Advice needed for problem with '87 245 B230F (237,000 miles).
I have lived with an engine hesitation/miss just off of idle for over 40,000 miles, but lately the condition has worsened.

When pulling away from a stop or revving the engine in neutral, there is a slight cough right off of idle. It happens every time I open the throttle. Once moving, acceleration is smooth at all engine speeds.

However, in the last month or so, the car will start normally and as soon as I put it in gear, the idle drops and the car dies. This only happens when the engine is cold and it will always start right back up. It will die every morning when putting into gear unless I quickly put it back into park to increase the RPMs.

Overall performance is sluggish and the engine died once when braking hard for yellow light.

Here's What is New(er):
Spark Plugs, Wires, Cap & Rotor, Air & Fuel Filters, Fuel Pump Relay, Throttle Body Cleaned, Vacuum Lines OK

After reading a few posts, I'm suspecting something like the knock sensor or timing off. Any ideas?

Chris

Chris,

I don't see how this could be the knock sensor.

I think this is an interelated problem with the idle air control valve, fuel pressure regulator, and/or O2 sensor.

My thoughts are that the air fuel mixture is changed temporarily when you first hit the accelerator. The FI system has to adjust quickly (in milliseconds) in order to prevent the stall. Your system is not compensating quickly enough and hence the engine stalls out or dies. If the instantaneous fuel pressure is not maintained properly you will get either too much fuel or too little. If the O2 sensor is too slow to respond, it will prevent the proper air/fuel calculations by the computer.

I think the problem is in this area. Have any of these been replaced recently, or are they due?

Good luck!

TomD
'86 240
'93 240

Dude, mine has been doing the exact same thing. One guy on this board replaced all the same stuff that you did, and the airmass meter and his still did it. I haven't gotten much response to this question, hopefully you will so I can fix mine too. Mine is also an 87'.

My 87 did the same thing when I got it, and after replacing a lot of the same things, it's improved now, but still did stall once and still occasionally dies in reverse. It came with a shiny new AMM so I know that's not it.
I also saw one at the shop recently, drove in and wouldn't start later in the day. The sad fact with these cars is, the wiring harnesses are going bad. Things are unpredictably shorting to each other, and this can cause all manner of fuel injection and ignition problems. I haven't replaced mine though I have a "known good" 87 harness in a box... I will only do it if it really desperately needs it. It is a big job... and it goes through the intake manifold which is a real *****. You can look for indications of harness failure at the firewall (big gray connector), along the intake, especially under it going to the sensors, and the loop going under the front pulley (the first place to go, but the exposed wires are readily repairable.)
My usual list of suspects includes all the items already replaced so... hopefully the problem can be pinpointed more closely.
Rob Bareiss, New London CT

Don't get your hopes up about it being fixed with a new wiring harness, either. My '86 has a new harness and it still gives these same symptoms. So does my '84, only worse.

Nobody really has the andwer to this "$64,000 question"

I have read everything on this board from air intak leaks to bad in-tank fuel pumps to bad ECU's and temp sensors.

While no solutions concur, the symptoms common to everybody include insufficient idle while cold and that annoying stalling when placed into gear.

So, what inputs and/or mechanical conditions control the idle when cold? there, I believe, is the locus of the problem.
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'Most Improved Patroller of the Year' Blue Mountain Ski Patrol, Palmerton, PA