apie2546

Just had the intake manifold replaced on my 86 t/a fi 305. Water pump has well. Had a pretty awesome coolant leak. Now I got it back from the shop and they said it threw code 41 and said it was running lean. Which personally it always smelled like it was running rich but I just said okay and went on my way. Now here's where it gets interesting..

I love to drive so as soon as I got it back I drove for a while. About 40 miles. Here's what happens. On initial cold start it idles real rough and hesitates and ses light is on. After about 5 minutes or some wot it goes away. The only thing is a barely noticeable rough idle. Drove Highway for a while and no hesitation and no ses light. It goes away almost instantly. Pull off Highway and still no issues. I turn it off and back on and it idles rough, ses light and a light hesitation. Then it all magically goes away.

I've checked most visible vacuum lines and couldn't find a leak. This is a pretty specific issue so I was wondering if anyone had any advice on it.

Nothing looks unplugged. Still sounds good. Just would like to get this rough start smoothed out

Rolling Thunder

I'm going to take a guess and say it is running rough until it switches into closed loop operation. When you first start the car its running in open loop mode which basically means the ECM ignores the 02 sensor. When it switches into close loop mode this is where it starts to take the o2 sensor readings into account and make adjustments the the fuel mixture. To sum it up, if you have an issue and your in open loop mode the ECM cannot account for or try to adjust the fuel mixture to compensate for it. In close loop mode, the ECM will try it's best to correct the fuel mixture.

Since I assume you do not have a scan tool, first things first lets ring out and deal with whatever codes are present in the ECM. Code 42 has to do with the ignition timing. Essentially what its saying is the ECM cannot control the ignition timing either because the EST signal is not being grounded out when it should be ignored or it is being grounded when it should not be. Several flow charts available online which show how to troubleshoot this online if you do a search for obd1 code 42.

I would also be curious to pull a few spark plugs and see if they are running lean or rich. Particularly the two in front vs the two in the rear.

apie2546

So I went to pull the actual code this morning and there wasn't a thing. Started up and idled fine and drove it to work.

When I started it back up after I went in to clock in it turned on just fine. Idled up to 1300 and dropped down probably because of all the rain. It idles a little rougher than before but really nothing I would write home about. I still think I will take it back to my mechanic since I have spent upwards of 2k there.

rusty vango

any time the CEL comes on there HAS to be a code stored. you can check your codes and post your findings here and we can help you out.