Several problems today- What's wrong with my car?

[TheRedSlantnose]

Today I took my Slant out for a drive after having sat in the garage for two weeks due to the weather keeping it indoors. All was fine at first, but after driving on the highway for several miles, something went wrong somehow. When I took it out of gear, the engine idled only for a split second, and then it died. It ran again when I put it back in gear, so I continued driving, but whenever I needed to take it out of gear again, I had to manually idle the engine by keeping my foot on the pedal.

As I continued driving, I noticed two new problems: the air/fuel ratio dropped down to 10.0 and stayed there. Normally, my car's air/fuel ratio runs between 12 and 15. The other problem was presumably caused by the drop in the air/fuel ratio; acceleration was severely weakened, with the boost only reaching 0.4 bar, when it normally goes over 1.1 bar.

Seeing my car was just barely running, I headed home, but just a few minutes from my house, the engine died again and this time would not start at all; it cranks, but refuses to idle. I immediately went ahead and checked the engine, but I couldn't see anything wrong with it; the distributor plugs were all in place, the vacuum pipes weren't loose, and no parts seemed to be missing either. I also checked the interior wiring and fusebox, but saw nothing immediately. I did however notice something unusual; normally the intercooler would warm up from driving, no matter how the weather was, but this time it was cold while the turbo remained hot.

My Slant runs without any problems 99% of the time, with many of the problems being relatively minor, but this was the first time I ever had to get it towed home.



For now, I think a fuse must have blown or one of the relays or even the fuel pump had crapped out, but I don't know at the moment.

Any ideas on what may have gone wrong? All theories are welcome as I obviously need to get my car running again.

Thanks,

[wildturkey]

Vacuum leak?

Get the car to as close as you can to an idle. Then spray a can of general purpose water dispersant spray or carby cleaner around all of you inlet plumbing. One connection at a time. Don't get to heavy handed around the ignition system as you will have a fire on your hands.

You need to check every single point from your air meter to your injectors, including the turbo inlet / outlet, intercooler and inlet manifold gaskets.

The theory is the aerosol spray is a fuel. If you have an vacuume leak and you spray fuel in it, you will momentarily correct the air fuel ratio and the engine will rev up.

It is not easy to glance at all the possible points where it could leak so you need to be systematic and thorough.

[TheRedSlantnose]

Originally Posted by wildturkey

Vacuum leak?

Get the car to as close as you can to an idle. Then spray a can of general purpose water dispersant spray or carby cleaner around all of you inlet plumbing. One connection at a time. Don't get to heavy handed around the ignition system as you will have a fire on your hands.

You need to check every single point from your air meter to your injectors, including the turbo inlet / outlet, intercooler and inlet manifold gaskets.

The theory is the aerosol spray is a fuel. If you have an vacuume leak and you spray fuel in it, you will momentarily correct the air fuel ratio and the engine will rev up.

It is not easy to glance at all the possible points where it could leak so you need to be systematic and thorough.

I can't really do that, because if I try to give it gas right after it cranks, it doesn't run at all. It just goes "Broom" and dies.

[16Volt]

Sounds mixture related as evidenced by you AFR readings. WUR problem? I would be curious to know what it does once the motor is stone cold. Does it smell pig rich? Pull a plug. Just my thoughts, I am sure someone will chime in to have you check your CIS pressures.

[wildturkey]

Take it to an expert.

[oilonly]

It's great that you have an AFR gauge to tell how lean or rich you are. Over the summer I had a problem where the car would go rich 10.3 after about a ten minute drive and it ended up being the CDI.

[dos531]

I can tell you that if you had a vacuum leak then at idle the afr would go leaner not richer, so I dont believe that is the problem. I would definitely check the cold and warm pressures first.

[TheRedSlantnose]

Originally Posted by 16Volt

Sounds mixture related as evidenced by you AFR readings. WUR problem? I would be curious to know what it does once the motor is stone cold. Does it smell pig rich? Pull a plug. Just my thoughts, I am sure someone will chime in to have you check your CIS pressures.

Well, when I demonstrated the problem to the driver of the tow truck, he did say it smelled like it was running rich. My car has been running rich since I bought it, but only by a small amount. A service receipt from its previous owner in Colorado stated it was tuned to run rich in order to adjust to whatever they did to it, I forgot exactly what though, but probably for the higher elevation. I've been meaning to take it to get re-tuned for the lower elevation of Texas, but I haven't done that yet.

[TheRedSlantnose]

Originally Posted by wildturkey

Take it to an expert.

That was my last-resort if I can't fix it myself.

[Akila]

Check fuel pumps, both.

[Tippy]

Are you CIS or Carrera 3.2? Totally different approaches to solve rich conditions.

[TheRedSlantnose]

Originally Posted by Tippy

Are you CIS or Carrera 3.2? Totally different approaches to solve rich conditions.

Carrera 3.2.

[Tippy]

First thing would be to check your cylinder head temp sensor (CHT).

Bet it crapped out.

[JFairman]

Check your rear fuel pump relay. It supplies 12 volts to the rear fuel pump and the heating elements on the bimetallic springs in the cold start warm up regulator and auxiliary air regulator.

If that relay isn't working the car can still run on just the front fuel pump but the heating element on the bimetallic spring in the cold start/warm up part of the control pressure regulator will cool off and control pressure will drop down to where it would be during cold start and the air fuel ratio will be too rich.

[Tippy]

Check your rear fuel pump relay. It supplies 12 volts to the rear fuel pump and the heating elements on the bimetallic springs in the cold start warm up regulator and auxiliary air regulator.



If that relay isn't working the car can still run on just the front fuel pump but the heating element on the bimetallic spring in the cold start/warm up part of the control pressure regulator will cool off and control pressure will drop down to where it would be during cold start and the air fuel ratio will be too rich.

It's Motronic EFI.

[koenig911]

Plugs may now be fouled from running rich preventing you to start. Remove a plug and check if wet with fuel.

You will need to check what is causing the rich condition at part throttle and at idle.

Could be Air flow meter.

Also check for some help:

Pelican Technical Article: 911 Carrera Engine Starting Troubleshooting

[Tt surgeon]

Could be cdi box I suppose.

[TheRedSlantnose]

Just a little update to this thread:

I took my car to the shop today, and it turns out the problem was the 90-degree elbow on the intake had slipped off of the throttle body at the bottom, which allowed too much air to go into the engine, thus preventing it from running.

A while back, one the stainless steel support bars on the intercooler broke (which I've since replaced with a new one I had fabricated), combined with the engine's vibrations may have been the cause of the intake slipping off of the throttle body.

Thank you all for the responses

[Tippy]

Happened to me many times too. Had to make a brace to keep it from popping off.

[T77911S]

they can also get soft and collapse under boost.

had a friend that worked on one that was falling on its face in the upper RPM under boost. everything check out. then he grabbed that boot and it was soft.