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New TB and CAI - Stumbling / Small Backfire - HELP
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<blockquote data-quote="DT_C03RA" data-source="post: 11440657" data-attributes="member: 126401"><p>When he changed the upper and lower intake manifold he put all new o-rings on the injectors. </p><p></p><p>The car ran great when he changed the U&L intake manifold. I know because I personally drove the car and there was no stumble or anything. The car pulled hard all over in ever RPM and idled perfect. The car came with the 73 C&L MAF and ran great before the U&L intake manifold was put on and after, so I don't believe the C&L is the culprit to the stumble issue. And his injectors are the stock yellow/orange ones that from what he and I can tell are Ford's 19lb injector that came on these cars.</p><p></p><p>The bad gas/varnish smell started to occur when the new h-pipe was installed (a BBK high flow catted version) and the stock 4 catted h-pipe was removed. It only happened one time, but it left us stranded because the car would not start. A mechanic looked the car over the same moment this happened, as we happened to have it happen as we were looking for a shop to gut out the cats in the BBK h-pipe because the ceramic inside them was loose and causing a loud rattle in his exhaust. The mechanic hooked up his vacuum gauge and checked the fuel pressure and he determined it was the fuel pump. Well fast forward 20 minutes after we called AAA to come tow it (this was just right around Christmas and this shop was closing for 2 plus weeks, so we couldn't leave it there) and "I" said, "hey lets try it one more time," and to our surprise the car started and ran perfect again. </p><p></p><p>So fast forward a couple weeks. He decides he's had enough of the ****ed up BBK h-pipe and removes it and puts the stock h-pipe back in the car, but the bad gas/varnish smell keeps happening and causing the same scenario of not starting again and leaving him stranded.</p><p></p><p>Now here's where I'm going to lose some of you. In that time he also added the new CAI, 70mm throttle body and spacer to his already installed U&L intake manifold and THIS is when the stumbling issue started occurring. Remember the injectors have new o-rings, the MAF is still the same 73mm C&L that came on the car and ran perfect before and after the U&L intake manifold swap, but the only difference is he's added the new TB with spacer and CAI.</p><p></p><p>The only other thing done to the car to that point was the h-pipe being swapped out several times, and we all know the O2's had to be removed and installed several times, so it's entirely possible these O2's got damaged in some way. The h-pipe swap was done by a mechanic shop also, but the rest of the performance mods were done by Ninety3Coupe.</p><p></p><p>I'm not saying the O2's are the sole cause of the stumbling issue or the bad gas/varnish smell. But the MAF and O2's are somewhat related since the MAF tells the computer how much metered air is coming in and the O2's monitor the burn of the fuel and with all the times he's bumped up fuel pressure and the fact that the O2's have been pulled multiple times lately (not to mention they have over 90k miles and almost 20 years on them), it's entirely possible they are overly saturated, damaged or just not holding the proper voltage any longer, which in conjunction with the increased air flow the car's getting now, plus all the extra fuel that's being thrown at it now, the O2's could be skewing the readings and the computer is trying to compensate.</p><p></p><p>Now I know the 5.0's computers are very adaptive (unlike my Cobra and most any new car out there), so with that said, it's that fact that leads me to think if nothing else replacing the O2's to this point certainly can't hurt.</p><p></p><p>I mean the engine should be getting more than enough fuel (and yes it's probably very rich now), now that he's swapped out what he indeed did find was a failing fuel pump with a Walbro 255lph and he's added the FPR and gauge to assist in fueling. </p><p></p><p>Also from everything I've read and calculated those stock 19lb injectors should be more than enough injector for his power level with the fuel pump upgrade plus the FPR. It certainly couldn't hurt to go to a bigger injector and trust me he and I agree that some larger ones would be helpful, but unless one went bad (which we understand it could of) I don't think it's the injectors. Especially since the car pulls great at WOT and only stumbles in the 2-3k RPM range in normal driving conditions.</p><p></p><p>If anything I've said is way off, please someone correct me. I'm just stating the facts of what I personally know and have personally seen with this car.</p><p></p><p>Also the only mods this car had on it when he bought it were the 73mm C&L MAF, shorty headers, cat-back exhaust and a short shifter. That's it, it still had the stock U&L intake manifold all the way down to the stock paper filter in the stock air intake. Other than that, that's it, so this was not a highly molested Fox body. But now it sure the **** is! lol that's for you N3C!</p></blockquote><p></p>
