88 420SEL Surging During Acceleration - Page 2 - PeachParts Mercedes-Benz Forum

dpetryk · #16 05-07-2007, 12:55 PM

I agree with David. You should R&R the manifold and all the seals associated with it.

RC2007 · #17 05-07-2007, 07:53 PM

I suppose I could do that. Any recommendations on what seals are should be replaced? Thanks.

david s poole · #18 05-08-2007, 12:40 PM

this can be a long list.one of the most neglected items is the lower side of the fuel injected plenum.it is all rubber and only needs a small crack.also there was a mod made that may require a new flange[this costs more than the rubber].the manifold comes apart held by 4 screws in centre and there are 8 donuts that join the main plenum to the individual runners.you need to remove the intake and replace everything thats not metal.this will provide great peace of mind when making future diagnosis.one word of warning,most of the bolts that hold manifold down are allen heads,make sure to clean out the heads and tap allen into bolt with hammer to loosen threads.if you round out any bolt heads find a torx bit that can be pounded into the old allen hole with a hammer you will then be able to remove it.

dpetryk · #19 05-08-2007, 05:02 PM

RC2007 · #20 05-08-2007, 06:43 PM

Guys, I really appreciate all of your information and pictures. This car is my baby so as soon as I get my other car 88 300SE up and running again I will start the work on this one. Thanks Again, I will keep you all posted on how things work out.

just-n-time · #21 05-08-2007, 08:28 PM

Go to posts in my handle and you will find pics of intake job as well as some other work,as Dave said you would benefit greatly by replacing all of the rubber parts in the intake area,your idle is far to high cold start 1000 then settles to 650 or 750 tops.so if the intake rebuild dose not bring this down then you most likely will need to replace the icv. JNT

RC2007 · #22 06-04-2007, 07:15 PM

Well I rebuilt the whole manifold, installed all new seals, replaced the injectors and all of the seals, even replaced the fuel filter and pumps. The problem that I have is that most of the vacuum tubing has disentegrated. I have no idea at this point where anything goes. I did notice that the car is idling very rough but now it is at 750rpm in park instead of at the 1000-1500rpm before. It starts very slowly. It now sputters and hesitates at low speeds even worse than it did before, to the point where it feels like it is going to completely stall. If anyone could enlighten me as to where the tubing connects I would really appreciate it.

RC2007 · #23 06-04-2007, 07:33 PM

I forgot to mention that I also bought a new Idle Control Valve which I just installed on the car.

RC2007 · #24 06-04-2007, 09:48 PM

Well I think I have finally sorted through and got all the vacuum lines in place where they should be. The idle is fine but the car still sputters on occasion. I am wondering if I should replace the oxygen sensor.

raymr · #25 06-04-2007, 11:22 PM

I had this happen in cars when I got a tankful of crummy gas. Are you on the same tank, or have you had several fill-ups with this problem?

RC2007 · #26 06-05-2007, 03:19 AM

Just filled it up with some 91 Octane ($3.39/gal.) That is what I usually use. I am quite sure that the vacuum issue is dealt with. The car has never ran or idled so smooth as it does now. It is just that damn sputtering at low speeds like it isn't getting enough fuel under high demand. I am wondering if it might even be the Fuel Pressure Regulator.

just-n-time · #27 06-05-2007, 03:50 PM

Not likely to be gas related unless it is A plugged filter but that would show up more at high speed as it requires greater fuel flow! My thought goes to this question what controls the low speed balance? first is the air /fuel mixture set? second is the oxygen sensor good,third is the Eha at proper electrical setting? then is the potentiometer electrical reading correct? You can find this in the forum under my name or many others if you search..JNT

RC2007 · #28 06-05-2007, 09:38 PM

I think I might just bet on the oxygen sensor as it seems to be the original one. Just wondering if anyone knows where it plugs into so that I don't have to worry about splicing any wires. I would rather use the plug in connector if I can help it. Will keep you all informed...

dpetryk · #29 06-06-2007, 12:51 AM

Plug is located under the carpet on the passenger front. If you are willing to splice wires onto a 90 mustang 3 wire Bosch oxygen sensor you can save a hundred bucks.

david s poole · #30 06-06-2007, 11:09 AM

you have now got to the only other part that controls the fuel flow--the fuel distributor---i have been accused on this forum of suggesting a change of this part without enough info but my experience tells me that a dirty fuel dist[usually 150k miles is enough to have the condition even with good maintenance] is responsible for 90% of the fuel related problems in a cis or cise engine.they used to be prohibitively expensive,not so now.by the way it also sounds as though you need a new or rebuilt idle speed relay as your idle out of gear is too high.