The multitude of Motronic problems with the '84-'89 Carrera's is now comical to me!!!

[Tippy]

Since I've had my issues with my '87 Carrera, I've spent hours pouring over threads looking for things to check and wrote/spoken to the tuner of my car.

I cannot believe SO many cars have had the same surging idle, rough running, stumbling/hesitation/backfiring/surging/cutting out/etc. problems and the outcome seems never the same dating back to say '99.

I am on my 2 month anniversary with my stumbling/surging/backfiring issue and I still have not resolved - About to run my '87 Carrera off a cliff - still surging and backfiring.

There is so many members here who have suffered these issues, I can't believe it!

The problem boils down to not being able to do any kind of data logging or diagnostics. The average person has to trust a multimeter and that the sensor or component that maybe giving fits doesn't give an intermittent problem easily being overlooked.

Not sure how much more I can take of my car.......I've really thought of selling a couple of times because it is such a let down after I rebuilt my motor.

This now has been the longest time I've searched for a problem ever in a car.

Sorry for rant, but I'm sick about the whole situation and at times I just laugh how this is so hard to figure out.........

Guess my pride of fixing myself is getting in the way of resolving the issue.

[AVDCAV]

I feel yu. Ang in there "
I will say this. A while ago I had the same issues
Then my car was just dead . I tested speed and ref sensor
They were hairs away from being in spec. Bought the BMW ones
Which are cheaper. No bull. Started it up and it was like a new car
Never had a problem since

I had massive pulsing idle problems.

[McLovin]

Motronics is normally very reliable, and easy to diagnose.

Is this the car you are talking about?

"w/turbo (T60-1) 447whp - street tired, granny shifting 1/4 mile 12.4 @ 124 MPH"

[Tippy]

ADVAC - I changed the reference sensor but no change. I'm going to swap to the speed reference side next.

McLovin - yes, that is my car. How do you diagnose the system when you cannot see live time any data?

[rolls 912]

I havent read your other thread but why don't you borrow a mot. Box and see if that resolves the issue. Make sure you disconnect the battery when you are changing boxes. This will isolate immediately if it's a sensor or the box itself. Just my two bobs worth

[ant7]

Originally Posted by Tippy

Since I've had my issues with my '87 Carrera, I've spent hours pouring over threads looking for things to check and wrote/spoken to the tuner of my car.

I cannot believe SO many cars have had the same surging idle, rough running, stumbling/hesitation/backfiring/surging/cutting out/etc. problems and the outcome seems never the same dating back to say '99.

I am on my 2 month anniversary with my stumbling/surging/backfiring issue and I still have not resolved - About to run my '87 Carrera off a cliff - still surging and backfiring.

There is so many members here who have suffered these issues, I can't believe it!

The problem boils down to not being able to do any kind of data logging or diagnostics. The average person has to trust a multimeter and that the sensor or component that maybe giving fits doesn't give an intermittent problem easily being overlooked.

Not sure how much more I can take of my car.......I've really thought of selling a couple of times because it is such a let down after I rebuilt my motor.

This now has been the longest time I've searched for a problem ever in a car.

Sorry for rant, but I'm sick about the whole situation and at times I just laugh how this is so hard to figure out.........

Guess my pride of fixing myself is getting in the way of resolving the issue.

Hi Tippy,
realy sorry to hear you still havent found the problem, Cars can send you mad sometimes, especialy with the type of fault you have but as others have said, hang in there, my sugestion would be to start at the begining, and re-check everything, even things you think may have little importance, you may be surprised, wiring can often be the culprit. Take a break from it for a little while, and then go back to it with a fresh mind.
Realy hope you get to the bottom it.
Anthony.

[Vereeken]

I am on my second year with a stumbling at 3000 rpm on a CIS engine. So you still have 22 months to go ;o)

I lost my racing season in trying to find a stumble at full load. turned out to be the floaters in the Webbers that let teir head down. 6 months of looking.

Cars. No different then women. Upside is you can put them in a locker for a while.

The problem is that it all becomes too complex. Even with modern cars mechanics turn immediately to swapping parts instead of finding the issue. And that is with good documentation at hand.

Hang in there.

