1991 ZR1 ODB1 Port Location-Diagnosing Rough Running ZR1
 

A new 1991 ZR1 owner here, I have a few questions (yes, I did try the search button :)

Where is the ODB1 port located? I did not see it under the driver's side dash. Do I nee to remove any panels to get to it?
Which USB cable do I need to read codes using my lap top?

Very rough running car here...

Thanks!

Re: 1991 ZR1 ODB1 Port Location
 

if the 91 is the same as the 90, and I think they are, it's about half way down the interior colored panel that's by your knees and it has a black plastic cover on it that pops off. I don't have any softwear to read codes, just gordons plugs, but i'm sure someone will tell you what they use shortly.

Welcome to the forum. What seems to be wrong with your car?

Re: 1991 ZR1 ODB1 Port Location
 

It would not be unusual to find the ALDL connector stuffed up behind the drivers side hush panel. If the cover "Diagnostic Connection" is missing there would only be the connector visible and it's mounted towards the rear edge of the drivers side hush panel right of the column. It could easily be overlooked I'd guess if you didn't know where you were looking.

In this post you can see it's approximate location to the hush panel edge. It's a tough find for many:

http://www.zr1.net/forum/showpost.ph...95&postcount=1

Re: 1991 ZR1 ODB1 Port Location
 

Welcome onto the boards there.

If reading codes is the only objective, you can get it done with a paper clip (once you find the ALDL interface).

But scan software IS something good to have...

Cliff [Dynomite] will post a link for eBay cable listings, for laptop-to-ALDL connector.

I use this one from Moates:

https://lh6.googleusercontent.com/-j...0/IMG_5608.JPG

Re: 1991 ZR1 ODB1 Port Location
 

Thank you for all the responses!

I thought I looked pretty thoroughly, but will try again.
I just picked up the car (539) from Arkansas and drove it home to Chicago. The car was running slightly rough when I picked it up, but 100 miles in to ~700 mile trip it started to misfire badly with the check engine light periodically coming on. It limped the rest of the way home.

I had no choice, but to drive it the rest of the way, hopefully no damage resulted from that.

Another thing I noticed was the oil pressure gauge being always pegged to the max in the lower gears.

Currently my ZR1 has the power of a poorly tuned Chevette. :(

I found couple of vacuum hoses loose (MAP and pressure regulator), I also replaced PCV check valve assembly hoses with ones from jerrygaskets. It and the felt much better at first, but after a short test drive it reverted back to a bad misfire and shake.

So this is where I am now…
So ’91 ZR1 has a 12 pin ODB1 connector?

This one right?
https://www.moates.net/aldu1-and-cab....html?cPath=64


Thanks again!

Re: 1991 ZR1 ODB1 Port Location
 

There are enough of us here in Chicagoland to straighten the car out.
Welcome to the FBI.

Re: 1991 ZR1 ODB1 Port Location
 

In order of likelyhood the usual cast of characters that will cause a "Badly Tuned Chevette" syndrome are:

- Fuel injectors
- Coil packs
- spark plugs/wires
- Fuel pumps

If the fuel injectors are original, they are the most likely culprit.

Get one of the FBI (Fast Boys of Illinois) to pop over for a quick diagnosis, it will save you time, trouble and money.

'Crabs

Re: 1991 ZR1 ODB1 Port Location
 

Yep.....just tell us about how many miles on your ZR-1.........But as Crabs suggests.....start with Injectors :thumbsup:

Low Mileage ZR-1 Restoration (Audio, Injectors, Starter, Clutch Hydraulics)

Re: 1991 ZR1 ODB1 Port Location
 

If the injectors are original, replace them even if the problem turns out to be something else- they are gonna give you trouble- guaranteed.

probably if it kind of runs ok cold and then misses bad as it warms up- yeah, that's injectors.

Re: 1991 ZR1 ODB1 Port Location
 

~56,000. If I will be going through the trouble of pulling of the intake
I might as well also do the rest as suggested?

- Fuel injectors
- Coil packs
- spark plugs/wires
- Fuel pumps
- secondary solenoid
Anything else? Would like to remove as much emmissions related mess as I can (really don't want to pull the heads)