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more info. changed the cat, and muffler exhaust is free flowing and sealed. fuel pressure is 27 psi with the key on and engine off, 45 psi at idle, and 56-58 psi at WOT. the fuel pressure was responsive to pedal and did not surge when car surged also held a stedy 43 psi when i shut the engine off. so i can rule out fuel related problems. but this surging is really annoying and i would despratly like to get if fixed. so fuel is flowing well, lots of spark, free flowing air in and out. would a small vac leak or air leakin a gasket cause this surging and rough idle still have the missfire.

trf_ssei wrote:i was getting p0300 because of my intake gasket leaking, now after all new seals and gaskets in the top end its better but the engine is still not right. you can feel a vibration from the engine at idel and wot but not when crusing. any suggestions?

The EXACT reason im scared to do my PLIM!

Read the plugs please. For some reason, I think the fuel pressure sounds high. I seem to think it should be about 35-37 at idle, and jump up to 43-45 with the vac line off at idle. Correct me if I'm wrong.

higher fuel pressure shouldn't make it surge or missfire though. another thing i tried was spraying carb cleaner all around the vac line connections and basicaly everything i could that sealed against the block. im thinkin its not air leak any more. mabey its internal i dont know, im just frustrated and feel like giving up. im going to check the spark plugs tonight because i changed them before i did the lim gasket, after that i give up. i dont want to dig into the engine to try and figure it out.

Could it be a clogged fuel injector? Maybe changing the fuel filter and adding a really strong fuel system cleaner like Amsoil PI would help...

Pull the plugs and check the gap, color condition. How old are the plugs and wires? did the PCV valve get installed correctly?

what should the gap be with autolite 104s, 180 t stat, high flow cat and cold air. does the gap change.

.45 to .5 is what most people run when blown, but I could be wrong.

i would check the coils i had exact same thing , matter of fact it got worse when it warmed up do the ohmes test

I did check the resistance on the coils and their all within spec.

rharper wrote:i would check the coils i had exact same thing , matter of fact it got worse when it warmed up do the ohmes test

oh and i almost forgot . the check engine light has been on with the random missfire code. today i started it and it felt pretty smooth even after it was warm (that was this morning). check engine light still on. and tonight after work it started and ran smooth didn't surge or vibrate at all, like there was never a problem. also the check engine light is off and i didn't turn it off or reset the computer. does this sound like an electrical problem and maybe not engine component related?

hey guys been a while since i posted on here. im still havin the same problems just to recap and add some new information. my 98 ssei was running really rough and surging and i thought it was only the lim gasket. changed that and it was better but still not 100% the check engine light was intermittantly on and off by it self over the coarse of a couple days. now it hasen't been on in a few months with no difference in the rough running and surging. last week i steped the gas to about 50% kicked down to 2nd from 3rd and the car stalled and then jerked and started again by its self like it was a manual trans. i've already done several checks for vacuum leaks, nothin. i don't know what is causing this. injectors were mentioned and i ran cleaner through but no change. could the injectors be bad. FPR, i dont know, sometimes its worse than others. please help thanks in advance

See if you can replicate the stall/fall out condition by power braking the car (50-75% throttle). Don't do it too long because it gets the tranny very hot. If so, check for bad motor mounts and/or rubbed through wires under the hood.

front motor mount is going. ill check the wires tomorrow. but it always cuts out, not dies but its like the engine dumps power and regains it very quickly. almost like there is a dead spot. it reminds me of an electric motor with dirty brushes. lol thats the best comparison i can come up with.

Have you tested your ignition coils or have spares to swap in?

How is the idle? Is it only doing this when driving? When was the last time you cleaned the MAF and checked the TPS?

trf_ssei wrote: more info: worse when engine warm.

Vacuum leak. Keep looking.

Wrong info posted above. Your plug gap should be stock at .060 unless you're running a smaller pulley, which I don't see in your signature.

just had a thought on the way home from work. i now know all the motor mounts are shot, could that be enough to give the car false knock and make it surge? would bad kr make it surge? the vibration from the engine through the car is pretty bad when i stand on it. also if i step it down from a stop it will make a weird clunking noise only under extream load in first gear. sounds like exhaust hitting underbody but its not.

trf_ssei wrote:also if i step it down from a stop it will make a weird clunking noise only under extream load in first gear. sounds like exhaust hitting underbody but its not.

That may be from bad mounts or transmission problems? Might want to fix the mounts and re-evaluate everything.