so I have a 89si with a b20b swap, converted obd1, running great for 6 months with no problems until the other week.

I was out driving for about 30 minutes and it was running fine, and I pull up to my house to park and I do a uturn to whip around into my spot, and right when I dropped it outta gear and the idle went down, it was running veryyy, rough, the 400-500 rpm range, lots of missing and wanting to stall out. My tach was acting strange so I'm not certain, may have been lower.

There are no CEL at all. First thing I did was check timing belt, dead on, couldn't check dizzy timing accurately. Went thru full range checking for improvement with no results, still ran very poor. Then I ran a compression test and replaced the spark plugs, compression test turned out good. After that I had a buddy let me try his dizzy, no change at all. With my buddies dizzy still on I swapped in a different set of plug wires. No change. Next thing I did was deep cleaned all of my grounds and made sure they were all getting solid contact. The battery in the car is only 6 months old maybe. I've checked tps calibration and it's spot on. I've looked over my vaccum lines and from what I can tell they looook fine, that doesn't mean much tho, I'm just trying to run it as little as possible cause it doesn't sound very healthy at all.

All input appreciated, thanks!

 

Ive been trying to find someone with an ecu I can try but haven't had any luck.

 

check the valve lash. too tight will cause crazy rough running and misfires

 

Would that happen so suddenly like this tho?

 

Fuel pump?

 

Know anyway to check it? Or diagnose it?

 

On my race car with B18C type R engine, one time at the track the idle speed suddenly dropped and stayed really low. I forget if the CEL came on, but when I checked for codes (Hondata S300), it showed a code for the IACV valve. The car got thru the weekend OK as it would run OK on track, but would just idle really low. I tried cleaning the IACV valve but that didn't fix the issue, but I then found a few replacements at my local Honda wrecking yard that did fix the issue. I'm not sure if the B20B has the IACV valve, but if it does, then it might be a factor. - Jim

 

Yeah I was thinking about trying to grab a few from pick a part last time I was there but didn't see any at the yard I went to. That would be a cheap fix so it definitely couldn't hurt to find one.

 

it can yes. usually the symptoms will creep in gradually, but depending on temp of the valves it can be a sudden change. if it's been more than 20k miles since valve lash was adjusted, it's overdue anyhow, so either way you should check it out.