The vehicle- 1989 Ford E-150. Factory built as a 302/AOD speed density injection combination. It has been converted to a 1984 351W H.O./C6 MAF injection drivetrain. The MAF fuel injection stuff is from a 1993 Ford Mustang with a 302HO motor.

The problem- computer is throwing a code 13- can't control low RPM idle. And boy is that the truth. Ever since I did this swap about seven months ago, the engine has had a bad time idling. Sometimes it is silky smooth, but most of the time it is rough. The usual symptoms are rough running and, if I sit still long enough either in or out of gear, the engine begins revving up and down like the computer is hunting for the right timing or the right idle speed.

Last week I replaced the crappy old battery with a new one and upgraded to a 3G alternator. Having the battery disconnected means the computer lost all of its memory and had to reprogram itself form scratch. The idle-hunting and rough idle was noticeably worse after the alternator upgrade, to the point that now it will stall when I come to a stop unless I double foot the pedals. When it stays running, the van will idle very roughly at around 500-600 RPM in park.

Like I said- the van has had this problem since the engine swap and fuel injection upgrade. I have run the diagnostic tests many many times and the only code I am getting anymore is 13, but even that is intermittent. It gets 17-20 inches of vacuum at idle (I can't get a constant reading) until it starts hunting for the right idle speed. I have replaced cap, rotor, plugs, fuel filter, air filter, O2 sensor, and IAC valve (twice).

Off idle the van runs awesome. The power is incredible all the way up to 4000 RPM where I let my foot off the gas since I am lapping the speedometer at that point (seriously- my van can go "M" uphill). I don't have any formal measurement, but I would estimate my 0-60 time in about 7 seconds, not too shabby for a 6300 pound van hauling four adults and a weekends worth of luggage.

Past fuel pressure checks have shown the fuel pressure to be in spec. The new fuel filter and off idle performance leads me to believe that this is not a failing fuel pump. Also, I replaced the catalytic converter when I did the upgrade, so I know that isn't clogged.

I am really at my wits end on this one. It is at the point where I don't want to drive the van for fear of it stalling at a stop light or while I am parking (it did both of those to me multiple times this last weekend).

Anybody have any ideas? I have good vacuum, good fuel pressure, new fuel filter, new spark plugs, new air filter, new cap and rotor, the timing is rock solid at 10 BTDC (checked with the SPOUT disconnected), and off-idle performance is amazing. I would suspect the IAC valve but I have changed it twice and I still have this same problem.

Bad injectors maybe? I ran some seafoam and fuel system cleaner through it when I first did the swap.


HELP!

 

What wiring did you transfer from the Mustang?
Both the injectors and plugs are wired for the 351/HO firing order right?
Are you running one or two O2 sensors?

 

I used the mustang harness to make an overlay harness for the injectors. I repinned the factory harness at the computer to match the Mustang pinouts (and triple checked the wiring before I put it all back together).

The injectors and the plugs have the 351/HO firing order (also triple checked).

I am running one O2 sensor with the output split to fool the computer. You actually told me how to do this in an earlier post I made.

At this point I am really leaning towards the injectors since those are the only old parts I am still using. Thew fact that the problem comes and goes also suggests faulty injectors to me. Unless someone else has another idea.

Another odd thing is that today, for the first time, I was unable to do the cylinder balance test using my OTC2000 diagnostic computer. The OTC sat there for a long time without doing anything and then said "NO DATA." It used to go through the whole test and drop one cylinder out at a time and compare RPM drops to tell me what, if any, cylinder(s) were not putting out at much power as the rest. Today, nothing. Don't know if it means anything.

Thanks Conanski. You have continuously answered all of my newbie questions. Without your help I would never have gotten this far, or even attempted this swap. I know I am close to getting this fixed because the off-idle performance is just incredible.

