Wtb: 1991 zr-1 ecm
12-17-2015, 11:12 AM
#3
Pro
Thread Starter
How much are you asking for it?
That being said, this relates to a 1991 ZR-1 that I'm looking at to purchase. I also have another current thread in the C4 section of CF entitled "1991 ZR-1 Performance Question" that explains the situation and includes the following from Dominic Sorresso and Paul Workman:
Quote:
Originally Posted by Dominic Sorresso View Post
Sounds like the secondaries are not working. Vacuum leak?
Turn ignition ON. Listen for fuel pumps. Also listen to hear if Vacuum Pump in right front stops running or continues. If it keeps running, then leak.
Any codes?
And from Paul Workman:
First off, both of these issues are usually simple fixes. So, I wouldn't hit the "reject" button just yet!
W/ all due respect to Crabs, and he may be right, it is always best to treat multiply failures (tach and WOT issues, in this case) separately. If they have a common cause, fixing one will fix the other, but to jump ahead to conclude a common cause off the bat...well, we've all been down that rabbit hole at one time or another!! Take 'em one at a time, for now (at least) is my recommendation, FWIW. Oh, and IF the ECM is bad, Marc (and others) has a line on getting them repaired. No worries there, except for the $$ which would be the owner's headache IF the ECM is in fact bad (I'm betting is isn't, at this point).
Dom mentioned checking the vacuum circuit. In case you or your mechanic is unaware, here's more FYI on that:
The Secondary Port Throttles (SPT) are vacuum actuated. Vacuum is provided in normal driving by the engine from the plenum. However, at/near sustained WOT, plenum vacuum drops too low to hold the SPTs open, and that is where that vacuum pump takes over. By verifying the operation of the pump, it serves as a 'first step' in diagnosing the integrity of the SPT system. The pump running and then shutting OFF, signals at least the vacuum lines and reservoir (under the plenum) are operational. On the other hand, if the vacuum pump continues to run and not stop, there is significant leak that may affect the SPT operation. On the other hand, if the pump does not run at all, then there a problem can be narrowed to the operation of the pump itself - in case your mechanic is unaware.
The pump under the passenger headlight maintains vacuum to operate the Secondary Port Throttles (SPT), primarily when at/near WOT. If the pump cycles on for (let's say) less than 5-10 seconds and remains OFF for at least approx 2-3 seconds minimum, the integrity of the SPT circuit is sufficient to not cause and issue with the SPTs opening. However, if the pump does not shut off, disconnect the vacuum connector where the line enters under the plenum and hold your thumb over the open (pump-side) end. If the pump immediately shuts off, then you have an issue under the plenum.
Also, you or your mechanic can measure current draw to the twin fuel pumps. (With the ignition switch OFF, current draw of 8-10 amperes indicates both pumps are drawing the prescribed current. (The pump test connector is the little black connector on a short red wire, justting out of the big wire loom - about 3" inboard of the ECM.)
The tach, I think is a separate issue; likely related to the instrument cluster itself, or possibly the ECM, as Crabs suggested. I would start by servicing that connector (as they tend to get "frosted" over time, I find).
Honestly, the symptoms you're describing are typical of ZR-1s that have been sitting a while; typical 20+ year old "stuff" that once fixed yields a very fine machine indeed!
The issue might be just how much troubleshooting/fixing is the seller willing to do. And, no offense intended, but the ZR-1 made up less than 2% of all the C4s built. Consequently, there aren't many good techs out there that have even seen an LT5, let alone work on one. In other words, he may be fumbling around w/ it but not understanding what he's doing - and the fact the car has those issues after he's worked on it points to his inexperience! Just sayin...
All this said, perhaps the best option is to have a ZR-1 owner, that is familiar with these cars, take a look at if and report back. That has worked very well or other perspective buyers, especially where (as in this case) the local "talent" isn't up to snuff.
That being said, this relates to a 1991 ZR-1 that I'm looking at to purchase. I also have another current thread in the C4 section of CF entitled "1991 ZR-1 Performance Question" that explains the situation and includes the following from Dominic Sorresso and Paul Workman:
Quote:
Originally Posted by Dominic Sorresso View Post
Sounds like the secondaries are not working. Vacuum leak?
