Cabby gremlin driving me nuts! - starting and horn problems

[jerseyjon]

I purchased a cabby early summer and thanks to everyones help on the forums I have had it running top shape for the last month or so. However, all of a sudden it has had problems starting - randomly. Sometimes it will start right up and purr, other times it will start, jump to 15k rpms and then drop to below 5k. When it does this it will either stall right away or spit and sputter for a while - until i give it gas and it dies. Also, when I give it gas it wants to stall, but then if I ease off it picks back up and continues to do this...mostly resulting in a stall. Occasionally it just wont start at all. Heres where the gremlin comes in...When it does this and I get it running long enough to drive, after about 5-10 minutes it just "pops" into driving normally. This has happened a few times and is currently just not starting. This is obviously my main concern...
Already fixed/replaced: new fuel pump relay, vacuum lines, AAR, CSV, CPR, battery, plugs/wires/distributer. I'm thinking it might be maybe the voltage regulator or ignition coil maybe? Any suggestions?

Now onto the horn...Basically I know it is shorting out because it only works in R,1,3,5. When I hit the horn my voltage meter drops significantly. My question really is - has anyone ever scene or heard of anything this strange happening before?

Thanks for the help!

[Briano1234]

For the jumping idle, I would clean all your connectors.
Then look below.

For the horn, that is easy.
Replace all your motor mounts as the engine torque is pulling on your grounds.

Now there is a ground that some folks can't see readily. It is from your frame to your steering racks gear box. It is that ground that gives the horn buttons theirs.

For the jumpy idle and general sluggishness as you are indicatimg by the wonky horns....
I would also replace the battery to your frame ground, and from the frame to the transmission.
Then from the drivers side rear valve cover nut to the frame.

Then I would be looking to the fuel pumps, but only after repairing your grounds.

[jerseyjon]

Thanks Briano, I assumed the main cause for a lot of my problems has been faulty grounds. Being that the car is 25 years old I am always finding broken wires and random odds and ends. My only curiosity though is this: if the connectors are dirty/corroded/etc - which in fact I'm sure most are, why would the car drive normally after 5-10 minutes of driving? It seems to be a starting voltage problem, but I am obviously no expert. Thanks

[Briano1234]

Because if the Ground is faulty, that is the main ground then you are using the wires on your sensors to supply the grounds for the whole car. That is the ground from a sensor is going through the gauge, or ECU to power something. Do you really really really want to use your ECU to ground the starter? I DON'T THINK SO.

And when you have a good ground the sparking that it makes when intermittently connecting will electrically weld it.

[x-cube]

Dammit, I love this guy Briano1234, he really knows his stuff, makes you want to rebuild the entire car over. Briano1234, I say thank you very very very very much.

[jerseyjon]

Update:
I checked the grounds and everything is well grounded, engine and body, and cleaned any corrosion or build up. I found the cause for the horn problem though, in r,1,3,5 the linkage touches the power-steering line and grounds it out. I hooked up the meter and found a faint voltage..like .08-.15 on the PS line. also when the PS line is grounded- horn works. So after following it back and searching for any possible culprits I found nothing. There is also a voltage reading on the PS unit itself, but again no live/shorted wires anywhere in sight. As for the the intermittent starts, got me! I'm still leaning towards a bad ignition coil as a possible reason..or again just a gremlin.

[kamzcab86]

You may also have a faulty ignition switch.

After replacing all of those fuel/air-related parts, did you
a) check and fix any vacuum leaks?
b) check and adjust the air-fuel mixture? If not, go to http://www.cabby-info.com/cis and get to work.

You may also have a sticking air-flow plate: http://www.vintagewatercooleds.com/tech ... cismaf.htm .

[Briano1234]

Update:
I checked the grounds and everything is well grounded, engine and body, and cleaned any corrosion or build up. I found the cause for the horn problem though, in r,1,3,5 the linkage touches the power-steering line and grounds it out. I hooked up the meter and found a faint voltage..like .08-.15 on the PS line. also when the PS line is grounded- horn works. So after following it back and searching for any possible culprits I found nothing. There is also a voltage reading on the PS unit itself, but again no live/shorted wires anywhere in sight. As for the the intermittent starts, got me! I'm still leaning towards a bad ignition coil as a possible reason..or again just a gremlin.

