Brad Huff

Guys I need some help with this. I'm at the base of the mountain as far as the learning curve with EEC-IV efi. I bought this 1990 5.0 Monster Miata a couple of years back and have only been able to drive it about 8 miles. It's pretty much stock although it does have aluminum heads and a slightly higher performance cam. The thing initially died coming off the transport and the problem was traced to a faulty TFI module. I replaced that but did not replace the stator in the distributor. I was told that they either worked or they didn't. It ran ok after that albeit a little rich. The fuel pump sounded like a high-speed screeching electric drill, so I replaced it. It was a Walbro 255 and I replaced it with a Detschworks DW200. I also put it under computer control as opposed to the direct jumper method. I have a breakout box connected so I can read voltages with my Fluke 88 and initially had a left bank O2 sensor that was outputting very low voltage. I replaced that. Long story short, it now runs like total crap. I have a GTC 505 ignition analyzer, and it shows ignition misfires on about 3 cylinders. The distributor cap rotor, wires and spark plugs are new. I've tried almost everything, and I can't figure out what I'm missing. I Know that I should probably change the stator, But I'm afraid that the guy that built the shortblock might not have put the retaining clip on the oil pump driveshaft. I can't get a response from him, and his shop is now out of business. I would think that if the stator were the problem it would show up equally on all cylinders. There was some rust in the fuel tank. I spent about 5 hours cleaning it and got it all pretty good. I even bent back the baffles so I could get to all of it. The fuel filter is new. The regulator is stock and doesn't leak with the vacuum hose disconnected. I've got about 39 lbs at idle. I'm wondering if leaking fuel injectors could be responsible for the misfires? I've tried 2 computers and the results are the same. The caps are new, and the signal return traces are intact. Right now, I'm just trying to get it back to where it was so I can get it out of my garage and back to storage before the weather turns cold. I know that I have probably left out a lot but I'm trying to give enough information without overwhelming you. Thank you in advance for anything that you can provide. Please ask for any other information. -Brad

jrmotorsports55

1. Pull spark plugs. Are all cylinders firing, looking like good burn? Are any covered in gas signaling no ignition/dead hole?
2. Sounds stupid, but is the firing order right for the cam (HO vs non-HO)?
3. Have you checked that all injectors are firing by checking for "clicking" while running?

Few things to get more info.

Brad Huff

Thank you for responding Jason. I replaced the spark plugs along with the distributor cap and wires about 3 weeks ago. They were pretty much black or at least dark brown signifying a rich condition. The engine did not run any better. I pulled a couple of the plugs after about 30 minutes of idling, and they were black. I pulled codes and got a 91 when I ran the KOER test. I checked voltages between pins 43 and 46 on my breakout box and read point1 volt (.1). I replaced the O2 sensor on the left bank and then discovered that 2 of the 4 wires had backed out of the connector so the sensor was inoperative giving the computer false data. It was telling the computer that the left bank was lean, so the injectors were running rich to try and compensate. I repaired that issue but although the spark plugs are now a better color, the engine still runs poorly. The engine never runs well even in open loop with the prewritten tables. It's cold performance is similar to a carbureted engine with no choke. You have to modulate the throttle to keep it running. This engine ran fine a year and a half ago when I brought it home from storage to change out the screeching Walbro fuel pump. I ran out of time before winter set in because of the rusty fuel tank as was previously mentioned. I also have the video that the PO sent me confirming the operation. I have 2 EEC-IV computers that are for a 1990 5.0 GT Mustang that I have tried. The one that came with the car has a chip in J3 although I have not pulled it to try to see what it is. I have a Jaybird but I don't know enough yet to understand what I am doing. The engine supposedly has a fairly stock cam. About all I could get out of the engine builder is that It's symmetrical with .480 lift and 224 @.050 duration, if I can believe him. The heads were supposed to be Edelbrocks but are very suspicious. They have a 3037 cast into them, and I suspect that they are ProComp Chinesium specials. This might turn out to be the real cause of my problem. The other computer is a A9L that is untouched. J3 is still coated with the insulating goop. I had to repair the signal return trace on that one. The previous owner must have used it with the wrong O2 sensor harness. It now reads like it should. My GTC 505 showed severe misfires on cylinder 5 and inspection showed too much anti seize had gotten down on the porcelain causing the problem. I have since cleaned it off twice and it's better. Not perfect, but better. The thing is, even after cleaning the plug the engine still runs with a miss. It would not even come close to the Rolls Royce wine glass on the air cleaner demonstration. I tried both firing orders. The HO firing order is what came with the car and that is how I left it. I have not checked the injectors with a stethoscope. I will do that. I just figured that with the plugs being black, that probably wasn't the problem. I started this project by going back and trying to redo all of the half done or poorly done things that the previous owner did. Things like connecting the CEL light, connecting the NGS so the computer could give KOER codes. Another big one was reconfiguring the air intake. They had the MAF straight out of the throttle body a couple inches away with a small air filter right over the passenger side exhaust header. I got a Mustang snorkel hose and ran it similar to a 90 GT Mustang. I expected big results, but it did not happen. I then suspected that they tuned it that way, so I hooked everything back up the way that it was hoping to restore the performance that it had. This hasn't panned out. I know that they routinely jacked with the throttle screw on the throttle body which is a big no-no. So right now, I need a sense of direction. Do I go back to the poorly designed air intake? Which computer should I use? I need to chart a course and stick with it. Right now, there are too many variables. Anyway, thanks for listening. I'm sorry for the long post but I'm trying to give as much information as I can without overloading you guys. -Brad

