LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

Cam and Injections issues.

Old 03-21-2019, 09:08 PM
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Cam and Injections issues.

So my brother has a 93 LT1 camaro with OBD1 port and ECM. He recently had the engine rebuilt, bored .030 over and replaced the stock cam with the LT4 Hot Cam. Since the engine has been installed it has had a problem with running extremely rich to the point that it is flooding the crank case with fuel. He was first told it was the ECM and bought a JET performance chip and also had a custom chip built as well. Neighter chip solved the issue. He was told he had leaky injectors so he replaced the injectors with what he thought were stock replacements but he put in the 24lb injectors. I was told on another forum that the stock injectors are actually 22lb injectors. New stock replacement fuel regulator as well. I see that many people have run this cam in many late model 350 engines with TPI, TBI, etc.. From Vortec to LT1. it is a very mild build not far from stock just being bored .030 over. If ECM chips and new injectors did not solve the issue with it running so rich what is the problem. is the cam to large in lift and duration for the stock injection or ECM? Could it be another problem with electronics such as MAP sensor MAF sensor 02 etc..? Had anyone had this problem before after replacing the stock cam with the LT4 Hot Cam ? Any insight would help. I'm beginning to think it is a mechanical issue with the build itself maybe a mistake in honing or such.
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Old 03-21-2019, 11:00 PM
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Re: Cam and Injections issues.

What other mods beside the LT4 HOT cam? Were 1.6 full roller rockers installed with the HOT cam? Headers? If headers, were O2 sensors converted to heated sensors? CAI? Do you know who burned the “custom chip”?

Have you scanned it for codes? Have you checked the fuel pressure? Things like exhaust leaks before the O2 sensors, misfires, or faulty O2 sensors or O2 sensor wiring can cause the ECM to see a “false lean” condition, and respond by dumping in fuel the engine doesn't need.

Problem with putting a cam in the 93 is the fact that it runs speed-density, does not have an MAF sensor. That could explain poorer results compared to the 94 and up MAF LT1’s. Speed-density has to calculate the mass air flow, based on cylinder displacement (which has been changed by the over-bore), volumetric efficiency (which can change with a CAI, headers and a more aggressive cam), and the readings from the MAP sensor and the inlet air temp (IAT) sensor. Have you observed the MAP and IAT readings using a real-time ECM scanner or data logger? Do you have any idea how the O2 sensor reading are responding to the seemingly rich condition? Have you accessed the long term fuel trims?

I would strongly recommend that you download free Scan9495 data logging software, which is specifically designed to log the 93-95 computers. While the software is free, and the author is a member here to help you with any install issues, you will need to buy or make the correct 12-pin OBD-1 cable, Info in this thread:

I can help you interpret the data logs.

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