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My 92 is a real 'dog' most the time except When cold outside... What could be wrong??


JAG1

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When ambient temps are around 30 my 92 just comes alive with power. It's amazing :hyper:.Most other times it's a real slow dog. What could be wrong? There's no intake leaks either.It's gotten so bad on warm days I have to wait till traffic's clear for a whole mile otherwise it's like cuttin' in front of someone:duh:

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Check for a stuck waste gate. Fuel and air filters good? Air leaks in the fuel system or week lift pump, does it start and run smooth otherwise?The Air to air coolers make a big difference from what the 1st gens had for sure and it is apparent when your 1st gen get some colder intake air.

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92 6BT engine are really simple fuel systems. I would look at the diaphragm on the AFC and fuel pin and check it for holes, make sure the fuel pin isn't sticking. Since boost controls the fuel pin and the fuel makes or breaks the power I would check that out first.Stock air system on a 92 should have intercooler (air to air cooler) and already have a cold air intake in the front passenger side of the radiator support.

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Thanks to guys....The trucks starts easily on cold mornings without the grid heaters and block heater not plugged in. A little rough for a moment or two but always smooths out nicely. It has new air and fuel filters. Lift pump has about 20,000 miles on it but a small very slight leak nearby. Been working on that one... just always a bit wet but, with no drips on the ground.How do I check and where is the AFC diaphram and fuel pin??Oh yeah... a couple times on warmer days it came alive but only happened about 3 times a year ago. Now it never does unless it's cold outside it runs great then.

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Don't the VE pumps have a KSB solenoid to alter the timing slightly to aid cold starting?

Yes. Its controlled by the IAT sensor and connected with the Fuel cutoff solenoid.

How do I check and where is the AFC diaphram and fuel pin??

Posted Image

The under the cap where the smoke screw and the starwheel is at will contain a diaphragm, spring and a fuel pin. The star wheel sets the prelod on the spring vs. boost. The fuel pin should be marked before removing because is ca be tuned by twisting. You'll see the offset of the pin when removed. My buddies 92 had dried up grease on it and tend to stick. After clean up and re-lubing it worked fine.

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Thank you for the pic and explanation. What I'm hearing from you guys, if Iam careful, I will be able to open this cap and see right away what to look for.Thanks again.

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Yes.

There is a diaphragm right on top mark its position it came out. Then pull straight up. It might hang up on the fuel pin push it down and then pull back up. Then you get it out and be able to clean and lube the pin again. Check the wear of the pin as well. Turning the pin position will either steepen the fuel ramping or make it milder.

Here is a modified pin...

Posted Image

Here is stock to wild.

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Under the cover..

https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcS3lwyi8v6uRkvmU0uJ2WtOk8yr35H_Gy47qoe2F7CQ-YUaYCVZiQ

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Thank you. Thank you. Thank you. That's amazing. So clean the pin and relube with a light film of grease and check the diaphragm. Take note of its orientation with the mark.

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Okay I did as described above, checking diaphram and cleaned and lubed the fuel pin. Maybe runs a little smother but still has the same lazy horse power as it was.

 

What to check next? I rechecked all clamps and hoses.

 

How do you check for waste gate problems?

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How do you check for waste gate problems?

 

If you have the stock turbo on your 92 its a non-waste gated turbo so there is nothing to check with that.

 

Something worth checking would be the fuel shut off solenoid, sometimes the rubber plunger can have pieces come off and that could possibly restrict the fuel flow through the injection pump if a piece is big enough.

Edited by bjytech
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Thank you, I will report back on this sometime between now and New Years.

 

 

Do you just take it apart or take it off the pump to see?

 

I know very little about injection pumps .... I will try.

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Problem solved.....Not sure what did it. Bj's suggestion showed everything clean and in order on the solinoid However the electrical connection was loose and dirty. I fixed that. Next I pulled the fuel pin one more time to turn it to the left a little bit since the power seemed worse from my first attempt.

 

Thanks to everyone here and now the truck even has more bottom end torque. It's great!

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