboten' screw on the kugel...DONT adjust it...once the car is warm and misbehaving put a few sheets of folded paper or aluminium foil under the lever...you'll see that this verboten screw is the end-stop for the spring loaded mixture lever...putting something under it temporarily richens mixture...if that works then again dont adjust the screw..look for why the mixture would change...air leak most likely.

don't think that alt, zeitschalter, could start valve could cause what you describe.

[torquewrench80]

Always start with the basics. Spark plug condition, points condition and proper dwell angle, condition of cap and rotor, fuel pump pressure - should be 2 bar or about 29 psi. You have to T into the line from the fuel filter to the Kugelfischer Pump. Test the alternator with a dvom with the engine running. You should see about 14.7 volts at the battery at about 2000 rpms. If all of that shows good, check the compression. Not saying it's bad, but it's a good idea to rule it out. Let us know how you make out.

Edited July 5, 2017 by torquewrench80
additional notation about compression

[mvliotta]

Could be a combination of things causing you to go lean after warm up. 

 

My '72 tii had a lean sputtered at mid throttle after warm up due to a combination of 

1) weak coil

2) old ignition wire

3) cracked plastic intake runner

4) mis-aligned cam in tuna can

 

Religiously following the tii tuning guide was instrumental.

 

I would also confirm the operation of the warm up regulator in your case... make sure it rises above the lever to the KF pump and shuts off just about all of the air going to the throttle body. 

 

Good luck.. it's a journey, a very enjoyable one as you sort it out. 

 

Vince

[Ncbimma]

Great response here! 

 

I've checked plugs and have normal carbon build- not burnt/white or sooty. The one thing I cocked my head on was the threads on some of the plugs were just slightly moist- I get no clouds out the muffler so not sure if it's a gasket issue- I hope not. Wires are newish from PO... will need to check if they spark properly, along with rotors and cap.

 

I am moving the crankcase breather and some other smaller clothed tube to a vented can (they were previously y-joined and dumped into the old air intake elbow which was cracked and falling apart).

 

I was going the route of a new fuel pump, filter etc. already, in case things were getting starved. Have a Bosch 69418 on hand already. I will check current pressure prior to doing anything though.

 

 

Edited July 6, 2017 by Ncbimma

[ray_]

Check the in-tank fuel screen also.

 

And get a proper air box

 

Good luck,

[achman]

This sounds like a fuel filter/debris issues to me. Has nothing to do with running lean IMHO. When the car has been running for 15min it has sucked up debris to clog the in-tank filter and possibly the filter by the radiator. Don't go start replacing parts that have nothing to do with the issue. This is either a fuel starvation issue or a spark issue.

Do you have points or electronic ignition?

With either-- correct coil? Resistor or no?

 

1. check for 29psi fuel pressure at pump inlet. If not, determine if issue is wiring or pump. Switch to 5-series electronic fuel pump.

2. Check for correct timing, Tii is sensitive to correct timing. Check dwell if points.

2. Check in-tank fuel filter screen and tank for sediment. Replace fuel filter with correct MANN filter by radiator. Install flowing correct direction.

3. Install proper airbox/Mahle air filters

 

[ColinK]

1 hour ago, achman said:

2. Check in-tank fuel filter screen and tank for sediment. Replace fuel filter with correct MANN filter by radiator. Install flowing correct direction.

 

 

While you're at it, replace the fuel hoses with the correct high pressure fuel lines from a dealer or Blunt, don't use "normal" fuel hoses as they won't stand up to the pressure.  

 

Also, in your picture, are the high pressure lines from the KF to the injectors wrapped with tape? 

If they are cracked or leaking you need to replace them. 

[Ncbimma]

3 hours ago, ColinK said:

Also, in your picture, are the high pressure lines from the KF to the injectors wrapped with tape? 

If they are cracked or leaking you need to replace them. 

Not cracked. It's some kind of plastic slinky coil thingy around the lines- was there from the PO. I just left it there.

 

I plan to check filters and pressure this wknd.

 

I think the Bosch pump I have is for a 5er. 

 

Fuel lines is a good call. I will look into that next.

Edited July 6, 2017 by Ncbimma

[jgerock]

As stated above, plus check those plug wires for continuity and resistance. Your coil is a blue one (commonly has internal resistance). Better choice is stock black or red one with external ballast resistor.  What plugs are in it?  Tii's are sensitive to plugs and valve clearance.

 

Sure sounds fuel related to me but these cars can have weird issues that even stump the experienced folks.

[GoldLion]

Hi there, just a brief additional comment.  There is a small tube running from the crankcase breather tube to the throttle body in a stock setup.  If you are deleting your crankcase breather tube then make sure you block the resulting 'hole' in the throttle body as this is a hidden air entry point and will cause a slightly lean condition in the future. Unlikely to be contributing too much to your current issue, but reconnecting that hose solved surging/backfiring issues in my car some time ago.  All the best,

 

Daniel

[achman]

Also definitely use NGK BP6ES or BP5ES plugs

 

NON-resistor copper plugs

[Ncbimma]

Changed out the filter by the rad for a new higher capacity unit- simple swap... and checked the in-tank screen.It was mostly discolored but not gunked up or anything. I didn't see much sediment on the bottom of the tank but didn't take a great look- I'm too scared of having a powered light near all those fumes!

 

Car still behaved in similar fashion- ran for about 10-15 mins just fine (It was like 100* out!) then began to sputter and lose power. Alternator red light pulsed at first but would steady glow with any throttle input- and any stabs at the throttle caused the sputter- but the car would idle- just at a low RPM.

 

I didn't check the fuel pressure yet, nor did I replace the pump under the body- It was too damn hot to get under the car and I didn't want to stink up my garage with spilled fuel.

 

Back to the checklist...

[gallian93]

if you've gone through the basics and found no issues (although less like the cause, haven't heard about your voltmeter results on the battery)..

My vote is a vacuum leak somewhere... the pumps fuel delivery curve is compensating for the extra air at high RPM but that not at idle...

I would invest in a can of carb cleaner and go looking for it...

GL

Omer

[torquewrench80]

10 hours ago, Ncbimma said:

Changed out the filter by the rad for a new higher capacity unit- simple swap... and checked the in-tank screen.It was mostly discolored but not gunked up or anything. I didn't see much sediment on the bottom of the tank but didn't take a great look- I'm too scared of having a powered light near all those fumes!

 

Car still behaved in similar fashion- ran for about 10-15 mins just fine (It was like 100* out!) then began to sputter and lose power. Alternator red light pulsed at first but would steady glow with any throttle input- and any stabs at the throttle caused the sputter- but the car would idle- just at a low RPM.

 

I didn't check the fuel pressure yet, nor did I replace the pump under the body- It was too damn hot to get under the car and I didn't want to stink up my garage with spilled fuel.

 

Back to the checklist...

Did you try and blow through the fuel filter? This will tell you if it was plugged/clogged/restricted. Of course, you need a little experience with other filters to see the difference. Comparing it to a new one is a good start. Just don't inhale through the filter, you will regret it.