jrmotorsports55

OK, I chased some similar bad running in my old Monster and it turned out to be that the A/M MAF and ECU did not like each other. What MAF housing/sensor are you running (stock/A/M)? One recommendation that I would make is if you can get your hands on a stock Ford MAF/sensor to run with the stock A9L, see how it runs in that configuration. These old MAF setups are very particular with setup, just clocking the MAF can change things based on airflow changes over the sensor. I ended up having a custom tune done with my setup and it cured all issues for my ECU/intake/MAF setup.

mrmustang

Agree 100%, MAF can be fickle and need adjustment and only use the A9L, or maybe even buy borrow another A9L, which is the most user friendly with minor mods

On top of that, check all of your multi PIN connectors to see if one is either not seated, or broken, which will throw the signal off to the ECU.

Finally, with the heads suspect, have you done a compression check?
Pull distributor and reset at TDC on compression stroke to play it safe
As previously stated, check for proper firing order afterwards.

Bill S.

Brad Huff

The throttle body and MAF are stock1990 Mustang GT, as far as I can tell. As far as clocking the MAF, I tried to set it up like the pictures that I've seen of Fox body Mustangs. I'm a little worried about the health of the valve train, only because of the things I've read about ProComp heads. There is a slight bit of clatter on occasion, but the plugs all seem to be burning the same. I'm wondering if it would be wise to pull the upper intake and the valve covers so I can have a look. The MAF is doing something because there is a major reaction when I pull the connector. The engine will barely run at all with it disconnected. -Brad

jrmotorsports55

One other thing I would look in to with the multiple ECUs/maf is what injectors it has in it. Are they the stock size orange 19 lb injectors, or different. If bigger injectors and stock MAF, with no tune it will run really rich. I know this is kind of an obvious one, but wanted to throw it out there.

Brad Huff

They are the stock #19 orange injectors. Should I try to clean the MAF? It is stock. Also wondering if I should keep my Fox body style snorkel air intake or go back to the configuration that they had for now. -Brad

jrmotorsports55

Yeah, I would try cleaning the MAF at the very least. I would try running it on the stock MAF, stock elbow, and stock ECU just to see what happens if you have not already.

mrmustang

Brad,

Reviewing your posts, and your old posts, I'm suspecting that either your replacement fuel pump installation is faulty, or both of your current ECU's are. Find yourself a replace A9L and plug it in without fiddling with it. Also check to see if you actually have fuel pressure. Start with the very basics, fuel, spark, compression. If you "adjusted" your MAF, call a friend who knows what he is doing to double check your work. All of this hunt and peck, with electronic tools you really don't know how to use, may be part of the problem. Take a step back, breath, and start from the beginning, don't second guess, just revue the basics one at a time.

1: Compression check
2: Check for spark at the distributor, consider pulling it and re-indexing it to make certain it is not 180 degrees out
3: Fuel pressure (did you ever purchase a replacement that fit, or did you force fit the slightly oversized unit in place)
4: Borrowed, or purchase a stock A9L, do not open it up, just plug it in, as you fiddled with the current unit, made a repair, but may have unintentionally friend the unit with a static charge while you had it out. Just like a laptop/desktop computer, the ECU is susceptible to static catastrophes.



Bill S.

