Power problem
 

98 EX 5spd

It has been getting significantly worse. Started out as a light stutter around 2k rpms, but has grown badly. I'll be accelerating, or driving down the highway and the power will cut out either for a split second, or for a long while. When it cuts out for more than a split second, i have to release the throttle and reapply, or floor it and power will be back on. Often, power cuts out completely like i took my foot off the throttle, or it cuts back on power a good bit. It makes driving very shaky as it constantly fluctuates, and i often have to floor it everywhere. It happens so much that i'm constantly battling it even on short drives. Constantly flooring or pumping the throttle.

One thing i noticed is that if i maintain speeds above 80mph, the issue doesn't pop up. I made a 4 hour trip this weekend and had to set cruise control at 80+.

Things i've replaced: plugs, wires, cap & rotor, ignition coil. I've ran seafoam intake and through brake booster and 2 other types of fuel system cleaner. I'm not spitting any codes whatsoever, except an oil pressure code for the vtec solenoid (havn't gotten around to buying a new one yet). I also got a throttle body from ebay with a different map & tps sensor. Didn't change a thing.

I don't think its an ignition issue because my MPG is 28-30 city/hwy mixed. Also, the car doesn't backfire. The only thing i can think of is a fuel issue. I was thinking either the FPR or the fuel pump, but i have zero issue with startups. It always starts up quick without issue.

another note:

I can often hear a very light whistling noise sometimes coming from the engine when it happens. Not sure if its related.... I hear absolutely no knocking or pinging when it happens though.... which i thought was odd

4 cyl or 6 cyl...No stored codes beside the 1259..Have you cleaned the egr ports?

no other codes.... 4 cyl

Only heard of EGR ports clogging in 97 and below. Ran seafoam through brake booster as well which should have done something, but there was no change.

Also may be worth mentioning, car has 250k, but the engine has 150k. The previous owner had a shop swap over a new engine after overheating and did a halfass job. Random lines weren't routed right, in fact the AC was routed poorly and one of the metal tubes was rubbing against my clutch arm and finally wore a hole through it. Now i have no AC. I have to get a replacement pipe from the dealer & recharge the AC now.

I'm worried that he may just not have hooked certain things up that would normally have spit a code by now??

nothing?

Those lines typically do not wear out, so I would consider buying one from a junkyard, if you have a pick-n-pull nearby.

The 98 4-cylinder has an egr port. It runs up the passenger side of the intake manifold and into the throttle body (or the upper intake). You would have to remove the upper part of the intake manifold to clean it out. Seafoam will not clean this out. It may be worth a shot.