I need some help. I have searched through this forum a few times but i could not find an answer that seemed to fix the same symptoms that my car is showing.

When driving the car it runs great until the engine oil temp gets to around 140 and from there on it will sputter really bad and will start popping if you press the gas all the way down.

I have already replaced multiple parts that mechanics have told me was the problem but the problem wont go away... I have new: spark plugs, ignition wires, ignition coil, distributor control module, MAF, fuel pump.

I am willing to try anything at this point because my favorite car will get me where i need to go but it has to cool all the way down before i can drive it back home again.

 

How old is the o2? And test your ICM and make sure they used thermal grease on it.

 

To my knowledge the o2 sensor is original to the car.

 

How many miles? Any codes?

 

No codes at the moment. 130000 miles. I drove the car as a daily driver just a couple weeks ago and it worked perfect.

 

Over due normal maintenance and that is what mine did with no codes.

 

Use an ohm meter to check the resistance across the fuel injectors terminals when the engine is warm. They should all read over 15 ohms. Common problem on the 88-up cars.

 

I tested the injector resistance and all of them on the driver side are reading 15.5 - 16.2 where as on the passenger side of the car they read front to back as 17, 17, 14.7, 13.8.

 

I'm guessing your issue is when it goes into closed loop. Before your "mechanics" start tossing more parts, why the fuel pump and MAF? What have they done to determine it is bad? O2 sensor, I can agree since they are subject to harsh conditions every second your car is running. Unlike the O2 sensors (I toss them every 5 or 6 years), I don't think there is a "lifespan" on the MAF. Why the fuel pump? How did they determine it was bad? What did they replace it with?

My suggestion if you want to keep the car is to get yourself a good SCANNER. A code reader is an expensive paper clip at best so toss that. Get yourself a fuel pressure gauge and compression tester. Those are not expensive and can be used for other cars.

Do you have the old MAF? If so, you can run comparison readings with it using the scanner. If there is little deviation at a given condition, the MAF is probably good.

Fuel pressure. When you turn the motor to run, does it pressurize? To what level? Does it hold pressure for a couple of hours after you turn the key off? Engine running and hose to the regulator off, what is the pressure? Take it for a WOT run with the hose off. Does it hold a steady pressure at WOT?

Engine temp. I don't GAS what your gauge says. I only care what the ECM thinks and you need the scanner for that. IF the ECM thinks the engine temp is 30 degrees when it is 140, it is going to toss fuel and run rich. Your gauge might be spot on but if the ECM doesn't give a rip. It goes off the sensor in the front of the manifold, IIRC.

If you cannot solve it at this level, you might need a real mechanic and not a parts replacer. In the old carb days, you had a few things so guessing was as good a way as any, which I suspect is how many carb mechanics made their living. In EFI days, you need to understand what is going on.

With scanner, check for air leaks. See what your IAC counts are. Engine at operating temp and everything but motor off. IF they are less than 20, turn the adjustment screw out, rev and repeat. If you have backed the screw out all the way and still have 0 or cannot get 20, I would say we need to investigate air leaks.

REGARDLESS of whether this solves the problem, I would send your injectors out and clean your Throttle Body while you are at it. This old a car has crud. I just got a 99 S320 MB with 100K on the clock. Injectors flowed around 170cc and all over. After cleaning, they flowed at 190cc. I do this every 3 years. Take the IAC off the TB, remove the IAC housing, clean everything with brake cleaner. Spray the IAC gently with brake cleaner, wipe the pintle off. New gaskets. Use scanner to set IAC to 20 counts.

 

Doesn't tell me anything other than the coils are probably ok. If they are Multecs, I'd toss them. If not, send them for cleaning and testing: https://www.fuelinjectorconnection.c...-domestic.html

Or rebuilt set: https://www.fuelinjectorconnection.c...injectors.html and scroll down to gasket set. You don't reuse condoms so don't reuse paper gaskets.

Until you do this a few times, you won't realize that there will be buildup of crud. On my DD cars, I do it every 3 years and there is still deviation. However, this tests and cleans the injectors instead of dumping snake oils, whiffle dust or mouse milk into the tank and hope it does the job.

 

We replaced the MAF because i was getting code 36 and after replacement the code was no longer showing I kept the old MAF just in case. (i havent thrown away anything that I have had to replace), the fuel pump was replaced because it when tested with a fuel pressure tester it wouldn't give sufficient pressure. Also the ECM has been replaced because after the car started sputtering I took it to a local alabaster shop called "Victory" and they looked at it for 2 days and said the ECM was bad, so i had it replaced and nothing at all changed so i took it back and they said that the new one was also bad after consulting a classic car shop they said neither had a problem thankfully it wasn't that expensive and now i have an extra just in case something stupid happens.

When it comes to getting a scanner I got an ALDL OBD1 to USB cable to use with my computer thinking that it would work but i could never get it working correctly so I guess i will have to get a real scanner if there are any suggestions please fire away.

I wont have a response for the other test until Monday for Tuesday thanks for everything so far I hope i can get some good results.

 

Before you do anything else, change out the Oxygen sensor. After 27 years it is definitely due. For some reason, the O2 sensor is often overlooked for maintenance/replacement. On an '89 I believe the recommended mileage for replacement was 60k - you have over double that on your car. After you change it, report back with what happens.



Edit: after you replace the O2 sensor, if it is still running bad after going into closed loop, you may want to look at/replace the coolant temp sensor.
I have a later engine so I found a Youtube video supposedly showing the location of the sensor -

 

I don't have a MAF but I thought Code 36 is for the burn off relays? Insufficient fuel pressure. Did they pinch off the return line to see if the regulator was bad? 2 bad ECMs in a row? I wonder if they are just guessing.

Might I suggest you take a trip to Autozone and borrow their scanner. If it works, buy that one. I would try to get one that does BOTH the OBD1 and OBD2 stuff so you can use it for other cars.

 

Before I replace the O2, I would get a reading and see what it does AFTER just to see.

IIRC it is in the front of the manifold but check what the temps say they are via the ECM and use an infra red gun on it.

 

Sounds like you might be missing the cause. IF the injectors are out of resistance range, they will cause misfire and or no starts, particularly warm.

Get the ohm spec and go w/ it.

 

Injector R&R.