Stumbles @ WOT!
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Joined: Aug 2003
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From: Soddy Daisy TN
Stumbles @ WOT!
Hey guys. I have a problem I hope you can help me with. I have just modified my 85 L98 with Edelbrock alum heads, Comp roller cam and lifters, Edelbrock Hi-Flo intake base, Hedman hedders, no cats, no smog. I'm still using the stock injectors, fuel reg, plenum, runners and stock ecm.
Now with all that said, the car idles good and runs strong. But from a rolling start, say 10 mph I can stand in it and just as the rear tires start to braek loose and fishtail she suddenly stumbles. If I accelerate less aggressively I can run up to 5000 rpm and still pull. But a sudden WOT from sit still, she stumbles and I have to back off a bit. Do you think I'm asking too much of the stock injectors and fuel reg? Can I upgrade to bigger infjectors and use the same stock chip? I could use a little advice. I don;t want to lean this baby out. Also no check engine lights or running hot...ever. What do you think? I'm all ears..
Now with all that said, the car idles good and runs strong. But from a rolling start, say 10 mph I can stand in it and just as the rear tires start to braek loose and fishtail she suddenly stumbles. If I accelerate less aggressively I can run up to 5000 rpm and still pull. But a sudden WOT from sit still, she stumbles and I have to back off a bit. Do you think I'm asking too much of the stock injectors and fuel reg? Can I upgrade to bigger infjectors and use the same stock chip? I could use a little advice. I don;t want to lean this baby out. Also no check engine lights or running hot...ever. What do you think? I'm all ears..
Team Owner
Joined: Aug 2000
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From: San Pedro CA
gee... all that work and still on the stock ECU and injectors? If there is one thing I have learned about the early ECU's, they are SLOW SLOW SLOW at adjusting to conditions.
Is your timing ok?
You see, the L98 wasn't designed to go much past 4500 RPM, so you are already outside the operating envelope!
Personally, I would think chip is your next best course of action, plus better injectors, an adjustable fuel pressure regulator and a new fuel pump. I doubt you need a high flow, just a fresh one.
Is your timing ok?
You see, the L98 wasn't designed to go much past 4500 RPM, so you are already outside the operating envelope!
Personally, I would think chip is your next best course of action, plus better injectors, an adjustable fuel pressure regulator and a new fuel pump. I doubt you need a high flow, just a fresh one.
Last edited by bogus; Sep 1, 2004 at 02:19 PM.
Team Owner
Joined: Jul 2003
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Id go with Fatter injectors, and a Adjustable fuel Pressure Regulator, as Bogus said.
also, check your Throttle position sensor, and your Fuel pump relay on the firewall.
I had a stumble at WOT too, it turned out to be that a poorly adjusted TPS ate my new plugs up. also, could be bad plugs, or plugs with bad gap, or bad wires...
check the coil, and cap too...
Good luck!
also, check your Throttle position sensor, and your Fuel pump relay on the firewall.
I had a stumble at WOT too, it turned out to be that a poorly adjusted TPS ate my new plugs up. also, could be bad plugs, or plugs with bad gap, or bad wires...
check the coil, and cap too...
Good luck!
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From: Soddy Daisy TN
I appreciate the info and will take it to heart. My timing is good, TPS checked out good, plugs are brand new and are running a nice tan color. Don't know about the fuel pump relay. Just as you guys, I suspect I need more juice coming in. Been talking to Moates about ECU's. He recommends later model also if I decided to change. Looks like I have a new project at hand. Any one else had this problem?
Thread Starter
Instructor
Joined: Aug 2003
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From: Soddy Daisy TN
Originally Posted by drumboytroy
I appreciate the info and will take it to heart. My timing is good, TPS checked out good, plugs are brand new and are running a nice tan color. Don't know about the fuel pump relay. Just as you guys, I suspect I need more juice coming in. Been talking to Moates about ECU's. He recommends later model also if I decided to change. Looks like I have a new project at hand. Any one else had this problem?
Oh, and also, what size are my stock injectors and what do I need to go to? And what kind of fuel regulator? Thanks a million guys!
Team Owner
Joined: Aug 2000
Posts: 40,156
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From: San Pedro CA
Injectors, I cannot help you with. I am not versed enough in their specs on an L98.
However, you will want to get an Adjustable Fuel Pressure Regulator.
You have some choices, too. I got the Accel, mainly, because I allready had a FP gauge! Why rebuy? But other makers have AFPRs with cool little gauges on them. Holley, Edelbrock (I think) among others.
However, you will want to get an Adjustable Fuel Pressure Regulator.
You have some choices, too. I got the Accel, mainly, because I allready had a FP gauge! Why rebuy? But other makers have AFPRs with cool little gauges on them. Holley, Edelbrock (I think) among others.
Drifting
Joined: Apr 2003
Posts: 1,379
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From: rome ny
before you can analize the problem you need to know if you are running rich or lean at wot. usually a stumble at high rpms is caused by a rich condition. not saying that something else might be wrong. but you need to start there and if you are if the range of 12 to 14 afr then you need to look somewhere else like weak spark.
just because your plugs are a tan color doesnt mean that you afr is correct. you could be at 14/1 at cruize and 11/1 at wot and the plugs may now show.
just because your plugs are a tan color doesnt mean that you afr is correct. you could be at 14/1 at cruize and 11/1 at wot and the plugs may now show.
