# CIS-E Fueling Issue



## vwgroundpilot (Mar 7, 2004)

I have a 1986 Golf GTI 1.8L 8v with the stock CIS-E fuel injection. Engine has been modified with the following:

Factory dual-outlet manifold and downpipe
No cat (running a “test pipe” with O2 bung)
TT 2.25” cat-back exhaust with Spintech muffler
Opened up airbox
K&N filter
European “G-grind” hydro cam
TT adjustable cam gear (set to 0 degrees)

Engine (including stock FI hardware) has 169,000 miles on it… and it’s all original (25 years old)

I recently had the injectors out to replace the seals and seats, because they were old, hard, and cracking (vacuum leaks around the fuel injectors… not cool). Tested the spray patterns and they sucked, so I removed the injectors and soaked them in Sea-Foam fuel additive/cleaner. Test patterns weren’t flawless after that, but they were decent. One thing I noted was that the patterns started off rough but improved as I moved the air plate up during the test (so patterns improved with greater pressure at the injector).

I’m having a couple problems that I believe are related to fueling, but before I go throwing money at injection parts, I want to try to diagnose this intelligently.

1)	Hesitation at cruise. When rolling down the freeway at 65 mph, ~3400 rpm, part throttle, there is an intermittent “drag” feeling. Like when you hit a puddle of water or a big headwind gust… except the road is dry, the air is still, and there’s nobody in front of me generating turbulence. I’m thinking that at part throttle the air flow isn't huge so the DPR hasn't bumped the fuel pressure high enough to maintain a good injector pattern. But… that’s only one possibility. I also don’t know how healthy the DPR is, or the accumulator, or the pressure regulator, or the ignition coil, or the knock sensor… etc.

2)	Knocking/rattling at part throttle and low load. When the engine isn’t fully warm, it sounds like it may be predetonating, as I get a slight rattle with part throttle at 2500-3000 rpm. Here’s what makes it confusing… I don’t think it’s running lean, because my fuel economy has been in the toilet and you can smell the gas in the exhaust at idle. Injector pattern? Ignition timing? Cam timing? I’m wondering if the injectors are giving me a partial spray… basically, the actual vaporized fuel to air ratio is “lean”, but mixed with unatomized fuel droplets.


I’ve played with the cam timing and ignition timing, but can’t seem to get it to run right (hence why the cam is currently set to +/-0 and ignition timing to spec per Dr. Bentley). I’m pretty sure the injectors aren’t in great shape, but I don’t want to throw money down a rat hole.

So anyway… will replacing the fuel injectors alone solve the problems outlined above? Is there anything else wrong with the CIS system? Will a rebuilt CIS system be capable of properly fueling a 2.0L block under the stock 1.8L 8v head?

Thanks in advance! :beer:


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## tweesner (Feb 27, 2011)

I've been getting that same 'knocking/pinging' lately on my car, like your'e running poor fuel and its pre-detonating, but it happens even when I'm running 'super' unleaded. Oregon does run E10? fuel I think so that may? have something to do with it in my case? I also have sporacic idling issues, and I've replaced the injectors and seals and checked all the vacuum lines...
I'd sure like to get some suggestions as well as to how to resolve this


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## vwgroundpilot (Mar 7, 2004)

Well, I live in WA and work in OR, so I fill up in whichever state it's cheaper or more convenient. Always fill up with Chevron Super Unleaded (91 or 92 octane depending on the station). IIRC, both states have the 10% ethanol req't. My car doesn't seem to run any differently regardless of where the gas came from. I remember driving it in Arizona with no ethanol, though... it ran quite a bit more smoothly.

So I did some work and have an update to the problems outlined above:

Actions:
--Replaced the cap/rotor/plugs
--Replaced the knock sensor (wire harness on old one was disintegrating)
--Replaced the WOT and idle switch assembly on the throttle body (idle switch button had disintegrated)
--Replaced the intake boot at the throttle body (old one was cracked, though not all the way through)
--Cleaned out the idle air screw passageway with carb/TB cleaner (did NOT adjust the screw)

Positive results:
--Fires up to a dead-steady idle until warmup circuit turns off, then slight lopey idle (sounds great).
--Knocking/pinging is less pronounced and more sporadic.
--No more continuous popping/cackling on decel... just momentary pop/crackle as I come off the gas, then a normal air-pump "THRUMM" as it shuts off the fuel. (this is correct behaviour)

New problems:
--Now sometimes it "diesels" when I shut it off (runs roughly for several seconds after ignition switch is turned off).
--Sometimes it will "idle" at 1600-2000 rpm after I take my foot off the gas (intermittent).

Old problems:
--Still get the intermittent hesitation/drag feeling when cruising at 3000+ rpm. Feels like hitting a deep puddle or a stiff headwind.

Haven't yet run a full tank of gas through it, so I can't comment on the fuel economy yet.

I think the high idle problem may be a byproduct of my overzealous cleaning of the TB assembly... I need to re-lube the throttle butterfly hinges and see if that fixes the intermittent high idle. It's also probably overdue for an ISV cleaning.

