'88 TPS code.

[mnewman]

I can get behind that.

 

[Shran]

Just curious, when you attach it, do you just slap it on or do you have to rotate it one direction to line up with the throttle blade and then back again to line up with the screw holes?

I've always had to do method #2, it will fit the first way, but it won't turn at the same time as the throttle blade does.

 

[mnewman]

I had to rotate it, press on and rotate back to line with the screws. Same as you said.

 

[mnewman]

FYI, this truck has had the cats cut off of it. It does have a muffler. Not sure if removing back pressure from these makes a difference or not on these engines.

 

[RonD]

No, it doesn't

And just FYI, no 4-stroke engine runs better with any "back pressure", that is misinformation from long ago, a "myth" if you will

Car makers started using scavenging exhausts back in the 1940/50's, i.e. "headers", these create a LOWER pressure at the head's exhaust ports to pull exhaust out leaving more power in the crank, usually mid-range RPM has lowest pressure so best "free power" added, but you can make them for low-range or even high-range power increase, but not all 3

What happened, and where the "myth" comes from is that people would install larger pipes on the heads, "free flow" setup, and then go for a test drive
"HEY, What The F***, I LOST POWER!!!!!!"

Incorrect conclusion was, "this engine must need back pressure"

What they lost was the added free power from a scavenging exhaust manifold they just removed

The scavenging exhaust happens in the manifold, the size and length of the pipes and the size of the collector are all engineered to set when the lowest pressure will occur, low RPM, mid RPM or high RPM
Even drag racers use this when each cylinder has a single exhaust pipe, the size and length of this pipe WILL give a lower pressure at the exhaust port at a specific RPM so near that RPM the extra power will be felt

Some people use "X" or "H" crossovers on Dual Exhaust systems to squeeze a bit more out of this scavenging effect

But as long as you use the same size pipe, or larger, from the end of exhaust manifold to tail pipe, you won't effect the scavenged power
Rangers all came with mid-band scavenging exhaust manifolds

 

[mnewman]

Thanks for the info Ron. I didn't know all that!

I braved the crappy cold and wet weather to mess with it a bit yesterday. I won't say the vac hoses look good but nothing seemed to be leaking. I ordered a new PVC valve since the current one isn't correct. I set the anti-diesel screw. The truck will now idle about 7-8 RPMs when warm. IAC is working.

It wants to stall coming down from a throttle goose about 50% of the time. I am actually thinking that might be related to plugs/wires/dist. When it almost dies it starts missing pretty bad and doesn't recover unless I hold the rpms up for a 10+ seconds. Even then I can hear it skipping every so often. Since it's not consistent I'm hopeful its ignition/fuel related and not mechanical.

When I get back out I will slot the TPS to get it in range which I'm hoping fixes the last of the hesitation. It's way better than it was. I'm also going to pull a plug or two before I fire it up next time to get a visual on them.

 

[rusty ol ranger]

I maybe wrong but i believe that "idle screw" is used for adjusting the TPS.

@adsm08 can help there.

The idle is controlled with the IAC. IIRC to adjust the tps you run it at 2000rpm (make sure engine is at temp) for 2 minutes, unplug IAC, adjust screw, then plug iac back in.

Unhook the battery cable for 30 mins to reset the ECM.

As a side note my 2.9 was doing the same thing (kinda, but my symptoms wernt just at idle) and it turned out to be bad injectors. I fought the issue for over a year and finally replaced the injectors and im now at 7000-8000 trouble free miles.

I dont like disagreeing with @RonD cause hes usually right, but i do believe that screw is for tps adjustment.

 

[mnewman]

I still think I'll have to slot the TPS. At the extreme end of backing it off the TPS wasn't in range. I think it was still like 1.24-1.3 volts at that point. I've got the Ford shop manual now so I'll see what it says.

It wouldn't surprise me if it's got one or more crappy injectors. I am pretty sure the truck sat for a long time before someone slapped some parts on it and sold it. The guy I got it from had zero history on it and only had it for a couple months. I plan on running some cleaner through it but I want to get through winter before I license it. I picked up some of the liquid molly stuff which I'll add when I finally put fuel in it. I have seafoam in the fuel now as a stabilizer.

 

[rusty ol ranger]

Mine sat since 2006 when i aquired in it 2018. It was a one owner truck though.

I was having the same issues you were, it ran like shit/stall when id back off the pedal or downshift, idled kinda rough, and it would actually do the same shit goin down the road once it got warmed up.

2.9s also like to rust the fuel rail, New ones arnt available but if you do your injectors make sure to clean the rail...GOOD.

I believe at idle my TPS reads like .99.

 

[Paulos]

Were the micro filters on your old injectors clogged? Like Rusty said, the fuel rails have been known to corrode on the inside, then the corrosion brakes loose and plugs the filters on the injectors. When I rebuilt my complete fuel system I also cleaned the fuel rail (acid bath). No issues since then.

I have also found that "rebuilt" or "re-manufactured" injectors aren't necessarily the way to go. I first got rebuilt injectors, but one would intermittently stick wide open. Buying new injectors solved the problem. I bought Accel injectors through Advance Auto and used a 30% off coupon I found online (Rock Auto was way too expensive). It's been a year and they still work great.

 

[mnewman]

Well. Sometimes I miss the obvious. Multiple times. Glaringly in my face. The TPS I ordered and the one on the truck were wrong. After trying to slot the damn thing I looked at my other project truck only to realize that the connector index was supposed to be on the end, not the center like the one I'd been messing with. So I threw the 32 year old motorcraft sensor on there and no more codes (other than the neutral sensor). Voltage reading was .96 volts on the TPS reference circuit.

Still missing randomly so I pulled off the cap and rotor... I expected them to be thrashed and they are. I'm hoping the rest of the hesitation goes away with the tune up and putting some miles on with injector cleaner. Either way she's much happier now than when I got it.