 

According to my book, that code 13 means it can't control low RPM idle DURING KEOR self-test. Just about the only things that can cause this are a bad IAC valve, faulty wiring, or a defective computer. Since you've already had two different IAC's on it, I think you've pretty well ruled that out. That just leaves the ECM and the wiring. Start with the latter. There should be two wires on the IAC connector. One of the wires should show a constant, steady 12V between it and ground whenever the key is on. The other is a little tougher to check as it is the wire by which the ECM modulates the ground for the IAC. The best way to check that one is to disconnect the ECM 60-pin connector and check the resistance of the wire between the IAC connector and the computer connector. It should be .1 ohm or less. Also check the resistance between that wire and ground before you reconnect the ECM. There should not any resistance read to ground. If the wiring checks out OK, then I'd suspect the ECM. It's very possible for the IAC control driver within the ECM to be bad and the rest of it be just fine.

 

Oy. Thanks for the input. I guess I will be breaking out the multimeter.

 

Seems that a correctly set & functioning TPS with a smooth resistance sweep would be critical to controling low RPM idle as well, but I've seen no mention of it so far.

Also, how is your set up fed air? Early "foxes" that had open filter element mods frequently suffered from hunting idle due to fan wash. Mine did till I built a shield for & have had no problems since.

 

I swapped the TPS out for the one off of the old 302 that worked fine. I will double check it and swap it out again.

Here is the air intake I cobbled together to go from the truck dual barrel throttle body to the Mustang single barrel MAF sensor:





I am fairly certain that the fan has no effect on the air going into the cone air filter on the end of the tube. The MAF sensor is mounted directly behind the cone air filter. This is not an ideal setup and I am actively looking for the mid 90s factory van air intake pieces that go from the two barrel throttle body to the single big hose.

One thing that I forgot to mention, if the van is idling and I unplug the MAF sensor, the idle smooths out and the engine runs much better.

 

Are you calibrating the TPS for 1 volt output at idle when you swap them? That's important. With the position of the TPSon the truck intakes, it's not easy to do. In a van I'm sure it's even harder.

 

That is on my list of things to do, but I haven't done it yet. I believe the last time I checked the TPS voltage it was something like 0.85 volts. Not ideal, but close.

And yeah, I can only dream of having as much space as a truck around the engine.

 

You're farther off than you think! That might be your problem. Recalibrate that before you do anything else. The easiest way to do it is to pull the throttle body off put leave the TPS plugged in. Turn the key on and then backprobe the pins in the connector with needles or safety pins to read the voltage. Now you can loosen the screws and tweak the idle output voltage. It needs to be as close to 1.00V as possible. Within a couple of hundredths is about as far away as you want it to drift.

 

It might perform better with the TPS set closer to 1V, but as far as I know, anything under 1V is considered idle position. If it were above 1V at closed throttle, I would suspect the TPS as the source of the idle fluctuations, but since it's below 1V, I don't think that's the case. I think there's more to the smoothing of the idle as the MAF is unplugged, like two sensors are in conflict or something. I didn't see it mentioned anywhere, but you don't have a vacuum line left on the old MAP sensor, do you? I would think there would be a code for BAP out of range or something to that nature if the vacuum was still connected...

 

Vacuum line to the MAP is unplugged form the MAP and the nipple on the intake is capped.

At this point I am leaning towards faulty injectors, possible faulty wiring to the MAF, a bad MAF, or some other mystery gremlin.

 

I am just finishing up the exact swap you did only in a 89 Bronco do this first click hereThe Corral
Mine is having problems Idling at cold start up but fine after it is running for a few minutes it does just fine I have already contacted a guy about maybe remapping the fuel table if backing the timing down doesn't work I did relize it was so hight until I got my timing marks put on.

 

Tanks, I'll give that a try. The weird thing is that after I ran the KOER self-test, the idle smoothed out and it no longer stalls. However, it does still hunt for the right idle speed unless it is in park or neutral.

 

When I did mine I landed the MAF signal that is supposed to go on pin 50 to 51 it ran great but with a code 66 and cel on. I got that all worked out and then it started idling silly I was a little confused on that one. I'm planning on putting my 9.5:1 351w with ported heads here in a little while i'm tring to hold off with the tunning till then. What state are you in?