93 surges and dies

[gt_stang88]

For the last year or so my 93 ex has been surging and some times stalls at start up and at stops. Now with the warmer weather I have the AC on at it does it all the time and worse than before. I have replaced the IAC valve, changed plugs,plug wires, o2 sensors , and cleaned the MAF. Nothing has help. Runs fine when driving and has not loss power, just surges and dies sometime. Please help.

 

[marragtop]

Have you pulled the engine codes?

 

[Opera House]

Could be a fuel problem. If you are ready to get serious, get a meter and monitor the fuel pump current while you drive. This is easily done by pulling the pump fuse and bringing lamp cord into the cab to the meter, about 5A. Crimp on wire connectors fit into the fuse socket. I found a sticking fuel pressure regulator that way. This will confirm that it is at least a fuel problem.

 

[Glacier991]

In the for what it's worth, TPS comes to mind as well.

 

[gt_stang88]

I checked for codes but there are none. Checked KOEO and KOER codes. When I hook up a meter should I olny 5Amps all the time, What if I get more or less what would that mean?

 

[verlane24]

My 93 had a similar problem late last summer.... it didn't stall all the time, but the idle would surge and drop randomly, especially after driving around for a while.

Tried it the TPS at first; when that didn't work I checked the fuel pressure. The pressure was low(but not real low) at idle, so I swapped the fuel pressure regulator out (175K miles and it had never been changed) and that solved my problem.

later
brian

 

[410Fortune]

Check the fuel pressure
Listen to the fuel pump
Replace the fuel pump relay
Replace the fuel filter
Replace the fuel pressure regulator (if pressure doesnt check out)

My $$$ is on a fuel system problem, seen it 100 times, just like you describe.

 

[gt_stang88]

I replaced the fuel filter and fuel pressure regulator today, it helped a little bit, but still surges? I checked fuel pressure before and after and both was 40psi key on , and 30 psi running. Any more sugggustions?

 

[Opera House]

Pump current roughly relates to pressure. At high vacuum conditions( idle) the current will be lower, at WOT the current will be higher. It only increases about 0.3A higher at WOTthan at idle. Current will actually drop about 0.2 from when you start it till the pump warms up to normal temperature. The engine will still run if pump voltage drops down to about 6V since about 80% of the fuel is bypassed back to the tank. If you really had a regulator problem, you should disconnect the battery to reset the computer. Mine didn't learn for 200 miles and had poor performace till it was reset. Pump current doesn't really tell you anything specific other than if it drops below 4.8A there is some kind of fuel delivery problem. If you don't see anything strange with the current when the engine stumbles, the problem is elsewhere.

 

[gt_stang88]

It's been about 2 weeks since I replaced the fuel filter and fuel pressure regulator, I reset the computer and I think the surge is still as bad as before I did the work. I'm thinking about putting the old FPR bad since it didn't work and put the money towards other parts to try fixing the problem. Any more suggestions on what to try maybe the TPS sensor or EGR valve? Any help will be helpful. Thanks.

 

[travish_1]

I had a surging problem too. I had to replace my Throttle position sensor (TPS). Good luck!

 

[gt_stang88]

Ok replaced the TPS and cleaned the MAF sensor 3 days ago and still runs the same! I'm about to give up on the problem. I think I might try testing/ replacing the EGR valve. Help me please.

 

[travish_1]

Did you check you fuel pump relay? On a different occasion, I had to replace it as well. My car would start only sometimes, and when it did it it surged up and then died after a few moments. It was a cheap fix so try that.

 

[1993XLTFAM]

I have a 93 that used to surge at stops after the engine was warm.
It would rev up to over 1500 rpms and then drop to about 700. Never stalled though. It would only do this after the engine was warm. The problem was traced to the positive battery cable. It was worn and shorting out. The cable was worn near the air intake, about 12 inches from the battery. Please let me know what you find.
BTW - after replacing the cable, I slit a piece of heater hose and put it around the positive cable.

 

[gt_stang88]

I just checked the pos. cable and it's not worn throught but is very corrioded where the cable go to terminal so i'll try replacing that. By the way did you get one from ford or go to a parts store? thanks for the help, Matt

 

[1993XLTFAM]

I got one from a dealer for about $45. If you are able, you can cut off the terminal, clean up the cable and replace just the terminal. The routing of the cable makes replacing it a little difficult. There is a clamp that holds the cable in place near the oil pan that I could never get to go back on correctly.
If your cable is not shorting out like mine was, then replacing the cable
probably won't solve your surging problem. Of course it is something you should fix any way. My cable was shorting out against the underside of the air intake. The cable had been rubbed bare. When you find out the cause, please let us know.

 

[travish_1]

Did you check you fuel pump relay?

.

 

[Private_Joker]

93 and A/C works?!?!

You have a 93 and your A/C works?????

Did you replace your A/C with the 'new' stuff? not R12 I think..

PJ