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I have a 90 5.0 that has developed a strange problem. When pulling away from a stop or gearing done under normal throttle the engine bucks and runs very rough in 1st and second.In high gear it does not like to cruise under 2000 rpm,stumbles along. Accelerating harder then everyday driving and it runs great. Know things get strange. I have tried many changes and each one fixed the problem from 10 to 150 miles but the problem returns. At first I just increased the fuel pressure a couple of pounds.Then more over the next month untill it hit 50lbs. I did not like it so high so I set it back to 39, ran awfull so I set it back to 50 lbs but this no longer worked.I've tried replacing Fuel pump, filter,wires, cap, rotor, dist.,msd ignition, fuel regulator,(also blew out the return line and this one worked for 150 miles. Blew out return line again no change the second time) o2 sensors and fuel injecters were new a few months before the problems. Could it be injectors?
Mods are: e303 cam, 1.7 roller rockers,bbk 65mm tb, c&l 76mm maf (recal. for injectors.),24 lb injectors,stock heads ported and polish, stock ho upper and lower ported,under drive pullies,egr and air pump removed,msd dig6+ ignition, mac shorty headers and 150 shot of nos. Its strange. Like I said each change seemed to fix it but it returns. I evan replaced one plug wire and it worked for awhile. Once the problem shows up it won't go away untill a change is made. I've also tried reset the computer and this made no change.
 

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I hate fuel injection, but here goes some more things to check.

1. Check the TPS to see if it's set to .89-93 with the engine off, but the key on. That should get it to the high .9s when the alternator is turning.

2. Has the ground for your computer come loose?

3. I don't know what the fuel pressure should be on 24 lb injectors, but set it back to what it should be, pull the battery hot for 30 minutes, then hook it all back up after doing the things above.

4. Does it run fine with the MAF unplugged? It could be the MAF. If you just oiled your air filter, some oil could have gotten on the hot wire and could cause this greaf. Also, I hear some people have had problems with the C&Fs going bad, but that's true of all MAFs.

5. The timing could have slipped. Pull the spout and check the timing at idle.


I'm fighting crap like this, too. In fact, tomorrow I'm running to Napa to try another computer because mine is running so dang rich. When EFI works, it's great. When it doesn't work, it's outrageously expensive and really frustrating trying to figure out why it doesn't work. Good luck.
 

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My bet is the C&L meter. If you can, borrow a Pro-M or Granatelli meter (calibrated for 24's) and try it. Or, swap your 19# injectors back in and try a stock meter. Did you pull any codes? I wouldn't be surprised if you get a lean HEGO code.
 

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Very similar problem here. I posted earlier in the week that I am dumping the FI and going carbed. I got a lot of responses and people willing to help, but nothing seems to be changing the problem. WFO is the best it has ever been. Low and mid range, It is missing badly
 

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Have you put the system through diagnostics yet? If not, thats where you need to start. I'd pull the codes at a minimum but better yet do the KOEO, KEOR, actuator/sensor tests, etc. You can buy a nice digital code reader for under $50 that will do all that for you. Its the best place to start.

I'd also agree that your C&L is a suspect. Drivability issues similar to yours with their meters seem to be commonly reported.

If you havn't already go here as well for help/advice: http://www.corral.net/forums/ and more specifically into the 5.0/5.8 tech forum. Do a search for your symptoms.
 
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