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New FD, altitude change
I just bought my first FD ( not new to the engine ) car is a half bridge, s366, power FC, IGN-1A coils, car has great fuel pressure, adjusted the TPS that was slightly out of spec, car ran phenomenal in VA where I bought the car, now that I’m at 4800 +/- altitude car bucks like crazy and hesitates on throttle tip in, tries to stall, have to keep the gas pressed a little when it’s cold because it won’t hold idle, car is pulling -10 or so Inhg, what could cause this drastic change in drivability, is the tune just that far off now? Engine has about 350-400 miles on a break in, engine was rebuilt by Angel Motorsports, ANY help is greatly appreciated as I’m not comfortable driving the car because it just plain feels wrong. Boost AFR is about 12, cruising I’ve seen as high as 17.. please help |
If nothing else was changed then I would start troubleshooting with the tune. The change in tps adjustment shouldn't affect it that much unless you did it wrong. The other option would be to go back to va and see if it still does it.
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Living at sea-level Florida I'm not that familiar with tuning cars for altitude differences. But that sounds like more than just altitude, and 4800 feet altitude isn't that much. I go to Deal's Gap in North Carolina every year and make a run up the Cherohala Skyway which is 5400 feet in elevation - car runs perfectly fine as does the 50 other RX-7's and RX-8's behind me in the caravan.
Hate to say it but I would start with a compression test to be certain the engine is healthy then start troubleshooting other systems. Dale |
I didn’t think the altitude change would’ve been enough either personally but the engine is literally on 350 miles on the break in, how could the engine have been hurt already? |
Originally Posted by Bimmer_Tyler
(Post 12321370)
I didn’t think the altitude change would’ve been enough either personally but the engine is literally on 350 miles on the break in, how could the engine have been hurt already? Almost always a poor quality build, though I certainly don't think anyone here is accusing of whomever built the engine or sold you the car would do it knowingly. I'd agree on definitely doing a compression test ASAP but first if you have the ability with either the FC commander or FC edit just throw like 5-10% more fuel at it when its warmed up. If it seems to get better there's a good chance you've found your culprit. |
Angel motorsports is pretty reputable in my opinion, and it ran damn good before I had the car transported, the only difference is the car changed physical location. I doubt it would’ve all of a sudden lost compression or something.. I’m at a loss here feeling like shit because I can’t drive my dream car that I could finally buy. I don’t know what else it could be |
Also I don’t have a datalogit and have yet to learn how to tune, how would I go about adding fuel... |
Re-check your TPS calibration. The symptoms you describe are exactly what you'd get if it were not adjusted correctly.
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I will check again. There does seem to be slack in the throttle cable but the tps is showing closed values and wide open values within spec so I assumed that was okay. I seriously appreciate all the help from all of you guys. |
Something old schoo and just to check, but working on the tps, did you pull the vacuum line off the map sensor? |
Nawh I didn’t, I did double check the vacuum line though and it is connected and not leaking or brittle |
A new engine isn't safe from failure, could have had something get sucked into the engine or a seal caught on something and snapped. It's worth doing a compression test just to rule that out - I've seen people chase their tails going through EVERY system in the car when it was a problem with the motor the whole time.
Could also be something like a failed coil pack or plug wire. The car as it sits should be able to start, idle, and drive even with a rough tune. Dale |
Originally Posted by Bimmer_Tyler
(Post 12321387)
Angel motorsports is pretty reputable in my opinion, and it ran damn good before I had the car transported, the only difference is the car changed physical location. I doubt it would’ve all of a sudden lost compression or something.. I’m at a loss here feeling like shit because I can’t drive my dream car that I could finally buy. I don’t know what else it could be |
The car will run and start and drive/ idles great. It’s under throttle tip in it hesistates like a pig and bucks then if I give it more pedal it clears up. I’ll check compression if I can get to it I’m changing the plugs today almost feels like fouled plugs too, I’ll check them all. Hopefully its not hurt. |
Originally Posted by Bimmer_Tyler
(Post 12321546)
The car will run and start and drive/ idles great. It’s under throttle tip in it hesistates like a pig and bucks then if I give it more pedal it clears up. I’ll check compression if I can get to it I’m changing the plugs today almost feels like fouled plugs too, I’ll check them all. Hopefully its not hurt. |
I’ll check for any vacuum leaks, I didn’t see anything but I will check. TPS fell out of spec again so maybe the TPS is just fucked. How do you check IGN-1A coils? |
Another thought - if the secondary throttle plates are not closing all the way, or are binding such that they don't open smoothly, that could cause some bucking. I had that, but not as severe as what you describe.
Also at that time I replaced the O2 sensor - that also got rid of some of the bucking and throttle tip-in issues. There is an old thread I started on that fix - link: https://www.rx7club.com/3rd-generati...ensor+throttle |
It could very well be the tune. At elevation, the very light throttle applications run less load on the map then at sea level. Plus a lot of tunes are garbage and not smoothed out. The issues would present themselves at idle and very low loads only if the map isn't tuned well.
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I responded to your PM.
We'll have to take a look at your map and datalogs, starting with a comparison between the default Power FC map and the map that's loaded into your car. |
My situation is very similar to yours, as I bought my car from LA and I now live at 4500 ft in NM. The only difference I noticed when making the climb and since I've been here was that the car ran significantly richer. I went to Colorado Springs and had it tuned, ran phenomenal ever since. I'd suggest getting the car tuned in your current location or as close to your elevation as possible. Could be getting too much fuel.
However, if I were a betting man, I'd say vacuum leak. I've had the bucking problem on many of cars, and 1 on the FD and its almost always been a vacuum leak. Just comb through everything slowly and you'll find it. It'll also help to have a vacuum hose diagram handy jic. |
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