YNVDIZW124

Naw, not on these cars. Maybe you just have a lot of junk in ur tank. If your car has been sitting for a long amount of time at any time in it's life it could have gathered rust in the gas tank or the fuel lines. What i would do is to remove the fuel filter and check it for any solids.

You know a rough idle can even be caused by a fan clutch. I would start with stuff that is cheap to fix and DIY. If you want your car to run as smooth as silk then you have a long way to go. Remember making car payments cost more than doing tune ups on a car that is already paid for that's why i still drive mines.

Follow what yatch master said and if that makes somewhat of a change then you know where to start....

I'm sure this car will last you another 10 years at least. I already have 6 years with mine 4 more to go, and it's already a 21 year old car.

ps2cho

The car is physically misfiring because you can hear it. The idle speed goes +- 100-200rpm depending on how bad its misfiring. You can watch the rpm's go up and down when idling...its not solid at all.

As for sitting -- Yes this car absolutely sat for a while. As we understand it..the car was stolen in the first 10,000 miles..but was shortly recovered afterwards, but the owner refused to take it back so it sat at her house for a while...then the owner that we bought this off had it under a tree for 9 months without a start...so there are two occassions that I know for sure it was sat doing nothing. (63k miles in 19 years must mean it sat for a while) I have personally done 12k miles since I bought it 18 months ago.

Now, if the fuel tank is bad...then should the fuel filter should show the condition of the fuel tank? If its bad...then the fuel tank is bad too?

White_Knuckles

He's suggesting debris found in the fuel filter may be an indicator that the tank is corroded. Cars that sat usually have brake and wheel bearing issues. The suspension also is in question. But the topper is fuel system concerns with clogged fuel lines, lacquered injectors and rusted tanks.

As your car has several miles under current use, you can rule out most above evils. The fuel system is suspicious and inspecting the filter is easy. Buy a new one to toss in for good measure. The tank may be releasing crud check the replacement filter in 30 days. Tanks can be serviced with a chemical liner treatment (after removal) if determined really bad.

I've followed this issue from Mercedes Shop, man what a bugger. I would seriously hand that bad-boy off to a pro shop. They will need a detailed list of efforts to date. The car's too nice to let it continue suffering. I still believe it's ignition or injector related.

ps2cho

I wish I could...but being a college student with no money...well that answers your question. I was a little apprehensive about paying $80 for the diagnosis at the repair shop LOL!

But yeh man I'm trying all different forums in the hope that someone will post something good like the last few posts as now I have something to go off. Hopefully the fuel filter will indicate what's going on. I mean anything that can at least lead me in the right direction is gold. Once I am in the right area then its just replacing it all.

One of the things that I have also read through my hundreds of posts trying to figure the damn thing out -- The O2 sensor, as I understand it, is not used when the car is cold, correct? So therefore, seeing as it does not misfire for the first 5-10 seconds of starting in the morning, the O2 sensor cannot be the culprit (not to say it's not fouled due to the oil pre-valve stem seal replacements, just in terms of the main culprit) because otherwise it would shake right away as soon as I start the car up...am I right?

EDIT: Oh that reminds me, they had the the suspension done as well -- new struts and all. The previous owners put quite some money into the car.

White_Knuckles

Sorry bro, didn't mean to add pain with my "pro" suggestion. You wonder when you may go mad chasing something? At least your progress has been successful so far eliminating and improving things.

The diag. test you haven't reported on is the pull individual plug wires to determine if it's one cylinder or moving around randomly. Please post results. Isolation is the key to solving.

ps2cho

Oh no man, no pain with the pro suggestion. It's all good.

I have let the car idle and pull each plug separately to see if one plug made the car misfire harder...and there was no difference. The misfires are just random sputtering.
^ If that was the test you meant.

Yacht Master

ps2cho,

Judging from the condition of your plugs, it is safe to say your gas contains some extra things. That heavy white deposit is caused by organic material in the fuel. I don't know how the tank is installed in the wagon but you need to get in the tank and check it. Take your time, that wagon is worth it.

