Hmm..FPR?

[jhammel85]

I've got a strange problem with my 87 Ranger, 2.9, auto, 4x4...

I have a problem with my truck when I 1st take off when the truck is warm. Sometimes it happens when its cold as well but not if I let it warm up..

If I run the truck and shut it off, It fires right up (as usual) but about 30 seconds in, especially if I get in it and go, it starts to lope like crazy and stutter. It has yet to actually stall out on me but it chokes itself out and then it revs up and all is well.

I wish I could pull codes but I cant since someone cut the return signal wire to my diagnostic plug. (still looking at that one..)

I've replaced the Engine coolant sensor, thermostat (unrelated of course), 02 sensor and thats about it.

I just went outside and I pulled the lines from the Fuel Pressure Regulator and it smells like gas, strongly. No gas is in the lines but it does smell like it. I cycled the key a few times to see if I could get a drip. The line to the brake booster smelled of gas and so did the line going to the MAP sensor as well. The oil *might* smell of gas but its faint. Even the throttle body smells a little of gas....

Any ideas? I was thinking maybe it chokes itself out or loads up on gas @ start up but the reason why I dont notice it when its cold is because I let it warm up for a minute or two before I take off...I might have to do that when its warm to verify...

Dont know if its related but recently it has stopped to raise RPMS when I put it in part..maybe the Vac. mod. on the Trans?

 

[jhammel85]

Little update........

I drove the truck a ton yesterday and everytime it starts warm it idles around 1400 or so...backs down to about 12....10....then it hesitates a little.....after a few seconds it finds itself and its good to go.

 

[off_road_junkie21]

o2 senior

 

[IMenriched]

yes it could be a faulty O2 sensor again

test rather than just replace...if you suspect the FPR then you need to get pressure readsings.

likewise for the O2 sensor..http://www.therangerstation.com/tech_library/O2Sensors.htm

 

[jhammel85]

Yeah, a fuel pressure gauge is expensive (at least what Ive seen) but I'm thinking of getting one. It would come in handy more than once I'm sure!

As far as the O2, it is new BUT I will definitely be testing it and its circuit.

My problem is defintiely odd. Warm or cold, it'll miss once it 1st drops itself down to 800rpm. After it chokes out its fine. It runs rich when it happens because it smells like pure gasoline.

Well, I'll get to testing and I'll post up what I find. Thanks

 

[jhammel85]

Alright, small update...

I spent my lunch hour at work poking around on the truck. I tested the voltage of all but the O2, I'll post that up when I do.

I found that the TPS swept OK but it was set @ .70. Much lower than the .90 +- thats recommended. It took many turns so I really feel like its going to make the RPMS skyrocket. If so, does that mean the TPS is getting weak or would you say there's a vac leak somewhere? At WOT, the TPS showed a voltage of 3.8. According to the Ford Fuel Injection Website, WOT would be 4.538. Little low eh? Maybe it is getting weak....its the original sensor.

Heres what else I found...

MAP - 5.1 voltage, Engine cold. (hmm..should of checked frequency I'll be redoing this one. )

IAC was 11.8 @ the red wire and 11.8 @ the Green. Should be OK. I've cleaned it before when this 1st started with no luck. However, I will try to calibrate it tonight according to instructions here: http://www.broncoii.org/techpages/eeciv/index.htm#TFI Timing: (11)

Coil was also 11.8.

Another thought is my brake booster. Its always made a ton of noise. The idle doesn't change when I'm braked so I would imagine that the diaphragm inside is fine. when I say noisy, I mean that I can hear it hiss in the cab. Especially when brakes are applied or when the truck is shut off....hmm...time to spray that area and check for vac leak...

What do you think? So, I would put my money on the TPS..

 

[jhammel85]

Truck idles cold at about 2500 now, about 1200 in drive. I knew it was going to be high

I tried to adjust the IAC Valve by the instructions I had from Broncoii.org http://www.broncoii.org/techpages/eeciv/index.htm#TFI Timing: (11)

I found something that might lead me in the right way! When I unplugged the IAC and started the truck, the truck acted the same. So maybe the IAC is stuck open??
I brought the idle down as noted, shut off the truck and watched it go back to the correct RPM (800-850). When I connected the IAC it started running a little rougher and started hunting for idle. This could very well be the problem. When I disconnected the IAC while it was running nothing happened. After trying this a few times, it started responding by me unplugging it. Now I can't get it to NOT respond to me unplugging it. It doesnt die completely but it does drop idle back down to 650. Maybe it is OK....

I really have no idea what to think........
The thing is...I adjusted idle on the screw as it was noted on the site. This put my voltage back down around .7 or .8. So if I am throttling back the TPS then I cannot see that being any good either...what do you think? I haven't seen anything I'd say thats concrete evidence that its one or both of these to be honest.

By thr way...other than this, the truck runs great! Any help is appriciated!