Brad Huff

Bill,
Thank you for your response. I ran a compression check on this engine. It was rebuilt by a firm known as "North Texas Speed and Machine". This is who the previous owner, "Ace Paintless Dent and repair" in Lewisville Texas, used to build the engine. I guess the shop is now out of business and any information about the rebuild is sketchy at best. The engine supposedly has only 5000 miles on the rebuild. It was tuned by an outfit called "Auto Science". The heads were allegedly Edelbrocks but I believe them to be ProComps. I ran a compression check, and they are all 125. Low but even across the board. I believe that the ProComp heads have a bit larger combustion chamber which would account for the lower compression. I replaced the fuel pump with a Deatschworks DW200 which is giving 39 lbs at the schrader valve. The spark is good as determined by my GTC 505 ignition analyzer and my Sun SS70 oscilloscope. I have not removed or otherwise disturbed the distributor. It is where it was when I received the car. It ran fine when I first got it for the 4 miles that we drove it from the transport to the driveway of the storage garage. That's where the TFI module died. After I replaced it, the engine started and ran fine, except for a low speed bucking problem. The fuel pump was so loud that I felt it could go bad at any time, so I replaced it. I was surprised to see that it was a Walbro 255lph. I knew that they were loud but the noise that one made was excessive. Several other people commented on it as well. After looking back at a video that the previous owner sent me, it's obvious in the background. As far as the computer goes, I feel the need to explain myself about my electronics experience. I am also an Extra Class amateur radio operator. I have a basement full of signal generators, oscilloscopes and the like. I passed the basic electricity and crystal set stage over 55 years ago. I would consider, however, trying a third computer. That is if I can find one reasonably priced to try. I don't need a stack of these things sitting around. I already have a lifetime supply of tools and components that I will probably only use once. LOL. That seems to be a male trait. I have many cars, too many just ask my wife. One of them is a Sunbeam Tiger. I built a HP289 back around 1982 and transplanted that engine, it has 351 windsor heads, which was commonly done in those days. Anyway, I hadn't started it for about 6 months, and I needed to move it yesterday. I hopped in, it cranked one revolution and fired right up. Idles like a sewing machine. Holley 4118 carb, solid lifters C3OZ-C cam. Sometimes simpler is better. There are times that I have given thought to doing that with this car, but I wouldn't really learn anything about fuel injection then would I? It wouldn't be that big of a deal since this is just a toy. I keep coming back to the thought that it did run fine at least in his video and for the short trip to the storage unit. I would even live with the low speed bucking and trailer-hitching if I could get it back to where it was. The Tiger has none of these low speed problems. I'm telling you all of this not to toot my horn but to bring you all up to speed about my capabilities. All of you guys are way ahead of me as far as what to expect when fuel injection problems occur. I can't help thinking that I'm missing something simple though. None of this is rocket science. I'm seriously considering signing up with Michael Decipha's services as far as tuning goes but I realize that I will need to make a decision about those cylinder heads before I spend any tuning money. That will be way down the road as I need to get this thing running first. I am torn between whether this is an electronic issue or a mechanical one. It almost seems mechanical in nature. That is why I think I need to have a look under the valve covers. One other thing, I did not mention before is that the EGR has been removed and blocked off. I don't think that should affect the idle however as that doesn't come into play at that time. Please correct me if I'm wrong about that. I figured that is why there was a chip in the computer to begin with. I don't know if the changes that they made to the computer were really necessary based on the limited upgrades to the engine. Feel free to comment about anything here as I can't learn if I don't get some sense of direction. Again, sorry about all of this rambling. I appreciate all of you guys taking the time to help educated me. -Brad

mrmustang

I'd reclock the distributor, or at least see if it is close to #1 at TDC on a compression stroke.

Removed EGR on a stock A9L won't affect the idle or running issues you appear to still have.

As for the Sunbeam Tiger, if it's rust free, I'll gladly take it off your hands at a fair price for both of us.


Bill S.

