Resolved Stumble issue upon acceleration (1987 GT)

[FoxDude87]

Yea, that’s right. As I said, it unlikely, but it’s free to test. Did you try the old distributor to see if that cleared things up? I’m sure others more knowledgeable will chime in on the pump issues.

It's worth a shot to probe the fuel pump connector and even swap out the distributor with the original with some new thermal paste on the TFI. I think I could do both tests tomorrow. I appreciate your help, same to the others helping me out on this.

 

[Mcmahst]

I would do the distributor first, then if that doesn’t improve the situation, do the pump voltage test. You’ve got to drain the tank before you remove it, so that’s when I would do that test. Good luck.

 

[Noobz347]

Yea, that’s right. As I said, it unlikely, but it’s free to test. Did you try the old distributor to see if that cleared things up? I’m sure others more knowledgeable will chime in on the pump issues.

That is a great idea.

 

[Blown88GT]

You said the fuel pump is new, can you verify that again?
The only reliable way to test it is under load, i.e. driving it with a fuel pressure gauge monitoring.
When it stumbles under acceleration, if the pressure momentarily drops & then returns to normal, there's your problem.
The idle tests mean nothing, the flow tests mean nothing. Don't waste your time doing them.

 

[FoxDude87]

You said the fuel pump is new, can you verify that again?
The only reliable way to test it is under load, i.e. driving it with a fuel pressure gauge monitoring.
When it stumbles under acceleration, if the pressure momentarily drops & then returns to normal, there's your problem.
The idle tests mean nothing, the flow tests mean nothing. Don't waste your time doing them.

Within the last year or two I had the fuel tank replaced. I also told them to throw in a new pump w/sending unit as well. I'm under the assumption that the pump is fairly new.
Driving with a pressure gauge is definitely the best way to test it, I agree. I just don't have the parts for that unfortunately besides the fuel pressure gauge that hooks up to the fuel rail valve. I appreciate your input. Thank you.

 

[LX2C]

Hi. I had the same issue and mine was the MAP sensor.

 

[nickyb]

I just fixed a similar problem, my new dist. Was a bad one. And I replaced a bunch of stuff that didn't help.
Just put a new dist. And in and problem solved

 

[FoxDude87]

Everyone, I ran a quick experiment regarding the distributor, and so far it has fixed my issue.

I was going to put my original Ford factory distributor back in the engine.
But I wanted to try something first and im glad I did.

I kept the new aftermarket (LMR) distributor in the engine and removed the TFI module that came with it. I placed my original Motorcraft Ford factory TFI module on the distributor. ( added a good amount of thermal paste on the back of the TFI too)

I started it up and took it for a drive.

So far, I've had no stumbling, misses or engine hesitation like before. It runs great even while cruising at the low to mid-range RPMs (where most the stumbling would occur).


1. I think the PIP sensor in the original ford factory distributor was going bad or is bad?

OR

2. The TFI module that came with the new LMR distributor is defective?

(Which I have read that these aftermarket TFI modules are not great; even though they say the modules are infact current Motorcraft TFI modules. I think the build quality is not up to par with factory original TFI modules).


Overall, I think this may have fixed my problem and I want to thank everyone who has chimed in to help me on this issue.

I'm going to take it out a few more drives before I deem this issue resolved.

 

[nickyb]

Great feeling isn't it

 

[FoxDude87]

Great feeling isn't it

You betcha bud. Definitely feels like I accomplished something this weekend.

 

[Tonys96Cobra]

Also, where did you buy your distributor. The one that you later found was the problem?

Rock Auto.

 

[Tonys96Cobra]

I did recently have a new distributor from LMR installed ( it cost me like $80)
I still have my old distributor. It's the original Ford Motorcraft.

I guess It's worth a try. What exactly was your 89' fox doing And what multitude of issues did you have?

I'll laugh if that's what's been causing my grief and confusion

Poor idle, misfires at low rpm, like going through a roundabout in 3rd gear at 1500 RPM, it would misfire until I got over 2k. Car would not idle with the AC on at all. All these problems were fixed by going back to the old Ford distributor

 

[Jarhead67]

Hello everyone. I'm new to StangNet, so I hope I can find a solution to my driving issue.

I have a stock 1987 GT convertible Automatic 5.0 (speed density) car. I've owned it for more than 12 years with my fair share of ups and downs and I love this car.

It has 66-67,000 original miles on the clock and I'm having an acceleration issue. It seems to stumble (maybe misfire?) On moderate acceleration right around the 1500-1800 rpm range.
It does this when the engine is cold or warmed up. If I get on it, the rpms will drop up and down just slightly, Then she will smooth out.

Recently a New distributor, cap, rotor, motorcraft TFI module, plug wires, motorcraft copper spark plugs (gapped .054), Ignition coil, 3G Alternator, starter + starter solenoid, IAC, TPS (set to under 1 volt , about 0.72 volts. WOT is 4.25 volts)
EGR valve w/ EGR position sensor, PCV valve + grommet at rear of engine, ACT sensor, ECT sensor (coolant temp sensor), NTK oxygen sensors (no catalytic converters), fuel tank, fuel pump, fuel pump relay and filter.

Checked for vacuum leaks with a smoke machine and didn't find any leaks.

Idles good at around 750 rpm in drive. Idle is close to 900 rpm in park.
Timing is set to 10° TDC and it was set when the mechanic installed the new distributor, IAC and TPS.



It seems to have good fuel pressure when I checked it last. It does this almost every time I drive it now. If I'm steady on the gas, it's less likely to do it. And I've noticed it will stumble a bit more if I'm giving it more gas driving up a hill or inclined road.

Any ideas on where I should go next?
FPR ? Injectors? Transmission ? Lol

One thing I noticed is that you have TPS set at .72 volts. That should be closer to .97 volts.
Also, did you do a base idle reset before setting TPS?

 

[FoxDude87]

One thing I noticed is that you have TPS set at .72 volts. That should be closer to .97 volts.
Also, did you do a base idle reset before setting TPS?

Car is fixed. It was the distributor TFI module or the worn out PIP sensor on the original distributor. Also, the TPS can be set at a range of 0.72. It doesn't have to be 0.97 to 0.98 volts. That's a myth and my car runs fine at its current tps volt range. As long as the volts are below 1 volt at idle and they steady increase to an approximate 5 volts at wide open throttle.

I've also done a base idle reset in the past but it did not perform well because the distributor turned out to be the issue.

 

[FastDriver]

Just got to this thread. I was gonna say that you should replace the TFI module and/or PIP sensor in the dizzy.... obviously! Don't know what all these other guys were smokin'