I need some help diagnosing a lean running condition on my van.

The vehicle:

1989 E-150. Van was originally a 302SDEFI/AOD combination. I swapped in a 351W/C6 drivetrain and upgraded the fuel injection to MAF. The FI wiring is off of a 93 Mustang GT, I spliced into the stock single O2 sensor to duplicate the second O2 sensor the computer will look for.


PROBLEMS:

(1) Will not idle by itself when cold. I have to keep my foot on the throttle. As it warms up it gets better, and when it is hot it will idle all by itself. However, the idle speed is still low (550-650 RPM) and the idle is rough.

(2) It has this annoying whistle once it gets warmed up. It is a high pitched "SQUEEEEE" that I can't track down. Th engine has 17-20 inches of vacuum at idle, so I don't think it is a big problem. I have taken the entire intact assembly off down tot the lower intake manifold and have found no signs of leaks.

(3) I am getting KOER trouble codes:

12- Cannot control RPM during ER Self-Test high RPM check.
41- No HEGO switching detected always lean (right side).
91- HEGO sensor circuit indicates system lean (left side).

Before I switched transmissions, I was only getting the 12 code. For some reason, switching from the dead AOD to the rebuilt C6 made my motor run lean. I did disconnect the battery while I did the swap, so the computer has reset itself, but why would it suddenly run lean?

The motor is a 351W with a cam profile nearly identical to the Edelbrock performer cam. The motor is an 84 HO motor that was originally carbed. When I switched to MAF, I kept the stock 19lb/hr injectors. Would the cam make upgrading to 24lb/hr injectors necessary?

I have tried three different IAC valves, including a brand new one, and the engine still won't idle smooth or idle on its own when cold. I have confirmed the timing is set at 10 BTDC. I am going to double check that the timing marks on the dampener accurately show TDC. It is a new dampener from Summit. I replaced the dampener and the timing set when I swapped motors.

The rough running, lean running, and whistle all indicate to me that there is a vacuum leak leaning out the engine, but I cannot find one. I have decent vacuum, especially when the throttle opens. Like I said, vacuum at idle is usually around 17 inches, and when I open the throttle is will go up to 20 inches. I have checked all the hard plastic and rubber hoses and all are good. Disconnecting all the hoses while the motor is running doesn't stop the whistle. I have replace the PCV valve and the PCV valve hose. Both fittings for hoses on the upper intake have been checked to make sure they are seated properly.

HELP!

 

Idle problems are often related to the TPS, have you checked it's output against the data on Ford Fuel Injection Ideally you want closed throttle voltage of 0.9 - 0.99v and a smooth transition through the whole range to WOT with no dead spots. If the closed throttle voltage is off try repositioning the TPS first before adjusting the throttle valve stop screw.. unless it looks like somebody has been messing with it.. in which case it may be wrong anyway.

The whistle at idle may be a gasket leak on the lower intake, this will be hard to find and could even be at some point under the intake into the lifter valley area. A leak like this will produce a lean condition, I guess you have confirmed there are no exhaust leaks upstream of the O2 sensor and the smog system is either all intact or completely removed?

 

TPS sensor puts out .85 volts. Smog system is completely intact, hooked up, and functioning. No exhaust leaks upstream of the O2 sensor. I really hope it isn't the lower intake manifold to head gaskets. I replaced those when I swapped motors, and I used RTV sealant on the front and back of the intake. I torqued the lower manifold down per factory specs. Oi. I don't want to take that all off again, but I guess I will have to check.

I'm off for a test drive.

 

that mustang ecu will be looking for 2 o2 sensors. have 2 sensors in each header collector or just below and wire it up properly.

 

The test drive was a success. The van has LOADS of power and idled silky smooth once the motor warmed up fully. It even shifted into gear once I put in enough transmission fluid! I'm glad I already had a Lokar kickdown cable so I could just hook it up to the throttle body.

At the advice of Conanski, I spliced the driver's side O2 sensor feed into the existing passenger side O2 sensor feed. Conanski reports that this is how Ford recommends you do it in their MAF conversion kit.

I am in the process of taking the intake manifolds off to clean and replace the gaskets.

 

Tore it down to the heads. No obvious gasket sealing problems, but I did find a couple injectors with damaged tips. Enough to make it run bad? I don't know.

Waiting for the RTV sealant to dry and then I am reassembling.

 

I'm cursed. I put it all back together, torqued the lower and upper intake manifolds down as per the factory instructions and to the factory torque (22-32 ft-lbs). I started it up.

I started it before I filled the radiator. When I started it, it started up smooth and actually went to a high idle like it should when cold. No chugging, no missing, much smoother. Thinking I had the problem licked, I began filling the radiator. As I filled the radiator, I noticed I had forgotten to plug the MAF sensor in. I plugged in the MAf and the engine immediately almost stalled and then began chugging and idling rough. Shortly after that I began hearing a bubbling/hissing sound and white smoke began pouring out the tailpipe. Argh. Apparently I didn't get one of the lower intake gaskets seated properly, so now it is leaking into the intake manifold. Looks like I get to take it all apart AGAIN.

Anyhow. Is it possible I have a bad MAF? Before I plugged in the MAF and the radiator fluid reached the cylinders, I actually thought I had the problem solved. Would a bad MAF make the van run like poo? I already tried cleaning the MAF with some MAF cleaner spray.

 

yea a bad maf would make it run like poop.

 

I had forgotten that I added some Seafoam to the gas tank to clean the injectors. I now suspect that the white smoke is not radiator fluid, but the Seafoam doing its thing. I'll try a new MAF sensor before I rip it all apart again.

 

GOT IT!!!! It was a bad MAF sensor. Motor runs much better now. I will do the code checking etc.. tomorrow, but it is vastly improved. Thanks for the help!