HELP with 1.8 FI

[kevinseven]

Please help...I'm caught in a fuel injection downward spiral. I've been making one wrong adjustment after another on my 1975 1.8L.

When I come to a stop the engine idle would be stuck at just under 2,000. If I feathered the clutch it would drop back down to around 1,000. I'd monkey with the idle screw at the throttle body but it would always sit above 1,000 or the needle would bottom out. I just couldn't get that magic 850 RPM like the book says.

Last night I started plowing through some troubleshooting and besides finding that my hoses are pretty ragged (but don't seem to be leaking) I've got all sorts of other issues.

1). I'm lacking a TDC mark on my fan so I'm going to have to do that check from below the car like that tech note says before I can get a relieable timing set. I replaced the plugs, points, rotor, condensor, coil, wires, and cap week before last. But the lack of mark pretty much stumpped me until I saw that tech note. But my timing could be off.

2). How closed should that Aux Air Valve get? I put it in the freezer and I could see through the hole. I hooked it back up to the harness and flipped the ignition and didn't see a tremendous change after severl minutes. One Bosch manual tells me I should get a 12V reading at the harness (i.e. shouldn't a test light come on?) but I don't read anything. I think I was sucessful in tracing the harness wires back to the relay board but that only raised more questions.

3). My relay board has no relays in the two slots marked for the FI in the manual. I see a relay there for the hearter blower but the others are empty. Are these only used for the 2.0? I assume so becuase the car had been running for the past year without the relays.

4). My decel valve seems to be functioning. I Plugged the one hose and blipped the throttle and the valve had suction.

5). I pulled the Air Flow Meter and used an ohm meter to check the resistance across the terminals listed in the Bosch manual and they were within spec. The vane moves freely. I popped the top off and inspected the electronics inside and they appeared ok. I resealed and replaced the cover.

6). I turned my attention to the throttle switch and yanked the body off. My throttle switch only has three terminals and no way to rotate the switch on the screws to adjust the curb idle (or whatever you call it). I downloaded a diagram from here or the club site that showed more than three terninals and mounting points with hash marks and a way to swivle the unit on the mount. Do I have some throttle switch form a volvo or is this right?

I put it all back together and went to leave this morning and the car starts up fine. It idles -- I turned the screw to get me back to 850 and it held pretty steady. I backed out of the garage and went to pull away and the car petters and dies?

Too much air? Too much fuel? False air? Sticking Air Flow Meter? Surely it's something I did.

kevin
1975 914 1.8L
atlanta, ga

[Dave Bell]

Been there on the 1.8... but mine is purring like a kitten now... even down to 400 - 500 rpm.

Replace all your ragged hoses that are "not leaking".... Air leaks are what screw up these FI systems and make your 1.8 run lean.

Replace old T connections in the air hose also as they are often cracked and leak even if they don't look like they are leaking.

You can richen up the mixture at idle by turning in the adjustment screw located near the exit side of the air flow meter. Turning the screw in closes off the aux air flow path through the air flow meter and forces the meter to monitor more of the idle flow, thus the FI computer will inject more gas at idle.... back it out later to pass smog if necessary.

Re adjust idle screw on the throttle body and try out the car.

On the Aux air regulator, if you have it out of the car, you should be able to watch the passage close after you hook it up to a 12 volt source. I believe that it will heat up on its own and close off the air flow.

Check the resistance of your Cylinder Head Temp Sensor. Should read higher when cold and lower when warm... see Haynes manual for specs. Lots of folks throw in an extra 500 ohms or so into that circuit to richen the mixture. I wired in a rotary switch in series with the CHT sensor and mounted it to my dash. Now I can select, 0, 600, 1200, 1800 or 2400 ohms to add to the CHT value. I usually dial in 1800 at start up for an extra rich mixture. After a few blocks/minutes of driving and warm up I drop it down and usually cruise around with 600 ohms of additional resistance in the circuit. When warmed up, the car will idle anywhere between 400 and about 800 RPM pretty smoothly... but things were not always that way.

I find that even with the engine warm... there is some kind of warm start, low idle, problem still so I will often dial in 1200 ohms if the car has been sitting off for more that 5 or 10 minutes... then back off again to 600 ohms after a minute or two.

