Wierd startup probs.

  • Thread starter 5point8LiterImportEater
  • Start date
5

5point8LiterImportEater

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I don't know what this could be but when I start up my truck sometimes it roars to life then chuggs down to somewhere around 500 rpm and occasionally dies. when it doesn't die it revs back up to 1000 rpms and it dives back down then it goes to perfect idle. it is wierd. It just started this after I put on my NOS system. I don't think this is the prob though because it doesn't always do this. could I have a regulator problem or what? I did have to have the fuel pumps replaced because of a stupid problem where the rear tank didn't return the fuel there but to the front one and over filled it.
any help would be greatly appreciated.

Thanks Chris.
 
Chris,
First of all your problem is that you have a Ford. You should buy an Import, they are much more refined and well-tuned....
:eek:)
Anyways..Im going to eventually post on the War Zone what the announcer said at MAR when those R/T's ran right after we did..I think that is just cool as hell.

Call me tomorrow (Friday) after you get off work...Im off at 9 and well go let our Lightnings munch on some imports or R/T's if its not raining.
cya Chris,
Tommy
 
How did you plumb in the nitrous? SOunds like a vacuum leak to me. Or perhaps a gunked up IAB.

Later!
Jeff S.
 
I had a similar problem with my '94 Lightning, after lots of hair pulling, I checked the voltage of my throttle position sensor, and adjusted it to (I believe) .92 volts.
 
I sometimes have the same surging at startup problem, it idles erratically and sometimes dies. This only happens occasionally in the mornings and then the truck runs fine for the rest of the day so i'm not sure what it may be?..I was thinking o2 sensor while it's cold or maybe the TPS..any ideas?
 
Thanks guys I will check all of the above. Jeff I know I had a vacuum leak and I solved that with some hose clamps. I can't find any more leaks, but I will look. I will check back with this probably sunday some time and post how the truck checks out.
Chris
 
Hey guys get this it has gotten much much worse. The damn thing is chugging down to 500 rpm and going up to 1000 rpm something like 5 to 6 times and it spitting out some serious shit out the exhaust. I have checked the plugs after every pass with the nitrous and haven't used the nitrous but like 4 times at all. I don't think this is the problem. I even took off all the vacuum lines and hooked up the origional one. that did nothing. this is getting out of hand. now at stop lights it is chugging down to 750 rpm's and surging to 900. OH yeah it also looses all fuel pressure when it is shut off. I thought these things *fuel injected cars* were supposed to keep some pressure in the fuel rail. do you think this could be a rich condition that has possibly ruined a O2 sensor? please give me some feed back fellas. and does anyone know how much an O2 sensor is? what about a T.P. sensor?
thanks chris.
P.S. oh yeah this got worse last night and I haven't gotten to use the nitrous in like 4 days. so I don't think I have ruined the motor all of a sudden. I haven't abused it.
 
This sounds like a problem I had. Truck almost died every time I stopped the truck, did die several times and just generally ran bad. Turned out to be the fuel pressure regulator. Had it replaced and no problems since.

Good Luck!!!
Tim L
 
You need to invest in a fuel pressure test kit (has to be for FI though..not an old school vacuum/pressure gauge) and see what kind of FP you have, both at idle and at cruising speeds. Any MIL (check engine light) appearances? A sensor failure will show up...specifically an EGR/MAP/O2/IAB. Let us know what you find...

Kyle
 
Thanks guys. Tim. I replaced the origional one with a billet one from Aeromotive a while back because of a startup problem that turned out to be the fuel pumps. I will take the truck to where I got the regulator put on and see if they will try another one to see if this solves the problem. And probably wednesday I will have one of my friends use his code scanner to pull the codes from the comp. it is flashing the check engine light every now and again. any more info or things to check would be greatly appreciated. Hey does anyone know what the "offical" fuel pressure is supposed to be. You know the numbers directly from ford. and if any of you guys are in St. Louis and ever need some help give me a call. I am more than willing to help out those who help me.
Thanks, Chris.
 
Chris,
Dont forget to call me Monday around 7pm. Rob should be home by 6:30, Im off at 8:30, so if you want to meet up with me at work around then, Ill try to set it up to where we can go over there and hook his scanner up to it then.
Give me a call.

Tommy
 
Hey guys, I got it checked and it came up with an O2 sensor code so I changed that and it is no better, what is the fuel psi on these things? *factory numbers* and I am going to get out the ohms tester and see if maybe I have a bad sparkplug wire or something. oh yeah how do I test the tp sensor?
thanks chris
 
coupla thoughts -

1. Dirty / whacked EGR? This will make everything about life bad.

2. Idle air bypass - funky thing on the side of the throttle body (what I think Ford calls the ISC-BPA?) If this gets crud in it, it will cause undue stess to owner of vehicle and a pretty hairy surge / stall attitude from the truck. Most folks say to remove ISC and clean all the exposed internal air channels with spray type carb cleaner, (B12).

Ford EEC guru Probst says to leave the inside of a "coated" throttle body alone, but does the throttle move smoothly (gooey crap on throttle shaft)?
 
White,
Thanks for the Ideas, I have a feeling it is the idle bypass valve, I just remembered that when I installed the nitrous, the nozzle threads shed off some shavings, now I haven't found any evidence of engine dammage*they were damn near microscopic* I do think that possibly some may have gotten caught up in the idle bypass valve.
The throttle body and throttle blade looks clean, and moves freely, I hope this isn't any source of my frustrations. that would ruin my day.
 
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