1999 Firebird Surging Issue

[hearsedriver]

Hey guys. New member here with a newly acquired 1999 Firebird. A quick history of the car. 6 years ago, it quit running and was pushed into the owners garage where it sat until I purchased it. Absolutely beautiful car inside and out. It had a bad fuel pump which I replaced . After driving it a 100 miles or so, I found that the lower intake gasket was leaking coolant on top of the engine so, I replaced it also. The car starts and idles perfectly. The issue Im having is a surge while driving it until it warms up. Its a mild surge that is rhythmic at about once per second with maybe a 50 -100 rpm drop. After it warms up, it never surges. I have cleaned the injectors, replaced the fuel pressure regulator, replaced the spark plug wires, and cleaned the MAP and MAF sensors. I get no CEL or codes whatsoever. Im beginning to wonder if I am feeling a TCC lockup issue. The trans fluid looks good but I dont know when it was last serviced. Do you guys have any ideas on this? Thanks, Cliff

 

[melsg5]

Any chance you have an advanced scan tool to check things when driving.
If it happens only when not fully warmed up, look for a minor vacuum leak, small crack in a hose.
Other thought is temperature sensor not providing correct temperature to ECM

 

[hearsedriver]

Any chance you have an advanced scan tool to check things when driving.
If it happens only when not fully warmed up, look for a minor vacuum leak, small crack in a hose.
Other thought is temperature sensor not providing correct temperature to ECM

I have one thats about 20 years old. What should I keep and eye on ? I did get a PO442 code a few days ago but figured it was a loose fuel cap. I couldnt find a leak in the evap system. I've looked for a vacuum leak but cant find anything obvious.

 

[melsg5]

Did you clear the code and did it come back.
When fully warmed what does the temperature read?

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[hearsedriver]

Did you clear the code and did it come back.
When fully warmed what does the temperature read?

Yes, I did clear the code and it hasnt came back yet but I've only driven it about 60 miles. The engine temp gauge on the dash reads about 210 when fully warmed up. I installed a 190 degree thermostat.

 

[hearsedriver]

I almost forgot. When it is surging, if I maintain my speed with my right foot and lightly apply the brake with my left, the surge goes away immediately. That made me think it might be a torque convertor lockup issue.

 

[melsg5]

One source shows on a 350 with 700 trani the plug for the converter, 4 wires, left side of transmission near shift cable. Unplug it and it won't lock . See if that effects the surging.

 

[hearsedriver]

It does it when its cold up until the temp hits about 200F. I can see the tach move about 100-200 rpm in a rhythmic motion and can feel it too. If I lightly ride the brake pedal, it goes away which makes me think it the torque converter slipping. Isnt TCC lockup suppose to happen only after the transmission fluid temp reaches a certain point? According to my scanner, the TC is getting a command signal once I reach about 1800 rpm. Im pretty lost when it comes to transmissions. Anyone here have any suggestions? Thanks

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[melsg5]

Never heard of transmission temperature related to lockup. Did you try unplugging it?

 

[hearsedriver]

Im just going by what the service manual says. I havent been able to reach the TCC plug yet. I think its on top of the transmission.