StopLookGo

I hope someone can help me with this idle problem I've just started having. It's a C2 tip. Only mods done to the engine is a long J pipe. Up till about a month or so the idle has been fine except when reverse gear is engaged. Idle drops down to about 400rpm or lower but the engine doesn't cut out. Recently, after going for a quick drive the car would idle at 500rpm or lower when at stop signs, parking etc. When cold it idles fine. I've had the car brought to a local mechanic to have my wires and plugs checked and he gave them a clean bill of health. Yesterday I cleaned out the ISV with a liberal amount of WD40. I was expecting a lot of gunk but it was just a little bit of black goo that came out. The car idled the same. I swapped out the DME relay with a brand new spare. Same thing. I've gone through a few threads and I just end up getting lost because I have a rather simple mind
Due to my location I don't think there are any places that have a Bosch Hammer handy with the exception of the $tealer$hip. I will ask them after the weekend.
What else should I be looking at? Throttle body needs cleaning? How would I do this? A new O2 sensor? thanks in advance.

Goughary

How old is your battery?

Also...don't trust a shop that gives you a good bill of health for your plug wires. That's one of those things you really have to look at yourself. Get a multimeter and check each wire that it reads close to 3ohm. Still doesn't tell you abt cracks or arching, but will tell you that the wire actually is connected inside the boot. I had a few that were not connected and two shops and "an expert" told me my wires were fine because they "looked" ok...

Also...if you have beru dist caps and rotors, take them out and inspect them. Mine were horrendous last time I got stuck using them. Will only use bosch now.

How many miles on your coils? And just as matter of course...Shake out your air filter. I find that if I don't replace mine after pollin season it gets clogged.

Flea18

I had a similar problem with my 5-spd (except for the reverse issue) and we ultimately figured out it was a combination of a bad O2 sensor, a bad ECU, and a vacuum leak. Youtube has some good videos on how to test your O2 sensor, just be careful not to strip it during removal. Look for loose vacuum lines or loose hose clamps on the six air intake tubes. ECU will have to be checked by a pro.

Feudal Serf

An easy way to isolate an ignition problem is to unplug one of the harness connections from the coil control module. Try running on a single set of plugs then do the same on the other coil. If no change in idle then i would focus on vacuum or O2 sensor. A scan tool such as durametric can tell you if timing has been retarded due to ignition problem.

Good luck
FS

Navaros911

Could be a fuel pressure regulator issue.

There is a vacuum line running to it. Unplug it and watch if there is any fuel dribbling out. If there is, you have a FPR that is faulty.

StopLookGo

WRT to the battery and coil pack, I just got the car at the beginning of the year so the condition of both items are unknown. I suppose I should change the battery for peace of mind. I have a new air filter though. I'll look up how to use a multimeter and check the wires myself.

I'll have a look for any loose vacuum hoses and check the intake tubes.

Which is the coil control module? and can I disconnect it while the engine is running?

I will also check the FPR.

Thanks all.

edit-

just had a quick look around the engine bay checking for loose hoses etc. Everything looked to be okay, so I tried to get the vacuum hose off the FPR. How are you guys managing to get any purchase on that little hose? My hands aren't exactly large but I can't seem to fit them through the tiny gap.

Ducks964

I know someone will chime in on the best way to check each coil, but i would not mess with them while the car is running. Too dangerous IMO.

sml

first thing i would be doing is a bosch hammer (or equivalent) system adaptation

StopLookGo

just a quick update. I went ahead and got a brand new battery since I have no idea how old the battery I had was. Unfortunately it didn't solve the idle issue. I'm still hoping the simpler and cheaper suggestions will work.

boxsey911

If I understand your first post correctly you are concerned about a low idle and not a hunting idle? If it's just a low idle, I would check to see if the idle microswitch is being engaged when it's warmed up.

RichieRoo

Hi there

I like all the suggestions posted, I just thought I'd add another possibility.

I had a similar problem with my Tiptronic C2 and the symptoms were very similar to what you're describing.

In my case the Tiptronic ATF fluid was low which caused the torque converter to engage a bit more than usual at idle, which lowered the revs. This was most pronounced in reverse – even to the point of stalling.

Here is a link I added to the DIY section which describes the symptoms in more detail (at the end of the post) and the top-up procedure which seems to have worked for a few of us.

Best of luck finding a solution.

Rich

Navaros911

Good point on the idle switch... and easy to test.

Idle switch test:
With the engine bay open and engine not running, push the throttle cable down. You should hear a click... and when you release it, another click. If that's not the case your idle switch is not engaging.

To check the coils:
Unplug the large plug connecting to the bottom of the plug control unit. It is a very wide plug and you need to push down on the wire to get it off. Once you disconnected one, try to start the car. If it starts and runs fine, everything is good. Turn the car off, reconnect it and try the second one. You find the coils on the left hand side when you look down the engine bay. Follow the central wire from the distributor cap to the top of the coil. Then look down at the base of the coil. Just underneath it are the coil modules.

FPR:
I can just get my hands down there, but it's very, very tight.
Try from a few positions and remove the heater pipe if you need to. I worked blind, but didn't need to remove anything.

pcarplayer

Just changing the battery won't help. You will need to have your car's idle adapted using the Hammer or similar. Essentially, the tech should do the adaption while the car is hot (oil up to temp) and all the ancillaries on (lights, aircon, window wipers, etc). This puts extra load on the system tricking the adaption to setting a slightly higher RPM. This can help though may not solve an underlying issue completely.

Indeed, if you let your battery run below a certain voltage and start your car the effort required may drop the batteries charge and thus unset the idle adaption even though the car starts ok. I always use a trickle charger to maintain the battery

StopLookGo

with regards to the idle switch test, the ignition must be in the 'on' position?

just an quick update. Between managing a 5 month old infant and his 3 year old sister I managed to find a few minutes to check out the FPR. With the help of a pair of needle nosed pliers and many scraped knuckles and the occasional swear word I managed to get the vacuum hose off the FPR. Only to find out I had ripped off a chunk of what seemed to be some rather perished rubber. I started the engine and although there wasn't fuel dripping out, I noticed it was quite wet. When I turned off the engine the fuel started dripping out. Does this mean the FPR is bad?

Jacke2c

If you removed the vacuum hose from the Fuel Pressure Regulator (FPR) and fuel flows out for any reason... it means the diaphragm has a hole in it and it is bad.