Crossfire tuning
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
The Hypertech chip may or may not be right for your L83 engine. I can't recall if it was Hypertech, but at one of the aftermarket chip suppliers, I spoke with a tech who kept talking about a Mass Air Flow sensor. The L83 engine uses Speed Density, and does not have a Mass Air Flow Sensor. So, if you can make sure the Hypertech chip you have is actually correct for an L83 Crossfire engine. It might not be.
Thread Starter
Racer
Joined: Jun 2012
Posts: 325
Likes: 36
From: Colorado Springs Colorado
I apologize in advance if I'm misinterpreting or misunderstanding anything that's been written, like the comment above...
The L83 engine sets its own timing via the computer, and the knock sensor mounted in the engine on the passenger side. The user does have to set the base timing, with a lead at the distributor disconnected. This is important, and might be at least partially the cause of backfiring. I recommend setting the base timing per spec, and then reconnecting the lead at the distributor. Then with the timing light, you can see the computer is advancing the timing per its programming.
The Hypertech chip may or may not be right for your L83 engine. I can't recall if it was Hypertech, but at one of the aftermarket chip suppliers, I spoke with a tech who kept talking about a Mass Air Flow sensor. The L83 engine uses Speed Density, and does not have a Mass Air Flow Sensor. So, if you can make sure the Hypertech chip you have is actually correct for an L83 Crossfire engine. It might not be.
And before you get much further into this, I'd really recommend balancing the throttle bodies. I've had two Crossfire engines, one on a Collector's Edition 1982, and one on a 1984 Z51. Both had issues, worse on the 1982.
Other things to check include the throttle position sensor, if that is not set correctly, the computer will be working with bad data, and garbage in garbage out.
The computer in the 1982 is behind the driver's seat right next to the battery. This brilliant design move results in not only no real air flow for cooling the computer, it also provides ample opportunity for fumes from the battery to seriously corrode the computer and connections thereto. Ask me know I know.
So, I'd check the computer and connections to it. Might be surprised to see how much caked on minerals there are on and inside the computer. Mine was in very bad shape.
Also, there is a vacuum hose running from the manifold to the Manifold Absolute Pressure sensor mounted on the firewall. Critical that not be leaking or missing. In fact, any vacuum leak will play hell with a Crossfire set up, since the MAP sensor checks vacuum and in turn the computer uses that info (among other sensor inputs) to set injector pulse width...
Another problem might be the Coolant Temp Sensor at the front of the block. Some of these used a single wire, grounding thru the sensor body. Bad idea, corrosion sometimes interferes with proper grounding. A bad CTS can throw everything off, not only on the L83, but on the L98, say in a 1990 behaving badly (again, how would I know that...). If the CTS is not right and the computer always thinks the car is cold, the extra fuel could conceivably cause backfires out the exhaust. Just a thought.
Getting an L83 to run right can be a hair pulling experience, and at best seems to be iterative. If you have a factory service manual, you can pull codes off the computer which can be quite helpful.
Hope this helps a bit, the FSM and this forum have lots of good stuff on Crossfire/L83 - which when running right is better than I think most people give it credit for...
The L83 engine sets its own timing via the computer, and the knock sensor mounted in the engine on the passenger side. The user does have to set the base timing, with a lead at the distributor disconnected. This is important, and might be at least partially the cause of backfiring. I recommend setting the base timing per spec, and then reconnecting the lead at the distributor. Then with the timing light, you can see the computer is advancing the timing per its programming.
The Hypertech chip may or may not be right for your L83 engine. I can't recall if it was Hypertech, but at one of the aftermarket chip suppliers, I spoke with a tech who kept talking about a Mass Air Flow sensor. The L83 engine uses Speed Density, and does not have a Mass Air Flow Sensor. So, if you can make sure the Hypertech chip you have is actually correct for an L83 Crossfire engine. It might not be.
And before you get much further into this, I'd really recommend balancing the throttle bodies. I've had two Crossfire engines, one on a Collector's Edition 1982, and one on a 1984 Z51. Both had issues, worse on the 1982.
Other things to check include the throttle position sensor, if that is not set correctly, the computer will be working with bad data, and garbage in garbage out.
The computer in the 1982 is behind the driver's seat right next to the battery. This brilliant design move results in not only no real air flow for cooling the computer, it also provides ample opportunity for fumes from the battery to seriously corrode the computer and connections thereto. Ask me know I know.
So, I'd check the computer and connections to it. Might be surprised to see how much caked on minerals there are on and inside the computer. Mine was in very bad shape.
