NEED HELP! Rough cold start and BAD mpg!!

[jerseyjon]

Cheers all, new to the forum! I recently purchased an '85 5-speed cabby and have run into a few problems. Whenever starting from cold it idles very rough and is shaky, but idles properly after a few minutes of warm-up. If I engage the clutch and accelerate it before it has warmed up it is bogged down and barely crawls -again until it warms up. The previous owner replaced the fuel lines and injectors before sale. I just replaced cold start valve hoping to solve the issue but to no avail and am stuck trying to figure out what is causing the issue. Also, I just recently took a drive (80-100 miles maybe?), filled the tank before the trip and was close to empty on return. I didn't notice any leaks but do smell a rich gas smell when starting and initially idling. Any suggestions would be more than appreciated!!!

As a side note, i found that the previous owner has what i believe to be the fuel pump relay hard wired ( white wire) to one of the other fuse slots (10 or 11 I think). It sounds like it stays on all the time and I'm not sure if this is normal or just some faulty/poor wiring. Haven't checked the haynes yet as to where the wire is supposed to go, but any advice would help!

[Briano1234]

Cheers all, new to the forum! I recently purchased an '85 5-speed cabby and have run into a few problems. Whenever starting from cold it idles very rough and is shaky, but idles properly after a few minutes of warm-up. If I engage the clutch and accelerate it before it has warmed up it is bogged down and barely crawls -again until it warms up. The previous owner replaced the fuel lines and injectors before sale. I just replaced cold start valve hoping to solve the issue but to no avail and am stuck trying to figure out what is causing the issue. Also, I just recently took a drive (80-100 miles maybe?), filled the tank before the trip and was close to empty on return. I didn't notice any leaks but do smell a rich gas smell when starting and initially idling. Any suggestions would be more than appreciated!!!

First Welcome to the TRF.

That is a sign that you have a sick cabby. I am not a CIS guru, but look for Vacuum Leaks, look just replace all the vacuum lines that you can see, (there is a brass screw on the back of the throttle body). If it turns easily by hand then you have a bad o-ring. Count the number of turns that it takes to take it out, Write that number down. Go to a hardware store and buy a replacement o-ring. Wrap the thread of the screw with 3 wraps of teflon tape and reinsert the screw and tighten it back the same number of turns.

One of the CIS guys will jump in, but I say it is time for a complete tune up. Cap Rotor wires plugs. and Check the timing.....
Some times folks will goose the timing because they can't find the vacuum leak.....


As a side note, i found that the previous owner has what i believe to be the fuel pump relay hard wired ( white wire) to one of the other fuse slots (10 or 11 I think). It sounds like it stays on all the time and I'm not sure if this is normal or just some faulty/poor wiring. Haven't checked the haynes yet as to where the wire is supposed to go, but any advice would help!

Get thee a Bentley You will be glad you did. Also this welcome thread is useless with out pictures of your ride.

Nope that isn't normal, although you will not have a wonky relay keep you from driving.

[jerseyjon]

Thanks for the quick reply! I forgot to mention that the plugs, wires, and cap were all changed at the same time the injectors and fuel lines were. it may be a timing issue, but would that not affect every start-up and idling or just cold starts as it appears to be doing now? I'll get some photos and video links to it starting cold asap.

[Briano1234]

Timing is everything.

A good joke and no timing is a flat thing.

Start out with the basics, (pull your plugs to see if they are are working correctly or is one misfiring).
Replace your vacuum lines.

Then set your timing.....

[kamzcab86]

Welcome to TRF and to the topless world!

1. Check for and fix any and all vacuum leaks... better yet, just replace all of the lines and be done with it. Vacuum leaks occur at the injectors and the idle adjust screw (both use rubber O-rings) as well.

2. That hard-wired fuel pump relay is a bad thing. Buy the proper fuel pump relay and install it (it's pretty inexpensive). A picture or two of your fuse/relay panel will help diagnose what the crazy previous owner did. To ensure that you're looking at the right relay, look at the proper diagram: http://www.cabby-info.com/electrical_system.htm#Fuse .

3. If the fuel pump relay has been hard-wired to run continuously (bad and very dangerous!), that's an indication that the previous owner took the "easy" way out to solve a fuel-related issue. After replacing the fuel pump relay, test the fuel pumps and their output pressure to ensure that they are still in good shape; if they aren't, replace them.

4. Clean the air flow sensor/fuel distributor: http://www.vintagewatercooleds.com/tech ... cismaf.htm .

5. Ensure that the control pressure regulator is working properly: http://forums.vwvortex.com/zerothread?id=2812736 .

6. Test the Lambda (oxygen sensor) system as outlined at http://www.cabby-info.com/cis#Table .

7. Most importantly, check and, if need be, adjust the air-fuel mixture and idle: http://www.cabby-info.com/cis .

8. It sounds like a fuel issue more than anything, but if the warm-up idle is still poor after doing the above, test the auxiliary air valve. The irregular warm-up idle could be due to a faulty AAR.

9. Buy yourself a Bentley Service Manual and chuck that Haynes in a cabinet.

[jerseyjon]

Thanks for the help...but still a long way to go...
Updates: it turned out the cold start valve had a break in the circuit - fixed. The auxiliary air valve is disconnected -I have no idea what it connects to as i have cut wires from the previous owner. I have exposed: red/white and brown coming up from under the engine, 2 brown/white and red/brown coming down from the other direction.(this is all around the cold start valve and AAR. Out of the clip for the AAR i have a cut green/white and darker green/white and have no idea where they go. I haven't had too much time to pull anything off but these are obvious problems. Another thing, I found a flat ground wire coming from the coil up on the firewall...I assume it attaches to the engine somewhere but don't know where. hmm..what else is going on with this car. I fixed the fuel pump relay -it had gone bad so it was replaced. in solving that problem however i lost my instrument cluster somehow(not a fuse) but i'll post that in the electronics section.

[Calimus]

Jon, I'll see if I can get you some nice high rez pics of the cold start & AAR wiring this weekend. I just checked my current pics and don't seem to have any that would help. Keep your eye's peeled, should have something up for ya soon.

[jerseyjon]

That would be great and much appreciated as i cant find any diagrams anywhere else. I got a brand new WUR and AAR installed today and am just waiting for the engine to cool before seeing if it helps. After checking the voltage on my nest of random wires i decided to connect the AAR to a red/wht and brown which supplies 12v. It seems the old AAR was faulty in that the valve would not open all the way. Now there are just a few brwn/wht wires leftover which I assume just ground out somewhere. I'll update again when I finf anything out. By the way, thank everyone for all your help!

[kamzcab86]

From the fuel pump relay is a red/white wire that splits off to the CPR/WUR and the AAR. The Bentley Manual shows only brown wires connected to both. The green (dark)/white wire goes to the cold start valve and its thermo time switch, as well as a red/black wire. There is a brown/red wire that goes from the Jetronic (Lambda) controller to the OXS thermo switch, and a brown/white wire that goes from that thermo switch to ground at the CSV.

There is a blue/white wire, a red/brown wire and a brown wire that are zip-tied to the CSV, which are test wires for the Lambda system:


The flat ground wire attaches to the valve cover with one of its hold-down nuts.

[Calimus]

Kammy, thanks for getting that pic up. Seems like everytime I need to take a pic of find some information for someone around here, life gives me a big kick in the ass. Been a rough week. Sorry I didn't get that up.