84 engine PLEASE help

[84toy]

OK, I'm totally frustrated after 3 days of being unable to get my engine running. I pulled the engine and tranny for a tranny rebuild about 3 weeks ago. While out I replaced plugs (Bosch Platinum), new wires and totally cleaned the engine. Everything went in fine but all it will do is momentarily fire and die over and over. Fuel pressure is good and holding. Spark is excellent. If I hold it full throttle, the engine will take off and scream and sound great until I let off the throttle and then it stumbles and dies. It is like I have a major vacuum leak but I'm pretty sure everything is installed properly and I have checked everything I can think of. The one thing I am worried about is when I cleaned the engine if I got water in something but I don't know why it would act like this. I've never been so frustrated in my life!. Any suggestions appreciated

Paul

[AFJuvat]

1. Are all of your vacuum hoses routed and attached properly.

2. Are all of your sensor connectors connected.

3. Is there water in the sensor connectors (particularly crank, ref, and head temp)

4. Did you, perchance, move or damage the speed and reference sensors when you removed\installed the transmission. they need a clearance of 0.8mm from the edge of the flywheel.

5. Could you have moved\lost\damaged the pin in the flywheel?

6. Pay particular attention to the vacuum hose that goes from the chassis to the vacuum system right above #3 and to the back side of the intake boot - that is the primary vacuum line on the car.

AFJuvat

[marcesq]

With the engine off work the accelerator linkage and listen for the micro switch clicking (very small click) when the linkage is a rest (idle position). If you do not hear a click try gently pushing the linkage against the switch until you hear a click. If the latter happens, get someone to start the car while you work the linkage pushing it down to engage the micro switch. If you some how changed the linkage dimension the idle switch might not be ingaged.

Also did you change/clean out the idle control valve??

Did you do anything to the AFM (air flow meter)??

[ChrisBennet]

Are you saying it will run fine at any throttle position except idle - like if you have throttle pressed enough to go 1500 rpm?
If so, might it be possible that your idle stabilizer is not working? The idle stabilizer ISV (right in front of the throttle body) should vibrate when the key it on even before you start the car. The ISV allows a metered amount of air past the throttle body when the throttle is closed i.e. during idling.
If the "off idle switch" doesn't signal that the throttle is closed, the computer won't activate the idle stabilizer i.e. no air will be allowed around the closed throttle plate. The off idle switch may not be working if the throttle linkage is a little too tight. If you pull up on the throttle linkage at the throttle you should hear a faint "click" from the switch.
Just a wild ass theory...
-Chris

[marcesq]

Chris: Now that was scary

[84toy]

Thanks for the replies guys. Here is more info.....
Flywheel was never off, idle switch is working and adjusted properly. It will NOT really run anywhere except full throttle. It won't run anywhere from 1\8 to 7\8. At initial start, with no throttle, it will try to idle (very roughly for a few seconds) but won't. ISV is vibrating with key on. I'm not sure how I could have damaged the speed and reference sensor taking the transmission off but I suppose it is possible. Is there a testing procedure for them? How sensitive are they to water? I checked the main copper vacuum line when engine was out and replaced the hose at the plastic Y because it was cracked. I'm wondering if it is somewhere in the sensors since I understand that the DME ignores all inputs at full throttle but I don't know which ones would cause this to happen and if you let off the full throttle for a moment to keep from an over rev, it will die and won't recover even if you go back to full throttle again. (you have to start it at full throttle to get it to rev) While apart, I had added SSI's and new O2 sensor and I even tried the old sensor but didn't help. Is there a way to test the AFM? One more additional comment. If I pull the hose from the idle stabilizer and squirt some fuel in the manifold, it will start easy and idle for a few seconds and die and this would indicate a lack of fuel issue. Can't find any vacuum leaks. More comments appreciated. I could really use the help, I'm totally stumped and frustrated.

Paul

[AFJuvat]

I would go through, disconnect, clean, and reconnect all of the hensor connections. Reverify that the vacuum lines to the fuel pressure regulator and dampener are conected.

AFJuvat

[ChrisBennet]

Marceq types faster than I do so he'll probably beat me to this but here are some sensor tests:

Head temp sensor: Causes full rich condition when disconnected. White connector in the 3 connector set. Sensor reads ~3600 ohm cold, ~300 ohms hot. Reseat connector. Shove a resistor of proper value into connector and see if car works to "test" that sensor.

The speed and reference sensors: Can only be tested with a scope. They seem to be working enough to start the car. I wouldn't suspect these.

Off idle and full throttle switches: You can electrically test these, they're just switches. The full throttle switch looks like a throttle position sensor (but it isn't) on the side of the throttle body.

Air flow meter: Check connector at least. The AFM gets ignored on this car at WOT. Reseat connector.

It's just a matter of time but someday I'm probably going to mix up two of the connectors in the throttle area by accident. Any chance you did this?

-Chris

[marcesq]

After doing all of the above, find someone with a Carrera and throw his/her AFM on your car . . . . you probably will find the answer.

Did you disconnect the O2 sensor and try to run the car??

[jester911]

Try one thing if you will. Put your old plugs back in or if you don't have them put some standard single electrode plugs in. I changed my plugs to platinums a while back and it did things similar to what you describe.

If it doesn't work it is no loss. Some of these cars seem to do ok with the multi electrode plugs and some don't.

[84toy]

I did not install the multi ground plugs, just a standard Bosch Platinum plug. I have found something wrong. When you turn the key on, the fuel pump comes on and STAYS ON. As soon as the key switches on, 87b terminal makes contact. I took the cover off the main\fuel pump relay and both points\coils energize as soon as the key goes on. According to the manual, 87b should only close "when certain parameters are met" such as engine cranking. My understanding is the fuel pump should not run when the key is on. Also the manual says there should be voltage at the injectors with the key on and mine does not (probably would have flooded anyway). I disconnected all the sensor wires and 87b still makes contact as soon as the key is switched. I am starting to suspect the computer. Any thoughts out there? Many thanks to those that are helping.

Paul

[Dan Owens]

If you hosed down your engine to clean it there's a very good chance that you got water inside the electronics for the Air Flow Meter. They're inside the black or dark grey cap on the front bottom of the AFM. There are some tests you can do to check the output and different throttle positions. When they get wet they act in the way you're describing. If you do a search on the archive for Air Flow Meter you should find it. I think I'd be looking here first. If you can borrow a good one from a friend you can swap it out as it's only a couple of bolts.

[Jim Smolka]

Try reversing the speed reference sensor and the TDC sensor. Could be that the two are reversed??

Also, check that the vacuum hose to the brake booster is connected. And the multi prong eletrical connector in the back of the motor and behind the engine heater motor.

[84toy]

I had marked all the wires but tried switching anyway. Vacuum hoses are all installed and correct I have checked everything 10 times. It has to be something not obvious like the computer or a sensor. I need to send my computer to Steve Wong because my chip is soldered in so he is going to test the computer in his 84 and that will rule out that portion of the puzzle. Thanks for the suggestions

Paul

[Dan Owens]

I don't believe it won't run at all with the sensors connectors switched. If it runs when you squirt fuel in into the system then it's most likely fuel supply related. That narrows it down quite a bit. I'm still putting my money on your AFM being bad. Mine did the exact same thing and that's what it was. If moisture gets inside the unit then it shorts out completely or partially and won't send the right signal to the DME computer.