You should change the filter only after proving the tank is clean.

ps2cho

Oh no that is not what my plugs look like now. Under the picture I said that is what they were like BEFORE we did the Valve Stem Seals. The plugs are absolutely perfect now. That buildup was from the oil leaking into the combustion chamber through the leaky seals.

I only posted the picture because I thought it's very interesting and who knows, if someone in the future has plugs that look like mine, or he describes them like mine, you can tell them Valve Stem Seals from me

YNVDIZW124

Don't spend your money on a shop because you'll probably figure it out with our help.

Now I'm 90% certain that it's your fuel distributor that's the problem. Also change the o2 sensor with a 1990 mustang 3 wire bosch sensor. This should fix most of your idle problems. I had a 230 from Europe that had this problem with the idle going up and down when it misfired.

Get one here...
http://cgi.ebay.com/ebaymotors/Merce...QQcmdZViewItem

I'm going to the junk yard this weekend and maybe i can find you a cheap one..

ps2cho

Yeh I looked last night at those on ebay (that one specifically). I definately want to replace the distributor. Firstly because the tech said it was rusty and 2 because its one those things you replace. So there's two reasons. Hey man if you find one cheap I promise you I'll take it! Otherwise I'll have to ebay one or something. New is far out of my price range.

Just curious, why a 1990 Mustang one?

shadowgriffen

It is Identical and perhaps the same (?) you will have to splice it though.

Yacht Master

YNVDIZW124

I agree with you the problem is fuel related. Replacing the fuel distributor may be in order, This like premature valve stem seal failure is caused by contaminated fuel, I have yet to see a CIS distributor go bad on clean fuel.
Our friend needs to follow an order here. It is simple steps in order.
This assumes ignition is fully functional and no vacuum leaks.

1. Prove tank clean.
2. Replace fuel filters & check fuel accumulators/puls damp, and evap lines.
3. Check fuel pressure and volume at fuel distributor.
4. Pass one tank full of chevron gas with 2X techron added approx 500 miles.
5. Replace O2 sensor reset idle mixture with freq disconnected.
6. Change oil, that techron knocks a lot of crap loose.
By now the idle should be smooth if not then.
7. Find the vacuum leak.the one you missed first time.
8. Check exhaust back pressure, cats may be impacted by oil and bad fuel.
9. Replace fuel distributor.

In many cases a new O2 sensor will fix most the problems, execpt problems that contanminate the O2 sensor, so every thing up stream should be clean before a new one is installed.

ps2cho

Ok that's what I will do!

Thanks so much guys! I'll go with those steps now. Hopefully I can get round to doing the first few steps this weekend so we can see if that is the problem.

Fingers crossed again!

EDIT: Isn't this something that they test at a smog station? I had it smogged 2 days and ago it passed...Would posting the results prove anything? It was real close on a few tests. (It was alot worse at idle than when speeding up due to the misfires)

Yacht Master

Ya, if you can post up that info it would be big help.

YNVDIZW124

I totally agree with Yatch Master, he's on the right track but i would follow his list just a little different. There is nothing wrong with what he said but like most people I have a different way of doing things you know.

1. Take a wire brush and clean you distributor cap and rotor. (they can cause a miss but i don't think this is the problem)
2. Replace Fuel filters & check fuel accumulators
3. Check Fuel Pressure Regulator
4. Fill up half a tank with 91 and 1 bottle of lucas or techron injector cleaner
5. Italian Tune up.... get on the freeway and floor it a couple of times...
6. Change the oil.... I use mobil clean 5000 10w40
7. Replace Fuel Distributor
8. Adjust Fuel Distributor ( I disconnect the idle control valve and then adjust it)
8. Replace O2 Sensor
9. Find any vacuum leaks if problem is still there.

You need a new O2 sensor because you where running rich for a long long time so it's probably time for a new one. A 1990 mustang with a 5.0 is the same that it's used on mercedes except with out the connector. You will have to attach the old connector with the new sensor.

ps2cho

If you click on it I have a larger resolution one. Maybe this can give any indication of something?