Turn ignition ON. Listen for fuel pumps. Also listen to hear if Vacuum Pump in right front stops running or continues. If it keeps running, then leak.
Any codes?
And from Paul Workman:
First off, both of these issues are usually simple fixes. So, I wouldn't hit the "reject" button just yet!
W/ all due respect to Crabs, and he may be right, it is always best to treat multiply failures (tach and WOT issues, in this case) separately. If they have a common cause, fixing one will fix the other, but to jump ahead to conclude a common cause off the bat...well, we've all been down that rabbit hole at one time or another!! Take 'em one at a time, for now (at least) is my recommendation, FWIW. Oh, and IF the ECM is bad, Marc (and others) has a line on getting them repaired. No worries there, except for the $$ which would be the owner's headache IF the ECM is in fact bad (I'm betting is isn't, at this point).
Dom mentioned checking the vacuum circuit. In case you or your mechanic is unaware, here's more FYI on that:
The Secondary Port Throttles (SPT) are vacuum actuated. Vacuum is provided in normal driving by the engine from the plenum. However, at/near sustained WOT, plenum vacuum drops too low to hold the SPTs open, and that is where that vacuum pump takes over. By verifying the operation of the pump, it serves as a 'first step' in diagnosing the integrity of the SPT system. The pump running and then shutting OFF, signals at least the vacuum lines and reservoir (under the plenum) are operational. On the other hand, if the vacuum pump continues to run and not stop, there is significant leak that may affect the SPT operation. On the other hand, if the pump does not run at all, then there a problem can be narrowed to the operation of the pump itself - in case your mechanic is unaware.
The pump under the passenger headlight maintains vacuum to operate the Secondary Port Throttles (SPT), primarily when at/near WOT. If the pump cycles on for (let's say) less than 5-10 seconds and remains OFF for at least approx 2-3 seconds minimum, the integrity of the SPT circuit is sufficient to not cause and issue with the SPTs opening. However, if the pump does not shut off, disconnect the vacuum connector where the line enters under the plenum and hold your thumb over the open (pump-side) end. If the pump immediately shuts off, then you have an issue under the plenum.
Also, you or your mechanic can measure current draw to the twin fuel pumps. (With the ignition switch OFF, current draw of 8-10 amperes indicates both pumps are drawing the prescribed current. (The pump test connector is the little black connector on a short red wire, justting out of the big wire loom - about 3" inboard of the ECM.)
The tach, I think is a separate issue; likely related to the instrument cluster itself, or possibly the ECM, as Crabs suggested. I would start by servicing that connector (as they tend to get "frosted" over time, I find).
Honestly, the symptoms you're describing are typical of ZR-1s that have been sitting a while; typical 20+ year old "stuff" that once fixed yields a very fine machine indeed!
The issue might be just how much troubleshooting/fixing is the seller willing to do. And, no offense intended, but the ZR-1 made up less than 2% of all the C4s built. Consequently, there aren't many good techs out there that have even seen an LT5, let alone work on one. In other words, he may be fumbling around w/ it but not understanding what he's doing - and the fact the car has those issues after he's worked on it points to his inexperience! Just sayin...
All this said, perhaps the best option is to have a ZR-1 owner, that is familiar with these cars, take a look at if and report back. That has worked very well or other perspective buyers, especially where (as in this case) the local "talent" isn't up to snuff.
12-18-2015, 09:01 PM
#4
Burning Brakes
ECM I believe are the same for all ZR1s its the PROM that is different. ECM I have is from a 91z that was flipped. I would sell both ecm and prom for $500 shipped.
Last edited by Mike 92LX; 12-18-2015 at 09:46 PM.
12-27-2015, 05:18 PM
#5
Pro
Thread Starter
I bought car
The owner and I negotiated and reached an agreement. I will be taking possession around New Years or the week after. I am interested in buying your ECM and anything else you may have left over. I have no documents, owner's manual or anything else. Do you still have the "pizza box," owners' manual, parts or anything else that I need or can use to bring the car up to "NCRS" standards or modify it to make it faster?