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topless cobra
04-19-2010, 06:10 PM
Hello everybody. I have a "03 Cobra and I really need some help. I put a 2.8 inch pulley on and a belt tensioner, UPR cold air, NGK TR6's, and upgraded fuel pumps. Well, the engine wants to cut out and just lay down about 5500 rpms in any gear. What could be the problem? Thanks for any responses.

inerceptor
04-20-2010, 09:15 AM
:scratch:

topless cobra
04-20-2010, 06:34 PM
Yes I did have a dyno tune, sorry, left that part out. According to him, my a/f ratio was right on the money. Don't know exactly what that would be but I'll ask him.

ausie
04-21-2010, 06:26 AM
It sounds like the ECU is pulling spark either due to intake plenum temperature or lean A/F caused by pegged MAF meter, or drop in fuel pressure either related to injector duty cycle, clogged or weak injector flow (may need cleaning) or replacement of fuel filter. What was the tuner using to tune the car? If you have a hand held tuner with the tune in it you could data log parameters such as fuel pump duty cycle, fuel rail pressure across injectors, fuel injector duty cycle to determine if the fuel system is maxed out based on your injectors. Also you mentioned that you have the UPR CAI. The CAI kit may be the culprit causing a pegged meter due to the bend in front of the MAF meter. If you have the ability to data log, you could also monitor MAF counts, or flow rate, spark advance, and many more parameters to determine what the ECU is doing at any RPM, load, etc... There may be a solution if you are still using the stock MAF meter and your tune was not set for another MAF meter such as the SCT BA-2600 , BA-3000, etc... In the case with the stock MAF meter, I would replace it with a 95mm PRO-M meter. The Pro-M meter can be calibrated for your application, all you need to do is specify the fuel injectors, and if there is a bend in front of the meter or not. I recently purchased the 95mm Pro-M meter for my vehicle but did not need to have the calibration for the bend since I am using an RAI kit. If it is not the MAF, it may be the increase in exhaust temperature and glowing red cats if the A/F leans out. It sounds like the ECU is operating in limp mode. Another thought, if the A/F was solid and all was well from the dyno tune, go back to your tuner and have then run a road test with their tune to verify proper function of the tune. Is the fan comming on? if not, check the large 50 amp fuse in the engine bay in the power distribution box next to the battery. Another trick would be to dump the EPROM memory by disconnect of negative battery terminal and press the brake pedal for at least 15 seconds. Wait about 10 minutes and reconnect the battery. This would clear all of the accumulated learned data so the ECU can relearn new parameters with the new hardware in place. Before jumping to any suggestions, contact your tuner with your issue first since they should stand by their tune and support and correct any issues if there are any.

puzzle13
04-21-2010, 06:54 PM
Check your spark plug gap ... running that amount of boost the gap can be no larger than .035 and .032 will work just as good. Too much gap will make it flutter and falter at the higher rpms. Ask Dan at Pro Dyno!!
Hello everybody. I have a "03 Cobra and I really need some help. I put a 2.8 inch pulley on and a belt tensioner, UPR cold air, NGK TR6's, and upgraded fuel pumps. Well, the engine wants to cut out and just lay down about 5500 rpms in any gear. What could be the problem? Thanks for any responses.

ausie
04-22-2010, 12:30 PM
Check your spark plug gap ... running that amount of boost the gap can be no larger than .035 and .032 will work just as good. Too much gap will make it flutter and falter at the higher rpms. Ask Dan at Pro Dyno!!I would agree with Puzzle13 on this. :thumbsup:

I had a similar issue with my stock 04 Cobra which happened after pulling out of storage last year. Car ran great before it sat during winter, but when I took it out, it would bog down when under boost above 4000 RPM. I could ramp up the RPM staying out of boost and all was fine. Changed plugs gap at 0.035 and all was fine. Another contributor was caused by a dead battery (still had enough charge to get it started but the voltage dropped extremely low when starting which may have caused the EPROM data getting corrupt. When I changed the plugs I also had the battery disconnected which erased the EPROM data. Not sure if it was the plugs since I always gap at 0.035" but that was my first assumption. As for my battery, it should have been replaced but I was able to get it to charge up and hold steady.

If you are having issues with your battery that could also cause problems if the voltage is not stable enough (when under load). Battery voltage will fluctuate while driving based on RPM as the loads increase (fuel pump duty cycle, injector pulse width, spark load, and the cooling fan). If your battery has aged, I would have that checked out if the problem is persistent after gaping the plugs.

topless cobra
04-22-2010, 07:19 PM
Thanks a bunch for all the replies. I've got my plugs gapped at .035. I tried disconnecting the battery and doing the brake pedal thing as well but nothing worked. My tuner guy wants to replace some kind of module, I think it's called fuel pump driver module. As for the battery, it is the factory Motorcraft and it's 7 years old. It still has the green eye in it but that may not mean anything.
One more thing I'll throw out there for ya: I buy my gas at an independently owned gas station because they say their gas doesn't have any ethenal. I've heard alot of bad things about that stuff. I'm wondering if they are trying to save money and putting 87 octane gas in their 93 octane tanks. I had Chevron gas in it when my dyno guy replaced my fuel pumps and he swears it didn't cut out when he drove it. Just a thought, I'll just about try anything now.

ausie
04-23-2010, 03:40 AM
The changes made to the fuel system may have caused the mechanical pressure regulator in the fuel line to bypass in the fuel tank. Referred to as PPRV which is attached to the fuel line just above the fuel pumps under the fuel hat. I have read some threads about the PPRV, many have had similar issues with their 03's. There was a thread in svtperformance about it. Another issue may also be with the FRPS (fuel rail pressure sensor). If it was the FRPS it would generate a check engine code. It is probable you may have a coil issue. I would suspect that when your car was tuned, everything was fine. Sometimes parts will fail or become problermatic at any time. The best thing to solve the issue would be road test and data log up to the point where it begins to bogg just to get a good look at what is going on.