[mrpndev]

Hi,

I picked up 100k mile 89 300E for $500. It has sat for a long time and as a result, the car could barely move on its own power. CEL would flash intermittently as it would cough its way forward. I've so far replaced:

• fuel filter
• accumulator
• tested OVP relay (functional)
• replaced spark plugs (basic copper NGK's)
• removed ICV and flushed it with brake cleaner to see if it helps start up issue

Spark plugs were what helped the car for 3k miles. During this summer, when it gets really hot out, and especially when idling, the CEL begins to flash again and the car begins to sputter and sometimes even die. I'm at my wit's end as to what to look after next after reading a lot of articles on this forum.

Today, I pulled the plugs to see how they look, and they were already a bit cruddy. I did notice that cyl 5 and 6 wires came out with barely any force, so I tried to re-secure those a bit better.

The car has always needed a bit of gas when firing up as well, or else it would just die. It almost feels rough/knocking, until the oil pressure comes up, and then it's fine.

No issues with cold/hot starts otherwise.

Any suggestions are appreciated.

Thanks.

 

[plinker17722]

I would try and replace 5 and 6 leads to start with . When did you last replace the ht parts like distributor cap and the rotor and ht leads . The knocking your getting is 4 cylinders working and 5 and 6 not, this will make any engine knock..Whats is the CEL ? is this the red charging light if it is, then regulator in the aternator needs changing ..Check all the fuses in the fusebox you only need one fulty fuse to upset the apple cart .Then check out all the small bore vacuum pipes - and joints for splits .Tell us how you get on after this is your engine the M104 or M103 ? this is the M103 .

 

[mrpndev]

I would try and replace 5 and 6 leads to start with . When did you last replace the ht parts like distributor cap and the rotor and ht leads . The knocking your getting is 4 cylinders working and 5 and 6 not, this will make any engine knock..Whats is the CEL ? is this the red charging light if it is, then regulator in the aternator needs changing ..Check all the fuses in the fusebox you only need one fulty fuse to upset the apple cart .Then check out all the small bore vacuum pipes - and joints for splits .Tell us how you get on after this is your engine the M104 or M103 ? this is the M103 . View attachment 2645413

Yes, mine's the M103. AFAIK cap, rotor, and leads are all original. Last night I started to unplug the leads while my partner was in the car in gear to simulate the idle and it began to misfire, but it didn't feel the same as when it dies, if that makes sense. Then, once I was all done with seating the leads tightly, the car choked up again almost dying. I'm gonna start by replacing all of those.

CEL is the Check Engine Light that flashes all the way to the right of the cluster when the car starts misbehaving. You also reminded me that I actually replaced the regulator in the alternator as well, trying to chase down the difficult morning startup issue. Fuses are good.

I will check the vacuum lines as well and report back.

If it helps, some of the plugs were looking a bit lean while others looked rich. I might check the injectors for leakage with a butane torch and just order a whole new set.

 

[plinker17722]

You can pick up a tool to check the ht leads ,to see if they are firing,, you just hold it on the plug lead it sparks to say it live or dead .You can also use a timing light in line it is a good check for spark...

 

[Jayare]

Replace the O2 sensor. After 60-80K miles they are usually toast.

Sent from my SM-A515U using Tapatalk

 

[tuttebenne]

Now that 30 years have passed since these cars are new, the distributor dust shield should also be changed. They cause misfires when they fail. I'm not guaranteeing this is the silver bullet for your problem but no longer can an M103 be "baselined" for troubleshooting purposes if only the cap and rotor were changed.

 

[lowesguy]

Don't forget to check duty cycle, adjusts fuel mixture, should be around 50%, if its to low or high car runs like crap, info on how to do that is on the forum, search.

 

[mrpndev]

Now that 30 years have passed since these cars are new, the distributor dust shield should also be changed. They cause misfires when they fail. I'm not guaranteeing this is the silver bullet for your problem but no longer can an M103 be "baselined" for troubleshooting purposes if only the cap and rotor were changed.

Pulled apart the distributor cap out of curiosity (replacement should be arriving this week sometime), and found the points to be pretty soiled with carbon. The dust shield had literal chips in it, so I ended up ordering that as well.

