Rough acceleration after changing plugs/wires on Ford probe gt

Hello everyone!

I have a problem with a 1996 Ford Probe GT. I recently had to take my car to the dealership because it wouldn’t start. They determined that the problem was caused by a faulty battery cable which they replaced. The problem is that they also informed me that the car was missing very badly and needed a 700 dollar tuneup. Now, the car was operating fine before I took it into the dealership. So fine… I took the car without doing the repairs and decided to fix it myself. I replaced the plugs, wires, distributor cap and rotor. The car however, is still running really rough. When cold, it is almost normal but once it gets hot, the issue gets worse. When you accelerate, you hear the engine sputter and hesitate and will finally accelerate. Once at speed you don’t have any issues. When it sputters, theres a heavy fuel smell

I checked all the wires and one seems not to click all the way on the plug (and can be pulled out very easily) but somehow I don’t think this is the issue. Could it be some sensor?

Any help would be greatly appreciated,



Try and install that plug wire firmly on. Engines tend to act up when all cylinders are not firing.

Tune-ups today also consist of replacing air filters and fuel filters.

Other hesitation issues may be a vacuum leak or a faulty fuel pressure regulator which MAY be leaking allowing for the strong gas odor.


It is not a vacuum leak, I did the oil cap test and the engine quit as soon as I took it off, so it is not that. I did not think of the fuel pressure regulator. I replaced the wires and it still does the same thing. I drove it for a while to get a better idea of what it is doing.

1.- when cold, no sputtering or rough idling. When I press on the gas, it accelerates normally
2.- Once hot, starts to sputter when accelerating, but not so bad if I ease the accelerator in. Almost dies if I tromp on it…

When cold it’s ok.

When hot it hesitates.

Are you getting a CEL when this happens? We need a starting point to diagnose the fault.

I still think it is a fuel supply problem. But that’s JMHO.

Perhaps an engine temp sensor is faulty? I don’t want to drag this out so…

To narrow this down we need some tech help.

What say guys?

This sounds like a problem where the veh may be running lean, when the veh. gets warm enough, it goes into something called “closed loop” where the ECM relies on the various input sensors throughout the engine to maintain proper fuel/air ratio going into the cylinders. it sounds almost like a stuck IAC motor. before you start your car in the a.m., unplug the connector to the IAC. (you may set a trouble code and the MIL may come on, if it’s not already on.) see how your engine fares after it warms up. If the problem has gone, then you’ve found the culprit. Take the iac off and clean/reinstall/and plug it back in. If no help, then replace the IAC motor.


Yes, the check engine light is on and is blinking (I tried reading the codes but the unit I borrowed from Checker could not make a connection with the computer) I will need to disconnect the cable so that I can clear the memory and start fresh, perhaps take it to somewhere else to have them read the codes.

I really appreciate your help on this…


Thanks for the reply! I’ll take a look at that … IAC stands for? (sorry, I’m a little ignorant on this type of thing…)

I really appreciate all your help…

The symptoms are of a lean running engine. When the engine is cold, the engine coolant temperature sensor (cts) is sending a signal to the engine computer. The engine computer enriches the fuel mixture until the cts tells the engine computer that the engine is warm; then, the engine computer stops the fuel enrichment.
Replace the dirty fuel filter. Measure the fuel pressure. Use an MAF Cleaner to clean the MAF (Mass Air Flow) sensor. Use a spray Carb/Throttle Body Cleaner to clean the throttle body bore and throttle plate, and the iac (idle air control) valve.
Get the check engine light codes read and bring them here for comments and advice.

if you disconnect the battery the codes will be erased. then you will have to wait for a while for the codes to reset. so don’t disconnect the cable, get the codes read.

what shape is the scan plug? a rectangle, or a trapezoid shape? if it is a trapezoid shape then the obd2 scanner will fit. get the actual codes and post them here.

Clarify what the problem is with getting the code reader to read. When you say that the code reader, “…could not make a connection with the computer”, do you mean that you were able to plug it in without difficulty, but, that the screen on the code reader said, “NO CONNECTION”?
Did you remember to turn the ignition switch to the ON position, and, then, press the button to read codes on the code reader?

The black plastic flexible pipe from the air filter to the throttle body may have been disturbed while installing the plugs, etc. It the connections aren’t tight, or if the pipe has cracks, as the engine pulls back on the mounts, air can enter and cause a lean mixture. Brake-torquing the engine usually confirms this problem. BE VERY CAREFULL.


I would connect the reader (obd2) would give me trying to connect then fail “could not make a connection to your computer” or something like that… don’t remember the error exactly, tried about 4 to 5 different times. Yes, I did have ignition switch in the on position. Happened once before when taking unit to autozone to have the codes read. I’ll try to go somewhere and see if they will read it and give me the codes.

I just recently replaced the flexible pipe from air filter to throttle body, at one time this was cracked so I just purchased it a few weeks ago… (80 bucks for a piece of plastic… wow) But I’ll check it again… thanks!


I’m trying to find where the IAC valve is on this thing… I have the chilton manual but I can’t find where the IAC is…no diagram

ok, checked the air intake tube… no cracks, everything plugged in tightly…
cleaned MAF sensor, reinstalled
cleaned throttle body - reinstalled.

I located the Idle air valve/motor (underneath the throttle body) and I’ll unplug when cold to see how it fares. I did check that this part is almost 500 bucks, and it looks like it is a bear to take out…

Now, I did confirm this… it only sputters when laying the pedal down hard or when having to accelerate quickly. If just driving normally, easing the gas… works just fine…no sputters, nothing…

snip ok, waited until the car was cold… I disconnected the Idle air Valve/motor… didn’t seem to do much, waited until warmed up, still sputters when tromping on the gas…

I want to thank all of you for helping… I really appreciate your suggestions and help… I’ll keep you posted tomorrow.


ok, now all my theories are shot…

when driving to work this morning… car would sputter even when cold when accelerating suddenly (this at least is consistent)
occasionally would sputter even when accelerating slowly, but would level out after giving it a little more gas… usually after going above about 3000 rpm.


What brand of spark plug did you use? Some engines are really sensitive to the type and brand of plug. This car is actually an import dressed like a Ford. I believe the engine is Mazda. I know they hate Champions and Autolites. I use NGK for all my Mazda engines.

A blinking CEL indicates a serious problem, and you shouldn’t be driving it. A cheap problem can turn expensive if you keep driving.

Have you verified that the spark plug wires are routed properly?

Look the engine over thoroughly. You may have left something disconnected…like the electrical plug to the MAF (Mass Air Flow) sensor, or a vacuum hose. Put a vacuum gauge on the intake (vacuum hose). Use the two pages of instructions which are usually, in any Haynes, or Chilton’s, repair manual to analyse the vacuum gauge readings. Click on this link for the vacuum hose diagrams for the Mazda V6 which is in your Ford Probe.
When you are trying to get the code reader to connect, wriggle the ignition key (switch in ON, or, RUN). With the engine running wriggle the ignition key. Results?

Here is a picture of the idle air control valve: ht,APP417524/vehicleId,2142402/initialAction,partProductDetail/store,1140/partType,00207/shopping/partProductDetail.htm