91 SEFI - High Speed Stuttering

I have a '91 w/ 1.9L SEFI that is stuttering at speeds above 55 mph. Checked codes and got a 21 (Coolant Temp Sensor out of range) and a 24 (Air Charge Temp). After clearing codes and going for a short drive (no high speed - no stutter), code 24 was re-set.

Reading several previous posts on stuttering at cruise speeds seems to point towards plug wires as a likely culprit. Jet Li recommends using 9mm wires. I would try the "watch wires in dark" trick, but am thinking that since this happens at high speed, the possible arcing may only be happening at high speed as well, and watching wires at idle/no-load might not necessarily rule out an ignition wire problem. Would the high speed condition also correspond to higher cylinder pressures and higher spark voltages? This may be consistent with arcing/missing at high speeds. Any suggestions would be appreciated.

I once had that problem with my 1.9 with brand new wires. After a couple days of frustration I figured out that the plug wires were "leaking" at the boots under hard acceleration and arching on the cylinder head. A little tune up grease in the boots and all was good.

I have a '91 w/ 1.9L SEFI that is stuttering at speeds above 55 mph. Checked codes and got a 21 (Coolant Temp Sensor out of range) and a 24 (Air Charge Temp). After clearing codes and going for a short drive (no high speed - no stutter), code 24 was re-set.

Reading several previous posts on stuttering at cruise speeds seems to point towards plug wires as a likely culprit. Jet Li recommends using 9mm wires. I would try the "watch wires in dark" trick, but am thinking that since this happens at high speed, the possible arcing may only be happening at high speed as well, and watching wires at idle/no-load might not necessarily rule out an ignition wire problem. Would the high speed condition also correspond to higher cylinder pressures and higher spark voltages? This may be consistent with arcing/missing at high speeds. Any suggestions would be appreciated.

Chances are if the cars plug wires are arcing it will do it at any speed. Try to look in the dard while the engine is both cold then after a typial run check it while warm.
One easy thing to do (according to a fellow board member) is to clean the wires making sure there is no grease or grime. (wd-40 website says thier prduct is good for this and it help protect the wire) Then do like someone just mentioned about putting some silicone in the boot (ford recommends every time you remove a plug to re apply the silicone) finally you could proberly do a resistance check on the plug wires to see if they are still in specs. While your at it check your plugs/gap. All these tips are easy before you go spending money on plug wires. (my personal thought is replace the wires)

Thank you for these helpful suggestions. I'll try them and report back.

I have a '91 w/ 1.9L SEFI that is stuttering at speeds above 55 mph. Checked codes and got a 21 (Coolant Temp Sensor out of range) and a 24 (Air Charge Temp). After clearing codes and going for a short drive (no high speed - no stutter), code 24 was re-set.

Reading several previous posts on stuttering at cruise speeds seems to point towards plug wires as a likely culprit. Jet Li recommends using 9mm wires. I would try the "watch wires in dark" trick, but am thinking that since this happens at high speed, the possible arcing may only be happening at high speed as well, and watching wires at idle/no-load might not necessarily rule out an ignition wire problem. Would the high speed condition also correspond to higher cylinder pressures and higher spark voltages? This may be consistent with arcing/missing at high speeds. Any suggestions would be appreciated.

The CTS and ACT sensors are 'information input' type and control fuel, by pulse width of the injectors, ignition timing, and EGR valve operation.
I suggest you start with the information supplied by the onboard diagnostics. Check for loose connectors, corroded terminals at the sensors. If this doesn't eliminate the codes, check them for proper resistance and or voltage output.
If you need help or instruction on 'how to' check the sensors, let us know.

I have a '91 w/ 1.9L SEFI that is stuttering at speeds above 55 mph. Checked codes and got a 21 (Coolant Temp Sensor out of range) and a 24 (Air Charge Temp). After clearing codes and going for a short drive (no high speed - no stutter), code 24 was re-set.

Reading several previous posts on stuttering at cruise speeds seems to point towards plug wires as a likely culprit. Jet Li recommends using 9mm wires. I would try the "watch wires in dark" trick, but am thinking that since this happens at high speed, the possible arcing may only be happening at high speed as well, and watching wires at idle/no-load might not necessarily rule out an ignition wire problem. Would the high speed condition also correspond to higher cylinder pressures and higher spark voltages? This may be consistent with arcing/missing at high speeds. Any suggestions would be appreciated.

I had a similar problem and read in another post somewhere to check the thermister wires on the mass airflow sensor(on the left of the airbox). You can access the wires by removing the mas housing from the airbox, take the screen off and you can see the wires. I had some crud built up on one of the wires, cleaned it off and power has improved dramatically.