Help Throttle Issue

[mbsickness]

I just encountered a running issue with my car which I can only describe as a throttle issue. The car is a 1994 C280 with about 95K on the clock. Tonight while accelerating from a stop the car lost all power but stayed running as rolled to the side of the road. Upon putting car in neutral the car idled normally but when I tried to rev the motor the engine would not speed up beyond 2K rpm. Once it hit 2K rpm it would just cut out and then catch itself around 500 rpm and then back up to 2K rpm. The engine would continually cycle this way. Finally I shut the cara off and then upon restart all was fine and I drove the car home 40 miles without incident. No Check Engine light and no codes stored or pending. The MAF was replaced a year ago at 89K miles. Wiring harness was replaced in 2002. Thanks in advance.

[strictlyspeakin]

I've got nothing helpful for you sorry.

I wonder if that is the infamous limp mode...

[xvvvz]

Yeah, it sounds like limp home mode. Let's hope it is just a one-off fluke thing.

[mbsickness]

Well, I have driven the car a bit more and noticed the following:

1. On startup the engine idles properly at 700rpm in neutral
2. After a mile of driving the idle is at 1100rpm in neutral and remains at this level for the duration of the drive.
3. If the engine is stopped and immediately restarted the idle goes back to 700rpm
4. The cruise control does not work.

Any ideas?

[mbsickness]

I'm beginning to think the throttle actuator is at fault as I just took the car for a spin and before it goes into "high idle" mode the cruise control worked. If it wasn't a $1200 part I would just replace it.

[mbsickness]

Well I spoke too soo as this morning it acted up again. Pulled over and the car idled in gear just fine but would not rev beyond 1500rpm regardless of if it was in neutral or in gear. Even if the accellerator was slowly pressed the engine woul cut at 1500. Like last time everything was fine on restart. No CEL no codes. If this is the throttle actuator am I damaging anything by continuing to drive the car?

[Sulaco]

I'm 95% sure you're looking at an eroded wiring harness on the throttle body actuator.

Yeah, it's $1200, but if you know of ANYONE who's reasonably good with a soldering iron, they can rebuild the harness for it with some ease. It only takes a decent soldering iron ($40), about $20 worth of military spec wiring, and an hour or two of expertise and steady hands.

If you remove the "market value" of the whole thing, you could probably get a local TV repair guy to do it for $100. Considering the nature of your alternatives, you could offer someone $300-$500 and still save yourself from spending a whopping $1200 for a new/rebuilt one.

FYI, all rebuilt/refurbished ones have had the wiring harness rebuilt the same way.

There's a guide online somewhere on how to do it yourself. I'm practicing my soldering skills on my guitars/amplifiers so I can do it to my 1994 C280 with stock throttle body actuator.

[mbsickness]

Here is an update that may help someone in the future. Just to elimiate the MAF I swapped in the one from my C36 and the probllem remains. Just for completeness the C36 hasn't missed a beat so I believe the MAF is eliminated. The problem with the high idle became progressively worse and I parked the car until I could locate a throttle body. A few days ago I replaced the throttle body with a used unit and it appears that the problem is now resolved. The idle is no longer high (1100rpm), the cruise control is now working and the engine is more responsive to my throttle inputs. The car drives completely differently, smoother shifts, more responsiveness, and what seems like a good 15% increase in power.

[Sulaco]

What did you do with your old throttle body? I'm itching to get my hands on a dead one so I can tinker.

[JRE320]

Could it be your fuel regulator?