Brad Huff

Bill,
I have checked the timing and it is spot on. At least it is using the marks on the harmonic balancer. It does not backfire or pop back. As I explore the various sensors and their purpose it becomes very logical how this thing is supposed to work. My problem now is making the correct diagnosis as to whether this is an electrical/computer problem or a mechanical problem. The miss effect that I feel is throughout the operating range. That is, it isn't just at idle. It never smooths out as the rpm's increase. I have not taken it out on the road for fear of really damaging something. That's why I think that I need to check out the valve train. I have heard horror stories about the ProComp heads and bad valve guides and rocker arms that don't line up properly. I guess my main question at this point is whether a MAF or a clogged injector could make an engine feel the same way as if there was a mechanical problem. I keep finding the "one more thing" that the builders did that was wrong and hoping that fixing that issue will correct the problem. So far it hasn't. Things like the BAP sensor connected to manifold vacuum instead of being vented to atmosphere. Out of curiosity, do you know how radical you have to get before a tune becomes necessary? As far as the Tiger goes, there will probably be a day that I will consider its future. I promised the guy that I bought it from that he would have first right of refusal. He sold it to me back around 1980 because he was getting married and needed the money for their new house. I will keep you in mind however. LOL. There will be that one and a couple of other ones that will need to be considered. I've always had blue blood (Ford) and a love for anything Shelby, or at least the Shelby concept. That's what drew me to the V8 Miatas. I think Shelby would have been pleased after all it does follow his philosophy. That is, a small, nimble light weight car with a V8 engine. I had considered a Cobra replica, but they really aren't too practical. Besides I have found that the Miatas have more foot room. As I have gotten older, I have developed an appreciation for most anything that starts and runs. At least as far as a daily driver goes. -Brad

mrmustang

Brad,

At this point, given your posts here on this thread, and your previous posts, everything is suspect. Perhaps grab a shop manual for a 93 Mustang, disconnect the battery, and start reviewing everything, wiring, vacuum lines, multi pin connectors (my last V8 Miata had one pin bent and caused me days of headaches trying to sort out a rough running situation), etc. Start from scratch as if you were building the car from the start. In regards to radical, I had a 90 "7-Up" convertible with an aftermarket cam, larger injectors, true Edlebrock aluminum heads, Cobra upper and lower intake, and supercharger that ran on a stock A9L ECU .

Tiger wise, I get where you are coming from, I've owned two in the past, also multi Cobra ownership (currently have an ERA 289 FIA), multi V8 Miatas (wife won't drive the cobras, but loved the V8 Miatas, go figure) and my 70 shelby convertible......I toy with getting rid of the 2006, 2.5L Ford Duratec powered Miata GT, and building or purchasing another V8 miata, something mildly modified, fuel injected, a really nice weekend cruiser, power steering, power brakes, and working AC, low property taxes (we pay a personal property tax on vehicles), you get the idea.....

Bill S.

Brad Huff

Bill,
Yes, that sounds like the proper way to go. It's too bad really because I bought this thing along with a second one about 2 years or so ago. Both were supposed to be turnkey perfect drivers. When the TFI module went belly up on this one I also wanted to change out the stator. I contacted the previous owner with questions about the engine. My concern was that the engine assembler might not have put the retainer on the end of the oil pump drive shaft. I did not want to pull the distributor and hear that awful clunk in the bottom of the oil pan. This man did a pretty good Sgt. Schultz imitation because he claimed to know nothing. The only words of wisdom that he could give me was that I worry too much and that I should hire a mechanic. Great thing to tell the guy that just spent money with you. The second car was not much better. What are the odds? Apparently very good. They are both project cars at this point. My desire to drive a well running V8 Miata prompted me to buy my 3rd V8 Miata. I just wanted something that I could drive and not have to work on right out of the box. This one is a Flyin' Miata build and is close to perfect. Like I said I've grown to like builds from all manufacturers. My real problem is finding time to work on any of them. I've got a couple of other cars that are projects as well and with trying to run a business time isn't really there to fix all of this stuff. That's the main reason that I bought cars that were already converted as opposed to doing it myself. As far as the Cobra goes, I should have bought one back in the 70's when they were affordable. That's not the only time that I wish that I had bought something. I remember back in 1976 driving by the local VW dealership and looking at the neat black 69 Fastback Mustang with the pie plate hubcaps and that really wide hood scoop. I probably should have gotten out and looked at it. It belonged to the owner, and he had a very fair price on it. Read that as cheap. I was pretty green in those days. Oh well that's the way it goes. The Miatas are fun, even the bone stock one that I have is a blast to drive. That Ford Duratec, is that the same engine that they used in the 95 Contour? We had one of those, 24 valve V6, and it was pretty fast. I wish that I would have kept that engine. Sorry, didn't mean to veer this far off the path. It's good to know what the stock EEC-IV can handle. I won't be so concerned with the tune. That knowledge alone was worth the effort to do this thread. -Brad