Engine stall problems - need help

[bpeter]

I have a 1996 C220 . The engine stalls occasionally (about once per week). It only happens when it is really hot outside (over 90F) when I am bringing the car to a complete stop. The RPMs drop slightly below 500 and it seems like they are not corrected in time to maintain idle. The engine always starts fine immediately after it stalled. When it is colder (e.g. morning and evenings) or lower temperatures (~80F and below) I don't run into this issue at all.
The engine temperature is in the normal range 85-100C (I replaced the thermostat about 20K miles ago). Also, when it is very hot outside, the engine seem like it does not have all the power it should have. I checked the intake air temperature sensor readings yesterday using the OBDII reader and it showed 137F while the outside air temperature was about 80F. I know the air will heat up a little bit before it gets to the IAT sensor (the reading seemed a bit high to me, but the guy at AutoZone thought it is often around 130 b/c of the engine heat).

Some items that I have replaced over time are the fuel pump (original Bosch), fuel filter and fuel relay about 15K miles ago. The new Bosch remanufactured MAF sensor and spark plugs about 2K miles ago. The air filter looked clean and it was replaced about 10K miles ago.

If anyone has thoughts about other items to check, please let me know.

[W202FTW]

I have a 1996 C220 . The engine stalls occasionally (about once per week). It only happens when it is really hot outside (over 90F) when I am bringing the car to a complete stop. The RPMs drop slightly below 500 and it seems like they are not corrected in time to maintain idle. The engine always starts fine immediately after it stalled. When it is colder (e.g. morning and evenings) or lower temperatures (~80F and below) I don't run into this issue at all.
The engine temperature is in the normal range 85-100C (I replaced the thermostat about 20K miles ago). Also, when it is very hot outside, the engine seem like it does not have all the power it should have. I checked the intake air temperature sensor readings yesterday using the OBDII reader and it showed 137F while the outside air temperature was about 80F. I know the air will heat up a little bit before it gets to the IAT sensor (the reading seemed a bit high to me, but the guy at AutoZone thought it is often around 130 b/c of the engine heat).

Some items that I have replaced over time are the fuel pump (original Bosch), fuel filter and fuel relay about 15K miles ago. The new Bosch remanufactured MAF sensor and spark plugs about 2K miles ago. The air filter looked clean and it was replaced about 10K miles ago.

If anyone has thoughts about other items to check, please let me know.

Sounds like a vacuum leak. Try running the vehicle in colder and normal weather conditions and listening to hissing noises.

[RemoLexi]

I had a somewhat similar issue with a 94 C220 last month, would start up fine when cold, but when it was hot it needed a little throttle bump to stay alive. The fix was a dirty throttle body. Over time they build up residue and don't get enough air passed to stay idling.

So I highly rec. grabbing a can of throttle body cleaner and removing the throttle body to clean the bore well with a rag especially the flap edges and where they close. Use ONLY throttle body cleaner as brake clean is abrasive.

.... Or yea you can have a vacuum leak as well. I'd check for that and clean the throttle.

[bpeter]

I cleaned the throttle body today. It was dirty. I used the CRC Throttle Body and Air Intake Cleaner. Since the car doesn't stall that frequently, I'll wait and report back in a few weeks if this solved the problem.

[bpeter]

Here is a quick update. I cleaned the throttle body. The engine used to randomly stall prior to the TB cleaning. It has been 10 days since I cleaned the TB and the car has not stalled once.

I did have one odd occurrence the very next day after I cleaned the TB. On that day I drove the car for approx 1 hour without any issue. I stopped and had it idling for about 2 minutes before continuing. When I gently pressed on the accelerator the RPMs started going up and down btw approx 700 and 1200. When I removed my foot from the accelerator, the engine went back to normal idle at around 600 RPM (it did not oscillate RPMs up and down). I could recreate the problem in park position (with AC on or off). I finally pressed harder on the accelerator (while in park), the RPMs went up to 3000-4000 range and when I depressed the accelerator, it went back to normal idle and I could no longer reproduce the RPM up/down oscillating problem. The issue did not come back since that first day after TB cleaning. I am not sure if my TB cleaning solved the problem and this first day was due to "the computer learning" or if I still have some other issue with idle control. I had no idle issues since that first day (so 9 days now).

If anyone has any additional thoughts, please let me know.

Attached is one picture before and 2 after TB cleaning.

Before TB cleaning:
1511

After TB cleaning:
1512
1513

[Sulaco]

Oh boy. Hopefully you didn't mess up the wiring in the TB connector. A large number of cars in 95 and 96 had biodegradable wiring in that cable which has since crumbled away letting wires connect to each other and short. This problem can be invisible for years since people rarely ever touch or move that cable. If you removed it to clean it for another issue and now it has issues when it went back in, you MIGHT have caused a new problem. I don't know if this affects the C220, though. I know it was a big issue on all the straight-6 cars from 94 and 95.

[RemoLexi]

While the car is in park and at a smooth idle, grab the round connecter to the air flow meter and wiggle it. If the car stalls or begins to choke, air flow meter and or wiring must be replaced.

You can also try to fiddle with the throttle body harness and see if it causes your car to choke or stall.

[bpeter]

Sulaco - I saw in a few other posts that the wiring in the TB cable can degrade and decided to clean the TB without removing it (I was worried about the wiring as well). So far I avoided slicing the TB electric cable open to check the condition of the wires. I wanted to see if there are any other issues first.

RemoLexi - I replaced the MAF sensor a few months ago with a Bosch refurb. It fixed the problem at the time. I wiggled (with reasonable force) the wiring and connector to the MAF and TB, however, the idle did not change.

Also, the OBDII reader does not show any codes. I think I would need a more advanced diagnostic tool connecting to the round diagnostic connector to show codes.

[bpeter]

I did leave out one item in my comments that may be related. The cruise control is also not working on the car. Is the cruise control actuator integrated with the TB in 1996 C220?

[Vetruck]

Mine was not working either on my c220- it is now that I replaced the TB.

I hate to say this to you but start saving your money because you DO in fact have the biodegradable wrining inside your and will definately have issues in the near future. My wire loom looked brand new and I though also being a good climate So Calif car I would not have issues- when I cut mine open boy was I surprized.

[bpeter]

The idling issue appeared again today. I recorded a video of how the car behaves. Here is the links to part 1 YouTube video:

Part 1:

http://youtu.be/7O5gZVn1p_A

The idling problem goes away after I press on the accelerator to push the RPMs very high. After that I can't reproduce the problem until it somewhat randomly appears next time. Based on the video, is the opinion that the TB needs to be replaced? Or should I have a shop read if there are any codes using the 38 pin connector? (nothing shows up when I just use the OBDII interface inside the car).

[bpeter]

And YouTube video Part 2:

http://youtu.be/Lwy1OVAh3Bs

[RemoLexi]

HHT sucks, so having a tech scan it with an SDS to catch the TB failing, just put the money towards a new TB. Chances are if the car isn't flagging codes, theres not much you can find with SDS/HHT.

[Sulaco]

I can also confirm the dead cruise control is related to the throttle body. I've read numerous cases where a new TB (or rewiring of the current TB) fixed their cruise control.

Of course, we're just pigeon holing the issue into the TB with very little information here.

My wife's 1994 E320 had a serious, serious idle issue that turned out to be oil leaking into the spark plug chambers from underneath their little gaskets on the valve cover, and oil slowly seeping through the threads and coating the spark plug itself, making spark very difficult at idle. Cleaned plugs, replaced each plug's gasket, fixed issue. That's another possibility. But could also be vacuum leak, MAF, intake air temperature sensor, plugs, plug wires, etc.