Hesitation on acceleration

[PT123]

Hi all!

My 2003 manual transmission base PT with 132,000 miles recently developped a strange behavior: on low RPM acceleration (rolling start from STOP sign in 2nd gear for instance), the acceleration will be interrupted very briefly once or twice; very annoying. To circumvent the issue I try to use higher RPMs with delayed upshifts, but there must be a better solution.

The problem seems to have gotten much worse since the last gas fill-up, although this is probably unrelated. Also, my mechanic overfilled the engine with oil, though he says it's ok, again probably unrelated. He says the acceleration problem will require all kinds of tests, I'd rather check with PT experts here.

Plugs and wires were changed on the car about 4 years ago. Air filter changed last month. Same error codes since the day I bought the car used many years ago: P1494 & P1495.

Any ideas? Thanks!

[rob342]

i can assure you that if the car has too much oil to the point it's a problem, the car will smoke profusely.

girl im friends with started adding a quart every time she got gas. when there's enough to be a problem, you'll see it.

[ptcruisersteve]

I would suggest checking the wiring going to the leak detection pump and the wiring going to the TCM under the battery. The wires might be rubbing on ground making intermittent short.

[PT123]

Originally Posted by ptcruisersteve

I would suggest checking the wiring going to the leak detection pump and the wiring going to the TCM under the battery. The wires might be rubbing on ground making intermittent short.

Will do, great advice. I knew there was a bit of corrosion on the battery connectors, didn't think this could be related but I'll start there and check all visible wiring around the battery. Thanks!

[PT123]

Originally Posted by PT123

Will do, great advice. I knew there was a bit of corrosion on the battery connectors, didn't think this could be related but I'll start there and check all visible wiring around the battery. Thanks!

I ended up changing the battery connectors that were badly rusted, but this didn't solve my problem, the car still jerks on low RPM acceleration, I have to gently brush the throttle to get the car moving smoothly from a stop or near-stop and punch it once I'm out of the trouble spot (from idle to about 1,500rpm). Very very unpleasant!

I guess the most probable causes are now plugs/wires or TPS...

[chuzz]

Have you ever cleaned the throttle body?

[PT123]

Originally Posted by chuzz

Have you ever cleaned the throttle body?

Actually I did just a few weeks ago, the car ran fine at the time and continued so for a few weeks before the power cuts got really bad.

I may be on to something. While inspecting the spark plug wires, I noticed that the plug that is closest to the oil filler cap (the only one I can pull out without removing the intake manifold) was loose. It came out with hardly any effort. It will click in when pressed onto the spark plug but it's not as secure as I'd expect a plug to be, I recall that these usually require more effort to remove. I suspect oil may have been spilled on the valve cover during a fill-up and some of it slowly made its way down the connector. The car runs much better now although it will occasionally get a power cut, nothing like what it did in the past few days. I think the best thing to do now is to take out the sprak plug and make sure the top connection is clean for a clean and secure fit onto the connector.

This said, I also wiggled a bunch of other electrical wires under the hood, I'm not sure what part of what I did improved things so dramatically...

Will report back. Thanks everyone!

[PT123]

UPDATE: after running fine for a few days, this morning the engine ran very rough on startup, I couldn't drive the car. I got a cylinder 1 misfire code (p0301), the same cylinder that I thought the spark plug wire was loose. Unfortunately, it's worse: the spark plug is loose and I can't torque it down, threads in the head must be stripped. I still managed to sort of hit a little bit of resistance while turning and left it there, the car runs fine but it's just a matter of time before the plug pops out again. I'm thinking that the threads may have been damaged and repaired before I bought the car many years ago, and the helicoil repair may be failing.

The plug will come out no problem, the threads on the plug look perfect to me, but when I put it back in it'll spin to no end, though after a few clockwise turns I can't pull it out so there is some bite. I tried swapping plugs and the same thing happens.

Is there any way I can tell from looking at the plug hole whether there is a loose helicoil (or similar device) in there?