Still Cutting Out At High RPMs. What To Try Next?
- Thread starter klmnla
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All the grounds were secured when I put the heads back on. I can run the car hard with no problem, and when I turn the air on it starts cutting out at WOT. Whats strange is that it keeps cutting out from that point on even if I turn the air off. Im not sure if its just acting up after warm up, but I suspected maybe the old battery was being pulled down when I turned on the air, even though the volts on the scanmaster still show 13.6. Im just going down the line trying every trick that I can think of.
The engine had audible knock when I first got the car, which seems to be fixed once I replaced the blown head gasket, motor mounts etc and got the cracked header welded. The compression and cam shaft have not been tested at this point. I rarely went at WOT when it had the audible knock, but I suspect it always had the problem with cutting out at WOT.
Maybe at this point a compression test would not hurt. You might want to look into those valve springs also. I've double checked pretty much everything. All the stuff you did i did to. I just changed the valve spring set up so as soon as it stops raining , i'll give it a go.
Let me know how it goes. I just replaced the cheap, small, 5 yr old everstart with a new duralast gold and cleaned out the intercooler real good. The volts on the scanmaster show 14.2 now. I noticed the fairly new 4-seasons AC compressor is making noise now and dropping the voltage when I turn it on, so probably need an oil charge or a warranty replacement. Its pulling down the battery an entire volt when I turn it on. I will test out the car at WOT some time tomorrow and see what happens, and probably without the air on.
As mentioned earlier,the computer is supposed to turn the compressor off at WOT.
Perhaps the AC compressor has been an issue that is just now getting worse. I would suggest driving the car with the AC turned off for awhile and see if that makes a difference in the way the car runs. Like mentioned earlier in the thread about the AC, that it's supposed to turn off at WOT but what if something is preventing that from happening.
Took my T for a ride and my problem was definitely valve float... It now pulls hard till 6000 rpm real easy. Knock retard issue is completely gone also. I know you've been having an issue with the A/C on, but if it still does it with the A/C off , take a look at those valve springs. I would of never thought it was the springs. We triple checked everything, from module to coil pack, grounds , plugs, cam and crank sensor, wires, and so on. One disappointment after another. I'm gonna sleep real good tonight. Keep digging your gonna find it .
Nick
Nick
I think Im going to replace the valve springs just because of the mileage on the car, and to possibly help with my current issue. Now I need to ask everyone what the best stock replacement valve spring would be. I also need to order a spring compression tool. This way I can air test the intake while the rockers are removed and the valves are closed. Also, this is probably the least expensive thing I will be replacing during this on-going problem.
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Well I drove the car for about an hour last night. Its still cutting out and popping under moderate to hard throtle, regardless if the AC is on or not. It seems to get worse after the car is driven a while. All the scanmaster numbers still look okay, AF hits 255 when Im at WOT and gettting up to speed, BL is at 127, MV look good, no knock, etc. Im going to go ahead and replace the valve springs, and do an air leak test on the intake while I have the rockers off and the valves closed. I will also go ahead and do a compression test also. Results to follow.
Man, I am still trying to get this thing to run right under boost. In the last few months I have replaced the valve springs, tried another new GM coil and ignition module from NOS4GN, replaced more vacuum lines with silicone lines, did the air leak test through the intake, no obvious air leaks. My scanmaster numbers are spot on, the int and blm stay at or close to 128, my airflow never reaches 255 at WOT, but stops at about 240, and thats with a new 3.5 inch LS1 MAF. The translator plus is set at all zeros, so no additional fuel or timing. It starts stumbling about 3 minutes after I start driving it. For the first few minutes, I can hit 15lbs of boost and it runs good. once it warms up, it might stumble before I even get to 5 lbs of boost. I have new NGK 5U plugs, 10mm taylor wires, rebuilt turbo, no more oil in the intake, new TB shaft seals, new Racetronics fuel sender with walbro 240 pump. and lots more. Could a bad torque converter cause the car to stumble? I ask because I have the infamous ticking sound down there. As far as fuel, its set at 42 with line off, it climbs to 50psi at about 5 lbs of boost, and to about 58psi at 15 lbs of boost. Ive spent 2 years trying to make this car run right. I really want to get this done before I start thinking about body work and paint. Everything works on the car and Im determined to get it right. Any advice is well taken.
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Sounds like cam or crank sensor. Are they both original? Aftermarket? Or?
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Check the crank end play. It might be moving far enuf to cause the crank sensor to drop the signal.
Leak down tested?
Compression tested?
Stock injs...Been cleaned and flow tested?
What do the plugs look like?
Leak down tested?
Compression tested?
Stock injs...Been cleaned and flow tested?
What do the plugs look like?
I would think 15psi should be enough to hit 255 airflow. Maybe the ignition module needs a hotwire? There are still so many possibilities. You're doing well at eliminating things though so stay at it. These cars take $ at times...and LOTS of patience.
Both of these items do wear out over time and spares should always be kept. Might as well check crank end play while you're at it and hopefully all is well. These cars are capable of lasting longer than what you have for miles but require atttention...and LOTS of patience. Good luck; it's worth it.
Both of these items do wear out over time and spares should always be kept. Might as well check crank end play while you're at it and hopefully all is well. These cars are capable of lasting longer than what you have for miles but require atttention...and LOTS of patience. Good luck; it's worth it.
I have a new capers cam sensor cap with the LED. The crank sensor was replaced with a GM sensor I believe. I have a compression tester, but have not done this. I need to look at how to do a leak down test. It does have stock 28lb injectors, but not cleaned and flow tested, but did replace all the o rings top and bottom.I have put 3 sets of plugs in during this process, just to keep them from being a possible problem.
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Put the stock cap back on....
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