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> Why won't my car idle right?
BPGREER
post Nov 16 2004, 06:36 PM
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OK, I'm once again stumped. My car just won't idle smoothly. It sounds like it's going to die, but then revs itself up a bit, then almost stalls again, then revs again... So, I thought it might be a vac leak. I had already replaced all of the hoses, but found that I had leaks on the air intake runner things, where they connect to the plennum. So, I disassembled everything, replaced those hose-type things, and voila! No more vac leak there. Problem is, still not idling right. It's just as bad now as before. One more thing, I slowly brought up the rpms from the throttle body, to listen, and I think I heard a couple of really quiet backfires. Maybe an exhaust leak? Could this cause a bad idle? Thanks.

Brian
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Bruce Allert
post Nov 16 2004, 07:06 PM
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(IMG:style_emoticons/default/icon_bump.gif)

Mines doin' the exact same thang dammit! (IMG:style_emoticons/default/headbang.gif) and sometimes it won't run unless I pump the gas... sometimes.

Changed the fuel filter hoping that would fix it BUT NO....... (IMG:style_emoticons/default/mad.gif)

Good weather is on its way & I wanna drive it (IMG:style_emoticons/default/driving.gif)

........b
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SirAndy
post Nov 16 2004, 07:22 PM
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QUOTE(BPGREER @ Nov 16 2004, 05:36 PM)
Problem is, still not idling right.

vacuum leak ...

(IMG:style_emoticons/default/smile.gif) did you check the throttle-body itself?
do you have the right (thick) gaskets between the intakes and the heads? did you mount them with sealant?

while the motor is idling, spray some brake cleaner around the suspected areas and see if your idle will change.
but careful, brake cleaner IS flammeable ...

(IMG:style_emoticons/default/wink.gif) Andy
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Mueller
post Nov 16 2004, 07:27 PM
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the intake plenum has been known to fail as well, which will cause vac. leaks
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BPGREER
post Nov 16 2004, 08:07 PM
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I checked with brake cleaner initially. Thats how I realized I had to take the intakes off and put new hose things on(I have no Idea what their called). After install, I checked again with the cleaner, and no more leak. I did use the proper gaskets, but did not use sealent, but I checked with the cleaner and there seems to be no leak there either. What's the best way to check the throttle body itself? My guess would be to take off the air cleaner, and spray aroung where it meets the plenum. Any other suggestions?
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muddboy
post Nov 16 2004, 08:18 PM
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my '73 has allways "hunted" for idle to a very small degree. The guy I trust that works on these things (and owns a pristine '74 2.0) told me thats normal as long as its within 100 or so rpm.

The only things I can think of that you havent tried, is check the vacume lines to the distributor, check the distributor itself.
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ws91420
post Nov 16 2004, 08:28 PM
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Not too familer with older FI. On modern FI hunting like you describe is generally a TPS.
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TheCabinetmaker
post Nov 16 2004, 08:36 PM
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Your idle should not "hunt". not even 100rpm. The throttle body must be properly set, then the idle adjustment knob (on the ecu) can be set to the proper CO.

Visit Brad Anders site and read, read, read!
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TheCabinetmaker
post Nov 16 2004, 08:36 PM
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opps, forgot the link

http://members.rennlist.com/pbanders/
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BPGREER
post Nov 16 2004, 08:52 PM
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I've read, read, read, I just don't always comprehend (IMG:style_emoticons/default/huh.gif) I've spent alot of time on the FI system, this is the one bug I haven't figured out yet. I set the TPS some time ago, do I need to reset it after fixing vac leaks? BTW, whats the best way to determine if you have an exhaust leak? What are some of the symptoms? Corrections? Thanks.
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TheCabinetmaker
post Nov 16 2004, 09:04 PM
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How did you set the tps?
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BPGREER
post Nov 16 2004, 09:09 PM
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I used the tech article fm PP with an ohmmeter.
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BPGREER
post Nov 16 2004, 09:11 PM
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BTW, I still don't understand about the co adjust, but it sounds like something that you have to go to the shop for. I just want to make sure I have everything else that I can do done before doing that. Most of the problems I've had have been relatively simple repairs.
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TheCabinetmaker
post Nov 16 2004, 09:21 PM
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Very good. It should be adjusted right. Be sure to leave some slack in the accelerator cable. You really need a CO meter to adjust it correctly, but you can get it close by ear. Turn the knob on the ecu ccw till it hunts, then back clockwise one click at a time till it evens out. If it doesn;t even out, then something is still not set right. Valves, dwell, timing, and tps must all be in sinc before the ecu knob will work as designed.
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ws91420
post Nov 16 2004, 09:24 PM
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The TPS is a varible resistor. What can happen is at the low end the windings will wear out. This can not be fixed by adjustments.
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JohnM
post Nov 16 2004, 09:46 PM
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In addition to VSQ's last very good basic tuning advice, check fuel pressure in spec. Often overlooked and assumed correct, if it is off this can make tuning/idle adjust an exasperating experience. If still having problems and can't find a vac leak, how about injector seals?
John
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BPGREER
post Nov 16 2004, 09:53 PM
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I set the fuel pressure to 29psi. I took the TPS apart before I set it to check the tracks, and it looked good. The car only has 62xxxmiles on it. Where on the ecu is the adjustment knob? Also, all new injector seals, fuel lines, cap, rotor, wires, plugs, fuel filter, valves recently adjusted (they were right on). Just to give a little background, the car sat in a garage from 1987 until this summer when I bought it in an auction.
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ClayPerrine
post Nov 17 2004, 07:12 AM
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QUOTE(ws91420 @ Nov 16 2004, 07:24 PM)
The TPS is a varible resistor.

Not on a FI system in a 914. The d-jet "tps" is actually a bunch of wiper contacts points that the arm slides across, kinda like a rotary switch.

(IMG:http://members.rennlist.com/pbanders/TPS.jpg)

The L-Jet system just has two contacts, one closed at idle and one closed at wide open throttle.


Remember, the D-Jet system was the first practical electronic fuel injection system ever put on a mass produced car.


Bendix developed an Electronic Fuel injection in the late 50s. It actually used Vacuum tubes, and had to be warmed up before the car could be started.
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TheCabinetmaker
post Nov 17 2004, 07:24 AM
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The adjustment knob is on the top left of the ecu. It may have a small rubber cover on it
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Bleyseng
post Nov 17 2004, 09:00 AM
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First set the timing to spec. 27 degrees BTDC at 3500rpms
Secondly, since yours is a 73 2.0l do you have the ballast resistor for the CHT and the right I think its the 017 CHT? You will never get it right if you don't have the right parts.
Then adjust the idle setting when the engine is hot.
There must be no vacuum leaks so all vacuum hoses should be fairly new soft and have a tight fit when they plug in. Like Andy said use a brake cleaner to test for leaks.
Test the AAR valve to make sure its closed after 5 minutes of running. These things tend to rust inside and not close or open.
Now adjust the idle rpm with the air bypass screw and the idle mix adjustment on the ECU as VSG914 said. You should have one or its been swapped out.

Geoff
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