Ok Ive had this issue since I bought the car with a stock LS motor and still have it happening with the new vtec swap.
Ill be driving on the highway at 3500 rpms at about 75mph steady then my rpms will start to drop to an idle. The engine wont shut off and wont pick up if I floore it while in the same 5th gear. Ill end up pulling over to the side with the motor idleing fine then get back in rather quick and it runs like normal. In some cases I dont even pull over anymore when it happends I just drop to 4th and rev to 6500 rpms then shift to 5th and it goes away until it randomly happends again.
I’ve had all the engine sensores replaced and the engine harness also.
My original obd0 harness was chopped to have the 00 itr engine obd2 sensores spliced. and the pwo obd0 ecu also was replaced, main fuel relay was replaced months ago and Ive calibrated the tps myself.
so Ive replaced most of the engine electrical and ecu so im stuck.
what ecu are you running?.. you stated that it was doing this with you’re old engine as well correct?if its the same ecu that you were running with the old engine that is definitely something to look at. hope ur not running any of those cheap ass “RACING CHIPS” mess up a perfectly good ecu. if u wanna power out of the ecu… get a hondata system and tune it properly.
another thing i can think of… do the revs spike? by spike i mean do they jump up and down?.. or does it just go to idle 800rpm?.. the ignitor inside the distributor is what powers the rpm tach. usually when this happens its a sign that u need a new ignitor or distributor. i know u said this was happening with ur old engine… are u reusing the distributor that u had in ur old engine?.. well all this is just something to keep in mind an look at…
let me do a little history on before and after, I had a stock 91 LS motor that ran obd0.
then I found a 00 jdm itr motor that ran in a 99 dc2 all obd2.
after much thought mainly do to money i decided to stay obd0 so I had to source out a vtec disstributore from a jdm obd0 b16a engine with a obd0 b16a pwo ecu. Im pretty much running the itr engine as a b16a with a chrome chip. My tunner dialed in all my mods, 62mm t/b, itr intake manifold, obd2 injecotrs and other goodies to help compensate for the extra fuel I needed on the b18c.
My original engine harness had all sensor plugs cut off and had the itr obd2 sensors spliced on, so I have new engine sensors that should of solved the issue.
This happend before my new setup and still happends now, the only thing im reuseing is the engine harness and throttle cable. Everything else is new or replaced since i needed vtec parts.
my idle doesnt spike or bounce not even on cold starts it just drops down to a normal idle of 1k, My setup required me to adjust the idle to 1k incase you guys are wondering. It feels like the throttle closed and no matter how much i floore it the rpms continue to drop, a total loss of power. I have to drop a gear and rev it high so it goes away. even whie driving normal from a stop Ill keep my rpms stedy at 3k and i can feel and see the rpms drop to 2800 so its something that is happening all the time but isnt an issue until rpms drop to an idle. Its kinda strange since it seems to happen more when im at 3k - 3,5k for a long time.
wow… i have never heard or experienced any of the symptoms that you are describing… im clueless… can anyone else help?.. any input on this would mean a lot… their has to be someone who has experienced this and has a remedy for such an interesting problem…
i also replaced the old LS motor for a new 00 itr engine with all 00 obd2 parts on it spliced into the obd0 harness.
New Main relay just replaced about 1 yr ago.
what about fuel filter? though it does sound ignition related, i’m just trying to think what, of the parts that you’ve left in there, would cause this.
you check for codes?
Sounds like the coil and/or one of the distributor sensors are failing. My MIL did not illuminate until the coil died and I was 200 miles away from home. I doubt that it is the igniter because when the igniter dies, you should see the tach needle drop to zero. Also, when the sensors in the distributor go, they will usually throw a code.
yeah it does, last code i pulled when the swap was done is 23 for the knock sensor… It wasnt hooked up so we had to wire it up and plug it to make the cel go away.
Subscribed… I’m also having a similar problem! I hope someone here can help figure this out…
My situation is a lil different though because the rpms drop for a moment ( engine decels while at WOT)but eventually out of no where Clunk! it surges and picks up like if i downshifted really hard. Usually hapeneds while driving @ 3k to 3,500 rpm’s for awhile.
Sorry not trying to thread jack here i know i wasn’t any help at all but I Hope you fix your problem.