# Odd running condition - rough running when hot - 86 CIS 8V GX engine



## speedbird119 (Apr 30, 2008)

Hey guys, (I posted this in the MK II forums where I usually am, but thought it would help to post it here too)... 

I've about run my course with this one. I used the Bentley/Search tool relentlessly... and still can't source the issue. 

Here's what I've got/done/replaced/cleaned/reworked in the last 2 months: 

86 CIS (early) 1.8L 8V GX engine code 

Car completely died a few months ago and started a landslide of issues that has me chasing my tail. I could get it to restart after a bit of effort, but it was not trustworthy and kept stalling out, so... 

I started at the rear worked my way forward and replaced with new (I used Bosch/Mahle/Mann where applicable): 

1) new in-tank transfer pump 
2) new main fuel pump 
3) new fuel pressure accumulator 
4) new fuel filter 
5) new fuel lines from the pump/filter/accumulator 
6) new CSV 
7) new fuel injectors (not Bosch), with new brackets/o-rings, etc. 
8) new cap & rotor 
9) new plugs Copper + Bosch 
10) new spark plug wires 

Car would restart OK after above, but then immediately white smoke from exhaust...fuk me, so: 

8) new cylinder head (Parts Place refurb hydraulic 1.8L 8V), new head gasket and ARP studs installed, all new intake & exhaust manifold gaskets 
9) replaced single manifold with dual-down manifold and downpipe from late MkIII 
10) new O2 sensor (single wire, but broke female plug end in process) 
11) new TT stainless from Cat back, all new seals/gaskets, hangers 
12) new CTS 
13) new oil pressure sensors .3 bar and 1.8bar 
14) new Thermo Time Switch 
15) all new coolant hoses 
16) cleaned the engine bay and all accessories... 
17) new battery with new 2 gauge positive cable 
18) cleaned and checked all grounds 
19) new coolant reservoir 
20) rewrapped all electric lines with new tubing 
21) new intake boots on intake (the large main and the throttle body connector) 
22) new vacuum diaphram booster on distributor 
23) checked all other vacuum lines, but still unsure if bad (believe them to be ok) 
24) new valve cover, MkIII gasket 
25) running 20w50 oil, new Mann filter 
26) new timing Conti timing belt and TT cam sprocket 
27) new intake filter 
28) new fuel pump relay 
29) all new fuses under dash 

unrelated - but I also put in new: 
30) passenger Empi axle 
31) new tie-rods and boots 
32) new radio and speakers 
33) new front seats and Recaro brackets 

So with all that... it cold starts good, holds a steady idle at 1K rpm, revs clean and strong from tip-in through full throttle. Sounds healthy. 

For the last week with test drives around the block...usually about halfway around...when it gets fully up to temp, it stumbles at throttle tip-in, motor sounds like it's missing, it'll rev and stay good but sounds horrible. Definite change in tone for the worse. One time engine completely stalled, which is when I replaced fuel pressure accumulator and that helped a lot. Thought I had if fixed even... 

But I also have a hot start issue that I don't believe is "starter" related. It will re-start, takes 2-3 times to fire up and then runs like total crap, rough, stumbles at initial throttle tip-in, can rev ok and will stay at idle after revving, but does not clear up and run smooth. It sounds awful too...especially compared to when it doesn't do this. 

My "new" cylinder head also has a ticking sound, but zero smoke out tailpipe means I might a bad "new" lifter in there somewhere or maybe not...just a loud head I'm thinking. My research says this may be normal and with almost no miles on it since replaced I haven't been able to drive it good to settle the head in (if that will even help). 

Timing is advanced to 6deg. Checked this so many f'n times...like I said when cold start in morning, runs perfectly. 

I've about had it with throwing parts at it. I've learned a lot since this started, but yeah... I'm done. Anyone?? Really could use some solid advice at this point. I've tried real hard to use the Bentley and search old related topics, checked timing umpteen times, vacuum lines, etc. 

Thanks from one beaten down MkII owner...