[QUOTE="DT_C03RA, post: 11440657, member: 126401"] When he changed the upper and lower intake manifold he put all new o-rings on the injectors. The car ran great when he changed the U&L intake manifold. I know because I personally drove the car and there was no stumble or anything. The car pulled hard all over in ever RPM and idled perfect. The car came with the 73 C&L MAF and ran great before the U&L intake manifold was put on and after, so I don't believe the C&L is the culprit to the stumble issue. And his injectors are the stock yellow/orange ones that from what he and I can tell are Ford's 19lb injector that came on these cars. The bad gas/varnish smell started to occur when the new h-pipe was installed (a BBK high flow catted version) and the stock 4 catted h-pipe was removed. It only happened one time, but it left us stranded because the car would not start. A mechanic looked the car over the same moment this happened, as we happened to have it happen as we were looking for a shop to gut out the cats in the BBK h-pipe because the ceramic inside them was loose and causing a loud rattle in his exhaust. The mechanic hooked up his vacuum gauge and checked the fuel pressure and he determined it was the fuel pump. Well fast forward 20 minutes after we called AAA to come tow it (this was just right around Christmas and this shop was closing for 2 plus weeks, so we couldn't leave it there) and "I" said, "hey lets try it one more time," and to our surprise the car started and ran perfect again. So fast forward a couple weeks. He decides he's had enough of the ****ed up BBK h-pipe and removes it and puts the stock h-pipe back in the car, but the bad gas/varnish smell keeps happening and causing the same scenario of not starting again and leaving him stranded. Now here's where I'm going to lose some of you. In that time he also added the new CAI, 70mm throttle body and spacer to his already installed U&L intake manifold and THIS is when the stumbling issue started occurring. Remember the injectors have new o-rings, the MAF is still the same 73mm C&L that came on the car and ran perfect before and after the U&L intake manifold swap, but the only difference is he's added the new TB with spacer and CAI. The only other thing done to the car to that point was the h-pipe being swapped out several times, and we all know the O2's had to be removed and installed several times, so it's entirely possible these O2's got damaged in some way. The h-pipe swap was done by a mechanic shop also, but the rest of the performance mods were done by Ninety3Coupe. I'm not saying the O2's are the sole cause of the stumbling issue or the bad gas/varnish smell. But the MAF and O2's are somewhat related since the MAF tells the computer how much metered air is coming in and the O2's monitor the burn of the fuel and with all the times he's bumped up fuel pressure and the fact that the O2's have been pulled multiple times lately (not to mention they have over 90k miles and almost 20 years on them), it's entirely possible they are overly saturated, damaged or just not holding the proper voltage any longer, which in conjunction with the increased air flow the car's getting now, plus all the extra fuel that's being thrown at it now, the O2's could be skewing the readings and the computer is trying to compensate. Now I know the 5.0's computers are very adaptive (unlike my Cobra and most any new car out there), so with that said, it's that fact that leads me to think if nothing else replacing the O2's to this point certainly can't hurt. I mean the engine should be getting more than enough fuel (and yes it's probably very rich now), now that he's swapped out what he indeed did find was a failing fuel pump with a Walbro 255lph and he's added the FPR and gauge to assist in fueling. Also from everything I've read and calculated those stock 19lb injectors should be more than enough injector for his power level with the fuel pump upgrade plus the FPR. It certainly couldn't hurt to go to a bigger injector and trust me he and I agree that some larger ones would be helpful, but unless one went bad (which we understand it could of) I don't think it's the injectors. Especially since the car pulls great at WOT and only stumbles in the 2-3k RPM range in normal driving conditions. If anything I've said is way off, please someone correct me. I'm just stating the facts of what I personally know and have personally seen with this car. Also the only mods this car had on it when he bought it were the 73mm C&L MAF, shorty headers, cat-back exhaust and a short shifter. That's it, it still had the stock U&L intake manifold all the way down to the stock paper filter in the stock air intake. Other than that, that's it, so this was not a highly molested Fox body. But now it sure the **** is! lol that's for you N3C! [/QUOTE]
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