Not sure where to go with troubleshooting the hesitation/drag at cruise. I can't replicate the behaviour in my garage under no-load conditions, so it's not like I can measure which sensor is doing what. My guess is O2 sensor, but don't know for sure. O2 sensor is only about 10k miles old... but the car was running like crap for part of that time (with no idle switch, it was dumping unburned fuel through the exhaust), and may have coated/damaged the O2 sensor.

Is there any way to clean an oxygen sensor?


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## ziddey (Apr 16, 2006)

Building a dpr test harness would be a good idea. Use extra wire so you can keep the multimeter in the car and watch dpr current as you drive.

O2 sensor may be on its last legs. Keep looking for those vacuum leaks. Are you sure the idle switch is closing now? I've never had issues with throttle bodies binding in normal weather. If so, you'd be able to feel it in the pedal.

Try running a bottle of chevron techron fuel system cleaner on your next tank. Some people suggest to use a bottle to half a tank for higher concentration.

Try seafoam through the intake and let it sit for a while to soak.

Are you sure you have the ignition timing set properly? IIRC, with cis-e + knock sensing, you just need to set it at 6*BTDC at idle.

What plugs did you use? Bosch coppers are best. Properly gapped?

In terms of the fuel injectors, you say that you have an immaculate idle when cold. Try unplugging the o2 sensor and see how it idles when warm. I know my injectors on one of my cis vw's are not flowing that well, and the idle is a bit rough. Not a problem off idle though. Either way, I'd look at the o2 sensor beforehand.

I've had dieseling as well on an 85 gli (pretty much the same as yours) when I had the ignition timing set too far off.

Fuel pressure is very important with cis, but gauges are expensive. If you don't know how old your fuel filter is, it wouldn't be a bad idea to change it. Just be careful in the area. Those hoses can be pretty rotten by now, especially with ethanol in our fuels now.

Make sure the hose connecting to the fuel pressure gauge is not connected to a vacuum source. It's supposed to see ambient pressure only, and it's not uncommon for some mechanic along the way to screw up and hook it up to the intake manifold. I can't see that causing a huge impact, but just throwing it out there since I've seen it on five occasions now.

If you don't want to build a dpr test harness, you can do pretty decent testing / tuning with just the o2 sensor. Checking the o2 sensor against a ground when warm should give you an indication of your mixture and how the ecu is responding. You can unplug the o2 sensor from the harness and measure it to see what the untrimmed mixture is. You may very well see that it will go lean, meaning you've got some sort of vacuum leak left to find.


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## vwgroundpilot (Mar 7, 2004)

ziddey said:


> Building a dpr test harness would be a good idea. Use extra wire so you can keep the multimeter in the car and watch dpr current as you drive.


Good idea. I have the a test harness from my local parts house (I think it's made by Techtonics, not sure). I never thought about extending the wiring back through the firewall so I could read it while driving.



ziddey said:


> O2 sensor may be on its last legs. _That's what I'm thinking._ Keep looking for those vacuum leaks. _Will do._ Are you sure the idle switch is closing now? _Yep, tested it electrically before installation and during driving. Shuts the fuel off somewhere between 1600 and 2000 rpm like it should._ I've never had issues with throttle bodies binding in normal weather. If so, you'd be able to feel it in the pedal. _I don't think it's "binding" so much as just staying slightly ajar when I take my foot off the gas. Could also be something else entirely that's keeping the idle up. Whatever it is, it's intermittent._





ziddey said:


> Try running a bottle of chevron techron fuel system cleaner on your next tank. Some people suggest to use a bottle to half a tank for higher concentration.


I always fill up with Chevron and just ran a couple bottles of Techron through it within the past two months (when I got this project running again and started driving it). Wouldn't hurt to throw another bottle in the tank when I fill up tonight, I suppose...



ziddey said:


> Try seafoam through the intake and let it sit for a while to soak.


I'll add this to the "to-do" list.



ziddey said:


> Are you sure you have the ignition timing set properly? IIRC, with cis-e + knock sensing, you just need to set it at 6*BTDC at idle.


I need to double-check the timing. Last time I had set it, I think the idle switch was no longer functioning, so it's probably off.



ziddey said:


> What plugs did you use? Bosch coppers are best. Properly gapped?


Bosch coppers. My German cars only get Bosch ignition parts. Properly gapped (I checked them when I pulled them out of the box and set them per the Bentley manual).



ziddey said:


> In terms of the fuel injectors, you say that you have an immaculate idle when cold. Try unplugging the o2 sensor and see how it idles when warm. I know my injectors on one of my cis vw's are not flowing that well, and the idle is a bit rough. Not a problem off idle though. Either way, I'd look at the o2 sensor beforehand.


I'll try unplugging the O2 sensor and see how it behaves.



ziddey said:


> I've had dieseling as well on an 85 gli (pretty much the same as yours) when I had the ignition timing set too far off.


Here's hoping a quick check/adjust of the timing fixes the dieseling. As stated before... last time I checked it was then the idle switch was non-functional, and from what I've read, that could adversely impact the timing at idle.



ziddey said:


> Fuel pressure is very important with cis, but gauges are expensive. If you don't know how old your fuel filter is, it wouldn't be a bad idea to change it. Just be careful in the area. Those hoses can be pretty rotten by now, especially with ethanol in our fuels now.


