Surging, missing, sputtering.

[TBI355]

.030 over 350, flat tops, stock heads shorty headers, true duals. Truck starts and idles fine most of the time. Occasionally it will start surging @ idle, 900 rpm down to 400 and back. runs really crappy while driving, like its only running on 2 or 3 cylinders. Mash it to the floor and it downshifts and clears up. Just put a new egr and tps. Temp guage working intermittantly. new temp sensor. still only works sometimes. Do I have a computer problem here? Any info would be greatly appreciated.

 

[TBI355]

Oh, and no check engine light.

 

[bluex]

Which temp sensor did you change? ChrisAU had a similar problem and it wound up being his O2 sensor, he also had no codes.....

 

[illinoisboy]

Well to me i kinda sounds like the fuel pump is going out, but im probably wrong. just my $.02

 

[bluex]

Ya would be a good idea to check fuel pressure too, I didn't think of that.....

 

[TruckinAin4Sissies]

Check your dizzy/drive gear. That was my issue.

 

[TBI355]

Well, I replaced the CTS thats in the front of the manifold, and the one in the drivers side head. I bought a Autozone Bosch 02 sensor and it made no difference. I also heard on this forum that anything but a Delco is junk. I replaced the fuel pump about a year ago, before the new motor. Got that at Napa. I believe its a Walbro. I'm leaning twords a computer problem. Possibly a cam compatibility problem. If I unplugged the MAP sensor I should see an improvement if thats the case? Im not sure what cam the engine builder put in it but he said its a bit hotter than stock. I'm going to stop over there Wed to see if I can get a cam card from him. Thanks for the input! Im open to more suggestions, and Ill keep yall posted.---Corey

 

[SAATR]

I wouldn't write the cam off just yet. Hook up a fuel pressure gauge and see where you stand on that first. If you can hook it up and route it over the cowl and tape it to the windshield so it's visible while driving, that would be even better. The idea is to see what your fuel pressure is doing when the miss/surge occurs. If it spikes or drops off when the problem occurs, you have fueling issues. I don't know if you've done anything to your ignition (I would assume it was freshened up with the motor) but that would also be a good thing to look over. I would also recommend a custom tune, to make sure your fuel and spark tables are where they need to be for your new hardware.