Hello all, new to the forum here. Been lurking for a while trying to find out a solution to my problem but nothing was even close to my predicament. I have a 94 F150 with the 302. My problem is this. When first started, truck runs great. Then, after being driven for even 10 feet, the idle shoots up to 1400, even higher on a cold day, when in park. Then it has this dead misfire you can hear in the exaust. Ive tried everything to fix this: New belt and tensioner, alternator, plugs, wires, distributor cap and button, cleaned MAF, IAC and throttle body, looked EVERYWHERE for any vacuum leaks or the sort. Heres where it gets weird. We tried adjusting the timing, and when we lowered it by about a degree it ran a little better (so it was right at about TDC), but the miss was still there and the idle was still horrible. We decided to unplug sensors to figure out what was wrong. When I unplugged the MAF, the truck ran better! Again not perfect, but a little better. Out of plain curiosity we pulled the sprout connector out that allows the computer to adjust timing and VIOLA! the truck idles right at a grand and the misfire is almost completely gone. Well theres a problem with that, now whenever the truck is pushed to WOT, it hits and bounces around 6000 rpm, feels like it looses first gear, then jumps back into gear and takes off like normal. Its the weirdest thing. Anyway, sorry for being so long winded but I wasn't sure what else to do, ive been trying to fix this for months. Thanks in advance for any help.



EDIT: I just plugged the SPROUT connector back in, drove it and the miss isn't as bad as it was for whatever reason, but the idle is still at about 1400 only when the SPROUT connector is plugged back in. MAKES NO SENSE somebody help!

 

Don't drive the truck without the SPOUT plugged in. As you noted, the SPOUT allows the computer to electronically control the timing- if you remove it, the computer can't compensate for the changes in engine temp and RPM and will default to its settings that allow the truck to run, and little else. You can seriously damage the engine if you haven't already.

You need to start by pulling any DTC's that might be stored. Just because you don't have a check engine light does not mean there aren't any codes to find. You can either use this method: Fuel Injection Technical Library » How To Run a Self-Test or by purchasing a code reader from your local parts shop. You can get one that will just read codes for about $30.

Get any codes that might be stored and tell us what they are, even if they don't seem relevant to the situation.

The next thing I would check is your ignition module. I don't know if the 94's had a TFI or not, but it's either going to be mounted on the distributor itself or remote mounted. Trace the wiring harness from the distributor to find it, remove it, and have it tested at your local parts shop.

 

The 94 is an OBDI system. No code readers I'm aware of. I believe the 94 has a PIP on the distributor, my 95 is that way.
Also if you have dual throttle plates on intake be sure they are both closing in sink. I had to replace my T/B because of this, mine caused varied fast idle, from normal to high.
Also check top bushing on distributor for slop. Also bring your engine up to TDC & make sure your harmonic balancer shows TDC. Ford balancers are known to turn. When the rubber gets hard the outside will turn, making your timing marks off. If it goes long enough it will come off & cause some real issues.
This is on top of the above suggests offered. You always unplug the spout to set the timing.

 

Eek.. what kind of damage could i cause? Ive driven like that for quite a while with no ill effects. And thank you to both of you for the help ill double check in the morning. By ignition module do you mean the box the coil wire leads to? if so i switched that with one i knew was good with no difference. And the throttle plates peaks my interest because if i let all the way off my gas pedal it becomes stuck per say and i need to give it a real nice tap to free it. Maybe somethig is stuck?

 

Get an OBDI code reader from the auto parts store, they're $20-$30 and work great. Pull codes first and go from there. Shotgunning parts is a bad idea. You may have a bad TPS, IAC, or intake leak.

 

The TPS is brand new, but i remember a while back when it spat out codes it said it was out of range and something about the ignition module but i guess i just dismissed them since i tested the ignition and the TPS is new. And i tried for SEVERAL days to find a vacuum leak with carb cleaner and couldnt find anything except for a bad maf gasket that i replaced. But im going to try with the codes tomorrow, it gets kinda difficlt when its blinking at you like that haha. Thanks for the help so far

 

A new part is not indicative of whether or not it's good. As far as the TPS is concerned, it would also depend on whether or not it's adjustable. If you got an out of range code of the TPS, it could be that it either wasn't installed correctly or perhaps the mounting screws weren't tight enough and it slipped out of place, causing the closed throttle position to change, relevant to the TPS.

If you can't keep up with the engine blinks, an OBD1 reader is a great investment if you plan to keep the truck for a while. Just remember that trouble codes are intended to point you in the right direction- a code for a sensor does not necessarily mean that sensor is bad.

 

ok im trying to track down a half way decent obd1 scanner... so basically ive simplified my problem down to this. Can anybody think of a reason why my truck would idle fine with the SPROUT removed, but jump up to 1400 with it in? It seems to run fine either way, unlike other threads ive read, but my only problem is a high idle.

 

When you pull the SPOUT connector, where is the timing? My '94 with the 302 wanted it at 10 BTDC.

 

With it in, I think it sits at about 12 degrees, but when at ten degrees it makes no difference, with it any lower really it starts to bog down and want to die. I don't remember if I mentioned it but when I unplugged my MAF, it ran better. Also, when I unplugged my IAC, it made literally no difference. So I don't know how all this helps. Im going to recheck my timing tomorrow with my buddys timing light and try to pull some more codes. Thanks keep the suggestions coming

 

10 or 12 degrees shouldn't make it wind up like that. 20 might. (Not that I'm saying you have 20 degrees of base advance dialed in; I'm more or less thinking out loud here.)

Sounds like the IAC is shut tight then, trying to slow a fast-running engine but not able to do so.

I know you said you cleaned the MAF, but did you test it? (If memory serves you want to read the voltage across the sensing element.)

Are you getting any HO2S codes? (You'll have at least two and possibly three on your truck -- one for each side and possibly one between the cat and the muffler.)