A few weeks ago I finally took the plunge and picked up an MAF swap kit from fiveology Racing. After I installed it the truck gained a ton of power and throttle response. But there were some driveability issues too, mostly under 1800 rpm's. I've been working on getting the bugs worked out and the codes cleared but have hit a wall. Now on cold startup, It'll start fine but tries to idle somewhere around 500 rpm's, sometimes dies, and has almost no power under 1750 rpm's. once the temp needle hits the "normal" range, it idles smooth at 750 and runs like a champ except for some very slight surging while cruising under around 1750 rpm's.

To give some background, about a year and a half ago, I did an engine and tranny swap with a 5.8l and zf 5-spd (had 5.0l and mazda 5-spd before). I completely rebuilt the motor from the ground up. Bored 40 over, crane cams 444232 cam, hedman longtubes, and K&N intake setup. Eliminated smog pump system. Every single sensor, actuator or ignition part on the engine was replaced with the exception of injectors. The engine and tranny came out of an 89 f250.

The codes that I get are as follows
CM: 122-TP sensor below closed voltage (I have fixed since then)
181-Fuel system at rich adaptive limits, system lean
189-Fuel system at part throttle rich adaptive limits, system lean
543-Fuel pump secondary circuit failure
556-Fuel pump relay primary cicuit failure

KOEO: 564-electro drive fan circuit failure (mustang code I believe)
563-high speed electro drive fan circuit failure (mustang code I believe)
565-canister purge circuit failure (need to pick up another, resistance is bad)

KOER: 412-cannot control rpm during high rpm engine check
136-Oxygen sensor not switching/system lean Left HO2S
172-Oxygen sensor not switching – system is or was lean –Right HO2S

I've gone through the vacuum system multiple times. I'm thinking that switching fuel tanks while driving is pulling the two fuel pump circuit codes. Also, according to a very detailed book on OBD1 ford fuel injection i have, the "1989 truck" fuel injectors had a different resistance reading than anything else (13.5-18 ohms vs 13-16 ohms). Maybe the mustang computer is sending the wrong amount of power to the truck injectors?

Sorry for such a long post, just trying to be thorough. Thanks for your help in advance.

 

Damn man, that's a whole host of issues. I would take a guess and think you have a possible wiring issue, or the tuning of the PCM wasn't done right.

That's why I ended up buying a 97' F350 with OBD2, so I wouldn't have to mess with the swap.

 

I know it looks like alot but if you break it down, the ones that matter are the KOER codes, running lean and the rpm check. I'm thinking maybe the IAC valve isn't opening or closing correctly. I have another one from the salvage yard that i'm going to try.

 

If your wiring is good, and your O2 sensor is good, like you said it could be your IAC sensor, possible vacuum problems, clogged fuel return line, etc.

 

Do you have dual O2 sensors on this or a single?

 

What's the catchcode on your ECU (big letters on the ECU connector label)? The truck is lean, and the computer is trying to add more fuel but it's not enough.

I'd suspect something is not right your MAF. A MAF can be fouled by oil/dirt from a K&N filter. Those early MAF sensors were also quite sensitive to intake geometry. They like a straight shot before and after the sensor, no sharp curves.

 

^^^ my question. (From Conaski)

I'd guess most of the other codes/issues stem from 02 readings/not readings.

Watching with interest for your resolution.

 

+1.. one of the biggest no no's with these MAF meters is to attach a conical filter directly to the end of it, and double bad if it's an oiled filter. Put a 1ft length of straight tube between the filter and meter and ditch the oiled filter for a dry version.

My question about the O2 sensors is tied to the codes that are present, there is no way the system should be at the rich adaptive limits with a relatively stock engine, but if the O2 sensors are reversed.. bank 1 sensors connected to bank 2 input and vise versa, the computer will fight itself trying to adapt until it runs out of capacity. Of course that assumes the motor doesn't have aftermarket heads and intake on it that you forgot to mention.

 

The catch code on the PCM would help. Some of the OBD1 MAF computers had more than one oxygen sensor, so if you got a computer that has that requirement and you don't have it hooked up, it could be playing havoc with your system possibly

 

The only pic of ecu doesn't have a stock sticker:

1985-96 FORD F-SERIES 5.0/5.8L (E4OD) MASS AIR CONVERSION KIT - Fiveology Racing

 

Thanks for all the replies fellas.

The kit does have two separate O2 sensors, right and left headers.
The computer to the best of my knowledge (supplied from fiveology) is a stock A9L from a 5spd fox mustang. They claim to completely look them over before shipping. The MAF meter is a C&L 73mm unit.

Thanks Again

 

Wait a second. You have an A9L PCM with a 5.8? Isn't that a 5.0 PCM?

 

Yes.. but it should still run fine, I had the exact same combo in my '90 and it ran better than stock.

I'd suggest you try swapping the O2 sensors, reset the PCM and see if it's better or worse.

 

I just got off the phone with Fiveology Racing. They said it sounded like a vacuum issue. I just went out and checked it and its at 18-19 in/hg; well within limits. He said if its not that, there's a good chance that the PCM is bad. The PCM's they use are the 1994-1995 mustang A9L's. I do have the air filter mounted directly on the meter but he also claimed they are made for it. I've also cleaned it twice now to ensure that wasn't the issue. The fuel pump circuit and fan codes are normal and I can fix the fuel pump codes so they don't come back. There isn't really a way to accidentally wire the O2 sensors switched without doing alot more wiring than required. Both the O2 sensors are new, the right side is the stock 4 wire (I have 2 and tried both with no luck), and the left is a mustang 3 wire type, also brand new.

If anyone is looking into an MAF swap, I highly recommend Fiveology. Their customer service and product are top notch. He said he'll have another PCM shipped out on Monday. I'm going to keep looking into it this weekend to verify it's the PCM, so if anyone has any other suggestions i'd appreciate it.

 

Keep us updated. If it's not vacuum or the o2 sensors swapped, very good chance your PCM is junk.