1986_IROC-Z

Hi folks, picked up a 1986 Iroc just a few days ago and it had supposedly been in storage for more than 10 years. 59k original miles. It now has brand new tires, the brake fluid has been swapped, fresh oil and filters, new battery, other fluids checked and topped off. Everything looks good and clean. I took her on her maiden voyage last night, first 54 miles back on the road. A couple of questions:

1. Hard start issue:
When I went to see the car before buying it, I immediately noticed the fuel pump didn't prime on key-on. I tracked it down to the fuel pump relay. Actually, I did somethings stupid, and I tried swapping the connector for the MAF power and the fuel pump relays around (same size relays--didn't even think they might be different), but, it worked. I did that based on a thing I read on here, someone suggesting to jump a tan wire with a green wire to check connection and I saw my connector at that relay didn't have those colors--but the one next to it did! Now, the pump primes on key-on. No CEL, and no CEL for the entire drive. I'm wondering if the connectors were accidentally switched and switching them back fixed it? The car starts easy when cold now, so I think the lack of the f/p priming was the cause of the hard start. How do if I know if the MAF is functioning properly? Would the CEL set if not?

2. Rough idle when warm, intermittent, when car brought to a stop
When I bought the car, I believe I found a vacuum connector for the EGR unplugged, with the bottom port plugged with a carriage bolt. I thought, "well, that's stupid..." and plugged it back in --reminding myself to test for proper EGR function before the drive. Got excited and left without that carriage bolt
Is it possible that the EGR valve is intermittently sticking? Sometimes when stopping, the car idles fine. What do you think might be the issue here? It only happens when warm, never when cold, and sometimes it idles just fine at a stop.

3. Oil
I have a copy of a service manual and it quoted 10w40 for the LB9 305 TPI. When I looked at the oil cap on the car, it says 5w30. Which is the correct weight? If I put the 10w40 in, will it really matter? I'm thinking I might keep it in there while I figure out all these starting and idling issues and then dump it once the engine is running clean and smooth depending on what the correct weight is.

Sorry for the long read...thanks in advance, and I'm happy to finally be a part of this community after many years of looking for the perfect 3rd gen to own and restore!

Camaro86IrocZ

iTrader: (1)

First off, Welcome.. Being an '86 with low miles check what number your prom is, they had some issues in the beginning..
http://www.gmtips.com/3rd-degree/dox/tips/ecm/prom.htm

The oil weight won't matter so much, I ran 20/50 in mine for years and only recently went back to what the cap says and now run 5/30 with STP additive.. I had my '86 in the barn for about the same amount of time

eseibel67

MAF problem will set CEL.


I assume you have fresh fuel in it. Get the injectors cleaned. You said you changed the filters, hopefully that included the fuel filter.


Use 5W30 oil as specified. Thicker is not better in this application.

1986_IROC-Z

Thanks guys. New gas; yes, new fuel filter; yes. I still think there's something going on with the EGR solenoid or a plug somewhere because the car runs beautifully until it randomly doesn't, but only when at a stop. But I need to read more on testing procedures and how to go about tearing into all that TPI stuff on top.

While driving I discovered that Cruise control doesn't work so maybe there's a vacuum leak somewhere. Or maybe the GM wonder-switch is just borked--the wipers won't work unless the switch is set on high, and they won't park themselves. So who knows.

Finally found a wiring diagram that confirmed the connections of the fuel pump relay and MAF power relays-- the yahoo before me had them swapped. It works better my way

Camaro86IrocZ

iTrader: (1)

I'd run a bottle of Chevron Techron fuel cleaner thru it, but that's just me, you would think with that low mileage the wiring wouldn't be touched, guess some guys just can't keep their hands off... If all else fails on the wipers, rain-x works really well..