# CIS-E Troubleshoot Mystery Super Happy Fun Time (Long)



## svenjamison (Oct 26, 2012)

Upon going over the previously perfectly running stock JT in my 86 4KQ and replacing various seals and hoses to ensure a lack of vacuum leaks I am confronted with an engine that runs as though it may have been better left alone. Bear with me if you will.. 

New Symptoms: 
Hard starting cold or hot 
Hesitates badly off of idle until about 3000RPM 
Seems to give good power after (higher) 3000RPM 
Ran perfectly before . 

What was done between when running well and then not so much: 

New intake manifold and valve cover gaskets 
New injector seals, lower inserts and o ring for inserts. 
Replaced injectors with good used (broke several original upon removal) 
New air filter 
Replaced some leaky plumbing in vacuum system (fuel tank vent hose and 4 way PCV hose mainly) 

What I have tried to remedy the problem: 
Installed different working fuel metering head, DPR, pressure regulator, same 
New fuel pump (done before issue) 
New fuel filters 
Checked injectors, all give good spray pattern (though not measured for %difference in volume) 
Pulls about 16” vacuum at idle at manifold 
Blocked all PCV vents, fuel vapor vents to intake boot, no change 
Inspected all vacuum lines, hoses and boots 
Timing at about spec 
Tested all wires on ECU harness as per Bentley 
New 02 Sensor 
Cold Start valve checked (no leaky) 
ISV checked 
Checked coolant temp sensor resistance 
Ignition bits replaced (Bosch) 
lines to diff locks/air conditioner hold vacuum. 
line to spark advance holds vacuum 

My initial impression was that perhaps the mixture was tuned around plenty O' vacuum leaks at some point in the past (plug for mixture was removed) and that after sealing the vacuum system back up the mixture was far too rich. I purchased an Innovate MTX wideband gauge and attempted adjusting the mixture at idle, with 02 unplugged, to stoich. Whatever mixture adjustment I attempt, to both lean and rich, results in the same issue. I attempted to measure the current at the DPR during all of this and was able to get no current any any time. The engine seems capable of running in closed loop, as disconnecting the 02 and/or DPR plug results in a noticeable difference in engine running condition. 
What is somewhat interesting is how the engine ran with numerous vacuum leaks when I purchased it. I have been searching and searching again for any additional leaks, but cannot fathom the vacuum situation is worse than when I started. 

So, where should I look for the answer? I read in several posts that by simply disconnecting the 02 and tuning the mixture to stoich at idle my mixture should be reasonable. This has not produced the desired result. When I get the mixture tuned at idle it goes lean and really wants to give up when I disconnect the DPR plug. Does that tell us anything? During the rocky, stumbling transition from idle to point where it begins running well, the wideband shows close to full lean (22.4) the whole time. Am I just so far out of spec on the mixture, or are the injectors perhaps bad? 

Please reply at your earliest possible convenience 

Sincerely, 

The Man With The All Wheel Drive Paperweight


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## svenjamison (Oct 26, 2012)

This is on an 86 Audi 4KQ with a stock JT, BTW.


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## nbvwfan (Aug 15, 2007)

Have you verified the sensor plate rest position and plunger stop length?
The plate should sit just below flush with the control plunger extending down and making minimal contact with the sensor plate pivot arm bearing.
Most CIS this measurement is 19mm, what you need to aim for is, while the fuel system is pressurized the sensor plate is pushed just about to the rest position (see Bentley procedure for plunger stop depth).

Bosch had a factory procedure for getting this (19mm) very close.
1. Remove one injector line from the fuel meter
2. Pressurize the fuel system by running the pump (jump the relay)
3. Turn the mixture screw CW until fuel seeps out the line port*. 
4. Back it off CCW 1/2 turn

*(if it seeps fuel when you prime the pump back it off CCW until it stops)

The above zeroes out the plunger/sensor plate position for basic idle/mixture.

The symptoms you describe seem to indicate either a preloaded plunger, improper sensor plate rest position, or too much plunger to pivot bearing clearance causing plate float and a lumpy A/F.


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## nbvwfan (Aug 15, 2007)

Additionally DPR current is + and - depending on how you are hooked up.
One is leaning and one richening.
Once you get the basic metering plunger to mixture set, you can hook up to the DPR to see what "bounce" you get.

And seeing this is a 5 cylinder Fuel meter, go by the procedure I outline in steps 1-4, or refer to the shop manual for plunger stop depth length. I believe you have a longer plunger stop length than the 19mm usually spec'd


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## t16vtricks (Feb 6, 2006)

*humm*

I had the same issue with my 1988 16v turned out to be the transfer pump was bad it would fall flat on its face at 2900 RPM found out this was the issue the whole time


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## nbvwfan (Aug 15, 2007)

I had my transfer pump go out too, rather the pickup tube; and once the reservoir would empty it would stall out.


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