# Rough idle



## Pauliwogg (Feb 23, 2008)

My 78 rabbit has a really rough idle when cold and the throttle response is very delayed. Once its warmed up it runs better and the throttle response is improved. I've checked the thermo time switch and the cold start injector and the wur. They all seem to be working correctly. It does seem to be running very rich cold. You can smell fuel. I'm wondering what to check from here. Thanks in advanced.


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## jhelmuth (Oct 10, 2011)

Pauliwogg said:


> My 78 rabbit has a really rough idle when cold and the throttle response is very delayed. Once its warmed up it runs better and the throttle response is improved. I've checked the thermo time switch and the cold start injector and the wur. They all seem to be working correctly. It does seem to be running very rich cold. You can smell fuel. I'm wondering what to check from here. Thanks in advanced.


same problem with my 85 8v...any updates on this problem?


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## ps2375 (Aug 13, 2003)

jhelmuth said:


> same problem with my 85 8v...any updates on this problem?


What have YOU checked? And is that 85' CIS or CIS-e? They are somewhat different in their controlling mechanism.


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## Glegor (Mar 31, 2008)

ps2375 said:


> What have YOU checked? And is that 85' CIS or CIS-e? They are somewhat different in their controlling mechanism.


same problem on an 86 golf cis-l

minus smelling rich when cold..

just replaced all 12 injector seals also..

A/F gauge always sits around stoich..

maybe the fuel pressure regulator on the front of the fuel distributor needs cleaning? only thing i havent done yet..


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## Pauliwogg (Feb 23, 2008)

I cleaned out the screen on my cpr. That seemed to help. I also replaced the vacuum lines that connect the auxiliary air valve to the decel valve and then to the throttle body boot. That seemed to help a bit. Right now I'm just making sure all vacuum leaks are taken care of. I found my fuel accumulator leaking and am going to replace that next and see what that changes.


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## Glegor (Mar 31, 2008)

just did a sea-foam treatment to try and free up the sticky regulator in the CIS unit.. helped, but its still not correct.

if you fire up my car, and dont blip the throttle until the temp gauge comes off the cold peg. it runs awesome. smooth as can be. but the second you give the throttle a little blip to excite the alternator when the engine is still semi-cold, all bets are off..

then it runs from 500-1200 rpms, up n down. then that will smooth out after about 1 minute, or if you babysit the throttle, and feather out of it after the searching idle, then it idles smooth also.

basically, floor the throttle till the engine revs clearly, then back of the throttle to about 2k rpms, then slowly let off the throttle the rest of the way, then it will idle smooth, and not buck when you give it throttle..

have replaced all fuel injector o-rings (all 12)
and checked for vacuum leaks..
checked timing, its advanced far enough to run right..

also misses on one cylinder occasionally on start up now too, but i attribute that to a head gasket getting ready to go tits up..

anyways, if anyone has any insight as to why CIS-Lambda runs like this, with NO VACUUM LEAKS, then im all ears.. edumacate me on what to fix.. im out of ideas, besides actually pulling the regulator, and visually verifying that it is not sticky, or causing my problems..

any possibility that this could be caused from the warm up valve on the intake manifold? i know its open when cold, and closes as the element in it warms up.. crappy idle only happens when car is STONE COLD..

car has done this from day one, and it cleared up a bit when i switched out the thermo-time sensor on the front water neck on the head.. you know, the biggest sensor on the water neck. brown or black plug usually..

maybe the CTS is bad? but why would that cause JUST A BAD IDLE when stone cold?


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## Heisse_mkII (Jul 24, 2005)

Mostly likely it's your head gasket that is causing the problem. You mentioned it was going tits up. I had a similar problem and checked everything and replaced a bunch of parts but it never fixed the problem. I finally found in the bently to do a compression test and pointed to my head gasket. That fixed the issue for me.


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## Glegor (Mar 31, 2008)

Heisse_mkII said:


> Mostly likely it's your head gasket that is causing the problem. You mentioned it was going tits up. I had a similar problem and checked everything and replaced a bunch of parts but it never fixed the problem. I finally found in the bently to do a compression test and pointed to my head gasket. That fixed the issue for me.


i think my head gasket is going tits up, but slowly. i have to add about a quart of coolant a month.

i MOSTLY fixed my idle issue tho. i have been using a 16v ABD intake pipe, and had the stock breather hooked up to the intake pipe, not to the top of the air box lid. well, i hooked my stock breather back up, and it fires up cold and idles smooth. it still has a miss when its cold tho. misses for a few seconds, then pops on all 4, another symptom leading me to believe my head gasket is going. it just misses momentarily, then clears up and steams a bit.

if i have to replace the head gasket, im going to drop my 16v/ABA in there.. i know changing head gaskets takes about a half hour, but more valves = BETTER. plus, it will be ready for a turbo when i can afford to drop one on, and surely a n/a ABA/16v will make more power than a GX engine w/ Neuspeed 268* cam?


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## anlxn (Oct 18, 2009)

Glegor said:


> i think my head gasket is going tits up, but slowly. i have to add about a quart of coolant a month.
> 
> i MOSTLY fixed my idle issue tho. i have been using a 16v ABD intake pipe, and had the stock breather hooked up to the intake pipe, not to the top of the air box lid. well, i hooked my stock breather back up, and it fires up cold and idles smooth. it still has a miss when its cold tho. misses for a few seconds, then pops on all 4, another symptom leading me to believe my head gasket is going. it just misses momentarily, then clears up and steams a bit.
> 
> if i have to replace the head gasket, im going to drop my 16v/ABA in there.. i know changing head gaskets takes about a half hour, but more valves = BETTER. plus, it will be ready for a turbo when i can afford to drop one on, and surely a n/a ABA/16v will make more power than a GX engine w/ Neuspeed 268* cam?


so did you check the lambda thermoswitch?
and do you really think a 8.5:1 16v 2.0 will produce decent power in comparison but then again the GX is only 9.0:1 IIRC........
What fuel management are you looking at? staying CIS would take some work but can be done
sorry for all the Questions


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