Also, there is a vacuum hose running from the manifold to the Manifold Absolute Pressure sensor mounted on the firewall. Critical that not be leaking or missing. In fact, any vacuum leak will play hell with a Crossfire set up, since the MAP sensor checks vacuum and in turn the computer uses that info (among other sensor inputs) to set injector pulse width...
Another problem might be the Coolant Temp Sensor at the front of the block. Some of these used a single wire, grounding thru the sensor body. Bad idea, corrosion sometimes interferes with proper grounding. A bad CTS can throw everything off, not only on the L83, but on the L98, say in a 1990 behaving badly (again, how would I know that...). If the CTS is not right and the computer always thinks the car is cold, the extra fuel could conceivably cause backfires out the exhaust. Just a thought.
Getting an L83 to run right can be a hair pulling experience, and at best seems to be iterative. If you have a factory service manual, you can pull codes off the computer which can be quite helpful.
Hope this helps a bit, the FSM and this forum have lots of good stuff on Crossfire/L83 - which when running right is better than I think most people give it credit for...
Thread Starter
Racer
Joined: Jun 2012
Posts: 325
Likes: 36
From: Colorado Springs Colorado
Oops, sorry for all the 1982 specific stuff, you are dealing with an 84 - that computer as I'm sure you already know is under the dash not near a battery.
Still, I'd check the Hypertech chip just to be sure. Otherwise the sensors between 1982 and 1984 are pretty much the same. And balancing the throttle bodies on either model year can make a bad running car work surprisingly well, on or off idle.
And pulling the lead at the distributor when setting timing is a must.
Best Luck with this...interested to know how it turns out.
Still, I'd check the Hypertech chip just to be sure. Otherwise the sensors between 1982 and 1984 are pretty much the same. And balancing the throttle bodies on either model year can make a bad running car work surprisingly well, on or off idle.
And pulling the lead at the distributor when setting timing is a must.
Best Luck with this...interested to know how it turns out.
Thread Starter
Racer
Joined: Jun 2012
Posts: 325
Likes: 36
From: Colorado Springs Colorado
Burning Brakes
Joined: Feb 2013
Posts: 1,173
Likes: 152
From: norway
I replaced all the sensors to include the map when I got the car back, have been using my FSM for everything, took the computer out and replaced the chip with the correct Hypertech model, like I said after today's adjustments to the timing, the car runs good, the only thing I have not done is to adjust the tbi's.
Drifting
Joined: Mar 2015
Posts: 1,275
Likes: 165
From: Utah
Check grounds as well, my car was super clean, and i think i was the first one to ever drive it in the rain...
i had grounding issues in the back, found out after a fuel pump upgrade.
i found nothing corroded, but still needed an extra ground strap to stable it out.
It also fixed my fuel gauge and weird random things with my turn signals...
i had grounding issues in the back, found out after a fuel pump upgrade.
i found nothing corroded, but still needed an extra ground strap to stable it out.
It also fixed my fuel gauge and weird random things with my turn signals...
Thread Starter
Racer
Joined: Jun 2012
Posts: 325
Likes: 36
From: Colorado Springs Colorado
seems to be doing ok, can not wait to get the Renegade to get a little more power. Does anybody has a header to recommend?
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Safety Car
Joined: Nov 2005
Posts: 3,532
Likes: 1,185
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
So, is it running OK now and NOT backfiring at WOT? I agree with Tom, the popping is more than likely a fuel issue (lean pop) or related. If you have access to a dyno, it would be nice to see what the A/F is doing through the RPM range and at high end. It would easy to see if you are going lean and increase FP to see how it responds.
IMO, DO NOT put the Renegade on your motor until you are 100% it is running absolutely correct...You may only create other issues and end up chasing your tail as it were.
10-12 degrees of timing should be OK, but maybe not. If it pings, back it off 1 degree at a time. FP is critical on a CF, ensure you are supplying the correct amount of fuel to feed the motor. The pump may be an issue as well. If you add a manifold, cam and new ECM before the motor is good to go, you WILL have issues. Just trying to save you a lot of possible grief down the road.
Also, if you buy a Renegade, thanks for your support. Good luck with your mods.
IMO, DO NOT put the Renegade on your motor until you are 100% it is running absolutely correct...You may only create other issues and end up chasing your tail as it were.
10-12 degrees of timing should be OK, but maybe not. If it pings, back it off 1 degree at a time. FP is critical on a CF, ensure you are supplying the correct amount of fuel to feed the motor. The pump may be an issue as well. If you add a manifold, cam and new ECM before the motor is good to go, you WILL have issues. Just trying to save you a lot of possible grief down the road.
Also, if you buy a Renegade, thanks for your support.
Good luck with your mods.
Last edited by Buccaneer; Oct 18, 2016 at 12:57 AM.