Did you find the frame to power steering rack ground? if not that is the reason.

You say that the linkages are hitting the power steering hoses? That sounds as if they have replaced the rack and forgot to hook the ground back up. You want to tie-wrap those hoses off the linkages as they will cause a wear through.

[sixsracing]

The idle/drivability issue may be caused by the frequency valve. It is located on the back side of the airbox, Bosch two pin connector. When you turn the key and start the vehicle this valve should buzz and continue buzzing. If not, then either the valve is bad or power has been interrupted. Check this out and post back.

Brian is correct on the P/S rack ground. If you have power present on a structural component then voltage is feeding back through the harness. Try using a pair of jumper cables to connect the P/S rack to the NEGATIVE post of the battery and operating the horn.

Bad ignition coils generally show there ugly heads by refusing to fire hot or not at all. Seldom are they intermittent.

[jerseyjon]

I agree. The frequency valve is ok, checked that. No vacuum leaks that I am aware of since I replaced most if not all the lines. I agree that it must be feeding hot back through the steering rack and causing the short/bad ground, I just cant figure out where. I pulled the fuses for everything in the steering rack that may have been interfering to try to narrow something down but that didnt reveal anything. I'm wondering if the starting problem is being caused by the same short that is screwing with the horn by pulling voltage elsewhere. Maybe. Where exactly is the ground for the steering rack anywhere? is it just a small brown wire connecting to the firewall about in the center? I'll have o take another look tomorrow. more updates to come, thanks to all those who've helped this far.

[Briano1234]

The steering rack ground is a brown wire that is attached to a screw (any screw on the metal rack) and then to a screw usually holding the mount for the rack to the frame.

[gull]

Running badly for 5-10 minutes, then running normally afterwards sounds suspiciously like the base mixture is off. After 5 minutes or so the oxygen sensor gets hot enough to work and the lambda control unit automatically adjusts the mixture using the frequency valve (this is called "closed loop mode"), but before that the frequency is fixed and the engine is running on a "best guess" set by the base mixture ("open loop mode").

I would check the control pressure, cold and hot, with a fuel pressure gauge. If it's off, you probably have a problem with the control pressure regulator. If it's OK, adjust the base mixture. There are instructions for doing this using a tach/dwell or duty cycle meter that work very well.

You should also check for vacuum leaks, a clogged fuel filter, or a clogged air filter -- anything that could affect the fuel/air mixture.

[sixsracing]

I see that you have replaced most or all components for the cold start system. Did you check for voltage/ground at the cold start valve and the warm up regulator? After 10 minutes of driving these would normally take themselves out of the equation and vehicle would straighten itself out. Minimum 11 volts is required at startup, a bad ground could be the problem here as well.

Even if you can't find the appropriate spot for a missing ground you can still use the jumper cable method to manufacture a temporary ground.

[jerseyjon]

Everything is grounded well beyond stock so I dont think that is an issue anymore. I just got done driving for a while and here were the symptoms: start the car and the oil pressure light was on- the center gauge(I know they aren't the most accurate) also showed extremely low oil pressure. The car hesitated a few times and stalled. I restarted the car again, same thing, but this time I gave it some gas and it settled into a nice 1000 rpm idle (loud since the exhaust sprung a leak somehow overnight- it's a devious gremlin for sure). A few hours later I start the car, same thing as before happens, drive 10 minutes, park and shut off car for 5 minutes. Start it back up, same thing, but now it wont "settle"- after 10-15 minutes of driving it kicks in.


By the way, the horn is now working. Thanks for the help with that one.

[sixsracing]

I'm starting to think that you may have an injector leaking down. Do you have a fuel pressure gauge? It's kind of tricky to install because of the banjo fittings but if you can it would tell you fuel pressure at initial startup and after shutoff you can monitor for pressure drop.

I'm thinking maybe one or two injectors are allowing fuel to flood the cylinders after shut down. This fouls the plugs and may account for your stumble.

Does the car accelerate well after it clears itself?

Any black smoke on hard acceleration or initial startup with a generous amount of throttle?