I spilled my latte at Carbucks (engine problems)

[RichMason]

Dear group,

I need some technical assistance with my 87 951. Since I bought it, I have had problems with the car surging/bucking/hesitating under less than full throttle up to 4000 rpm, especially when it is cold. I replaced the TPS, which had little effect. I removed the aftermarket chips, which improved the overall smoothness of acceleration but did not help the surging. Finally, my mechanic worked on the mixture when it was in the shop last week. I'm getting 0.0% CO (Co2 whatever the important one is) with the 02 sensor connected and 2.5% with it disconnected. The car starts fine and idles well. Do these numbers look appropriate? What else would you suggest I check.

[ae1969]

I would look for an intake leak, take a good look at the octopus of intake hoses underneath the intake, also the intake boot.

Under full throttle there is enough fuel to compensate for a small intake leak..... but if you have unmetered air entering the intake then you will have this bucking you may be referring to at part throttle.

[ronin]

I agree. I have a tiny bit of surging and stumbling under acceleration as well and believe that it most likely is the result of a leak. I'm not sure what the exact numbers should be, but your O2 sensor does appear to be working correctly

[magtech]

every check yuor fuel filter to see if its plugged?

[RichMason]

No...haven't checked that. Does the fuel pressure rise with RPMs so that a blockage at low rpms would resolve itself at higher ones?

[magtech]

i am not sure if it does... it could be a slew of things. but if your filter is plugged you would get sufficient fuel at idle and not enough when you need it..... maybe check the wires... see if they are arcing when you rev it up.

[ronin]

do you notice any black/grey smoke under hard acceleration?