Injector issue with 1990?

[XfireZ51]

If I am reading this right, ur cams are 238 intake/232 exhaust? Is this a 5.7L?
Pete could probably chime in, but bigger exhaust cams are not needed for a stock block LT5. And IMO, every motor is different and particularly one with non-stock cams will require custom tuning. I'm not suggesting that is the issue w ur ZR. Before tuning anything, u need to make certain that fuel, air, spark systems are all operating correctly.
Are ur secondary throttles removed or disabled?
Here's Pete's suggestion

http://www.zr1.net/forum/showthread....ight=Pete+cams

[jss06c6]

A lot of very qualified people have spent time trying to diagnose the issue(s). Without actual data, we're driving with one hand on the wheel and one eye closed. Each engine has a finger print. No two are alike and each require, for optimal performance and efficiency, an exact combination of fuel, air and spark. Making a change in your cams has a dramatic impact upon the volumetric efficiency of your particular engine. If you want to know how your setup is performing, I strongly suggest you get proper hardware and software to log engine data. Once you have this, you can post up a .CSV file so that Marc and others can properly diagnose what is really going on.

Sent from my QTAIR7 using ZR-1 Net Registry mobile app

[Top Toy]

Your cams are relatively mild with the exception of exhaust duration. Lifts are a little less than most at 0.42" intake and 0.41" exhaust. Intake duration at 238 deg. is in line with most but exhaust duration at 232 deg. is longer than most and would make tuning for low speed more challenging. Could be a contributor to your problems. Probably not optimum for peak torque/power either. If you still have operating secondaries, suggest you eliminate them. Makes tuning a whole lot easier if you don't have to worry about when those open up. Marc would need to know whether or not your secondaries are in service to give you a proper tune.

[cp1joel]

Hi all,

Once again thank your for all your input and advice.

I have been back and forth with Marc in regards to the cam size and tune.

His next recommendation as with a couple of you guys, is to log the data when driving and send the file to him. Have ordered the OBD1 connector and will do this as soon as it arrives.

He agrees that bigger cam's should not be added to a 350 engine, and this is contributing to my rough idle/lean issues.

He will try and smooth out the fuel and spark and we will see how we go from there.

He also agrees that if I am still not happy, I will return to the original cams. Should be making only 20hp less and smooth out the idle and drivability.

Thanks for all your help again and will keep you all posted

Joel

[XfireZ51]

Joel,

Let me suggest that u just replace the exhaust cams w the stock ones. It makes for a great combo. Very nice w good idle quality and smooth power. Had that setup for a few years and really liked it. Would recommend that to you.

[cp1joel]

Hey all,

So as I await for my obd1 reader, I decided to to start the car this morning. Put the key in the ignition and was surprised to hear that radiator fan come on continuously. The car starts but will die as soon as I stop giving it some gas. Runs terribly at around 500 RPM, stumbles and dies. Very odd as the other day it was fine and has never done this before. Took Marcs chip out and it still did the same thing. Disconnected the battery and no luck. Noticed service enginr soon light is on. I thought even if the fan was on continuously this would have no effect on how the engine runs. Trying to figure out where to start with this.

[XfireZ51]

Originally Posted by cp1joel

Hey all,

So as I await for my obd1 reader, I decided to to start the car this morning. Put the key in the ignition and was surprised to hear that radiator fan come on continuously. The car starts but will die as soon as I stop giving it some gas. Runs terribly at around 500 RPM, stumbles and dies. Very odd as the other day it was fine and has never done this before. Took Marcs chip out and it still did the same thing. Disconnected the battery and no luck. Noticed service enginr soon light is on. I thought even if the fan was on continuously this would have no effect on how the engine runs. Trying to figure out where to start with this.

Have u tried re-seating Marc's chip? When u turn ignition to ON, but do not start motor, does SES light flash once? It should if all is well w ECM.
Fans turning on with key ON is a sign of a problem w the calibration/prom. Its "limp home" mode.

[Ccmano]

Check the vacuum hoses on the MAP sensors.
H

[Hib Halverson]

Admittedly, I'm coming onto this thread late in the process. Nevertheless, I'd like to offer some opinions.

1) One post said the car made 380 at the wheels. That is about 464 at the flywheel–which is not bad for a 2-bolt motor which has cams, no headwork and headers. If this car is running as bad as suggested in posts by the OP, those dyno numbers are a bit suspect. The OP stated the "mechanic" said the engine was lean then rich in PE (secondaries enabled). Does this guy have any information more specific than just saying it's "lean" or "rich". If so, post the air-fuel ratio data he recorded during the dyno session. Actually, ask him for all the data from the dyno session and post it here.

2) The very first post states clearly that the engine runs ok after cold start and during early warm-up but once the ECT comes up, the idle stability goes away. Without seeing some serial data, I'm guessing, but I'll bet this engine's fuel trims are whacked when it's at idle/part-throttle in closed loop. It's possible that's because of the cal but, considering the cams are said by others here to not be too radical and it's got one of Haibeck's chips, at this point, I don't think that's probable because, as long as the engine specs, as communitated to Marc, were correct, his cals are usually pretty close.

3) The OP talks about the service engine light coming on. Why hasn't the mechanic involved connected a scan tester to the engine and read any current or history codes in the ECM?

4) I'd be looking at various engine controls components, like oxygen sensors, MAP sensor, vacuum hoses etc.

5)

Originally Posted by DRM500RUBYZR-1

(snip)With utmost respect to your current mechanic, I would suggest holding off a bit and going back to check out all of the basics before trying to fix a basic performance problem with an advanced dyno-tune.
Everything that you indicate as a problem, all seem to be simple misfire issues. Fuel or ignition are usually the culprit absent a mechanical problem, which is less probable, as you say it only happens at low RPM.
Look first for simple causes, perhaps multiple simple causes before investing thousands elsewhere.

"DRM500RUBYZR-1 gets the weekend "Beacon of Reality Award". Please consider his suggestions

6) Run the fuel pressure tests in the Factory Service Manual and post the results.

[cp1joel]

Hi all,

I checked the module and it seems to be connected fine. I took Marcs out and it did not make a difference.
SES remains on (does not flash), with radiator fan going.

Used a paperclip to to connect A to B but to no avail.
A to G worked fine and it threw 1- C41, H41, H74. Also 4 - Err

Am I correct to say that there is no communication with the ECM?

It just seems very odd that this could happen all of a sudden.

Thanks

Joel