Re: How to start a stubborn Fuel Injected engine?

The part your mechanic was referring to is the IAC, Idle Air Controller. Rather than using an idle speed screw on a carb to adjust the minimum opening of the throttle plate, the IAC allows extra air into the throttle body to increase the idle speed, and the computer adds extra fuel thru the injectors to balance the mixture.

If the IAC is stuck open, the engine will race. If you have a vacuum leak that's greater than the amount of air the IAC normally allows in, the engine will race (because the computer will close the IAC completely, and you still have too much air coming in thru the leak).

On a 1990 truck, you're sure to have brittle or cracked vacuum hoses, including any larger hoses such as to the PCV valve or to the brake booster. Check them all, and replace as needed. Spray carb cleaner or direct propane gas around suspected leaks to see if the idle speeds up. And replace the IAC, it doesn't work forever.

Bob

Remove the IAC. plug both holes and start the engine. If it still races,. you have a vacuum leak. If it doesnt, replace the iac. HTH, Ben

Thanks for the info. I have not found any bad vacuum hoses, although it's bery cold right now so I only looked quickly. I apprecaite this help because like I said, I hate replacing parts that are not bad. You said to plug BOTH holes. Where are these two holes? I know there is one under the IAC, which I saw when I removed it and sprayed it with PB Blaster. If there is 2 holes under there, I guess I didn't notice (it was cold that day too, so I was in a hurry).

When the engine was racing, I pulled the electrical plug from the IAC and the engine killed. (if that means anything).

BTW: What would be the easiest way to plug thee holes for the test?

Thanks again

FWIW, most of the problems I've noticed here (and my experience also) with IAC have been that the engines won't keep running. Time and again, cleaning the IAC has cured the problem (and saved some $$$). Check closely for vacuum leaks.

Have you had a check engine light on the dash lit up? If not, put a new iac on. If so, get the codes read and get back to us. hth, Ben

I almost always have a check engine light on, but the reason is because the oxygen sensor wires are ripped off. I knew about this, my mechanic said that in order to replace that sensor, I first need to replace the exhaust crossover pipe. That pipe alone is almost $300. It includes the Cat-convertor. This is mostly a farm truck, I am not going to spend a fortune on it, and to replace that exhaust and oxy sensor, I was quoted nearly $1000 (with labor). That's for a truck that cost me $600. My mechanic told me that on a truck as old as mine, running it without that oxy sensor is not really that critical. He said it would likely get a little better gas milage, but said it would take a long time to justify spending $1000.

When the weather gets better, I have a friend who has a pipe bender and saaid he could make me a crossover for under $100. That I will do, but he said there wont be any holes in it for oxygen sensor.

The truck does run pretty well, except for this racing. It's actually getting dangerous to drive. Yesterday I was on an icy road and the engine surged to 3000 rpm. I had to use the brake the whole time to hold it back.

What gets me is that I can be sitting as a stop light. The engine is idling at 600 to 700 RPM (normal). I am not touching the gas pedal or doing anything. Suddenly the engine RPM will increase to somewhere from 2000 to 3000 RPM for no reason, it may shoot up quickly, or may just gradully rise. It will also come back down by itself, either come down partially, or all the way back to the normal idle. In 5 minutes of idling, it may do this several times. It does not get this fast idle until it's warmed up. When I first start it, it idles normally.

I might have my mechanic put the code tester on it anyhow, if I can not find an actual leak. I can not drive it this way much longer. I have been driving my car the last few days and only using the truck for actual farm work.

