A serious problem

[8upZR1]

What type of scanner is this and where can I get one? Does the ECU run in its normal fashion when the pins are jumped? No one has posted that this will surely fry an ECU so I may do some extensive testing today, driving with the pins jumped.

I will post pics of the manifold as soon as I can. Hopefully I can do some dyno testing when the car runs right. My neighbor owns a dyno shop and will let me get a full day for $125. Can't beat that.

I have replacement components for most ignition pieces. Swapping pieces has not been fruitful so far. I have an MSD box hooked up. It has an indicator that blinks according to various problems and it says that the ignition is operating properly, for what it is worth. MSD supplies a plug for the harness so you can convert back to stock by simply unplugging the box and plugging in this plug. I do this with no result.

[We Gone]

Originally Posted by tomtom72

I'm just a hack but I think if you can drive the car with a scanner plugged into the data port....what's the difference if just the pins are jumped?...I would think to the EEC system there is no difference. How would the system know if a scanner was attached or if the pins were just jumped?

JMHO
Tom

I have to agree you need to hook it up to a scan tool at this point...Not sure where you are in GA but a buddy of mine in Fayetteville has a shop and does have a Snap-on scan tool..You may want to give him a call and see what he would charge to run a few tests.. he does know ZR-1s and has done a lot of work on them..

John @ Corvette Country 770-461-5211

Steve

[gbrtng]

Originally Posted by A26B

I'm a little confused with the "short runner intake." What exactly is that?

Your problem, being intermittent and worsening, sounds to me like an electrical issue. Loose connection, bad ground(s) or open/short in the harness. Part of it sound like it's restricted to closed loop except that once you reach 5000rpm it craps out again. If it were O2 sensors, you should have a code, same as with any other sensor.

I'm leaning towards a bent pin on the ignition module (easy to do) or bad ground(s). If you could data log, you might be able to chase it down.

If you have acess to another known good ECM, I would suggest trying that too.

I agree on the ECM - if it's flakey there's no telling what weirdness
can occur. You might not be able to log data either.

I fought with similar problems on my wife's L98 a few
years ago. That one would throw random SES codes which made
think it was a bad ground or related connector problems. Ran like
new with a good ECM.

Glenn
91-1341 and 91-9405

[tomtom72]

I bought a used snap-on MT-2500 scanner. I sometimes use it when I drive just to see what the ECM sees from the sensors. I know for sure that the guys that do "data logging" use software programs that let you hook up a laptop to the ALDL port and drive & record the data for play back later so you can study it. I'm not too swift on this 'puter stuff so all I know is there is a soft ware that you can buy, a cable to plug the laptop into the ALDL, and you can either use it on a dyno or you can do "street tunning" by logging the data(recording the data on the hard drive(?)) & look at it later.

Sorry that's all I know about this stuff.

A thought just hit me: If the scanner is plugged into the ALDL maybe it is just reading the data flow? Maybe if you use a "jumper" you are putting the ECM into test mode??? I know that I use my scanner to do the KOEO readings and I can start the car & watch as the data changes as the car goes from "open loop" to "closed loop". Stupid Q from me: you know that the ECM is good? If not sure I have a spare ECM with a 90 EPROM in it I could send to you to test if you think that would be of any use?


Tom

[Z Factor]

An option since you live in Georgia is to contact Aaron at SGC;

http://www.sgvette.com/

Let us know how things work out

[8upZR1]

I have two ECU's and three chips but no combo seems to solve the issue. There are some noticeable driving differences between the chips as there should be but nothing significant. I drove a little with the pins jumped and it didn't make a difference. I am going to look into one of these scanners. Maybe that will lead to some insight. I did a quick diagnostic with a voltmeter of the ignition module test port and everything seems ok. An oscilloscope would probably be the better test equipment but I do not have one. The Ref high, ref low, EST out, tach out, bypass line all look good before and after cranking.

[368zr1]

If you have the stock fuel injectors (Multec) they could be
causing your strange problems. If they are the original injectors, try ohming the coils out when hot and cold. Should be around 16 ohms.

[Gunny]

Aside from checking the obvious which it sounds like you've already done ...

1) vacuum leaks can do some nasty things with the proper running ... and even when you think you have them all, another one can creep into the equation.
2) someone mentioned cleaning the IAC ... I recently had issues with the IAC and even tho I cleaned it and thought it was OK, 98% of my problems went away with a new IAC. btw, prices for that sensor range from over $100 down to $39 or so from AutoZone. It's usually in stock.
3) another suggestion was to check your injectors ... I think that might be a good place to look very carefully. If you've got a couple of primaries and 2-3 secondaries not working, it might explain some of your symptoms.

Good luck on finding/fixing ... it will be worth it for sure.

I see that you live in the Savannah area ... I'm about 100 miles from you ... my schedule at the moment prevents me from driving down & taking a look, but keep us posted on your progress. I know that you'll get a ton of help here and you will get the beast running properly.

George Jones
Waynesboro, GA
1990 ZR-1
visit my site

[8upZR1]

I had checked the injectors a while back when bad hydraulic lifters kept the motor from starting. Back then they were good. The primaries are original, the secondaries are RC. I guess I will go back and recheck all of the injectors and sensors and their connections. I have not checked vacuum recently either but I am certain it is good. The fuel pressure spikes when you tip in the throttle so some vacuum is definetely present. I will have to check this as well. If only I had an extra 10 hours a day.