Michel

[j911brick]

Why don't you have a shop look at it?

[boyt911sc]

Originally Posted by Tippy

Since I've had my issues with my '87 Carrera, I've spent hours pouring over threads looking for things to check and wrote/spoken to the tuner of my car.

I cannot believe SO many cars have had the same surging idle, rough running, stumbling/hesitation/backfiring/surging/cutting out/etc. problems and the outcome seems never the same dating back to say '99.

I am on my 2 month anniversary with my stumbling/surging/backfiring issue and I still have not resolved - About to run my '87 Carrera off a cliff - still surging and backfiring.

There is so many members here who have suffered these issues, I can't believe it!

The problem boils down to not being able to do any kind of data logging or diagnostics. The average person has to trust a multimeter and that the sensor or component that maybe giving fits doesn't give an intermittent problem easily being overlooked.

Not sure how much more I can take of my car.......I've really thought of selling a couple of times because it is such a let down after I rebuilt my motor.

This now has been the longest time I've searched for a problem ever in a car.

Sorry for rant, but I'm sick about the whole situation and at times I just laugh how this is so hard to figure out.........

Guess my pride of fixing myself is getting in the way of resolving the issue.

Tippy,

There are a lots of guys like you in this forum. Who are determined to do and fix the problem himself. I'm in similar situation and don't give up easily. But there comes a point when you have to sit down and relax. It is not how hard you work but how smart you do the job.

Have you considered seeking someone to do it for you? A shop, anyone who has a lot of experience in this type of problem. I've done 3 engine top and bottom engine rebuilds this year and when I had problem which are very critical to solve, I consulted people who have done this work so many years. Their experience are very valuable and you couldn't find them in any shop manuals. Posting this thread is a good direction to get help. Good luck.

Tony

[Tippy]

Originally Posted by rolls 912

I havent read your other thread but why don't you borrow a mot. Box and see if that resolves the issue.

I wish I had that luxury but I put a thread on here soon after my other thread asking if anyone in my town has one. No one responded.

Originally Posted by ant7

Hi Tippy,
realy sorry to hear you still havent found the problem, Cars can send you mad sometimes, especialy with the type of fault you have but as others have said, hang in there, my sugestion would be to start at the begining, and re-check everything, even things you think may have little importance, you may be surprised, wiring can often be the culprit. Take a break from it for a little while, and then go back to it with a fresh mind.
Realy hope you get to the bottom it.
Anthony.

I have taken several breaks clearing my head and going over things over and over again to no avail.

Originally Posted by Vereeken

I am on my second year with a stumbling at 3000 rpm on a CIS engine. So you still have 22 months to go ;o)

I lost my racing season in trying to find a stumble at full load. turned out to be the floaters in the Webbers that let teir head down. 6 months of looking.

Cars. No different then women. Upside is you can put them in a locker for a while.

The problem is that it all becomes too complex. Even with modern cars mechanics turn immediately to swapping parts instead of finding the issue. And that is with good documentation at hand.

Hang in there.

Michel

Sorry to hear that! Wow. The woman metaphor, love it! I hear on you the modern mechanics.......no diagnostic skills.

Originally Posted by j911brick

Why don't you have a shop look at it?

Pride!!!!! My family has never taken a car to anyone to get worked on unless under warranty.

My dad also owns a restoration shop. Throwing in the towel would be a black-eye to the family. HEHE Just kiddin'......

[rolls 912]

Common guys. Someone local surely has a box they can lend tippy for 5 minutes while he swaps them over? Even if you drove around to his place? Tippy, you supply the beer.

[Vereeken]

I would recommend against going to a shop.

Not all workshops are called John Walkers Workshop or Wayne at Pelican Parts, nor do most of us live close by these people.

When I started on cars I put my trust in mechanics (Porsche, fast escorts, Mx5...).
Most of them if not all where very friendly and correct people but when it comes to troubleshooting these kind of problems they are only one page ahead of you in the book and that is not much. Second, they have to earn a living. So each hour spent on you car should be charged. Would you pay for that?

They are perhaps marginally faster then you in looking for the potential cause, but not that much faster.