I'll add this to the "to-do" list as well. I have a brand new accumulator, housing, and filter I bought a while back. I need to climb under there and install the filter. I wasn't installing the housing and accumulator right away because if I yank the CIS and install Webers, I'd like to keep the CIS housing and accumulator "new in the box" for if I ever switch back.



ziddey said:


> Make sure the hose connecting to the fuel pressure gauge is not connected to a vacuum source. It's supposed to see ambient pressure only, and it's not uncommon for some mechanic along the way to screw up and hook it up to the intake manifold. I can't see that causing a huge impact, but just throwing it out there since I've seen it on five occasions now.


Fuel pressure gage, or fuel pressure regulator? Which hose are we talking about?



ziddey said:


> If you don't want to build a dpr test harness, you can do pretty decent testing / tuning with just the o2 sensor. Checking the o2 sensor against a ground when warm should give you an indication of your mixture and how the ecu is responding. You can unplug the o2 sensor from the harness and measure it to see what the untrimmed mixture is. You may very well see that it will go lean, meaning you've got some sort of vacuum leak left to find.


I'll check the O2 voltage when I unplug it to see if there's a difference in idle behaviour. When I run the DPR wiring into the car to watch current while driving, I'll try driving with the O2 connected and disconnected, see what it does and whether it's making a difference.

Gawd I hate hunting for vacuum leaks on these old cars... it's like going on a wild goose chase. :banghead: I bought about a dozen feet of the small vacuum hose and I've been replacing every old piece on the car I can find, because it's pretty much all toast.


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## ziddey (Apr 16, 2006)

yeah, I meant to say regulator there.

as for testing with the o2 sensor disconnected, once the cts gets up to temp, you should see a steady 10ma through the dpr, unchanging. under wot, it should goto 12ma or something like that iirc.


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## vwgroundpilot (Mar 7, 2004)

Dunno when I'll have the time to do any of these diagnostics... but in the meantime, my fuel economy has _dropped_ to 23.5 mpg. :banghead: Car runs better, fuel economy is worse. Go figure.

In other news, it seems the cruise hesitation comes on when I open the throttle a specific amount (just shy of the WOT switch) at or over 3000 rpm. It will hesitate and start slowing down... if I push through that throttle position and engage the WOT switch, it starts accelerating again.

And now to hijack my own thread...
When my wife and I went on our honeymoon, we rented a C6 Corvette. That's a 6 liter, 400+HP, Chevy V8. Over 500 miles of driving around northern Arizona that week, and we averaged better than 29 mpg.

With gas prices being what they are, I can't afford not to buy a Corvette. It'd be more economical than my 1.8L 4-cyl Volkswagen hatchback. 

Since everybody loves pics...


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## vwgroundpilot (Mar 7, 2004)

New info...

--No longer dieseling on shutoff (knock on wood...)
--Still hesitating intermittently when under load at cruise.
--Checked vacuum line for the fuel pressure regulator, it's (correctly) connected to the atmospheric side of the airbox.
--O2 is still functional (idle went rich and stable when I disconnected it)
--Cylinder #1 is running lean, #2, #3, and #4 are running rich.


I received a Gunson's Colortune kit in the mail yesterday. Promptly took it out to the car (which was still warm from the commute home) and tested each cylinder. First off, when I pulled the plugs the #1 plug was nearly clean, whereas the #2, #3, and #4 plugs were all darkened and fuel dampened. Then when I tested each cylinder with the Colortune installed, #1 was definitively light and suffered from lean misfire, #2 #3 and #4 were mostly blue (stoich) at idle with occasional flashes of yellow (rich), and when run up in RPM they turned way yellow during acceleration and were borderline blue/yellow at steady-state. I knew the injectors weren't patterning very well, but this just confirmed the effects. You could even see yellow "sparks" on the blue backdrop where droplets of fuel were burning as they swirled around in the combustion chamber.

So... #1 cylinder is lean, #2, #3, and #4 are rich. I know the injectors have inconsistent patterns (checked by spraying them into a large soft drink cup). What else could cause dissimilarity in mixture? Fuel dizzy?

I think I'll try swapping the #1 and #2 injectors then retest with the Colortune. That'll tell me whether it's something to do with the #1 cylinder itself (fuel dizzy or air leak), or the injector.


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## bluetoes591 (Apr 3, 2009)

vwgroundpilot said:


> New info...
> 
> --No longer dieseling on shutoff (knock on wood...)
> --Still hesitating intermittently when under load at cruise.
> ...


Was this ever resolved? I'm having this exact problem. Cylinder #1 is lean, the other three are riich. Slight misfire at idle. Fuel Injectors aren't perfect, but have been cleaned and checked. Tried a different fuel line for #1. o2 sensor is new, CTS is new, plugs, wires, cap, rotor are new, injector seals and lower seats are new. It's driving me crazy.


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## ja50nSVT (Mar 9, 2021)

Anyone figure this out yet?


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