 

[jhammel85]

Update again**

Played with it a bit more today since its 45 or so out today...
I cleaned out the IAC (again). I'm taking it that the IAC is fine. Its moving freely still. After I cleaned it out, I was letting it run. It started to stumble for a few seconds (smelling of pure gasoline) then it started running fine again. I pulled the plug on the TPS and it reved up and was fine after that.... It does it almost every time it that it powers down the 850 rpm range for the 1st time. Say I start it cold and let it warm up by idling for about 5-10 mins. Once it climbs down, it stubles at 850 then its fine. Of course when the engine is warm it does it much faster. This never happens anytime other than start up.

I cleaned out the TB while I was there and sprayed around for vac leaks again. Still no luck.

I found a vacuum line that goes from the T that screws into the intake on the driver side. This is the one that runs off vacuum to the brake booster and FPR. However, I do have one more line that goes off of it, down to the left hand side (passenger) side of the distributor...right by the TFI connection. I tried looking for where it connects but It felt tight and I could not find where it went from the top or under the truck. I'm assuming to the mod. on the trans (auto). I'll be looking more into that to make sure its on well.


I really wish the previous owner didnt cut the SIG RET and TEST OUT wires on the diagnostic connector...I went out today and tried to find the old wires but no luck.

I'm really stumped.....I still wonder about the TPS after what I found....I just dont know..
Anyone?

 

[jhammel85]

I plan to go over it on Sunday. I plan to pull the cap and rotor and have a look as the plugs look good and so do the wires. I hope to find something...I know it doesnt take much to cause a miss.

Also, no more stuttering when 1st driven after being turned on. Theres been a time or two when it barely did it...Thats about all. Seems like cleaning the IAC one more time did the trick. I guess the spring was a bit gummy.

I'm still looking for advice on the TPS. Should it be replaced if at WOT its only hitting 3.8. I just don't want to waste my money on one if its OK..

Any help is very much appreciated.

 

[IMenriched]

I plan to go over it on Sunday. I plan to pull the cap and rotor and have a look as the plugs look good and so do the wires. I hope to find something...I know it doesnt take much to cause a miss.

Also, no more stuttering when 1st driven after being turned on. Theres been a time or two when it barely did it...Thats about all. Seems like cleaning the IAC one more time did the trick. I guess the spring was a bit gummy.

I'm still looking for advice on the TPS. Should it be replaced if at WOT its only hitting 3.8. I just don't want to waste my money on one if its OK..

Any help is very much appreciated.

on the TPS...did you check the voltages with a digital or needle sweep multimeter?? to more accurately see hesitations in the TPS signal it is recommended to use a needle sweep or analog meter.

3.8v does seem a bit low....how is your alternator output? should be some where in the neighborhood of 13-14v

 

[jhammel85]

on the TPS...did you check the voltages with a digital or needle sweep multimeter?? to more accurately see hesitations in the TPS signal it is recommended to use a needle sweep or analog meter.

3.8v does seem a bit low....how is your alternator output? should be some where in the neighborhood of 13-14v

That's a good point. I didn't think to check the output of the alt. I'll make sure to do that. I'll post up what I find. I'll make sure the belt is good and tight as well. I'm sure it is...Thanks!

I checked the TPS with both. It swept great with no dead spots at all. However, like I said, it didn't hit WOT at the right voltage. At least as I'm reading it.

 

[jhammel85]

OK, Did a bit of work today....

I replaced the ignition coil since the previous owners did a wonderful hack job on it. I guess at some point the female connector at the coil had caught on fire or something. It wasnt there but the people before me used female quick connects to connect both the pos and neg wires to the coil prongs. HOWEVER, the pos prong wasnt there so...instead of getting a new coil they just shoved the wire along with a female connector inside the hole. Nice huh? So with a new coil, new connectors and electrical tape, we're running much better. It still misses here and there under slight throttle and at idle every now and then but it has so much more power.

So...yep, the problem with running rich at warm start and slight miss is still here. Still wondering about the TPS I found this:

"•Closed Throttle can be anywhere between 0.6-1.0 volts
•Part Throttle is triggered @ 0.04 volts above Closed Throttle
•Full Throttle is triggered @ 2.71 volts above Closed Throttle"

So...If my TPS is at .9 and WOT is 3.8, then I am in spec with the TPS, right? So maybe thats not my problem

I pulled the cap and rotor and they really are new. No problems at all under there.

So....now what?
I still dont have any concrete evidence on this thing. I know its a sensor...it HAS to be...

 

[jhammel85]

Oh and one more thing... I'm not running the TPS at .9. its around 7.3. Why would I still be running high idle @ .9 if it was working right??

 

[IMenriched]

Oh and one more thing... I'm not running the TPS at .9. its around 7.3. Why would I still be running high idle @ .9 if it was working right??

I think you found the issue....looks like to me that the bottom end is within spec but the WOT is below spec.

 

[jhammel85]

I think you found the issue....looks like to me that the bottom end is within spec but the WOT is below spec.

Thanks IMenRiched. So I guess if the WOT end was not in spec, it would take a lot of turns of the idle screw to set it at .9? If so, its what happened to me.

I've taken the plunge to buy a new Motorcraft TPS. For 30 bucks, it'll be here in the next day or two. Once its here, I'll install and set @ .9. I really really hope the high idle (@.9) and this warm start issue is resolved!

Thanks again!