Please help, car runs rough

T

thundermax

Registered User
I researched as much as I could and canot find an answer.
I have 90sc auto all stock.
Cold start runs great, drive it for 5 minutes starts surging and running rough.
Has new plugs, wires, fuel filter good premium fuel. I bought this car a few months ago and it sat for 4 years; during drive home it ran great for about an hour then same thing started happening.

I removed crank pulley inspected balancer: no problem found. Tried new coil pack and DIS: problem still there. I bought a fuel pressure gauge to go on rail and it stays at 30psi at idle when it runs good (after first start) and it stays at 30psi after car is warmed up and is running rough.

I suspected a bad fuel pump but now I don't know because gauge reads same when car runs good and bad.

Pulled code when car is running: code 77 Wide Open Throttle not sensed during Dynamic Response Test.
Also had a code before for passenger side 02 sensor indicating a lean condition.
 
try checking the tps and iac motor's. may not be a bad idea to change the o2 sensor's if it sat for that long.
also try swapping the maff sensor or clean it with a q-tip and glass cleaner be real gentle with the wires on the maff. spray glass cleaner on the q-tip not the wires
 
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i'm going to go with tps or MAF also. try cleaning the maf first, then make sure the tps is calibrated correctly.
 
I got a can of maf sensor cleaner and cleaned the sensor with no difference; I verified that my fuel pressure is good: 31 at idle and when I give it throttle goes up to 40psi. Will go and check the TPS values at idle.

It seems that now after the car idles for a while, it will start to break up at idle as well; when you go from park to reverse or drive it does not want to idle steady.

I can rule out the fuel system pressure, DIS, coil pack, plugs-wires.
I know IAC wouldn't make a difference under load

I went under the car and the O2's don't look old they are NGK.

My vacuum with good idle is 18" at the most; I went through and resealed all SC plumbing. I know my last SC would easily have 20"hg at idle, I don't know if I should be too concerned about that

I don't know if cam or crank sensor would contribute to this, in my experience if either one is bad the car wouldn't run at all or would trigger a code.

Also I don't know if I could have a wiring harness problem, is there any specific spots I can check with wiring?
This old car is such a ~~~~ to diagnose, I'm too used to obdII
Thanks for the help, Max
 
after checking your tps voltage, swap your MAF out. cleaning it doesnt always magically make it work. its a heated wire, the element burns out sometimes and no amount of cleaning will fix that. after that, cap your intake and pressurize it to 15psi, check for leaks. your cam sensor is a possibility also.
 
thundermax said:
Pulled code when car is running: code 77 Wide Open Throttle not sensed during Dynamic Response Test.
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All that means is you didn't "goose" the throttle when you were supposed to during the test.

If you have the diagnostic tool, I suggest letting the car warm up and then when it's idling like crud, run the key on engine on tests, and initiate a cylinder balance test.

how is the fuel economy? Fuel pressure at idle isn't the ideal thing to only measure. ideally you want to measure it at idle, as well as have it setup so you can see what pressure is under load, going down the road.
 
yes definatelly temp. related
I'm willing to try swapping some sensors, which ones should I try first?

02's, crank, cam, maf? It has to be one of those.

What type of symptom would each one of those sensors give me if they were bad? I took out the cam sensor and it looks clean inside where the element sits.
 
ECT sensor. Its located on the pax side where the coolant hose comes out to feed the heater. It'll have a cable plugged into it.

It tells the EEC what temperature the coolant is, which affects the fueling and spark etc... and if its not telling the right temp.....

Fraser
 
Could the sensor be bad and still read correct?
I won't get to work on the car again until next weekend; I will drive it until it runs bad and unplug the sensors to see if makes any difference, if not then I will have to start trying new sensors.

Any other suggestions are welcome, I also thought of changing the crank sensor due to possibly breaking down to heat and it also directly relates to timing control.

The best way I can describe what the car is doing: I would start it up and it runs great, I can give it 10psi boost and it takes it fine; I would drive it down the road about 2-3 miles then first it will start surging at steady speed, if I give it any boost it will miss under boost and eventually it will run rough under any load and almost wants to die.
 
thundermax said:
Could the sensor be bad and still read correct?
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Read where? Unless you are data logging the motor or hook up a meter to the wires, you won't know what the sensor is sending. The sensor for the gauge is on the thermostat cover. The sensor for the EEC-iv is where you were told to look.
 
Mike8675309 said:
Read where? Unless you are data logging the motor or hook up a meter to the wires, you won't know what the sensor is sending. The sensor for the gauge is on the thermostat cover. The sensor for the EEC-iv is where you were told to look.
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Good point, I didn't realize that there was 2 coolant temp sensors. I thought that the one on t-stat outlet served both functions.
 
the one on the housing is a switch.

frit, good point, dont know why i didnt think of it myself. that sensor is cheap, comes off with a 1" wrench. just make sure you have something to grab the stem coming out of the manifold, or else it will try and thread out on you.
 
I'm not near the car right now. When I purchase this sensor is it the same part number as the one for the gauge? or is this specific ect sensor for ecm only and cannot be interchanged with the one for the gauge?
 
Ford dealer will have it, motocraft part # DY1145. Delphi, Four Seasons, Standard all make aftermarket versions. I'd personally try the dealer first, part should be around $40. If they want more, you can get the motorcraft part for $33 at www.rockauto.com
 
sinhumane said:
after checking your tps voltage, swap your MAF out. cleaning it doesnt always magically make it work. its a heated wire, the element burns out sometimes and no amount of cleaning will fix that. after that, cap your intake and pressurize it to 15psi, check for leaks. your cam sensor is a possibility also.
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This is good stuff. The maf is a tricky piece as I've read. An air leak is a strongpossibility as well. Do what sin said. If you haven't already. I've had the same problems before, and in the end it was none of sensors. Just a crappy seal on an IC tube.
 
Oh, and wiring harnesses. I once had a loose ground wire at the breakout box which caused all kinds of odd symptoms.
 
Thanks, I will install new ect on saturday and report back. As far as testing for air leaks, do I just cap the throttle plate shut and pressurize everything after the trottle plate?
 
new coil pack? make sure all plugs and wires are on correctly and snug. spray some electrical cleaner dryer fluid on coil pack.
 
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