snakeyes1837

hello all, I just picked up my new toy, its an 89, its in pretty decent shape, it has a few things that need some TLC, I just have a few questions if some of you can point me in the correct direction.


1. The car has 275/40ZR/17 wheels and tires on it now, would I be able to get away with putting on 245/50ZR/16 wheels and tires on it or will they have fitment issues? (im not the best with wheel and tire sizes)


2. I did a coolant change on it, took the thermostat housing off and to my surprise there was no thermostat in there, I put on in and now the temp holds good at 222 degrees and the fans turn on when they should. The only issue im running into is that when the car comes up to operating temp it starts idling very rough, it spikes to 10/1200 RPM and then drops off to around 4000 RPM and almost stalls out, every once in a while it will stall. I did take the throttle body off to clean it, the gasket is good and all the vacuum lines and hoses are all hooked back up. I came across this odd looking solenoid that I found out is the EGR solenoid. The 2 lines coming in are in good shape but the back of the solenoid has silicone on one port and a screw in the other (I have no idea if that is supposed to be, probably not). The car did idle perfect before I did the coolant flush and thermostat.


Any ideas of what can be going on would be great to hear because im at a dead end.

sluggballz

Welcome to the club!
I would think that keeping the 17's would be a better idea over putting 16's on. If you look around you can find deals on 17's on the interweb and sometimes locally. I bought my 17's online and had a local shop mount and balance them.
I have a 95 with an LT1, so I don't know the particulars about the L98. Maybe disconnect the battery and let the system reset. If that doesn't work then maybe check the IAC. Someone more knowledgable about the L98 will chime in shortly.
Good luck and welcome aboard

Jon Hekking

Can't answer number one, not much of a tire and wheel size guy either.

You need to get it on a scanner and see what happens when the idle changes. I had a similar problem that turned out to be O2 sensors, needed a scanner to figure it out.

Congrats on the car, post some pics

DinoBob

Idle surge may mean you have excessive air in the coolant. Check it out.

cormorant71

When I owned my '88 I had some idle surge, it was a weak fuel pump.

playsdixie

certainly wouldn't hurt to remove and clean the Iac if it's original...spray some tb cleaner up and down the vac lines to see if any cracks or leaks...idle will surge if there is.....welcome to the madness...there are a lot of knowledgeable guys who can help you....(i'm really not one,) just putting in my .02cents

cuengineer

There are lots of sites on the web that compare tire/wheel combinations. For example, you can go to http://tire-size-conversion.com/tire-size-comparison/ and put in the sizes. The diameter of the two you mention are less than 0.4% different so at 60 mph with the 17-in. one, the 16-in. wheel would be going 59.8 mph -- not much difference there. I have been looking for tires for mine and have been told by several dealers that tire choices in an appropriate size for 17-in. wheels are starting to be limited and that if I had 16-in. wheels, it would be even more limited. Based on that, I would try to keep the 17's. Tire manufacturers for performance vehicles seem to be heading more and more toward 18's and larger wheels.

spartangreek

I just had an idle surge problem corrected in my '88 4+3 corvette. It needed a new computer module...ECM. No problem at all now. There are a few different things that can cause it and needs to be checked out thoroughly. My mechanic hooked up his 02 meter to the engine and also monitored the computer sensors at the same time and was getting opposite info. The ECM said either rich or lean, (can't remember which) and his meter said the opposite. He trusted his meter and I had an extra ECM that was a remanufactured unit. He installed that using my original prom chip and all is well. It maintains steady idle around 700-800 rpm's now.

kenmohr

[QUOTE=snakeyes1837;1589617956]hello all, I just picked up my new toy, its an 89, its in pretty decent shape, it has a few things that need some TLC, I just have a few questions if some of you can point me in the correct direction.


1. The car has 275/40ZR/17 wheels and tires on it now, would I be able to get away with putting on 245/50ZR/16 wheels and tires on it or will they have fitment issues? (im not the best with wheel and tire sizes)





keep your wheels