Hello. New to the forum, and I need help. I own a 1993 F-150. Motor seized up about 5 years ago. It sat for a bit, then a local mechanic offered to build a motor for it. What I got was a 1991 5.8l in exchange for my dead 93 5.8l The mechanic told me it was no problem, and to just remove the emissions that usually went to the back of the heads, and crimp the tube to the EGR and the computer would just automatically adjust and be good to go...of course a year later he said to just learn to live with the issues too, so...well, from the second we tried firing this thing up, it would not run well at all! I had 5 different guys of varying experience come and look at it and they were all messing with the timing. finally got it to actually stay running eventually, but to this day I have numerous issues. 1) idles at about 1000 rpm. if i kick it down, it goes to about 850 then creeps back up. 2) choke always comes on at start up, even when its already hot. 3) idle surges a couple hundred rpm. 4) throttle stick on during cold weather. 5) it hesitates when i hit the gas. 6) on the highway, it jerks under acceleration. 7) smell of raw gas all the time. 8) fuel usage went from 16 to 5.3mpg!! This thing is a mess, and i cant figure it out. I am not a mechanic, but also can't afford to take it to one, so I'm trying to trouble shoot. I do not have any codes yet, as my code reader has stopped working. I have replaced the IAC, the TPS, the MAP sensor, did an EGR delete (just to make sure it wasn't the crimped valve doing it) changed the injectors twice, reset the flux capacitor, crossed me fingers and patted the hood, and nothing has worked. I'm at the point of just locking it and walking away, but I love this truck, so I am hoping for some help. Please take it easy on me, as like I say, not a mechanic! Thanks in advance

 

For the smell of fuel and bad mileage I would check the fuel pressure regulator by pulling its vacuum line off and see if raw gas comes out.

You have done so many things to that engine which makes no sense at all. Flux capacitor?? What is that?? There is no choke on a fuel injected engine. When ever you start deleting systems there's going to be issues. Put the engine back in its original configuration and begin to logically troubleshoot the engine from there.. Stop throwing parts at it. The idle speed is varying because air to fuel ratio is off and the computer is trying to compensate for it. Vacuum leaks, inoperative AIC, TPS issues can cause an irregular idle.

Finally, make sure its your code scanner and not the ECM which is the reason you cannot run a code test.

 

I agree and have a bit to add
The EGR delete is at least part of the problem
If the processor does not see EVP movement, it will be in limp mode or otherwise run like crap
Put the EGR back
An older one it means less but with no EVP you are doomed on a mid 90s Ford
You should have a rash of codes IMO and should start with getting a new scanner
What did you reset? We should all have a flux capacitor.
You have checked for an intake manifold vacuum leak?

 

I can’t put the EGR valve back. When I went to put the delete on, I found that the guy who built my motor plugged the hole entirely. So neither the valve nor the delete were making any difference. So perhaps that is the issue? When I was told “oh the computer will adjust”, I said I didn’t think that was how it works. I will replace my code reader as well. Thank you for the advice.

 

I also wanted to ask about the “no choke on a fuel injected engine” comment…ever since I’ve had the truck, when I start it, the idle would rap up to around 1200-ish rpms for about a min or so, then gradually come back down. With the original motor it would then come down to the 700-ish zone and run great. Of course now it comes down to 1000 and runs terrible as mentioned. So what is that “warm up” procedure it’s doing? I just assumed it was the “idea” of a choke, to get it warmed up…is this another issue that was present before the new motor then?

 

The idle speed is controlled by the computer with a specified amount air is metered into the intake via the IAC solenoid on the valve body. No choke.