Even a guy like JW has a list of usual suspects when troubleshooting a car. It is not that he can identify the problem by looking at it. He has to eliminate as well.

I agree that in the parts swap department they might have an easier time then yourself.

If I could give you one piece of advice it is to list your suspects again and go over them one at a time. This board is fantastic if you need to compile taht list.

On my race escort I had a list of 12 things to check. The float-level being one of them. Unfortunately for me the Float level was number 10 on my list because I had put it there as I was "sure" I had checked them at the end of previous season. -That and being ademant it was ignition not fuelling

On my 911 I worked my way through a whole list of issues. Sometimes I found something and sometimes not. If I look at where I started -an undrivable car- and where I am now - a light stumble at 3k rpm- I have greatly improved. Yes it has been 24 months. But hell I feel a lot smarter.

If you are fed up with the car. Put your tools down and come back in a couple of weeks.

Good luck.

Michel

[Hoss911sc]

Hi Tippy,

I too have struggled through troubleshooting an intermittent Motronic problem and its very frustrating. 2 years to find that the O2 sensor was the culprit in heavy rain conditions ... Now I have an intermittent stall challenge - another thread in here.

I also ended up suspecting the ECM unit. If you can't find a test unit locally, the shops that rebuild them can offer a test unit. There is a deposit and shipping but at least you can determine if that is the issue. I used Specialized ECU Repair and they are great to work with. I've seen references in the board for other good shops as well.

Good Luck.

[Tippy]

Originally Posted by rolls 912

Common guys. Someone local surely has a box they can lend tippy for 5 minutes while he swaps them over? Even if you drove around to his place? Tippy, you supply the beer.

Thanks for the plug rolls! I'd buy you beer if you were near me just for helping me out.

Originally Posted by Vereeken

I would recommend against going to a shop.

Not all workshops are called John Walkers Workshop or Wayne at Pelican Parts, nor do most of us live close by these people.

When I started on cars I put my trust in mechanics (Porsche, fast escorts, Mx5...).
Most of them if not all where very friendly and correct people but when it comes to troubleshooting these kind of problems they are only one page ahead of you in the book and that is not much. Second, they have to earn a living. So each hour spent on you car should be charged. Would you pay for that?

They are perhaps marginally faster then you in looking for the potential cause, but not that much faster.

Even a guy like JW has a list of usual suspects when troubleshooting a car. It is not that he can identify the problem by looking at it. He has to eliminate as well.

I agree that in the parts swap department they might have an easier time then yourself.

If I could give you one piece of advice it is to list your suspects again and go over them one at a time. This board is fantastic if you need to compile taht list.

On my race escort I had a list of 12 things to check. The float-level being one of them. Unfortunately for me the Float level was number 10 on my list because I had put it there as I was "sure" I had checked them at the end of previous season. -That and being ademant it was ignition not fuelling

On my 911 I worked my way through a whole list of issues. Sometimes I found something and sometimes not. If I look at where I started -an undrivable car- and where I am now - a light stumble at 3k rpm- I have greatly improved. Yes it has been 24 months. But hell I feel a lot smarter.

If you are fed up with the car. Put your tools down and come back in a couple of weeks.

Good luck.

Michel

Spot on Michel! You and I feel the same way. I don't want to throw tons of money on this problem since I just dumped thousands in rebuilding my engine.

Originally Posted by Hoss911sc

Hi Tippy,

I also ended up suspecting the ECM unit. If you can't find a test unit locally, the shops that rebuild them can offer a test unit. There is a deposit and shipping but at least you can determine if that is the issue. I used Specialized ECU Repair and they are great to work with. I've seen references in the board for other good shops as well.

Good Luck.

Yep, that is my last step and I really feel it is going to be the problem.

[daniel911T]

Originally Posted by Vereeken

The problem is that it all becomes too complex. Even with modern cars mechanics turn immediately to swapping parts instead of finding the issue. And that is with good documentation at hand.


Michel

Michel,
Swapping parts is actually a long tested and very effective method for fault isolation.

