Still troubleshooting

[msggunny]

Ok, so i thought my alternator was going bad. The RPM gauge would fall to zero while the engine was still running, which from reading the RAVE means that the alternator isnt sending signal out to tell the RPM guage what RPM the engine is running.

Put in a new (rebuilt) alternator and it did it again. Only once so far but still intermitent.

Anyone know of any other reason why it would do this?

Also its doing the "i want to run like shit when i feel like it" thing. It drove fine yesterday, when i went to work today she was a flaming cunt. Power would cut out, surge, fall on its face, etc. I could push the gas pedal a 1/2 in and nothing would happen and then it would surge, as though there was a distinct lag.

I did hook up a fuel pressure guage and drove it around the other day. Didnt notice anything out of the ordinary. However i did notice that the pressure will go up and down a bit depending on how much throttle i was giving it. (normal?)

 

[thospb]

Fuel pressure should stay within a few psi all the time. There are a lot of posts about poor quality in rebuilt alternators. You should have 14.2V +/- with the engine running, 12.6V at the battery with engine off and no loads. The old standby cause for intermittant problems is an electrical ground.

 

[mbrummal]

I think the fuel pressure regulator has a manifold reference. It will change with the the manifold vacuum and therefore the throttle position (higher pressure with more throttle).

 

[msggunny]

Fuel pressure should stay within a few psi all the time. There are a lot of posts about poor quality in rebuilt alternators. You should have 14.2V +/- with the engine running, 12.6V at the battery with engine off and no loads. The old standby cause for intermittant problems is an electrical ground.

Got 14.21 at the alternator and 14.16 at the battery (engine running)

As per usual she ran fine on the ride home and then started her shit 1 mile from the house. 30 miles she ran fine, guess she didnt want me to forget about her.

 

[discoverytowne]

Is there a check engine light?

 

[msggunny]

Is there a check engine light?

Nope.

No CEL, new TPS, VSS, IACV, spark plugs, 8mm magnicor wires.

Fuel pressure is good, fuel pressure regulator works fine.

My thinking is still ECU, Crank Pos Sensor, or Lucas is a cunt.

It started doing the "fall on its face while driving momentarly" thing again today. Hadnt done it in a few weeks.

 

[discostew]

If you have advanced evaps watch your tps when w/some kind of scanner when it happens. If you dont have a scanner then just unplug the fuel tank pressure sensor and try driving it .

 

[msggunny]

If you have advanced evaps watch your tps when w/some kind of scanner when it happens. If you dont have a scanner then just unplug the fuel tank pressure sensor and try driving it .

Done that, running a SGII and it reads the same when i release the throttle and idle. No fluctuations in TPS.

I did throw a 0451 code the other day and the gas cap was on correctly. It went away and hasnt come back.

i am going to unplug the sensor and see what happens.

 

[RoverbyProxy]

What are the condition of the grounds? Clean them as well.

 

[crown14]

Replace the ECU.

 

[msggunny]

New observation.

For what ever reason i never noticed that it only does it when the engine is warmed up well, it doesnt do it when i start up cold and drive around. It runs fine, idles fine.

Input from the coolant temp sensor maybe?

 

[cosmic88]

that is possible but with the coolant sender being a prob I'd think the symptoms would be less intermittent... rule out Fuel temp sensor is only a factor at startup and that value has no bearing on EFI after closed loop conditions are met.

AEL or no on your rig?

Ground issues can be intermittent like the others are saying.

As annoying as it would be have you been able to do a full continuity check of the harness from the sensors all the way back to the ECM plug?

 

[crown14]

For what ever reason i never noticed that it only does it when the engine is warmed up well,

... and the ecu is under the hood.

 

[discostew]

So it still acts up with the fuel tank pressure sensor unplugged ? It shares the ref. voltage of the TPS and causes what your describing when it gets shorted . You never mentioned having to restart it. If it doesnt stall when its doing that crap, thats relevant.

 

[msggunny]

So it still acts up with the fuel tank pressure sensor unplugged ? It shares the ref. voltage of the TPS and causes what your describing when it gets shorted . You never mentioned having to restart it. If it doesnt stall when its doing that crap, thats relevant.

Yes, its unplugged. No change in the way its acting.

It isnt stalling out all the way, right now. Just falling on its face. It was doing it a little while ago and then stopped. I am going to unplug the VSS again and run it to see if it will still do it.

Joel, once i get the ECU checked properly i will rule that out. I dont have the resources to run out and get one that is unlocked, especially if the one i have is good. (which i doubt, but still wont do until its proven bad) Getting it checked is high on my priority list but I dont have access to something that can read it and am waiting for a friend to hook me up when ever he can get around to it.


It is AEL.

 

[crown14]

Determine the pn on the ECU and find a used one. Sometimes replacing a D1 ecu is plug and play, sometimes is isnt- BUT if you get the green security box from the same vehicle you dont need to "unlock" anything.

Is the same ecu in the truck from the carwash incident a few years back?

 

[msggunny]

Determine the pn on the ECU and find a used one. Sometimes replacing a D1 ecu is plug and play, sometimes is isnt- BUT if you get the green security box from the same vehicle you dont need to "unlock" anything.

Is the same ecu in the truck from the carwash incident a few years back?

I have access to one, i just have to wait for my buddy to get a chance to get with me and do it. He has a T4 too, so if it needs "unlocked" we can do that.

It is the carwash computer.

 

[singingcamel]

Dumb question but you never know, Is all this happening with the Air on?

 

[msggunny]

no such thing as a dumb question (so I have been told)

No it does it with the a/c on and off.

Dumb question but you never know, Is all this happening with the Air on?

 

[Keanan]

Check/clean battery terminals and every ground. Also check connectors.