Get your timing set right and get your vavles set right. Make sure you set things up with the vacuum lines removed from the distributor. Are you running points??? make sure the gap and dwell is set right on the points.

Other stuff....
Take your throttle body all the way off and clean it out. I found that the intake side of mine had oil tar deposits sucked from the oil venting system and my vacuum ports from the throttle body were blocked up with this crud. Needed a piece of wire and solvent to clean them out... it helps to have retard vaccum to the distributor working at idle to make things run smoother.

I put some RTV on the throttle body seals and wrapped all the larger air connections with the type of stretchy rubber tape that effectively "melts" in on itself forming an air tight seal

Check the numbers on your distributor... the one that came on my car was from a type 1 VW...I went to the FLAPS and purchased and nice rebuilt 205 distributor for about $50 to $70 as I recall.

Check your fuel pressure for kicks and see if it matches Haynes spec.

I swapped in a Multi-Spark Electronic ignition, to supposedly help with emissions by providing better burning... expecially at lower RPMs.... but that swap did not fix the dropping out idle which was a lean condition and is fixed by stopping air leaks and riching the mixture.

Hope this helps.

- Dave

[Dave at Pelican Parts]

Dave is quite correct. A few more things to ponder:

The two "FI relays" on the relay board are only used by the 1.7 and 2.0 FI systems. The 1.8 has a "dual relay" that hangs off of the battery tray.

The AAR should have +12V when the flap in the air flow meter is opened, which turns on the fuel pump. I believe that it is hooked up to the same thing that runs the pump, just as on the 1.7/2.0 system. There should also be a ground on the other pin in the AAR's connector.

The TDC mark on the fan can be tough to see. It is on the rear part of the fan, and it is tough to get your head far enough into the engine bay to really see it. A mirror can help. I suggest getting the engine close to TDC, then slowly rotating the engine (you can push the car with the tranny in 5th gear) and using a mirror and flashlight to look. It may make sense to put some paint marks on the rest of the fan so that it's more obvious where things are.

The AAR should be pretty much completely closed after about 5-10 minutes of driving around.

The 1.8's throttle switch only has three contacts in it. I was not aware that it was not adjustable.

--DD

[kevinseven]

Thanks everybody. I'll be ordering a vacuum hose kit today.

Funny thing though, once I figured out why the car would stall out (some dummy forgot to plug the AIr Flow meter back in, hmm...) and got the car back on the road, the sticky idle was gone. Well at least for today. Either the car liked to have everything yanked out and cleaned like I did or I have some intermittent Decel/AAR valve issue.

I'll try and check the AAR current by manipulating the Air Flow Meter. But I'll bet it's a bum unit.

Also, I could have sworn my '74 2.0L would idle high for a few minutes while it warmed up. My current car doesn't do that.

kevin
1975 914 1.8L
atlanta, ga

[MidMike]

First of all I wish to thank both Dave's for the info. It's hard to find people who have knowledge of the often forgotten 1.8. Check your rubber elbow connecting the air flow meter to the throttle body. Today as I was digging down to remove the throttle body as mentioned by Dave ,I found a 2 inch rip in mine. I never thought to check it because it was replaced about 2 years ago. I repaired the rip with silicone and the car started right up and Idled perfectly. I could not find a new elbow three years ago so I had to settle for a used one (Automobile Atlanta).As far as a faster idle when cold,mine idles high then slowly slows down as the AA flow valve closes. Good luck with your 1.8 74 1.8

------------------

[tracer]

Thanks Dave Bell,

I had the same problem lately with my 1.8 with FI, engine starts and runs fine until it really is warmed up, then won't idle and surges and dies, very hard to restart. I added the 600 ohm resister in series with the cyl head temp sensor and works like a champ. Thanks for the help.

[kenschipper]

Similar symptoms '74 1.8 - if I leave it sit 10-15 after running it won't idle. Takes about 5 minutes of running again to settle backe to 800 at idle. Added 600 ohm resistor. No change. Any ideas. Also has a backfire when letting of throttle. Not there when cold, even more odd, not there after running on freeway. Sounds like the heat sensing is off or mabye vacuum leak (everything looks good here) or exhaust manifold loosle. (Tightened a couple of the nuts but getting to the others requires removing the heater ducting which will have to wait until later)

Thanks for any ideas you may have.