 

[neanderthal]

Your baseline tune up when you get a new car should be new plugs, wires, rotor, cap, oil change, trans oil change, brake fluid flush and change, etc. Every. new. to. you. car.

That way you can diagnose any maladies properly knowing the basics are taken care off.

 

[mrpndev]

UPDATE:

Replaced ignition coil, spark plug wires, distributor cap, rotor, and dust shield and this sheiße is still coughing when idling during hot weather. I’m at my wits end.

What else should I do? Fuel pump relay? Fuel pump itself? Idle control valve? Fuel pressure regulator? O2 sensor? Air flow meter?

I don’t want to be throwing parts at it left and right if I can avoid it.

 

[Jayare]

How many miles are on the O2 sensor? Have you pulled the ICV and cleaned it up, using brake cleaner or something similar? Are all of the ICV hoses plyable and fitting snuggley?

Jayare

Sent from my SM-A515U using Tapatalk

 

[mrpndev]

How many miles are on the O2 sensor? Have you pulled the ICV and cleaned it up, using brake cleaner or something similar? Are all of the ICV hoses plyable and fitting snuggley?

Jayare

Sent from my SM-A515U using Tapatalk

I unplugged it and it ran much worse. Did clean it out with brake cleaner.

o2 sensor has well over 100k miles.

 

[mrpndev]

UPDATE:

I moved and didn't have time to deal with the seized O2 sensor. Finally over the holidays, I was able to replace it.

The car runs without any issues when warm, but I am now having really terrible cold start-up issue. The car just keeps cranking and doesn't want to do anything. It has sat long enough for the battery to die and need a new one. I did notice however, that the long cranking is remedied when I gently touch the throttle body to give it a bit more air. It fires right up with this bit of assistance.

I unplugged the ICV and didn't see any fluctuation in revs like before. Is it dead? Is that what's causing it to not adjust the mixture for the cold weather?

Thanks.

 

[plinker17722]

I would clean out the IAC valve with whitespirits or turpintine .With the plug off the rear than it should rev up over 1000 rpm

 

[mrpndev]

UPDATE:

So the issue was an OVP fuse... I asked my partner to check and he half-assed it and said they were OK. I tested the OVP and found it dead. Before buying a new one, I've decided to look at the fuses... one of the 10 amps was dead. Car runs great now, but check engine light still comes on and it sputters sometimes.

It does that usually after idling for a while or being in a stop and go traffic. If I then hop onto the motorway, lift off the throttle, and start to lightly get back up on it, it will throw CEL and sputter. It's almost as though the fine throttle inputs upset it.

I'm also still having a bit of start up issues. I hear the fuel pump prime, but start up takes a good 5 seconds and requires a bit of throttle input. If I shut the car off and wait an hour, subsequent startup attempt fires up like a champ. This leads me to believe that the pump is not supplying enough pressure to start it. Can the fuel pump just be inefficient at its job rather than failing entirely? What about fuel pump relay?

Thank you.

 

[plinker17722]

First i would do a fuel presure test . . With a cold engine that been sitting over night ,,remove the airbox , Then gently push down on the throttle plate and see if it returns . Low fuel presure will stop the engine eventualy ,.May be your running on one fuel pump. You have 2 pumps by the way ,.You did say your check engine light came on show us a picture of ypur speedo i have the same engine but no CEL ..

 

[mrpndev]

I just replaced both fuel pumps. Car is fine for about 20 miles, then the check engine light starts flashing intermittently and it keeps sputtering. I’m at a loss at this point as to what I should look at next.

 

[LeftCoastGeek]

when my CIS car which had sat for a long long time had the sputters at idle, it turned out to be air leaks from the rubber seals around the injectors, and a couple of the injectors were sketchy too. the rubber boot that is between the throttle body and the air flow/fuel regulator assembly was cracked, too.

 

[tuttebenne]

^These are great suggestions. Once you rule out the injector seals and the rubber boot LCG is talking about you probably should be doing the fuel mixture procedure. The airflow meter and EHA both need to be dialed in to get the right performance. If you aren't equipped for this, you might take it to a specialist for this final step in the process.

 

[mrpndev]

I sprayed butane around injectors and did not experience any increase in the rev range. I did around the throttle body but that’s because it was out and open. I will inspect the rubber boot next.