Rough start and bucking at low RPMs

[PHILLY_SVT]

I recently got a new motor (93 Mark VIII w/40K) installed due to my rod bearings being shot. Car runs rich which I think a tune will fix but it may be part of the issue I am currently facing. On a cold start, it takes me 3 attempts to get it running. The first 2 attempts start and then sputters to a stall - even when pressing the gas. On the 3rd attempt, it runs just fine. I have tried priming the fuel pump a few times with the key without any change. The other issue I am facing is that the car is bucking or sputtering at low RPMs (below 3K) when I am just cruising. For example, I will be in 2nd gear in the neighbor hood going about 30 and it will be bucking and sounding like its missing.

Any ideas on what the issue is or some tests I can perform to narrow down what I am looking for? I was thinking O2 sensors or potentially the fuel pump (car has a new fuel filter).

 

[96GT226410]

I recently got a new motor (93 Mark VIII w/40K) installed due to my rod bearings being shot. Car runs rich which I think a tune will fix but it may be part of the issue I am currently facing. On a cold start, it takes me 3 attempts to get it running. The first 2 attempts start and then sputters to a stall - even when pressing the gas. On the 3rd attempt, it runs just fine. I have tried priming the fuel pump a few times with the key without any change. The other issue I am facing is that the car is bucking or sputtering at low RPMs (below 3K) when I am just cruising. For example, I will be in 2nd gear in the neighbor hood going about 30 and it will be bucking and sounding like its missing.

Any ideas on what the issue is or some tests I can perform to narrow down what I am looking for? I was thinking O2 sensors or potentially the fuel pump (car has a new fuel filter).

What intake manifold you running? The drivability issues sound like your IMRC's. Did you clean them or check them?

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[PHILLY_SVT]

I swapped my original setup over so I have my cobra injectors, manifold, MAF, intake, etc. IMRCs are zip tied. My short term trims are .8 - .95. I would think if the IMRCS where an issue I would see higher than 1. No?

 

[96GT226410]

I swapped my original setup over so I have my cobra injectors, manifold, MAF, intake, etc. IMRCs are zip tied. My short term trims are .8 - .95. I would think if the IMRCS where an issue I would see higher than 1. No?

If you zip tied them open and don't tune it you'll run like shit under 3,200 RPM's. If the control boxes work then I suggest taking the zip ties off.

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[PHILLY_SVT]

I am getting getting error code P1516 which makes me think they actuator is toast. I do have an SCT X4 so I could throw a tune on it if you know of a good one.

 

[96GT226410]

I am getting getting error code P1516 which makes me think they actuator is toast. I do have an SCT X4 so I could throw a tune on it if you know of a good one.

You might be getting the code because the IMRC's are zip tied open. Take the zip ties off, unhook the battery for twenty minutes, and drive it.

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[BW96Cobra]

Contact another tuner, use the data logging feature of the X4 to send them what they need, and upload their tune. I know BAMA helped me understanding exactly what was in the tune on my car. Give them a call.