fresh 2.3L giving me fits, need some help

[R100RT]

Background: '90 2.3L frsh rebuild with 30 miles on it. During road tests it developed a problem that I can't figure. The engine had 258,000 miles when it blew a head gasket before I got it.

It goes through the gears fine but when you start cruising, it stumbles and loses power. At WOT, the problem goes away like a switch was thrown. Sometimes, at cruise, the problem clears up with out going WOT. When this problem is occuring, the engine will not idle but starts right back up again.

I have vacumm checked all the components and they are good. I have tapped the TPS and there are no glitches when the throttle moves. I have checked the FGR valve and it is clear and I have tested with the vacumm to the EGR plugged to rule out sticking. It has a new O2 sensor.

It passes a KOEO test fine. It throws codes when I run a KOER test. The codes indicate problems with not being able to get the idle speed low enough and a lean condtion. It throws a 41 code once in a while on the road.

I sounds like a vacuun leak but i can't find it. It also could be clogged injectors not delivering the right fuel as well. Any other areas to look at?

Thanks,
Eric

 

[mr_woodster]

Ok the TPS sweeps fine, whats the base voltage on it with the t/b closed?

 

[Red_LX]

Sounds a bit like what my old '90 does sometimes...it kinda feels like it's loading up on fuel, right?

If you find out what the problem is, let me know because I was never able to figure it out.

 

[4bangen]

oddly enouph my 89 just started doing the samething?

 

[R100RT]

The TPS was reading 1.13VDC at idle. This works out to about 600 RPM with the ISS discontected(base idle)

I'm thinking injectors are clogged up after 258,000 miles. The codes indicate that it is running lean.

 

[mr_woodster]

The TPS was reading 1.13VDC at idle. This works out to about 600 RPM with the ISS discontected(base idle)

I'm thinking injectors are clogged up after 258,000 miles. The codes indicate that it is running lean.

Well, try setting your TPS to the correct setting.. * .90-.94 .
With the t/b closed (key on,engine off). Then lock it down.
It should now top out in the 4.x area.

 

[R100RT]

I thought of that but I didn't based on what I know about the computer learned whil I tuned my TT Fastback. The Tweecer info I had was pretty adament that the idle TPS should be less than 1. I always thought that this was based on making sure that the TPS doesn't max out and mess up the load calculation. I have three Ford EEC books and none of them talk about the TPS needing to be less than 1.0 at idle. They all say that the pot must be linier and noiseless. One book said that the IDLE TPS could be as low as .6 and has high as 1.5VDC.

My TPS hits 4.6 VDC at WOT. Perhaps, the MAP statagey is different. I talso doesn't exsplain why this car ran 258,000 miles with the TPS at 1.3 VDC, (I said 1.31 before but I was wrong). I'm ready to learn so chime in if you know a reason why the TPS needs to be les than 1.0.

 

[Willy0314]

bad O2 sensor?

 

[Red_LX]

Actually I was gonna try changing the TFI module on my Mustang to see if that changed anything (since I have a couple spares) but I never got around to it.

 

[R100RT]

Problem solved

I worked some more on the stumbling problem today. Suspecting either a MAP sensor problem, injector problems or o2 sensor problems, I pulled the plugs. If I had a bad injector, some plugs would look fine and others rich. They all looked identicaly rich. So, I ruled out injectors. Next, I checked the MAP sensor using my frequency meter in my VOM. The MAP checked fine. That left the O2 sensor. I pulled it and noticed it had four wires. All of my fords use three wire sensors. I figured maybe Kragens pulled the wrong part for me. I repleced with aspare sensor and ran the KOEO and KOER tests. Both passed so I took the car for a drive and it runs great.
Willy0314 gets the credit for the correct call.

Kragen sold me a Bosh 15716 sensor which is described as a four wire, OE, heated, cal part. The three wire part is 13942. I'm not sure if the new part was bad or if a four wire sensor won't work in a three wire setup.
Thanks, Eric