Car surges when I let off gas

[JChalfan]

Here's my setup: '90 5.0 5-speed, pro-flow maf, 24lb injectors, paxton SN92 blower w/ fmu.

I haven't been through the surging idle checklist, because I don't have much of an idle problem. If that's where I should be looking though, let me know and I'll stop wasting your time here.

The car was working great, then I pulled off the supercharger to do some work to it. I put the stock maf bracket back in with a cone filter on the end of the maf so I could drive the car while the SC is off. I disconnected the battery to clear the computer, and so far the car has been through probably 10 full warmup cycles.

So without the supercharger, when I let off the gas after accelerating or cruising, the car surges once or twice. It is more noticable in higher gears, especially 5th on the freeway. It happens right at the transition between being on the gas and coasting. I checked my TPS voltage, it is .96v. I don't have any disconnected vacuum lines or other leaks that I am aware of.

Also without the supercharger, when I first start the car when it is cold the idle surges a little (nothing too major) for about the first minute, then it is fine after that. I don't know if this is related to the surging when I let off the gas.

Anyone have any ideas of what could be causing this? There is no surging of any type while I am accelerating, just when I let off

The SC should be back on in a few days, maybe that will make the problem magically disappear.

Thanks.

Jeff

 

[jrichker]

Is the cone filter inside the engine compartment? If so that is likely to be the source of your problem. I would try clocking the MAF (rotating the MAF housing) to see if that helps. Otherwise, move the filter to inside the fender where the stock filter picked up air.

 

[JChalfan]

Yes, it is in the engine compartment. And come to think of it, I don't have the cover over the cone filter that I do when the supercharger is on. Perhaps the surging is from fanwash?

This setup is only temporary until I get my supercharger put back on, then I'll have the cover back over the cone.

Hopefully that will fix the problem. I'm not going to worry about it too much until after I reinstall my SC.

Thanks.

Jeff