Sputtering - 91 s5 convertible NA 13B
 

Hello. I have a 91 s5 convertible NA (Non-turbo). When I start it up, it starts fine, sounds fine, smokes quite a bit (but that's beside the point) for a minute or two, and most importantly revs straight up to red line without a problem. I start driving. 1st gear can go to red line without issue. Once I hit second gear (sometimes right at the end of first gear), it starts hesitating and sputtering. It won't rev over 4000 when the throttle is wide open (not even in neutral), but will go all the way to red line when the throttle is about half way or less. This continues in all gears (1st included) until I shut the car off. I can start it right back up and the process starts over again.

So far, I have pulled, inspected, and cleaned the EGR valve (twice) and the Catalytic Converter (which appears to be new or almost new). I have inspected for air leaks and have fixed any leaks that there were, with no real change in performance.

What's next?

Sounds like limp mode.

Pull the codes as instructed in the 2nd gen FAQ.

I'll double check but I haven't seen the CEL except when I first turn the key on before starting the car. Those lights are a little dim sometimes (at least the gas light is). That's another thing to fix later on though.

Actually maybe I was wrong. The CEL is not showing at all. Not even when I just turn the ignition on. I'll check the bulb. I have a sneaking suspicion that the man who sold the car to the man that I bought the car from disabled it. For now I'm flying blind. Any other tips?

Fix the bulb. :) Limp mode is generally caused by a failed metering oil pump and the codes will confirm.

Changed the bulb, still no CEL light. Could it be a problem with the ECU? Or is it more likely that the warning light board is bad? (Clock stopped working too)

I do not know if i am off base here, but have you checked your coils, plugs, spark plugs? just a suggestion.

I had my rx running good and experienced the same recently, in an 89 convertible na auto. I'm betting aaron's right on this one, as it was the fix on mine:)

Well the OMP is mechanically driven and works fine. I've checked the sparks and they are plenty strong. I think the full range TPS may be shorting out, but TPS's aren't cheap for these cars so I need to know how to test it with my multimeter. Specifically, does anyone know what the range of the signal voltage should be?

I have not got the CEL fixed yet, but will soon. I've discovered that the contacts in my warning light board are weak or the wiring harness itself. I will get that fixed sometime soonish. I will probably jam some pins or something in the connectors to tighten them up before trying to solder the connections.

The metering oil pump may be mechanically driven, but there is a servo inside that the ECU uses to control the amount of oil injected. If it has failed, it will go into limp mode. There are tests in the FSM for the metering oil pump. Another possibility is the full range TPS.

If the CEL doesn't light when the key is on but the engine isn't running, then there may be a problem with the board. A very common issue. It needs to be resoldered.

You may be right about the OMP. I've taken a closer look under the hood and can't find any wiring going to it. I'm going to get under it tomorrow and look for wiring that I couldn't see from above. I'm wondering if the wiring came loose or something.

A mazda mechanic told me that there were 2 OMP's used, one totally mechanical with no electronic parts, and the one you're talking about. But as I look around the web, all I see for the 91 13b s5 is the one that you're talking about. Damned misinformation.

ya..86-88 used mechanical OMP's and the 89-91 used the electronic OMP.
The Electronic omp is known to fail or starting to fail and be the culprit of Limp Mode.
The sad part about the electric omp is that you can't just unplug it and Premix.It has to be left hooked up in the electrical system for the Ecu to see,or else..Limp mode ..again.(plus the omp must be GOOD at the time of physically removing it off the engine,you can't hang a bad omp.)
That is why I like the s4!

You have a '91, so you have an electronic metering oil pump.

I currently have the same problem with my 91 vert. the throttle responds very well (before the engine is sent into limp mode) so I know its not the TPS. so the OMP is the only other reason for the limp mode correct?

Buy a new ECU. Send it to DTI for RTek 1.0. Install in car. Be done with it.

I just had the same problems. That fixed everything.... so far.

Uh, don't just buy a new ECU without at least testing a few things like:

-TPS (both full and narrow range)
-boost sensor
-AFM
-injectors
-metering oil pump

Ok I haven't had the time to work on it in a while. Went out and fired it up today (as I have every weekend) and immediately noticed the smell of a gas leak. I let it idle and peaked around under the hood to find a rather large leak coming from the drivers side of the engine, sort of under the intake manifold, near the area where the EGR purge solenoid is. I see what appear to be gas lines in there, but cannot isolate the leak because I don't have all of my tools at home. I noticed a couple of missing bolts near the EGR, but no wetness around them at all.

So, (1) are those tiny little steel lines gas lines and (2) is there anything else in that area that could be leaking gas?

I'm assuming that this leak is the cause of my loss of power because there are no blink codes from the CEL.

There are two fuel lines in that area. You can follow them up the firewall near the frame rail to the engine. The rubber lines connect to hard lines which disappear under the intake manifold.

Ok I found the leaking line and traced down where it's connecting points (firewall and engine connectors). To correctly replace this line I will have to remove the intake system and other things in the way. A major pain. I was wondering if it would be safe for me to simply buy about 3 or 4 ft of hose from Autozone, a coupling, and a few small clamps and run my own fuel line. Since the factory line goes from metal to rubber and back again, I would think that that would be safe. What do you think?

Removal of the upper intake is actually quite easy. Just label the electrical connectors and hoses, and it comes off in about 45 minutes the first time. Then the next time you do it, it will take 5 minutes. :)

Yeah but the upper intake is not what I'm worried about. I've taken it off before to clean out the EGR and replace some vac lines. The problem is that the fuel line in question runs up under that lower half along the side nearest the front of the engine, behind another fuel line (really pinned in by that fuel line, and then pops out on the other side of the engine. It's really kind of stupid that they put it in that way, but whatever. That's why I was thinking about just rerouting it.

Take a look at this picture:

http://i49.photobucket.com/albums/f2...ngfuelline.jpg

The tip of my finger is pointing at the leaking line. The red arrow points to the leaking fuel line and the yellow arrow points to the lower alternator bracket.

Okay I replaced the fuel lines. Now I'm trying to figure out how to prime the fuel system. Service manual says to find the yellow 2 pin check connector and bridge the wires, turn the key on for 10 seconds, check for fuel system leaks (not seeing any yet), and then start the car. The problem is that I cannot find the yellow 2-pin check connector where the manual says it is (front driver's side, near the battery and diagnostic green connector wire). Where the hell is this thing? Or is there another way to prime the fuel system? HELP!

It's part of the Emission harness and it is found near the passenger strut tower as the harness which feeds the Boost/Pressure sensor comes from the same harness that the check connector is part of. The connector is Yellow but is hidden withing a Black rubber boot. So, between the engine and the passenger strut tower is the Emission harness, and therefor the connector you are looking for.