'96 Escort Drivability Problem

I've got a '96 Ford Escort 4 door with the 1.9 engine and a 5 speed transmission. It has 178,000 miles on it. I have recently (within the past 1,000 miles...when I got it) replaced the plugs, wires, and coil pack. The current tank of fuel has a dose of seafoam in it (and I have not yet done the direct-to-vacuum-hose treatment yet)

I purchased the car so I could have a good, fuel efficient commuter, and I know it can be. However, it's currently returning 20 mpg mixed, and I know it should be doing much better.

I've been experiencing the following drivability problem:

At no- or light-load (not coasting, but not accellerating...just maintaining speed in traffic) it will buck fairly severely. It is NOT road speed sensitive, and it doesn't seem to be RPM sensitive. It manifests itself like a vacuum leak, timing problem, or sensor issue of some sort. You'll be driving along and it'll just start bucking back and forth. The best way to make it stop is to apply more throttle (quite a bit more) to increase the load. Letting off the throttle altogether also stops it.

Sometimes while driving, I feel the car go from running well...nice snappy throttle response...to running not-quite-as well. I get the feeling there is some sort of open-loop vs. closed-loop thing going on. When it's running poorly, it exhibits the bucking. Even if it's not bucking, when accellerating, it's just a little more sluggish than usual...UP TO a certain RPM/throttle point. Then it takes off like it should.

What I know:
This is an OBDII car (the first year of OBDII in escorts and the last year of this particular bodystyle, making it kind of a one-year-only deal).
All of the vacuum lines from the manifold look ok (though I haven't done any REAL checking of them...outside of visual).
I went to the auto parts store the other day and checked for codes...and there were none stored (quite suruprisingly).
The Check engine light seems to be non functional in my car...I've never seen it (but again, I did have the guy at O'reilly scan for codes).

So I figure this is probalby a sensor of some sort...but I'm not sure where to start. When it's running poorly, it feels like a flat/dead spot in a TPS. I figure it's possible it's something like an O2 sensor, an engine coolant temp sensor, or any other number of sensors that I don't know what they are (/Homer).

I assume the drivability and fuel consumption issues are probably related...and in any case, I want to fix them both if they aren't. I'm asking here because y'all are smarter than the escort specific boards...I'm very confident of that.

I have an EVTM (electrical manual) and a Ford shop manual (though for '95) for an Escort, as well as a Hayne's manual. So those could come in handy also...

Thanks!
Clem

I had a similar problem with my Miata, and just cleaned the throttle sensor.

When I felt the symptom, it felt as if it were going in and out of deceleration fuel shut off, and that's mostly triggered via throttle and engine speed (as long as you were over ~1200rpm.).

Disconnect the sensor, and see if it stays. Should throw a TPS code.

But that's where I would start.

(I kept the original sensor, since a replacement Mazda sensor was quite expensive- and it works fine, now.)

Eric

Almost sounds like the IAC might be sticking on or open. But then again you should get a misfire code or a bank 1 rich code if it is sever enough. But then again 96 OBD2 vs 2010 OBD2 is like comparing the Model T to a Veyron, especially in Ford products.

Try a new throttle position sensor. Fords treated their early EFI like a carb, and had a fairly aggressive accelerator pump function built into the ECU. When it sees a rapid change at the TPS it dumps in a bunch of fuel.

Unless you have a lab scope, or the TPS is absolutely shot, you won't see it on an ohmmeter or set a code.

I'm going to go out right now and drive around with the TPS disconnected and see what that nets me. Back in an hour...

Clem

All the above duly noted, though it sounds like an old-fashioned fuel pressure problem. Too much, then not enough. And dirty/clogged injectors, which the seafoam should help.

Clem, what happened to the BMW, or should we not go there.

I think that unplugging the TPS has isolated the problem (to the TPS, presumably). I just did a little 3-leg lunch hour errand trip as follows:

Leg 1: Unplugged the TPS and drove trying to replicate the conditions where the bucking happened previously. I couldn't replicate the bucking.

Leg 1b: Eat a salad in the car before I get my fingers grungy plugging back in the TPS.

Leg 2: I drove with the TPS connected and I did experience some bucking. Unfortunately, I wasn't able to drive as much as I wanted to really confirm that the car was exhibiting the behavior...but I'm pretty sure it was.

Leg 3: Disconnected the TPS once again and drove back to work. No bucking that I could discern (and you can't miss it when it happens).

I'm going to go ahead and leave it unplugged for another day or two and drive routes where I know it would happen if it were going to. If it happens again when I plug it back in in a couple days, I guess it's time to try some snake oil throttle body cleaner and/or a new TPS or such.

Regarding the BMW: I should be able to work on it tomorrow night for the first time in about two months. it's just been too cold to be motivated to lay on my back on the concrete floor (at my friends house, 15 minutes away) to get anything done on it. It'll go soon, now that the weather shows promise of warming up. As it sits, the transmission and clutch and flywheel are out of the car. I have a bunch of parts to go back in (clutch set, shifter bushings, tailshaft seal, clutch master cylinder, etc)...just waiting on time to do it.

Clem

ClemSparks wrote: I'm going to go ahead and leave it unplugged for another day or two and drive routes where I know it would happen if it were going to. If it happens again when I plug it back in in a couple days, I guess it's time to try some snake oil throttle body cleaner and/or a new TPS or such. Clem

Not knowing how much Escort TPS sensors are, I used some basic electrical contact cleaner on my Miata. Spray, exercise, spray.... Ok for a few years now.

But before heading to the part, no harm in checking on line how much a replacement is- it could be pretty cheap.

Eric

Well Duh! I shoulda checked earlier. I was assuming this would be like a $150 part...but it's more like a sub $50 part. At least on Rock Auto, anyway.

I'll still probably try to clean it up first, and then replace if it still acts wonky.

Thanks!
Clem

I tried all of those to fix an ailing CRX with EXACTLY those symptoms.

For all of them, adjusting them made a difference - a little better one way, a little worse the other way. Nothing actually got rid of it though.

The head gasket is blown. I can tell you this without even asking you to do a compression test. Just buy the replacement gasket now and ask your buddy to lend you the torque wrench.

chaparral wrote: I tried all of those to fix an ailing CRX with EXACTLY those symptoms. For all of them, adjusting them made a difference - a little better one way, a little worse the other way. Nothing actually got rid of it though. The head gasket is blown. I can tell you this without even asking you to do a compression test. Just buy the replacement gasket now and ask your buddy to lend you the torque wrench.

No...the headgasket is not blown.

In my experience, a car with a blown head gasket will not:
Drive all day long at any speed without overheating
do the above with no cross-contamination of oil/antifreeze
Do the above without loss of antifreeze

My car doesn't exhibit ANY typical signs of head gasket failure.

Besides...I have my own torque wrench. And I've done one or two of these before.