Decelerations and highway mode.
Decelerations and highway mode.
Hi All,
Sorry for the long post, but i'm running out of things to look at on this car.
I have NEVER, repeat NEVER been 'into' my computer. my car is a basically stock 1987 IROC. 5.7TPI, auto tranny. over the past 10 years, the car has basically been totally rebuilt (150k approx on chassis) we've replaced engine, tranny, brakes, rear, sensors, radiator, sensors, and on and on. And we have never been able to 'fix' a weird issue. the engine rpm jumps around when on light throttle. By this, i mean - when rolling downhill, the rpm will jump up 100-200, then back down again. Causing the car to slow down. The tranny was going out, so thought at 1st was tranny. rebuilt tranny, and removed lockup TQ (did it right, drilled the valves etc) pro-shop did all the work. No change. Replaced the engine (spun a bearing) about 3 years ago. Did TONS of work, sensors, egr, MAF, O2, and so forth, wiring etc, at same time. Problem became more noticeable with the increased compression. It will NOT freewheel at all going downhill, unless i put it in neutral. Its actually engine braking so much I can loose speed going down a pretty steep hill. My mechanic, who has TONS of experience with these cars (he's owned 6) can only tell me when he see's it happen with him, the car is going in and out of lean mode. But neither of us know why. It wasn't until I started thinking about maybe doing some computer mods now that its all restored and replaced, that i stumbled across the highway mode thread. I'd NEVER heard of that before. So, after all this rambling, the big question is: on a 1987 IROC, would that mode be enabled or disabled? (we even changed out the entire ECM at one point a few years ago thinking the computer was flaky. same symptoms) She now gets 23-24mpg hwy, and thats at 75mph cruise. So i'm thinking highway mode is enabled? She has always gotten those numbers when running right. I do not have a laptop, cable or software, my mechanic has a reading tool, but not a programming tool so this would be new territory for both of us. With the reading tool, how do we tell? Once we find out if its off or on, should i try and have fastchips.com just burn me a new chip? One thing of note, i am in colorado. This car lives at 6000+ ft altitude and above. She runs a bit hot with 90+ temps and A/c on already, so i DO NOT want to cook this new engine! I could sure use some expertise!
Sorry for the long post, but i'm running out of things to look at on this car.
I have NEVER, repeat NEVER been 'into' my computer. my car is a basically stock 1987 IROC. 5.7TPI, auto tranny. over the past 10 years, the car has basically been totally rebuilt (150k approx on chassis) we've replaced engine, tranny, brakes, rear, sensors, radiator, sensors, and on and on. And we have never been able to 'fix' a weird issue. the engine rpm jumps around when on light throttle. By this, i mean - when rolling downhill, the rpm will jump up 100-200, then back down again. Causing the car to slow down. The tranny was going out, so thought at 1st was tranny. rebuilt tranny, and removed lockup TQ (did it right, drilled the valves etc) pro-shop did all the work. No change. Replaced the engine (spun a bearing) about 3 years ago. Did TONS of work, sensors, egr, MAF, O2, and so forth, wiring etc, at same time. Problem became more noticeable with the increased compression. It will NOT freewheel at all going downhill, unless i put it in neutral. Its actually engine braking so much I can loose speed going down a pretty steep hill. My mechanic, who has TONS of experience with these cars (he's owned 6) can only tell me when he see's it happen with him, the car is going in and out of lean mode. But neither of us know why. It wasn't until I started thinking about maybe doing some computer mods now that its all restored and replaced, that i stumbled across the highway mode thread. I'd NEVER heard of that before. So, after all this rambling, the big question is: on a 1987 IROC, would that mode be enabled or disabled? (we even changed out the entire ECM at one point a few years ago thinking the computer was flaky. same symptoms) She now gets 23-24mpg hwy, and thats at 75mph cruise. So i'm thinking highway mode is enabled? She has always gotten those numbers when running right. I do not have a laptop, cable or software, my mechanic has a reading tool, but not a programming tool so this would be new territory for both of us. With the reading tool, how do we tell? Once we find out if its off or on, should i try and have fastchips.com just burn me a new chip? One thing of note, i am in colorado. This car lives at 6000+ ft altitude and above. She runs a bit hot with 90+ temps and A/c on already, so i DO NOT want to cook this new engine! I could sure use some expertise!
Re: Decelerations and highway mode.
All i can say is my HYmode is only in effect over 70 mph. I think it disables with a change in map or tps. It is like a steady state condition. I think GM disables HY-M for emmishions reasons. What i read. I can see it happening on WB. Kind of cool.
It may be DFCO. That I believe is enabled as no affect on emmishions. I can feel what you feel on my 03 dodge stratus. Pronounced. But not on my 03 Ford F150. A minor extent on my 84 Vette. I thinlk it is off at 25MPH for Vette. Same hill on way to work.
It may be DFCO. That I believe is enabled as no affect on emmishions. I can feel what you feel on my 03 dodge stratus. Pronounced. But not on my 03 Ford F150. A minor extent on my 84 Vette. I thinlk it is off at 25MPH for Vette. Same hill on way to work.
Last edited by Ronny; Sep 28, 2012 at 12:41 PM.
Re: Decelerations and highway mode.
EBL. Its datalogging is called Learn VE contained in its Whats Up display program. I believe it is also in TunerProRT but dont know for sure. It may show on their site.
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