'93 4.0 help

[sjranger]

Hey all,

I wrapped up my 4.0 swap this weekend but I seem to have some issues. Once I got it fired up the first time, it seemed to be backfiring in the exhaust end for quite awhile, at idle and when giving it gas. My first thought was that it was excess gas in the exhaust/cat from all the cranking prior to the engine firing. After about 10 minutes of idling, the backfiring went away, and only comes back when the engine is revved.

Also, when revved, I get a hint of black smoke indicating richness. Both O2 sensors are new, and I am no receiving any codes other than 522 [(O) Park/Neutral Position (PNP) or Clutch Pedal Position (CPP) circuit fault – PNP] and 528 [(M) System shows voltage at pin 10 (is A/C on ?) or pin 30 (PNP, CPP switch) - PNP].

The other issue is somewhat related to the engine operating temperature. I have a mechanical gauge installed, and I notice that the temperature would increase until the thermostat opened. When the temp was increasing until the thermostat opened the engine developed a miss. Once the thermostat opened, the miss went away immediately. My mech gauge is right next to the location of the computer sender for engine temp.

My theory was perhaps there was a air pocket in that area and as the comp reads the sudden increase in temp it cuts some fuel input?

I am going to insure that the pockets are all clear and try again, but does anyone have any ideas for these issues?

Thanks

 

[Downey]

have you cleaned your maf?

 

[sjranger]

I will give it a try, I am open to all suggestions

 

[Downey]

idk what else to tell you since you have new o2 sensors. i know the maf is over looked alot i know i over looked mine when i was having problems.

 

[sjranger]

Ran it again today when I got home and picked up 176 [(M) Oxygen sensor not switching - system is or was lean Left or Front HO2S - Fuel control]?

 

[np24]

you didn't by any chance get the o2 sensors plugged in backwards.
if you did get them backwards, it'll cause all kinda of drivability problems.

 

[Downey]

how do you get them back wards?

 

[np24]

plugging the left sensor into the right plug and the right sensor into the left plug.

 

[sjranger]

I dont believe so, the one with the pink/red wire loom was the passenger side correct?

Also, I reset the computer and ran the truck again and did not recieve the 176 code.

I attempted to run a KOER test, but after jumping the terminals and starting the truck I never saw the check engine light flash the Engine ID or anything else.

I really wish I knew what was going on with this thing, I'm almost ready just to take it to someone.

When I get home today I am going to pull the IAC, MAF and TPS and clean them all and try again.

Additionally, is there any way in which the O2 sensors can be tested? Until this point all my issues in this swap were with parts that should not be bad (plugged oil filter=no oil flow and a starter with a bad field) I could only hope that its something stupid causing these problems..

 

[feellnfroggy]

Is the backfiring when you give it gas or after you give it gas when it idles down. MIne is backfiring when idling down due to a bad MAF.

 

[sjranger]

From time to time it backfires while idling accompanied by a miss from time to time. For the most part however, most of the backfiring is after giving it gas and the 5 - 10 seconds following it.

I also noticed that quick blips of the throttle make it stumble badly, and stall. I am really leaning towards the MAF which I will clean today.

I also am going to pick up some new plugs and wires and give em a shot.

 

[wahl_7s]

From time to time it backfires while idling accompanied by a miss from time to time. For the most part however, most of the backfiring is after giving it gas and the 5 - 10 seconds following it.

I also noticed that quick blips of the throttle make it stumble badly, and stall. I am really leaning towards the MAF which I will clean today.

I also am going to pick up some new plugs and wires and give em a shot.

Idle down backfire could be exhaust leak!

 

[feellnfroggy]

It sounds alot like what mine does( 93 4.0), and the same thing my old 2.3( 92) did, and the same thing my 96 probe( 2.0) did. Ford made a slew of bad MAF's that went bad real easy, I suggest going to the pull a part and getting 2-3 MAF's off various 4.0s of your year (cheap, maybe 15-20 bux) and try them out. Do the used maf prior to the computer testing, cause most people want 50 bux to run a daignostic. Use dparts are cheaper, if you still have problem then do the diagnostic prior to buying the brand new Maf.



ALSO, CHECK FORD'S TECHNICAL SERVICE BULLETINS AND RECALLS. MY PROBE MAF WAS SWAPPED PARTS AND LABOR FREE DUE TO THE TSB ON THE MAF.

 

[sjranger]

Cleaned the MAF, TPS, and IAC today and the backfiring seems to have decreased slightly. Checked for vacuum leaks with some carb clean but didn't find anything. Also checked fuel pressure at idle and it was right around 32psi so the regulator seems ok.

I remember reading somewhere that it is possible to unplug the MAF while running as a diagnostic procedure. It stated that the computer can infer the air coming in through other sensors and should alter the idle.

When I tried this the engine died immediately, so perhaps the issue is another sender?

Tomorrow I am going to hunt for any sign of leaks in the exhaust end and hope for the best..

 

[feellnfroggy]

Cleaned the MAF, TPS, and IAC today and the backfiring seems to have decreased slightly. Checked for vacuum leaks with some carb clean but didn't find anything. Also checked fuel pressure at idle and it was right around 32psi so the regulator seems ok.

I remember reading somewhere that it is possible to unplug the MAF while running as a diagnostic procedure. It stated that the computer can infer the air coming in through other sensors and should alter the idle.

When I tried this the engine died immediately, so perhaps the issue is another sender?

Tomorrow I am going to hunt for any sign of leaks in the exhaust end and hope for the best..

The engine shouldnt have died, I run with my Maf unplugged 24/7 it runs better than having a bad maf plugged in. It stalls once in a while, but right back up. There is another issue. I think its time for a computer diagnostic.