What method did you use to clean the IAC? I am not going to replace it unless absolutely necessary. Do you know what they cost? I was quoted $110.00 I almost passed out....

snipped-for-privacy@invalid.com wrote in news:uun4p35klk7av3chhp4psqh935krmangjo@

It takes almost nothing to drill a hole and add a bung to put the O2 sensor back on. You are running in limp home mode now, very inefficient and poor power. KB

How difficult is it to change a Fuel Injected engine to a carburetor. The more I mess with this fuel injected engine, the more I hate it. Going back to a pre-fuel injection vehicle means getting something that's pretty old, and thus rusty and falling apart. Yet, I am finding that fuel injection is going to cost me a fortune for repairs. The cost of the parts are outrageous. I am a DIY guy, and am finding myself spending half my paycheck to pay a mechanic, and they dont always solve the problem until several trys. Rather than going back to an old rusty vehicle, I'd rather just remove the fuel injection and install a carburetor from an older Ford engine. How feasible is this?

Otherwise, it looks like my only other option would be to rebuild and older carbureted engine, and change the whole engine, removing all the emissions garbage in the process (which is not inspected where I live). It used to be so easy to work on the old engines. As long as the engine block itself was working, it meant that either the carburetor or fuel pump was dead (fuel problem), or it was the coil, distributor, points (or module), or spark plugs (ingition problem). These days there is so much garbage it seems the mechanics can not fix them without numerous trys and spending a fortune.

Thanks

Not impossible, whether the effort is worth it is up to you, It would depend on how much you'd need to fabricate.

I'd suggest you see if you can get on some decent tuning software/ scanner for your motor and get onto some good tuning forums. A good scanner will tell you a lot about your vehicle's state.

HTH

But what good will it do when the pipe is patched together and leaks?

That still dont solve the idle problem which is my #1 concern.

Like I said in another post, come warm weather I am going to do what I can to go back to a simple carburetor engine without all this modern garbage which does nothing but make the parts stores wealthy by selling costly parts, and make the dealers wealthy because people cant repair their own cars. I have a full size station wagon with carburetor. It's a Chevy, but the engine is the same size (5 liter). I get better milage with the carburetor. This fuel injection stuff is garbage. I have been driving cars with carburetors for about 40 years and they were easy to fix and dependable. Now I got this complicated pile of junk with enough unneeded parts to melt down and build a second vehicle, and it's always acting weird in some manner. The last feul injected vehicle I owned had the in tank fuel pump die, and would have cost 5 times what I paid for the car to repair. I junked that car.

If all this complicated emissions junk actually made a significant increase in gas milage, and really did reduce pollution at the same time, I might feel differently about it.

By the way, this truck did NOT have this idle problem when I bought it, this just started a week or two ago. The O2 sensor has been broken off since I bought the truck, so that is not the cause of the idle problem.

Makes me want to opt for a moped when I buy my next vehicle.

That was about the best post I've seen here.

I still have my trusty Commodore 64 & even after twenty five years of service, it has never seen a wrench taken to it. Try telling that to one of those wintel PCs.

The "pos with vista" will run win98 (or even Win1, if you want) no problem at all. It's the SOFTWARE that maked a Vista computer less than useable.

OK guys, figure this out, please.

It's been so damn cold that aside from looking for vacuum leaks (there were none), I could not work on it. I just had to use other vehicles most of the time, or deal with this thing racing. Remember, it was severely cold, at times it hit over MINUS 20 deg. most of the time it was around zero.

We got a couple warn days when the temp went up to around 40 Above. That was my chance to work on it. But one problem. When the temp got to 40, the engine never raced and ran great. Since then, the temp went back down around zero, hit 15 below one day, but has been on the zero to 30 Above. Ever since we had those 40 above days, the engine has not raced since. Something had to be frozen, but what?

This is just a thought. I am likely wrong, but what do you think? The in-tank fuel pump send the gas to the injectors (and associated parts). The way I understand it, any excess gas is returned to the tank. (Is that correct?). Obviously the supply gas lines worked, but what if the return line iced up? Would that cause excessive gas to the engine and cause it to race? Obviously any extra gas has to go somewhere. Does this make any sense? If not, what else could have frozen up?

Thanks to all.

There temps are in Farenhite (however thats spelled).

Definitely not. Too much gas would flood the engine, not make it race. You need more AIR to make the engine speed up. My bet is on a frozen throttle linkage somewhere.