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## speedbird119 (Apr 30, 2008)

Update - I just replaced the vac lines from charcoal canister to distributor to intake manifold. Basically all the small vac lines. The large hard plastic vac line from the brake booster is in great shape, no cracks or leaks I can find. I replaced the short hose connector from it to the side of the intake, just to be sure. 

However, it still runs rough when warmed up, feels like a misfire, stumbles slightly at throttle tip-in, revs clear it a little but never really goes away -- and the spark plugs look good...in fact all day today, other than first thing this morning, it's basically running like crap. 

Think maybe something is wrong with the air intake/fuel distributor area, or still something fuel related at the back perhaps I'm missing? I say that because as of today, the fuel gauge on the dash moves from full to almost half tank when driving, but shows full when stopped. I just filled up a few days ago and have driven less than 10 miles. I see no fuel leaks in the rear around the pump housing. That's brand new... f me. 

Any help guys? ...maybe it's a bad CTS, need another new one? I don't know, brain is fried...:banghead::banghead: 

Can an oil pump going bad cause this sort of issue? The oil pressure light flickered a few times when it was running so rough earlier. Trying to think of anything left. 

Distributor, coil and starter have not been replaced, but like I said, it starts and runs fine when cold. Starts with extra effort when warm and then runs rough and doesn't seem to want to clear up. 

All that's left untouched at this point is the lower end of the motor. I've not done compression check yet either, but exhaust gas is spotless though. I might have a bad downpipe connection to the new Cat, so I'll double check all manifold and exhaust bolts again tomorrow. It almost sounds like an exhaust leak, at least my neighbor thought so. 

One note on the exhaust, my old single downpipe manifold had the CO2 breather tube, the metal tube that is about a foot long and screws into the exhaust manifold. The "new" dual exhaust did not have that feature and is therefore not part of my "new" exhaust system, would that missing CO2 breather tube mess up my O2 sensor readings when warm?? 

At this point anything I can think of I'm throwing it out there. 

I did a lot of cleaning during this episode and the engine/bay is near spotless too, no drips or leaks of any kind with either oil, coolant, or head to block or manifold gaskets, can't see a drip of any kind...


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## rabbitnothopper (Oct 19, 2009)

since you replaced everything

did you test the fuel pressure?

did you check the duty/dwell?


90% sure this is your problem
http://forums.vwvortex.com/showthread.php?4655543-Rebuilding-a-CPR-and-adding-adjustability


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## speedbird119 (Apr 30, 2008)

rabbitnothopper said:


> since you replaced everything
> 
> did you test the fuel pressure?
> 
> ...


Thanks for the reply, I just moved and the car is at a good Portland area VW shop right now, and we tend to agree with your assessment. It's getting a compression check as well, #3 cylinder is making noise so we want to eliminate it as the potential issue of the rough running. 

Dwell checked out, in fact they reset all baseline elements for the car, timing, CO2 etc. and it helped a lot, but the stumble at tip-in is still there and the loud valve noise as well (even though we think it's not the issue, I might have a bad lifter too, or just a really loud head).

I'll report back as I find out more... cheers!


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## Jon85 (Aug 17, 2012)

when I bought my 85 golf it had issues when it got up to temp, come to find out the Hall effect sensor that is mounted on the ign. distributor was faulty. I noticed you hadn't replaced that yet. it works off of magnetism and after a while they weaken from heat. what shop in Portland did you go to by the way?


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## speedbird119 (Apr 30, 2008)

Double J Motorwerks...great shop! 

It's since been fixed. #3 injector was faulty, they were all new so we didn't think to check the injectors until we sorted the rest. Replaced all 4 injectors with new Mercedes spec Bosch ones, lesson learned there. Don't use the non-Bosch injectors, they have a 25% failure rate... lol 

We also replaced the lifters and with the new A-grind cam out I swapped in a new TT G-grind since the exhaust was all new and could really breathe...the car is a blast to drive again, and it's quiet where it should be. Money well spent all-around.


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