YNVDIZW124

Well that seems fine to me. Your hydrocarbons are at the edge of not passing but my car passed smog like that too. It just means that you have to fine tune your fuel mixture a little more because if you lean it too much it will raise your NOx and if it's too rich it will raise your HC

ps2cho

This was before he fixed the mixture as he said it was running too rich....hense raising my HC.

ps2cho

As for this...We have ran Injector cleaner (Seafoam was the name of the product) through the injectors and fuel additive in the tank.
(I have never seen a car shoot so much white smoke out when we put the injector cleaner in!)

I use 20/50 oil because we have a slight leak in the oil pan gasket..and it leaks less with 20/50. Need to get around to redoing the seal.

YNVDIZW124

Yeah I have a leak too and i used to put 20w50 but it looses power with such a heavy weight oil. I use mobil 5000 because for some reason it leaks the same as 20w50 and if i use another brand of 10w40 if leaks all the time. Also it starts leaking more when i need a oil change which is about every 4000 miles. I could go with 5000 but the oil filter wouldn't last that long. I was about a quart every month and a half but that's after 2500 miles or so. It's the top timing cover gasket that i need but 1 quart every 2 months is not bad so that's why i haven't fixed it either...

ps2cho

I have been doing some reading and apparantly the EHA can be adjusted.
I am reading that when the EHA is improperly configured, pressure to the lower chamber used when the car is idling and at low speeds (yes this is only when I feel the misfire) causes the car to chug.

I will take it off firs thing tomorrow morning and see if I can adjust it.

Yacht Master

Yes way rich, The electronic side of your fuel injection is not trimming the fuel. You can test the O2 sensor by checking the voltage it produces.
Start the car and warm it to operating temp, disconnect O2 sensor and read voltage, should be 7-9 volts.

I can not stress enough that your fuel system be clean before you install a new O2 sensor. Any contaminates, injector cleaners (techron, seafoam) top oil or any thing other than gasoline will ruin a new O2 sensor.

BTW you did say you had to replace the OVPR Fuse was it blown? and is it intact now?

ps2cho

Yes we changed the OVP because the car used to stall randomly when driving.

The previous owners replaced the O2 sensor and it didn't fix it for them...so something else is going on (but yes I will need a new one when I figure out whats going on because its most likely tarnished from the oil going through the engine because of the leaky valve stem seals).

I just did some adjustments to the EHA valve this morning and no difference
Did a 1/4 turn, started it up, did another 1/4 turn, started it up...no difference so did CCW 1/4 so I wouldn't be running too rich. There definately is pressure as the 2nd time I took it off, the gas sprayed out and made me jump...So I was careful the third time round.



I'll test the O2 sensor like you said this weekend.

ps2cho

After driving it for the rest of the day...it's having some really strange jerking movements when driving about 5-10mph...It like surges and doesn't respond as well to the throttle. I think I'll put it back to where it was as I think we have established the EHA is adjusted correctly (maybe its faulty, but at least its adjusted right).

Also, is the EHA not supposed to have any seals or rings or anything? It just bolts on with two screws to the distributor? You'd think it would have some sort of seal to stop it leaking out as there must be some sort of small gap in between.

White_Knuckles

You had a theory it idles smoothest on cold start-up where the O2 may not be monitored. Before you meter the sensor, pull the connector off to nix it from outputting to the ECU. Does the idle remain smooth?

Even if the history states it has been changed the sensor may be toast. I fought a double whammy with a flaky MAF and crank sensor failing at the same time. That was a dandy to troubleshoot.

You may have something with the cold start. What else is enabled or disabled in that condition? One thing is, the idle speed is increased and fuel mixture is richened for "choke" during those first few seconds. Too lean of a mixture at idle can create sputtering where the engine kicks around and sounds uneven.

Spotted the follow-up on checking individual plugs for effect. That doesn't eliminate ignition, just proves it's not a particular cylinder. Good luck Saturday.