1994 Ford Probe misfire/surging issues

[Brent_G]

Last night on my way home from hunting my car started acting strange. At idle it misses on 1-2 cylinders, one is pretty much a dead miss and the other is intermittent. At low rpms/speed it feels like the brakes are dragging and bogs quite a bit until 3500 RPM or so and on the highway the car has a noticeable jerk and misfire randomly anywhere from 55-75 mph (3100 - 3900 rpm). When it is doing this there is a definite change in the exhaust tone as if it is laboring.

This morning on the way to work, it was 22 out when i started it. Engine was completely smooth for about a minute and then the bog and misfire got progressively worse. When started hot the engine will struggle to gain rpm for about 20 seconds with multiple cylinders missing then suddenly it will rev up to 1300 or so, smooth out, then idle down. Once it idles down it acts as above.

When at idle, if you increase the rpm to 2k the miss is completely gone; when going down the highway if you run in 3rd or 4th and keep the rpm 4500 or so there is no laboring tone in the exhaust and completely surge/miss free. The car pulls strong all the way up to the 7500 rpm fuel cut and through every gear. I know it has to be an ignition problem but I cant trace what it could be.

73k on car - KLDE 2.5 v6
No codes flash when running or when the diagnostic pins are jumped.
New plugs, wires, cap, and rotor approx. 3k ago.
Premium 91 octane from a high traffic Shell station HOWEVER the this started happening about 70 miles after a fill up
Spark plug wells are dry and free of any oil/moisture
O2 sensors are new, as well as the crank position sensor, New PCV valve 10k ago.

Only thing I can think is either something ignition based or fuel, but everything is checking out good so far. Any ideas?

 

[OVERKILL]

What kind of coil setup does this car have?

 

[eljefino]

Can you get some of that computer freeze freon in a can and hit the ignition module?

 

[Brent_G]

Internal coil in the distributor

Originally Posted By: eljefino
Can you get some of that computer freeze freon in a can and hit the ignition module?


Everything is inside the distributor so not quickly and without moisture getting under the cap.

 

[Quest]

check IAC and also for vacuum leaks.

Q.

 

[Boomer]

Sounds like you may have a bad distributor cap (even though you replaced it). Check it for cracks and carbon tracks. Also, wait until after dark and start and run the engine in the dark (hood up, of course)and look for any arcing. This is a good way to see if you have one or more bad plug wires or any ignition wire carrying high voltage.

Check all of the grounds. Make sure that they are clean and tight. My son years ago had a Ranger that acted like this and sure enough he had a very loose ground wire that, once tightened, ran just fine. ANd Overkill is also on to something with the coil. A bad coil that is on its mlast legs can do some really quirky stuff.

Good luck and let us know what you find.

 

[jrustles]

Whelp, doesn't sound like the usual ignitor, that's a good sign. It seems like voltage leakage on the HT section, bad coil as pointed out or a noisy crank angle sensor. You should verify is it clean, snugged up, the leads are solid etc. Also are the points on the trigger wheel clean, aligned, how is the harmonic damper on the drive pulley? Is the bushing rubber cracked allowing for play?

Do you notice any signs of incorrect fuel trim, ie bad VAF,CTS etc?

 

[punisher]

Those old Probes had distributor/pickup problems.

 

[Brent_G]

I'm not sure if I have found the problem, however there are inconsistencies on the wear and build-up on the contacts inside the cap. 2 of the contacts have a lot more carbon built up on them, and they are ever so slightly loose. I have also narrowed it down to two cylinders that are missing, and one of the two is on the bad contact is the cap. The other is two away.

I have a new cap and rotor ordered, and new plugs for the two bad cylinders as well as wires to swap between to check.

I had a no start issue this spring which went back to the cps. I tested it and it fell right in spec, and after a cleaning of the connection and grease the problem went away. Tomorrow morning going to get the new cap/rotor in and check the connection again and go from there.

 

[99Saturn]

Is it possible to test the coil in a setup like the OP describes (coil internal to the distributor)? I'm having an inconsistent sputter/miss issue once the car is hot that I thought I solved a couple of thousand miles with new plugs but seem to have come back.

OP, did the new cap and rotor solve your problem?

 

[chrome]

In the K-series V6, a common issue is the rubber ribbed hose between the MAF and throttle body. At this age, the rubber tends to crack at the ribs, especially on the underside where you can't see. The crack allows in un-metered air, potentially causing your misfires and surging issues.

Pull off the hose, and inspect carefully.

Another problem area is the plastic vacuum reservoir under the intake manifold. The plastic tends to get brittle and cracks, again potentially allowing un-metered air into the engine.

This is difficult to detect, but check the operation of the VRIS actuators. If they don't work, there's a likelihood the plastic reservoir is cracked.

 

[Brent_G]

Originally Posted By: 99Saturn
Is it possible to test the coil in a setup like the OP describes (coil internal to the distributor)? I'm having an inconsistent sputter/miss issue once the car is hot that I thought I solved a couple of thousand miles with new plugs but seem to have come back.

OP, did the new cap and rotor solve your problem?


It did not solve it, but it has improved a decent bit. This thing is a rats nest of vacuum lines and after working on it a bit yesterday there is a definite leak somewhere.

Chrome, what is the best way to test the VRIS? It was throwing a code for an actuator around 5 months ago but it was parked right after for most of the summer. It has only been back in use for around 3 weeks and it has not happened since. Also the leak sounds like it is coming from the area under the intake so it could very well be the reservoir is cracked.

 

[chrome]

Brent,

The two VRIS vacuum actuators can be tested by placing a small square of paper at each actuator stop, so that the spring tension holds it in place. Once the actuator moves, the paper falls off.

You will need to bring it for a drive, as the engine needs to be under load and the full rev range used to actuated the VRIS systm. If after the drive, and one or both pieces of paper remains, there's a good chance the VRIS and vacuum reservoir may need attention.

 

[Brent_G]

Just took it out and ran 1st through 3rd twice, making sure to run it all the way to fuel cut in each gear. Both papers still there after so I guess it is time to learn the VRIS system.