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1995 E420 persistent pin 7 code 2, surging idle in D
- Thread starter winmutt
- Start date
Surging idle is likely related to vacuum leaks, if there are no other operational problems.
Very unlikely to be either T/LLR (assuming non-ASR car) or EZL, if the only issue is idle surge in gear.
Pin 7 code 2 can be a lot of things that have nothing to do with idle surging, btw. Need SDS / HHT-Win to pinpoint further.
Very unlikely to be either T/LLR (assuming non-ASR car) or EZL, if the only issue is idle surge in gear.
Pin 7 code 2 can be a lot of things that have nothing to do with idle surging, btw. Need SDS / HHT-Win to pinpoint further.
I'll setup a smoke machine. Drove the car all day yesterday and no surging at all, however I had a large oil smoke incident pulling out of a restaurant. Car started fine, I was in a parking deck and had to pay to get out, no smoke. Pulled out to a light, no smoke. Took a right and for the next block I had a lot of smoke, like Ceech and Chong were on tour again amounts of smoke. I immediately thought of a sticking PCV valve but reviewing the FSM 01-0400 I'm not seeing anything other than the orifice. In searching for a PCV I did read that the MOT valve can stick leading to large vacuum leak but that only vents fumes to the charcoal canister? The car is really running much better, shifts are happening as expected etc.
A few times under wot this am. Nothing at idle. What should Iook for with the PCV? All I see is hoses and the orifice, not sure how that can go wrong other leaks? This PCV system is odd, I'm used to a simple check valve.
At wot 4 out of 5 cam advances resulted in blue smoke. I think I'm going to wait digging into that until I have the exhaust done unless there is anything specific anyone can call out. Other than that car ran great all day with no surging. I parked the car from 1-5pm and still started up and ran ok no idle surge but with the wot smoke. One red-light wot with cam advance did not yield any smoke.
MOT valve is bad, which explains a lot but not everything. Applied a 9v battery with no clicking, blew out some stuff that could have been charcoal. Plugged the motor side off and car cold idled in drive just fine. A few minutes into drive it started surging again, but not the same and went away. I've got the smoke machine setup but the glue did not stick well. I will try again tomorrow with liberal application of the glue. Where do y'all input at? The one benz video I found pointed to using the brake vacuum line. I thought I would use the MOT line since I had it out but that didnt seem to take much in the way of air even though I pulled the glove off the MAF.
If the MOT valve is stuck closed, you can leave it alone. This seals the system and prevents a vacuum leak to the engine.
If the MOT valve is stuck open, you need to seal it off. Don't replace the MOT valve without also replacing the charcoal canister; if you saw charcoal particles, the canister screen/mesh has failed and you'll kill a new MOT valve. Just seal off the system, it doesn't need to be functional.
Good question about where to feed the smoke into, the metal vacuum line for the brake booster would be ideal. Don't think you want to use the MOT pipe because that goes to a fitting with a restriction, IIRC, on either .97x or .98x engines (one has the restriction, the other does not, I forget which is which).
If the MOT valve is stuck open, you need to seal it off. Don't replace the MOT valve without also replacing the charcoal canister; if you saw charcoal particles, the canister screen/mesh has failed and you'll kill a new MOT valve. Just seal off the system, it doesn't need to be functional.
Good question about where to feed the smoke into, the metal vacuum line for the brake booster would be ideal. Don't think you want to use the MOT pipe because that goes to a fitting with a restriction, IIRC, on either .97x or .98x engines (one has the restriction, the other does not, I forget which is which).
Smoke test FTW. I felt awkward walking out of the grocery store with a bottle of baby oil and a jar of large pickles, but dont ask, dont tell. Breather hose is busted at the boot where it meets the valve cover. Between the MOT valve and this I cant believe it ran at all!
Glad you found it. Get all those hoses while you can
I went cheap with Febi, we can count the days until they fail!Glad you found it. Get all those hoses while you can