Ken Schipper
Orange (Porsche says red but not in my mind) 74 1.8

[tracer]

Is your timing and valve adjustment correct? You should not be backfiring unless exhast valve is allowing combustion into runner tubes, be careful, the AFS will be damaged if it backfires past it and the items is $350+ for a new one. I ordered all new hoses even the runner tube hoses and have been very trouble free since getting my teener going again. If you need any more help I will do what I can. I'm by Sacramento.

[rockaria]

Originally posted by Dave at Pelican Parts
Dave is quite correct. A few more things to ponder:

The two "FI relays" on the relay board are only used by the 1.7 and 2.0 FI systems. The 1.8 has a "dual relay" that hangs off of the battery tray.

--DD

Thank you so much for this statement. The Haynes manual is not quite as helpful. So bascially I only need the one Relay at the bottom for the fan. I though something was missing with the other two marked for Fuel Injection and power, but my 75 1.8 was running perfectly. (Thought the previous owner had it wired funny!)

Thanks again,

Christopher...

[Serge914]

It look like I am not the only 1.8L owner with idle problem. I was ready to replace my throttle switch today but the new one I got has only two contacts, old one has three. They both have the same Bosch part number. I will try it tomorrow, it is only a switch anyway ?????

Kevin, where did you find that vacuum hose kit. I cant find it at PP.
I think AA was doing one.....

[tracer]

My idle problem was just fixed with the cyl. head temp sensor. When cold until about 15 minutes all was ok, then the engine would surge and sputter and die. Was very hard to start after. Put the $20 sensor in and all the problems are fixed. Went from 18-20 mpg to 30!!

[Jim Chambers]

My 1.8 started and ran fine when cold. Would not idle and ran poorly when warm. Tested all components with ohm meter. All ok. Replaced vacuum hoses. No change. Borrowed air flow sensor from a friend's car. My car ran perfect. Bought new sensor. Life is good.

[brain009]

Hey Tracer,

when you replaced the cyl. head temp sensor, how exactly did you get it out and the new one in? I need to switch mine out to see if that helps with warm idle problem that I am having. Any info would be great.

Thanks

[tracer]

I had to remove the runner tubes on the passenger side and used a deep 9/16 (I think) socket. (I didn't have a metric deep). Was only about 30-40 minutes.

[Dave at Pelican Parts]

Tools:
3/8" ratchet
Deep 13mm 3/8"-drive socket
Expendable 3" long 3/8" extension
Penetrating oil
Grinder

First, soak the head of the sender with the penetrating oil. The senders sometimes like to grab the aluminum threads and pull them out...

Next, take the grinder and knock off one corner of the end of the extension--the part that "plugs into" the socket. Don't take off half of the square, just enough to allow a wire to get through there without getting smashed.

Then thread the 13mm socket over the sender wire, push the wire to one corner of the 3/8" square hole in the top, plug the extension in so the ground-off corner goes where the wire is. Put the ratchet on that, very very carefully turn. Pray a lot that the threads don't come out with the sender...

One mechanic I know says that he gets the engine fully warmed up before he removes the sensor. Makes sense because the aluminum head expands more than the steel sensor--but then again, the aluminum gets weaker when it's warm, too...

--DD

[tbil]

Did this once with vice grips on the side of the socket as I couldnt find a socket with the right depth leaving clearence to fit a ratchet handle on. Did this last week and decided to pull the tubes which gives you full access and is pretty easy/quick. Good luck!

[brain009]

Thanks for the tips. Got it out and the new one in a decent amount of time. Dave that was a great trick with the grinder!!

Thanks

[brain009]

OK, I've changed the vacuum hoses and the cylinder head temp sensor, but I'm still having a problem with the idle, rough running when the car is warm, and the hard restarts. Would the next logical step be to replace the air flow sensor or add a 600 ohm resistor in series with CHT sensor?