I used to be a sonar technician on US Navy submarines. We carried a full set of "MAMS" or Maintenance Assistance ModuleS, basically a known good, tested and calibrated set of at least one of every electronic component in the sonar system. You used troubleshooting charts to isolate the problem, changed that module with a known good one, then re-ran diagnostics. Sometimes it fixed the problem, sometimes it exposed a new problem, and sometimes it told you where the problem wasn't. When you finally found the problem, you pulled a new card out of supply, and the known good MAM went back into the kit for next time.

The point is, they were absolutely invaluable. I wish it was practical for us to keep a kit around, one known good unit of every type of electrical part, just think of how easy that would make Tippy's life! Sadly it's expensive, but maybe it's the kind of thing a local PCA chapter could build over time and release on a loaner basis to frustrated owners? Just a thought...

Anyway, what modern mechanics are doing is not randomly changing parts. They are doing their best to isolate a problem, then test their fix to see if it is actually the problem.

Very quick example: Car died, no fuel pressure. First thought: "crap, my pump died." Second thought: "check the fuse, uh-oh it's fine, guess the pump died. I'll get a new one." Replace pump, still no worky. hmmmmmm? fuel pump relay? Yep. How much money did you just spend on an unneeded new pump? Now imagine this with electronic components... gets expensive mighty quickly, and the only way to test them is on a running engine. Whole bunch of time wasted.

Good Luck Tippy! I feel your pain!

-Dan

[daniel911T]

On the fun of L Jetronic troubleshooting:

I owned a '78 VW bus with a very similar Bosch fuel injection system to Motronic. I spent more than a year (through a Colorado winter) with a bus that wouldn't cold start without a bunch of starter fluid and would barely idle. Ran OK when going... just hated sitting still. (Even worse: it was an automatic!)

When I found the problem I wanted to jump off a building! There was one tube that had come loose from the main induction hose, the one that goes from the "gate" air sensor down to the manifold, simply hooked it up and all problems were solved.

When the problem started all I could see was $$$$$$$$$ and fear. I didn't even want to look under the hatch, and when I did there didn't appear to be anything wrong. I lived with that for a year. stupid.

Good luck with your troubleshooting!

[Tippy]

Daniel, I plan on making a "Motronic testing kit".

It will have reference sensors, idle microswitch, AFM, coil, etc....

[Rodsrsr]

I think its a good idea to change out the sensors regardless. They are now 30 plus years old anyway. I also used the BMW reference/speed & CHT sensors. (but that is not your problem) The ecu can possibly be defective but its unlikely. I don't remember your setup, but if your using a stock AFM on a push thru turbo, it wont last long. It sounds like it is running rich. If your running a rising rate FPR and don't have the plastic restrictor in the signal line than it will raise the fuel pressure too much. Bottom line is that your car is doing exactly what mine did on my old Supercharged setup. The FPR was simply raising the fuel pressure too much too fast. I used a BEGI which has two adjustments and once I installed the $2.00 plastic restrictor in the signal line car was 100%. (after 6 months of headaches) I don't know if Protomotive FPR has the 2 adjustments, but if your running larger injectors, RRFPR and a chip, it sounds like its a little overkill on the fuel. On my turbo setup I use stock injectors, BEGI FPR, stock chip with MSD boost retard. I also switched to MAF with split second controller. Car runs as smooth as a new BMW. (only .6 bar though)

[JeremyD]

really - most of the motronic stuff is not expensive.

I was one of those that had a stumble at 3500 rpm's - I changed plug wires and coil - then no more stumble. But that was only because I replaced the reference and CHT sensor less than a year before. Many of these systems are what - 20-25 years old. Electronics of that era just don't age very gracefully

[Tippy]

Rodrsr - You can buy a BMW CHT sensor?

I don't understand how the blow-through would be hard on the AFM? The barn door is a cast piece with nice structural ribbing. Curious on that one. It does slam it hard once boost builds I am sure of.

It appears to have a check valve, not a restictor on the FPR but I could be wrong. The FPR is a rising rate that is not adjustable. I am stuck with higher fuel pressures.

As far as fueling, yes, I have enough fuel pumps to power over 1000whp IIRC. The injectors though are really not that big for 500+hp.

The chip was only for running the 55lb Siemens injectors vs the stock ones I believe it had before (which I find hard to believe you can make 500hp with stock injectors?).