1988 300TE - Misfires - Where to go now?
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.
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.
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?
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.
Last edited by White_Knuckles; Nov 8, 2007 at 12:25 AM.
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.
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.
Last edited by ps2cho; Nov 8, 2007 at 01:23 AM.
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.
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.
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.
Last edited by ps2cho; Nov 8, 2007 at 01:35 AM.
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?
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.
Last edited by Yacht Master; Nov 8, 2007 at 01:42 AM.
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.
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
The Best of Mercedes & AMG
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..
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..
Just curious, why a 1990 Mustang one?
Last edited by ps2cho; Nov 8, 2007 at 03:04 AM.
Just curious, why a 1990 Mustang one?
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..
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.
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.
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:
Last edited by ps2cho; Nov 8, 2007 at 11:31 AM.
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)
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.
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.
(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.
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.
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?
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?
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.
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.
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.
Last edited by White_Knuckles; Nov 9, 2007 at 11:11 PM.



