sohcfun

whats up everyone i was wondering if you guys could help try to figure out whats going out with my car. it drives fine until i get going about 60 mph. then it starts (in the best way to describe it) jumping (the motor), and it sounds like it spits out a burst of air at the same time it jumps.

any ideas on what it could be or what i can try to replace to fix the problem?

thanks

Fabrik8

Spits out a burst of air from where...?

So when it starts misbehaving, does it matter if it's at part throttle, or at heavy throttle, or at a certain RPM (does it do it in 4th gear and not in 5th gear because the RPM is different at 60 MPH, etc...)?

TongWoo

sohcfun

Almost sounds like its from intake mani, and yes will happen in 4th and 5th gear, when it starts acting up, it will not aloow me to go any faster.. like I can put the floor and still won't go, nor will rpms go higher..

Fabrik8

So it's doing it at 60MPH in 4th and 5th gear...?

sohcfun

Yeah both 4th and 5th

Fabrik8

I would suspect a vehicle speed sensor problem, or some kind of compatibility problem. It almost sounds like the ECU is enabling the speed limiter.

The speedo and ECU both read the same VSS on all Civics as far as I know, so I'm not sure what would affect the ECU and not the speedo, unless the ECU is looking for a different number of pulses than the VSS is putting out. Oddly, the JDM speed limit is 112MPH I think, which is about double the 60MPH you're seeing. I really have no idea if there are differences in the number of pulses put out by the different transmissions though, but I think they're all the same. Maybe auto and manual trans differences, can't remember. Honda is pretty good about keeping things interchangeable though..

This could be as simple as a bad or broken connection at the ECU. I could maybe see a ground reference problem at the ECU causing the number of pulses to be counted as double, and the speedometer does its own counting so it would not care about any problems that the ECU is having. That's hard to swallow though, because it's a 5V square wave signal that shares the same ground with a lot of other things, so too much noise on the speedo signal would be more likely. Sorry, I'm mostly talking to myself at this point.

Something doesn't really add up..

So any speedometer problems, like the needle jumping or anything like that?

sohcfun

A couple of my friends a thinking maybe fuel pump?
But no, there are no problems with. The needle jumping at all, and strange thing is on my cluster the 55 mph is red/amber? And the rest are white


And I have a spare p28 and the house, were trying to plug it up to see if anything changes?

Fabrik8

If it was a fuel pump problem if would depend on the fuel pump flow and loading, and you should be able to replicate the problem at the same engine load and RPM in any gear (at speeds roughly dependent on each gear ratio). So if the problem happened at the amount of fuel flow for say 100 HP, the problem would happen at that same RPM and throttle position in 2nd gear, and 3rd gear, and 4th gear, etc. I just don't see the fuel pump theory making sense...

sohcfun

Yeah that's how I feel, I just don't know what to replace to see if it will fix it...I just tried pcv valve no luck tried fuel filter, plugs, wires,