Solved My van has a shudder when trying to maintain speed.

[Tony Oberkirch]

I have a 1995 Aerostar XLT, 4.0L, 2WD automatic, with about 210,000 miles on it. It had been running fine until this weekend. We had a cold snap, well cold for the Gulf coast, it dipped into the upper 20's. I started up the van and it was a little rough, but I suspected it was cold and would smooth out. When I accelerated it smoothed out, but it still shudddered bit at idle. When I got it on the road, up to about 45-50, it shuddered quite a lot while trying to maintain speed. Accelerating or decelerating it was smooth. I set the cruise at 45 to test and it shuddered so badly I turned around and took it home and parked it. it did not backfire, it was as if the timing had been changed. I would suspect timing belt or transmission problems, but it runs fine when accelerating or decelerating. I have not even raised the hood to troubleshoot yet. Any ideas or suggestions would be appreciated.

 

[Josh P]

Sounds like the torque converter. It fully locks up at 45 mph or so and unlocks when you let off the gas or accelerate. How old is the transmission fluid and how often does it get changed?

 

[Tony Oberkirch]

It's a little rough at idle, not nearly as bad as when driving at 50. That made me think fuel system or ignition system, rather than tranny.
The trans fluid is probably 7 years old or so. this is not a daily driver - It's a secondary vehicle that logs 3k-5k miles a year.
I've been driving my other vehicle and haven't had a chance to even raise the hood. I'll check the trans fluid first thing when I get a chance to look at it. I checked it within the last 60-90 days and it was ok. Still pink, no burned smell.

Based on this info, do you still think the torque converter is the culprit? Thanks Josh.

 

[Josh P]

If it smooths out then I'd doubt ignition, a miss would be the worst under load not at cruise. Same goes with the fuel delivery. Did the check engine light come on? Take it out for another test drive, try shifting the transmission to 3 and drive at the same speed as before.

 

[BrooklynBay]

Welcome to this forum! Check the vacuum lines for leaks.

 

[Tony Oberkirch]

Problem solved, not the transmission at all, it was a bad fuel injector. whew!

 

[BrooklynBay]

Thanks for the update. How did you figure out that it was the fuel injector, and how did you determine which one it was?

 

[Josh P]

I'm curious as well. Thanks for the update.

 

[Tony Oberkirch]

Don't take away my "Aerostar man-card"... I took it to a local mechanic I trust. $209.

 

[BrooklynBay]

I'm going to mark this thread solved. My 1995 van ran rough for a long time when I first got it. I found one cut fuel injector wire, a broken vacuum line, and a vacuum cap missing. I don't know how one of those wires got cut.

 

[Tony Oberkirch]

Hey BrooklenBay, I had a similar incident with my wife's 2005 Trailblazer. It had been running fine, but suddenly it lost power, and even had a "reduced engine power" light lit up on the dash. The wires on the throttle body appeared to have been crushed, and one was cut. I can't imagine how they got crushed or cut - they are on top of the engine, anything heavy enough to crush them had to happen with the hood up, and the hood has to be released from the inside. I used some shrink tubing and solder, and repaired them, and the power magically returned. Strange, unexplained things can happen to a vehicle.

 

[BrooklynBay]

Don't underestimate the mechanics performing inspections. One shop once cut the wiring on a relay module on my previous Mercury Sable. Another place unplugged the horn & wiper motor on that same car, and another place cracked the tail light on that car. None of them admitted to anything.

On my 1989 van, a guy deliberately drained my battery then told me that I needed a new one. I refused to buy one from him, so he wanted to charge me $10 for a boost. He didn't know that I had a dual battery system, so I turned the bypass switch, then started it. He was surprised that it started, so he wanted to be a wise guy. He wouldn't let me pull my van out of the shop. His mechanic backed it out into on coming traffic at full throttle reverse, then left it. A bunch of angry drivers were blowing horns & yelling while it blocked traffic.

On my 1995 van, one guy checking the front brakes put a pry bar into the caliper, and cracked my brake pads then removed a hard plastic washer fluid line. He told me that he couldn't pass my van for inspection because my brakes were no good. I replaced the brakes, and plastic washer fluid tubing, then went to another shop for an inspection. I wouldn't be surprised if the broken wiring on the 1995 van were cut by a similar type of person when the previous owner had it.

 

[Josh P]

Don't take away my "Aerostar man-card"....

 

[Icuff4cash]

Ever have rats eat your wires,I lived in Tucson in 2009 by the Sabino canyon park. My 2005 Honda Pilot was fine that night and the next morning I started it and the 4x4 light was lit and I had lights flashing. Took it to Honda 10 min later the guy had my harness in his hand. He said all 2005 and under cars the plastic has a smell that rats like and chew. The Honda dealer had replacement kits and it cost me 300. He said after 2006 there's a different plastic which solved the problem

 

[Icuff4cash]

Here is a VIEDO on how to test your fuel injector and how to clean it. I'm just trying to bring information,I have know idea what to do I'm a Holley 600-780 person any car after 1977 I'm lost.