ScottF

Ok, so, I have this problem. The car is surging at around 4,000 rpm while holding steady on the gas pedal. I have checked all valves, cleaned them out and did the seafoam thing. Checked coolant levels, compression, all checked out great. Recently put new plugs in, double checked to ensure proper gap, vacuum lines seem to be in good order, clutch is good. It only happens from 3,500rpm to 4,000rpm. The tachometer needle does not fluctuate when this happens but holds steady. It is especially noticable on stretches of road that have been newly paved. I have tried searching but all I come up with is surging at idle problems. Any help you guys could provide would be helpful...

BTW the stats on the car are as follows

Stock JDM B16B
Chipped OBD-1 P28 using an OBD-1 to 2 harness
Cold air intake

ScottF

No one else has had this problem?

ScottF

Anyone?

ScottF

ttt

ScottF

ttt

ScottF

Come on no one has had anything like this happen to them?

delsolproblems

The engine RPM bounces between 3500 and 4k, but the tach doesn't move? How did you determine that the RPM is surging if the tach is steady? If there is a problem, it would most likely be either an air/fuel ratio situation or an ignition problem. For example: The computer thinks the mix is a little lean because of the O2 reading. It adds fuel to compensate. For one reason or another, the mix wasn't actually lean (maybe from a sensor problem or weak ignition that leaves too much fuel in the exhaust). The extra fuel can either increase RPM if there's enough extra air or decrease RPM by making the mix too rich. When the extra fuel just begins to change the RPM, the computer immediately adjusts the fuel back to where it was to bring the RPM back to where it should be. When the fuel supply is back to where it was at the beginning, the computer will again sense the same lean (or rich) condition and will keep repeating the process. This and other very similar issues is often why RPM's bounce. I have no idea what part or system would be causing your ECU to make the incorrect adjustments but hopefully understanding the problem better will help you figure it out. GL

ScottF

It's not surging between the RPMs, that is when it happens. It feels more like a 100-200rpm surge. It's more a seat of the pants feel. What you described there, would it cause any harm to the engine? As I said, it's noticable, but not severe. When I get on it, the RPMs are smooth and VTEC hits hard at 6500 rpm. Would a bad fuel filter cause the problem? The guy at IMW who did the work on the wiring harness had to splice the 2nd O2 sensor into the first one to trick the P2P ECU I was running at first( that is a long story) to think that it had 2 good ones. However, the P28 ECU is OBD so it would not look for the second one, right? I do notice an occasional backfire pop sound when I let off the gas from time to time...

delsolproblems

Oh no, it wouldn't damage anything. It would basicly be like the first little hiccup of a problem starting before it gets bad enough to cause a misfire. Often, motors whose only problem is a surging RPM are otherwise in good condition. The previous example sort of demonstrates a situation like this. That motor would probably need a strong ignition and compression to not misfire when the ECU mistakenly maladjusts the A/F ratio. You can check your grounds, check the spark at each wire, check the ignition timing, test the intake vacuum, test the fuel pressure and/or check the engine sensors. Alternatively, you could go ahead and replace any parts that are due or you could just wait for the problem to exhibit more telling symptoms. Until there are more symptoms, there may not be any way to pinpoint the cause without major diagnostic equipment or checking everything, one system at a time. The fuel filter could be the culprit but it's not more likely than anything else unless you have reason to think so. Yeah, the P28 is fine with the one sensor and there would be a code if it wasn't. When you let off the gas two important things happen- compression decreases and intake vacuum increases, so you'll first want to check the MAP sensor, intake vacuum and the spark at all four wires.

shogee

check the tps voltages... at closed throttle it should be .5v and when you throttle it up voltage should go up smoothly, keep at around 3-4 where you have the problem and see if the voltage jumps around

ScottF

Thanks, I keep on top of maintenance, and am a little paranoid when the slightest problem comes up. Spark is good at all 4 wires, this was checked when I replaced the plugs 3 weeks ago, also they were properly gapped. What grounds would I check. When it comes to wiring I am not that proficient so some sort of starting point would be appreciated when it comes to that sort of thing... The fuel filter does appear to be original to the car( it does not look like it was ever replaced)...

@shogee, I do not notice the problem when the car is parked, it is only when the car is under load...


BTW, when I got the swap done, the shop dyno'ed the car, at the wheels it made 174 hp and 115 lb-ft of tourque. Is that about right for a B16B in good condition?

shogee

so it's tuned on the p28 right now? could be a tuning issue. sounds like a misfire to me though, very intermittent. replace the cap and rotor yet?